Aug 032014
 
The sun rises higher in the sky in summer, and travels around more of it, than in winter.

The sun rises higher in the sky in summer, and travels around more of it, than in winter.

Many of the preferred locations for prepper retreats are in areas that have substantial swings in temperatures between hot summers (daytime temperatures often in the 90s and sometimes exceeding 100) and cold winters (where temperatures seldom rise above freezing, even in the middle of the day).

That’s no big deal when you have unlimited utility power for heating and cooling, limited only by your ability to pay the electricity or gas bill each month.  But in a Level 2 or 3 situation, there won’t be any utility power, and creating our own electricity will be expensive and always in short supply.

We need to make our retreat structures as energy efficient as possible so as to minimize the need for heating and cooling.

There are lots of ways to improve the energy efficiency of our retreats, and most of these are totally ignored in ‘normal’ building design and construction because it makes little financial sense to, for example, spend an extra $50,000 when building your retreat, and to get a $500 a year saving in energy consumption as a result.  But in a Level 2/3 situation, the cost of the energy might rise from $500 to $5000 or more, and/or it might simply not be available at any cost, and so the financial equation changes drastically, making it more prudent for us to invest up front in additional energy-saving techniques in order to enjoy the benefits if/when we need to rely on our retreat and make do with less energy.

The good news is that not all these strategies need to be expensive or inconvenient, and some of them actually add to the livability of your retreat.  One such example is adding what in various forms can be considered either an awning, a brise soleil, a shade or a veranda (verandah – both spellings seem acceptable) to your retreat’s southerly (and much lesserly, east and west-facing) aspect.  (We’re not explaining what an awning, shade or veranda is because you probably know, but the term brise soleil might be less familiar.)

The clever aspect of such structures is that they interact with and take advantage of the way the sun rises in the sky.  In the summer, the sun quickly climbs up to a near vertical position before descending again at the end of the day.  In the winter, the sun slowly staggers part-way up the sky before sinking down again.  This difference is also more exaggerated, the further you move from the equator, and most of us are planning our retreats to be far from the equator.

sun

Note – as shown above – the sun rises a bit north of east and sets a bit north of west in the summer, but in the winter it rises south of east and sets south of west.

It covers more of the sky in summer, and you might notice appreciable sun coming in from west and east facing windows, and possibly even a little bit in northern windows too.  But it is the southern facing windows that most need the sun shading.

awningc

What this means – and as illustrated above – is that some sort of shading/blocking structure that prevents the sun’s rays from shining onto and into our retreat while the sun is high in the sky will reduce solar heating during the summer – the time of year when we most want to keep the sun off our retreat and out of our windows.  But during the winter, when we’re keen to get all the sunlight and warmth we can, the overhead structure won’t interfere with the sun’s rays at all.  Heads we win, tails we don’t lose!

Because these devices take advantage of the varying seasonal location of the sun, they can be fixed in position, making them potentially robust and low maintenance.

How much sun angle should they block?  One approach is to see the maximum angle in the sky for the sun in mid-winter, the angle at the equinoxes, and block off all angles greater than the equinoxes.  You can get this information from this helpful website – simply put in your location and then choose 21 December as the date, and that tells you the maximum height the sun reaches at your location in the winter.

For example, in Kalispell MT (48º12′ north) the sun struggles to reach 18.4º up into the sky.  Compare that to the summer solstice (21 June) when it reaches 65.2º.  At the equinoxes (21 March and September) the sun goes up to 42.2º – a number which unsurprisingly is sort of halfway between the two other numbers.

One other interesting thing is to note that the sun has risen to 42.2º in mid summer by 10.10am and doesn’t fall below it again until 5.10pm.

So perhaps it makes sense to accept something around the 42.2º point as the transition from when we want to allow sun into the house and when we want to block it.  That gives us full sun for half the year, and successively blocks off more of the sun during the summer season.

This calculation should be modified by an appreciation of what type of heating/cooling needs you’ll have at the equinoxes.  Will you still be wanting to heat the retreat, or will you be starting to need to cool it?  That will also influence how much shade cover you want above your windows.

Summary

Having some type of permanent shade over your southerly facing windows is a simple way of ‘automatically’ regulating and cutting down on the sun’s heat that transfers inside your retreat during the summer while not reducing it during the winter.

It is probably the most cost-effective thing to do in terms of improving your retreat’s energy efficiency and reducing its need for cooling during the summer.  Be sure to include shading if designing a new retreat, and be sure to add it if purchasing an existing dwelling structure.

May 142014
 
Which is more energy efficient to boil water?  This $10 plastic electric jug, or a $500 microwave oven?  The answer might surprise you!

Which is more energy-efficient to boil water? This $10 plastic electric jug, or a $500 microwave oven? The answer might surprise you!

We recommended either buying or making your own ‘Wonderbag’ type product and using it for an energy-efficient type of slow-cooking yesterday.  But what about cooking items when a slow-cook approach is not practical or possible?  For example, what is the best way of boiling water?

If you want to boil water, you probably have various choices – you can boil a kettle (or a pot) on a stove top element, you might have an electric jug, you could use an oven, or a microwave oven.

Now it goes without saying that using a regular oven would be a very slow and inappropriate process, but what about the difference between, eg, stove top, an electric jug, and the microwave?

We were able to exactly test the difference between an electric jug and a microwave oven, and we can empirically comment on the stove top as another alternative.

For our testing, we used a microwave oven that had a nameplate power rating of 1560 watts, and an electric jug with a nameplate power rating of 1500 watts.  We heated one liter of water in a glass container in the microwave, and one liter of water in the electric jug itself.  The electric jug did not have an immersion exposed element, but rather had a smooth base and the element directly below it.

We observed a rise of 34.9°C by the water in the jug, and 19.1°C by the water in the microwave during the two-minute period.  We also noted that the water in the jug was slowly continuing to rise at the end of the heating period – this was to be expected because the very hot electric element had some thermal inertia and was continuing to transfer energy after it was switched off.

So, a quick result is that there was almost twice as much net heating from the jug as from the microwave, even though the microwave was drawing slightly more power.  That would seem to argue conclusively in favor of using the jug rather than the microwave.

We were interested to know exactly how efficient each process was, so we did the calculation to compare the electrical energy consumed and the thermal energy created.

Two minutes of the jug at 1500 watts represents 50 watt hours of power.  Two minutes of the microwave at 1560 watts is 52 watt hours of power.

Increasing the temperature of 1L of water by 34.9 degrees requires 40.52 watt hours of energy.  So, for the jug, we got 40.52 watt hours of heat from 50 watts of electricity, which is an 81% efficiency rating.

For the microwave, the 19.1 degree temperature rise required 22.18 watt hours of energy, and we used 52 watt hours to create that.  This represents a 43% efficiency.

Clearly, the jug is much better than the microwave for heating water.

Where Did the Rest of the Energy Go?

You might be wondering what happened to the rest of the energy.  In the case of the jug, the balance of the energy was probably radiated away from the jug – heat from the sides of the jug, and more heat from its spout at the top.  An 81% efficiency rating is actually a reasonably good result.

The microwave’s much greater energy loss requires a bit more explanation.  First, we have the efficiency (or perhaps we should say, the inefficiency) of converting electricity to microwave energy.  This is generally thought to involve about a 40% loss of energy.  So, of the 52 watt hours that went into the microwave unit, 20.8 of them got ‘lost’ in the electronics.  More power was spent to spin the turntable, to illuminate the light, and to operate the fan (although these three things are all moderately low power drains).

Not all the microwave energy inside the cavity (and of the 52 watts, probably less than 30 watts actually ended up as microwaves) was absorbed by the water.  In addition, just like the heat that was lost out of the top of the electric jug, the open beaker we had the water contained within definitely was allowing heat to escape from the top.  If we had some sort of lid to put on the beaker, that would have probably made a measurable improvement.

So, the observed efficiencies are in line with the theoretical estimates of energy losses.

The Best Electric Jug?

If you don’t yet have an electric jug, we’d suggest you consider a plastic one, because the plastic will give you better insulation and have less heat loss through the jug sides than is the case with a pretty nice looking stainless steel one.

Our favorite jug (which is not the one we tested with) is this Proctor unit.  It is the one pictured at the top of the article.

It is plastic, it has a small minimum fill requirement, it has a fully exposed element for best heat transfer, and – wow – it is only $9 at Amazon.  What a deal that is.

Hidden Microwave Advantages

On the face of it, you’d think there’s never a reason to use a microwave oven instead of a jug when you want to boil water, right?

Well, actually, wrong.  If you are boiling a jug, you need to put a minimum amount of water in it, no matter how much water you need to heat up.  Indeed, our test jug suggests a 1.3L minimum fill (but note the Proctor unit is happy with only 300 mls).

With the microwave, you only need to put a single cup of water in it, if you are only needing to heat a single cup of water (a cup of coffee requires maybe 400 mls, depending on how large a cup you want).  In such cases, this may compensate for the microwave’s lower efficiency.

Stovetop Cooking Considerations

Okay, so that sort of explains the relativity of microwave ovens to electric jugs.

But what about boiling water on the stove top?  That is a bit harder to establish without special test equipment and digging in to the stove’s wiring or gas pipes to accurately measure energy consumption, and it also varies from case to case depending on the efficiency of the heat transfer from the heat source to the heat recipient (such things as the size and shape of the pot bottom, the size and shape of the element/burner, etc), the pot material (glass, aluminium, copper, steel, etc) and so on.  Two different scenarios could give you two massively different results, with one twice as good/bad as the other.

However, there have been some studies done which have clear and interesting results, and if we assume reasonably optimized setups, we can make some generalizations.

The least efficient form of heating is invariably gas.  You are lucky to get about a 35% – 40% efficiency from a gas burner on a stove – that is, for every three units of gas energy, you get one unit of heat transferred into your pot.

Regular smooth flat electric elements are rated as about 70% – 75% efficient, and induction cookers are about 80% – 85% efficient.

Another source claims 55% efficiency for gas, 65% efficiency for regular electric, and 90% efficiency for induction cooking.  As we said, a lot depends on the specific setup you’re using.  While the numbers are different, the relativity is the same.  Gas is the least efficient, regular electric in the middle, and induction way in the front.

In particular, if you have gas, make sure the flames do not spill over the sides of the pot.  That’s totally wasted heat.  Any time you see the water boiling first around the side of your pot, you know you are wasting gas heat and should turn down the gas.

For electric cooking, make sure the pot bottom sits flat on the element surface, and is clean.  Dirt acts as an insulation barrier, and if there are air gaps, then you are heating the air rather than the pot.

Induction Elements

Normally, when electricity is abundant and relatively inexpensive, no-one cares about the greater energy efficiency of an induction cooktop, and you have to be more specific about the types of pots you use with an induction cooktop, too.  Many of us also prefer the greater control of gas compared to traditional electric elements, and although gas is less efficient, it is also usually cheaper, per unit of energy, to use gas rather than electricity, so the efficiency issue is sort of cancelled out by the cost saving.

But WTSHTF and all energy becomes scarce and costly, it becomes very beneficial to consider an induction cooker.  There are other benefits to induction cooking, too – it is a bit like gas because it too can instantly increase or decrease the energy being applied to your pot, with no ‘thermal lag’ as is the case with regular electricity.  It can also do clever things like detect if your pot has boiled dry or not.

The good news is you don’t need to go out and buy a whole new stove top right now.  You can simply buy a single free-standing induction cooker.  Amazon has them for about $60 – $100, they are available elsewhere too of course.

We see some model induction cooktops are rated at 1300 watts and others at 1800 watts.  While you might instinctively go for the 1800 watt unit, there’s a potential small problem there.  1800 watts on 120 volts requires 15 amps of current.  So make sure you run it off a 20A rated circuit, and make sure you don’t share the circuit with anything else that consumes much power, or else you’ll trip the circuit breaker.

Needless to say, practice with the induction cooker, so you know its quirks and how to get best (and most energy-efficient) use from it.  And make sure you have the appropriate pots to go with it too – ideally pots the same diameter as the induction heating circuit.

Oven Cooking

An oven can be either an efficient or an inefficient means of cooking.  It is efficient if you are cooking large amounts of food for a long time; it is inefficient if you are heating up leftovers the next day.

You can sense this without needing to measure, just by doing a thought experiment.  Say you turn your oven on and heat it up to 350 degrees, then when it is hot, you put something in and cook it for 45 minutes.

How long does it take to heat the oven to 350°?  Probably about 15 minutes, maybe longer.  So there is 15 minutes with the oven elements on full, all the time.  Your oven probably has 3 kW – 5kW of heating elements; let’s average and say it has a 4 kW heater inside.  You’ve used 1 kWh of energy just to heat up the oven prior to cooking in it.  If you have a daily energy budget of 10 kWh, you’ve used 10% of it just to heat up your oven.  Ouch!

If you then have it cooking for a while, the oven is probably only cycling the heating elements on for 25% of the time or thereabouts, so for 45 minutes of heating, you might use another 0.75 kWh of energy.  So 45 minutes of cooking uses 1.75kWh of energy total, but if you were cooking something for more than twice as long, eg, two hours, you’d use much less than twice as much energy (ie 3 kWh for two hours of cooking).  The oven becomes more efficient, the longer it is cooking something.

The other issue to do with oven efficiency is how much food you have in it.  Most of the energy in an oven goes to keeping the air in the oven hot, and the heat transfer to the food is slow and inefficient.  It costs little more to cook ten pounds of meat or whatever in your oven than it does to cook 10 ounces of meat or whatever.

So, an electric oven is good for large quantities of food cooked for a long time, but it is bad – very bad – for a small quantity of food cooked for a short time.

Let’s come back to the ‘heating leftovers’ example.  Maybe you heat your oven to 350° then heat the item for 30 minutes.  That’s 1.5 kWh of energy.  Compare that to perhaps 6 minutes in the microwave, which would be 0.15 kWh – ten times less energy.  That makes for an obvious choice, doesn’t it!

Summary

There are several things we can conclude from all of this.

1.  If heating the same amount of water, an electric jug with immersion water heater is the most efficient way to do this.

2.  If heating less than half the minimum amount of water you’d need to heat in a jug, use a microwave oven.

3.  If cooking on the stove-top, induction elements are the best, and gas elements are by far the worst.

4.  Traditional ovens work best when cooking large amounts of food for a long time.  For small amounts of food, that only need a short time in the oven, it is usually better to use a microwave oven instead.

As preppers, we suggest you ensure you have three cooking appliances as part of your kit.  An electric jug, an induction cooktop, and a microwave oven.

May 132014
 
You can never save too much energy when planning for life after TEOTWAWKI.

The Wonderbag – something you can also easily make yourself – gives you a low energy way to make a high quality meal.
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You can never save too much energy when planning for life after TEOTWAWKI.

But there is more to saving energy than shivering in the cold, in the dark, in your retreat.  We need to rethink the underlying assumptions that are embodied in many of the everyday things in our lives – things that have been designed for maximum convenience and in the belief that energy will remain freely abundant and wonderfully inexpensive.

Trust us – even at 15c or more per kWh of electricity, that is truly ‘wonderfully inexpensive’ compared to what energy will cost you (or be valued at) when you have to make your own.

One of the greater consumers of energy in your house is your kitchen.  Many of the appliances in your kitchen are enormously wasteful of energy.  Think, for example, of your toaster – an efficient toaster would have a radiant element (the same as your normal toaster) but mounted horizontally, and then with the bread placed above it, so that the rising heat hits the bread, rather than goes out the top of the toaster.  We’ve not timed our typical pop-up toaster, but we’ll guess it takes maybe 3 or 4 minutes to toast two slices of bread, and at maybe 1500 watts, that’s about 0.1 kWh of energy for two slices of toast.  If you are setting yourself a total daily energy budget of, say, 10 kWh, you’ve used 1% of it just on your morning toast.

Add another 1% or more to boil water for your morning coffee (the chances are your jug requires you to boil a certain minimum amount of water, most of which is unnecessarily heated if all you want is a cup’s worth of water for a cup of coffee.  Modern jugs are nice and convenient, but are also not as efficient as old-fashioned jugs with an element that is immersed in the water it is heating, causing more/most (heck, pretty much all) of the heat to be transferred to the water it is heating.

Now look at your stove top.  Maybe you are cooking a meal, and you’re boiling potatoes in water for 20 minutes.  Every steam bubble that comes out of the water in the pot is wasted energy.  Potatoes will cook as fast at 211°F – right before the water starts sucking up more energy to boil – as they will at 212°F, and please don’t be like the people who think that food cooks faster in water that has a ‘rolling boil’ with lots of steam being given off, as compared to water that is gently simmering right around the boiling point.

The only reason we cook things in boiling water is because it is easy to control the temperature of boiling water, and makes for predictable cooking times.  How, in a typical kitchen, could you maintain water at a different temperature such as, eg, 210°F instead of at 212°F?

One more thing about boiling.  Did you know it takes five and a half times more energy to boil a given quantity of water (ie to take water at 100°C/212°F and change it to steam at the same temperature) than it does to raise the temperature of that water from 0°C/32°F (ie water right at freezing point but not frozen) to 100°C/212°F.  Converting water to steam requires huge amounts of energy, all of which is being unnecessarily wasted in your pot of boiling water, which would cook your food just as well at 99°C/211°F as it does at 100°C/212°F.

(If you want the actual numbers, it requires 333 J/gm to melt ice, 4.18 J/gm to heat water each degree C, and 2,230 J/gm to convert water to steam at boiling point.  As an interesting aside, this is the underlying principle of how a steam engine works – some of the energy that is absorbed when water becomes steam is then recovered when the steam drives the pistons and condenses back to water again.  The steam is merely another way of transferring and converting the thermal energy of the fire to the kinetic energy from the piston/cylinder.)

One more thing about boiling water in your jug.  Turn the jug off just before the water reaches the boil, and use that water.  You’ll save a measurable amount of energy.  Indeed, the ideal temperature for coffee is about 200°F, and a bit cooler for tea.

Your pot of potatoes isn’t just losing energy through unnecessarily boiling.  Feel the sides of the pot, and its lid too.  Feel around the bottom of the pot where the burner or hot plate/element is.  But be careful, because it is all very hot – and all that heat that you feel, and which is being dissipated away from the cooking food, that is all wasted energy.  About the only good thing that can be said for that wasted energy is that it is helping to heat your kitchen (but that’s actually a bad thing on a hot summer’s day – you then need to turn around and use more energy to run your a/c to take the heat out of the house!).

Now, you probably also have some sort of slow cooker/crockpot in your kitchen cupboards, too.  This confirms the fact that you don’t need to cook food fast (at 100°C/212°F) in order to cook it well, indeed some people say that slow cooked food ends up much better than fast cooked food.  Your slow cooker can be used for meats, vegetables, soups, stews, pretty much most things.  If you are like us, you probably seldom use yours, and in our case, we simultaneously love and hate the ‘slow torture’ of the tantalizing smells that come from it all day during the cooking process.

We are not suggesting you can save energy by using the typical crockpot/slow cooker that you probably have in your kitchen.  At least with the ones we’ve seen, it is still heating the liquid around the edges to beyond boiling, and the overall construction is not well insulated.

A Low Energy Slow Cooking Solution

What we are saying is that these concepts can be combined to create a ‘do it yourself’ low energy slow cooking device that will save you a great deal of energy.  In its simplest form, put whatever you want to cook into a regular pot, heat it up to boiling, then hold it right at about boiling until such time as the food has absorbed the first rush of heat energy from the water, then at that point, take it off the stove and wrap it up in insulation, then leave it to slowly continue cooking for however long it takes.  All the heat in the pot goes into cooking the food, rather than being wasted away.

This will take longer for a meal to be prepared, but it will also use much less energy.  And the time it takes is not personal time you need to spend standing watching, but simply elapsed time while the food ‘does its own thing’, slowly cooking away.  Prepare your evening meal at lunchtime, then come back and eat it at dinner time.

One approach to this concept can be seen in the ‘Wonderbag’.  Although designed and marketed as a device to variously ‘save the planet’ and suchlike, all the benefits they talk about on this page of their website apply with only very little change in context, to what our lives may be like in a Level 2 or 3 scenario.

The Wonderbag itself seems to be nothing more than quite a lot of foam insulation inside a fabric bag that envelopes your pot to keep the heat in the pot, cooking the food, after you’ve originally heated it up.  They sell the bags on Amazon for $50 a piece, which strikes us as expensive, but we’re told we should feel good about paying over the odds for the Wonderbag because we’re helping to save the planet in the process – as you see on their webpage, the more Wonderbags we buy, the fewer the rapes of women in Africa that will occur!

There are plenty of recipes on their site as well, and most slow cooker recipes can be used with little change (possibly slightly longer cooking times because the average temperature will drop down once you insulate the pot off the stove).

Note also some essential safety issues – don’t let the temperature drop below 140°F because if you do that, you’re entering the ‘sweet zone’ where bacteria thrive.  We’d be tempted to stick a remote temperature probe in the pot to monitor the temperature.  There are also some helpful questions and answers on the Amazon product page about how best to optimize your cooking style and pot selection, etc, when using a Wonderbag or any other similar product you create yourself.

How much energy would Wonderbag type cooking save you each day?  The Wonderbag site claims that ‘fuel and water usage extended by 60% or more’ so that seems like you are at least halving the energy required to cook a meal.  How much energy is that?  Hard to say, but coming back to the 20 minutes of boiling potatoes, plus 5 minutes to boil some other vegetable, and however many minutes to somehow cook some meat, it seems to us that you’re probably saving more than 0.5 kWh, but probably not more than 1.0 kWh, per meal you cook via an insulated cooker.  That’s not much when electricity costs you about 10c – 15c per kWh, but in the future, when energy is precious and scarce, this amount of energy saving becomes significant when you’re trying to live within a 10kWh or less a day energy budget.

Best of all, it doesn’t require you to turn down the heat and turn off the lights!  Instead, it gives you lovely flavorful tender and nutritious food.

Note :  Please see, also, our article ‘What is the Most Efficient Form of Cooking‘ for further discussion on the best ways to cook your food when energy is scarce and costly.

May 052014
 
The Champion 3100W inverter/generator - currently our pick as best small inverter/generator for Level 1 type situations.

The Champion 3100W inverter/generator – currently our pick as best small inverter/generator for Level 1 type situations.

(You can see our definition of levels one, two and three type events here.  It is a useful categorization that provides structure to your problem analysis and preparation planning.)

When some people – particularly preppers – start thinking about generators, they immediately think of enormous noisy diesel standby generators, in special generator sheds, and capable of providing tens of kilowatts of power for extended periods, drawing off multi-hundred gallon storage tanks.  Don’t get us wrong.  We love diesel generators with a passion, and we also agree there’s no such thing as ‘too much’ power.

But these types of installations will typically cost $10,000 and up, will guzzle gas at a rate of several gallons an hour, are definitely impractical for apartment dwellers, and frankly are overkill for the times when you have a short power outage lasting anywhere from a few hours to a few days.  In these short time frames, we can compromise some of the convenience we normally enjoy with abundant and available power throughout our home, and also avoid needing to adjourn to our retreat to ride out the problem.

All we want is a small convenient and ‘low profile’ portable generator that we can run without drawing way too much attention to ourselves, and keep the essential parts of our home operating.

No matter if you have major industrial-grade generators or not, we suggest everyone should have one of these small generators – and here’s the key concept.  Get a small one.  Don’t ‘over-engineer’ the problem and end up buying something that generates enough power for you to have every appliance in your house all operating simultaneously.  For a short outage, all you need is lighting, some essential electronics, and some power to share between your fridge and freezer at times, maybe a stove top or other cooking facility at other times, and perhaps heating or cooling at still other times.

How Much Generating Power Do You Need?

We repeat.  Don’t over-engineer things.  And note the question.  We’re not asking how much power you want, or would like.  We’re asking how much you need, in order to sustain life and a moderate level of comfort and security, for a short duration of no more than a few days.

So, to sustain life, you need air, shelter, water and food, right?  Let’s think about each of those.

Air – hopefully you already have air!  And hopefully also you can get fresh air without needing to drive some sort of fan or other motorized appliance.  So presumably this does not need power.

Shelter – a bit more complicated.  We’re assuming that you’re in your regular residence and it is unharmed, so you have four walls and a roof already.  But also part of shelter is some amount of heating or cooling.  You know the seasonal weather extremes for where you live and you also know what you have installed in the form of hvac appliances.  But perhaps for a short-term solution, you should not aim to heat/cool your entire residence, but work out a heating/cooling plan for just a couple of rooms only.

Maybe you have a central hvac system, and in the winter you only need a small amount of power to drive the fan, with heat coming from natural gas.  That would be ideal, and natural gas seems to continue flowing, no matter what happens to the power.  But, even so, humor yourself next winter-time.  Do a ‘what if’ worst case scenario test and see how many 1500 W heaters you would need to keep a central living area warm without your hvac.  Hopefully you’ll be able to get by with only one.

As for summer, again perhaps you have a central air system, but for the purposes of this exercise, can you also have a window unit that controls temperatures in just one room?  A small generator is probably inadequate to handle the power needs of a central air system, but is probably suitable for a typical RV sized 13,500 – 15,000 BTU type unit.

One other part of shelter – some lighting.  Perhaps now is the time to start picking up LED lights when you see them on sale, so that you are getting maximum light for minimum watts.  Indeed, the LED lighting is so good (and so long-lived) that there’s no reason not to use them all the time, in all your lights.

So – heating, cooling, and lights.  That’s pretty much everything you need for short-term shelter requirements, right?  Maybe you have something else to also plan for, like a cellar sump pump?  Try not to overlook anything else that might be essential.

Water – do you have any water pumps (under your control, as opposed to operated by the building you live in)?  If not, then hopefully (maybe) you’ll continue to get water from your taps during a power outage, and if you don’t, that’s a matter for another article.  And what about waste water?  Some people have macerator units on their toilets, or pumps operating their septic system, but other than that, most of us have gravity powered waste water systems (at least out of our house, beyond that, in the city system, there might be other issues, which are again outside the purview of an article about low powered home generators!).

The only other consideration about water would be if you wanted warm/hot water.  If you have gas water heating, maybe you have an electronic pilot light (although these are not so common on hot water heaters) in which case you need power for the hot water to work.  Otherwise, if you have electric hot water heating, that will be a problem, because the elements in your water heater probably draw 5kW – 10kW of power, and that is more than you should reasonably expect from a small portable generator.

There are two workarounds for that.  The first is a small ‘under sink’ type water heater.  The other is to simply heat up or boil water on your stove top.  Worst case scenario, if you have to go without long hot baths/showers for a few days, that’s truly not the end of the world.

Food –  There are a couple of things to consider when it comes to food.  The first is food storage – ie, your fridge and freezer.  Ideally you want to keep these powered up, at least some of the time, so you don’t have all the food in your freezer spoil, and so you are able to maintain a cool temperature in your fridge too, besides which, depending on the nature of the power outage, you might need that food to live on.  Find out how much power your fridge (and freezer, if separate) use when they’re running; we’ll tell you what to do with those numbers in a minute or two.

The second part of food power needs is cooking your food.  There are several ways you can prepare food using relatively small amounts of power.  Your microwave is an efficient and effective way of preparing many food items.  A small toaster oven is another choice, and a stand-alone hotplate/element is a third choice.  You might also want an electric jug/kettle for boiling water for coffee and other purposes.  Indeed, why limit yourself – get all these items (if you don’t have them already).  None of them cost much more than $50 a piece at Costco or on Amazon.

Make a note of the power requirements for such items.

Everything Else – Okay, now we’ve covered the absolute essentials, but what else might also appear on a list of things you really need to be able to provide power to?  We’d certainly agree that you need to have half a dozen watts on hand for your phone charger, and maybe a few more watts for a radio or even a television.  For that matter, in the unlikely event that your internet connection is up, we’d not begrudge you the power cost of turning on your cable modem, Wi-Fi router and computer for an hour or two, a few times a day.

Maybe you have some medical equipment you need to operate.  And maybe you don’t want to have your generator running 24/7, and so have some batteries that you charge during the day and run your essential nighttime electrical circuits from at night.

Adding it All Up

Now that you’ve made a list of all the items you need power for, you’ll see there’s probably nothing on the list that needs to be receiving power, every hour, every day.  So this is where you now get to make a little bit of power go a long way.  You do this by letting your appliances take turns at the power from your generator.

For example, you know you’ll only need cooking appliances on a couple of times a day.  You also know that your fridge and freezer can go quite well for an hour or so (fridge) or half a day or longer (freezer) at a time with no power (especially if you keep their door shut!), and you also know that you can ‘play games’ with any heating or cooling, so that some of the day it is on, but some of the day it is not.

So what you should do is arrange it that you either have a cooking appliance, a fridge or freezer, or some hvac equipment running, but never all of these items at the same time.  How do you do that?  Simple.  Have plugs from all the devices sharing one (or two) sockets.  That way you can only have one item plugged in at a time.  Maybe you have some devices that would take up all the power, and three or four other devices that could run, any two at a time, and one or two devices that can be on or off at any time and it doesn’t really matter, because the power they draw is so low.

What you’d do is you’d have the output from your generator going first to a power strip that has all the small power devices connected to it, and one remaining socket.  You would have a collection of plugs next to this socket, and obviously only one of them can be plugged in at a time.  You might have a plug for your a/c, and another plug going to something else, and then one more plug that goes to a second power strip, on which you’ve blocked out all but two of the sockets, and you have a collection of plugs alongside that, so that any two of them can be connected at the same time.

That way it is physically impossible to overload your system, because the way you have your plugs and sockets lined up prevents that.

You can – and should – also have a power meter in series with all of this to monitor the actual power draw (see below).  Or perhaps manage all this with an Arduino based power management system.

Allowing for Surge and Starting Power

Most electric motors draw considerably more power when they are starting than when they are running at their normal speed.  This surge or starting power draw can be two or three times their running power – in other words, a 1 kW motor might have a surge/start power demand of 2.5 kW.  Some types of motors will draw as much as four, five or six times their normal running power while starting up.

This surge/starting power can last for as little as half a second or as long as three or four seconds, and starts off at the very highest level and then steadily declines down to normal running power at the end of the startup phase.

Most traditional generators will quote you two ratings – a rated or standard load, and a peak or maximum load.  So if your theoretical motor, with its 1 kW normal power draw and its starting power requirement of 2.5kW was to be matched to a generator, you should get one with a rated or standard load of at least 1 kW and a peak or maximum load of at least 2.5 kW.

But what say you have four devices, each of a 1 kW standard load and a 2.5 kW starting load?  Does that mean you need a 4 kW generator that can handle a 10 kW peak?  Happily, no.  It is normal to assume that you’ll never have multiple devices all starting simultaneously.  Because the starting load is so brief, and also quickly starts dropping down from maximum, this assumption is usually acceptable in most environments.  So in this example, you’d want a 4 kW generator with a 5.5 kW max load rating.

Choosing a Suitable Small Generator

Our expectation is that you’ll end up with a power need in the order of about 3kW; maybe a bit less, and if it is much more than that, you’ve failed to correctly differentiate between ‘need’ and ‘would like’!

The good news is that there are very many different models in this general power range to choose from.  But that’s also the bad news.  How to make a sensible buying decision with so many choices?

Well, there are a few things to consider that will help steer you in the right direction.

The first is that you want the generator motor to be four-stroke not two-stroke (ie separate oil and gas, rather than mixing the two together).  Four stroke motors tend to be more fuel-efficient and more reliable.

The second is that you want the generator to be as quiet as possible.  Some generators publish ratings on how noisy they are, but unfortunately there’s no universal standard for how this should be measured.  If you see a noise rating, it should be quoted in either dB, dBA, dBC, or possibly some other type of dB measurement.  It would be helpful to know if it was measured at full load, half load, or idle (there can be more than a 10 dB difference between idle and full load), and at what distance from the generator the measurement was made.  Was it in an open area or an enclosed room?  Was it a hard concrete floor or something more sound absorbing?

It is difficult to convert between the different type of decibel measurements, because the different weightings or adjustments that are implied by the letter A, B, C or D after the dB vary depending on the frequency of the sound being measured.  As a rule of thumb, though, the same sound probably registers lowest on the dBA scale, and slightly low on the dBC scale, and higher on the plain dB scale.  You’ll seldom/never see dBB or dBD.  Oh, to add to the confusion, some suppliers sometimes use the term dB and dBA interchangeably, even though they are actually very different.

You can sometimes get a sense for how loud generators are, even if they are not specified, by reading reviews on sites like Amazon.  Chances are someone will compare any given generator’s sound level to another generator, and then you can start to work from there to understand at least the relative loudnesses, and if one of the generators does have a published sound rating, then you know if the other one is above or below that figure.

A good generator has a sound level of under 60 dBA under at least half load when measured on a concrete floor from 7 meters (23 feet) away and with reflective walls 100 ft (30.4 meters) away, and with a very quiet ambient noise background (ie 45 dB).

Another relevant issue is fuel economy and run time.  These are two slightly different measures.  Fuel economy can be thought of in terms of ‘how many kWh of energy will this generator give me per gallon of gas it burns’.  An easy way to work that out is to see how many gallons of fuel an hour it burns, and at what load level.  For example, a 4 kW generator, running at 50% load, and burning 0.4 gallons of fuel an hour is giving you (4 * 50%) 2 kWh of energy for each 0.4 gallon of fuel, ie, 5 kWh per gallon of fuel.  The more kWh per gallon, the better.

The run time issue is similar but different.  It simply measures how long the generator will run on a single tank of gas.  Sure, the more fuel-efficient the engine, the longer each gallon of gas will last, but probably the biggest factor in run time is simply the size of the gas tank on the generator.  Run time means nothing when trying to get a feeling for gallons/hour of fuel use, unless you know how many gallons in the tank that are being consumed.

In theory, you should turn the generator off when re-fueling, and even if you don’t do this, it is always an inconvenient hassle, and so the longer the run time per tank of fuel, the happier you’ll be.

Make sure you understand, when looking at a run time claim, what the load factor on the generator is.  Needless to say, all generators will run much longer at 25% load than at 100% load.

One other nice feature, although one to be used with caution, is a 12V DC power outlet that might be suitable for some crude battery charging, depending on what its true output voltage might be.  But be careful – charging batteries is a very tricky business and perhaps it is more sensible to charge the batteries through a charge controlling device, and from the generator’s 110V main output.

An obvious consideration, but we mention it, just in case, is the generator’s size and weight.  The smaller it is, the easier it is to store somewhere convenient, and the lighter it is, the easier it will be to deploy when you need it.  Oh – do we need to state the obvious?  Don’t run a generator inside.  You must keep the motor exhaust well away from the air you breathe.

Something that is often underlooked or obscured is the quality of the a/c power and its waveform.  How close to a pure sine wave is the power that comes out of the generator?  This doesn’t really matter for resistive loads like a heater, but for motors and electronic circuitry, the ‘cleaner’ the wave form the better.  The only way to be certain about this is to connect the generator output up to an oscilloscope, but that’s not something that is easy for many of us to do.

There is a new type of generator now becoming more prevalent which not only has an excellent pure sine wave form of a/c power, but offers a number of other benefits too.

Inverter/Generators

(Note – do not confuse an inverter/generator with a standalone inverter.  A standalone inverter converts DC power to AC power, typically from 12V DC up to 110V AC.  It does not have a generator connected to it.)

A typical generator (well, what we call a generator actually is a motor that runs an alternator) runs at a steady speed of 3600 rpm so that the power that comes out of the alternator will be automatically at 60 Hz (mains frequency).  The a/c waveform will be a little bit rough and noisy, which can be a problem when powering more delicate electronics.  Also, the engine is having to run at 3600 rpm, no matter if it is heavily loaded or very lightly loaded with power consuming devices because the frequency of the power generated is dependent on the speed of the motor.  This makes the motor noisier than it needs to be, and at lower power loads, makes it less efficient because it is using a lot of power just to spin itself around.  If the engine speed should fluctuate, so too will the frequency of the supplied power and that also can cause problems with electronic items.

Modern high quality generators take a different approach.  They generate a/c power at any frequency at all – it doesn’t matter what frequency, because they then convert the a/c power into DC power.  Then, in a second stage, they use an electronic inverter to convert the DC power into (at least in theory) a very clean pure a/c sinusoidal wave form at 110V.  You have a much nicer wave form, and because the generator can spin at any speed, the generator does not need to be so powered up if generating only a light load of power, making it typically quieter and more fuel-efficient (up to almost 50% more fuel-efficient).  On the downside, inverter/generators are currently more expensive, and have slightly more complicated electronics.  But for the type of application we are considering, they are usually vastly preferable.

Some inverter generators have a nifty feature.  You can double them up – if you connect the generator to another identical generator, using a special connecting cable that synchronizes the a/c output waveform of the two generators together, you can get twice the power.  You might say that it is better to have two 2kW generators rather than one 4kW generator, because that way, you have redundancy.  Anything could fail and you still have half your generating power.

Another nice thing about most inverter/generators is that they have been designed, right from the get-go, to be small, compact, lightweight, and quiet.  That’s not to say that they will be totally undetectable when operating, but they won’t be anything like as noisy as traditional generators that can be as loud as motor mowers, and if quiet operation is really important to you, some additional external baffling in the form of some sort of operating enclosure could drop the sound level down even further.

Their compact size and generally light weight makes it practical for them to do double duty not just as an emergency generator that gets ceremonially wheeled out of the garage when the power goes off (or, even worse, that resides in its own special building), but also as a go anywhere/take anywhere general purpose generator, useful for outdoors events, camping, remote building sites, and so on.

An obvious consideration for any generator is the cost.  With the constantly changing mix of models, ratings, and prices, we’ll not get too specific other than to observe that at the time of writing, it seems you’re likely going to be writing out a check for a little less than $1000 for a good inverter/generator with about a 3 kW rating, which is about twice what you’d pay for a regular generator without the inverter stage.  We expect this price differential to drop, but please don’t wait for that to happen before you get one!

Here is Amazon’s current listingof gasoline fueled generators.  Some are inverter/generators, others aren’t.  Some are California emissions compliant (CARB), others aren’t.

If we had to select a favorite, we’d probably nominate the Champion 3100W unit, or failing that, one or a doubled up pair of the Champion 2000W units.

How to Measure the Real Current/Power Used by Your Appliances

Devices such as this, costing $16 - $26, show you exactly how much power every one of your appliances consumes.

Devices such as this, costing $16 – $26, show you exactly how much power every one of your appliances consumes.

Maybe you have a computer with a 450 watt power supply.  Does that mean the computer actually is drawing 450 watts of power all the time it is on?  Almost certainly, not (a typical computer might consume only 50W of power, maybe even less, plus another 50W of power separately for its screen).  Maybe you have something else with a power rating plate on the back ‘110V 10A’ – does that mean it is drawing 10 amps all the time it is on?  Again, probably not.  A 10A rated device probably includes all lesser amounts of power too, and they simply put 10A on the plate as a conservative overstatement that wouldn’t cause them problems in the future.  (Note – resistive devices such as heaters tend to have more accurately plated power requirements.)

It is normal for appliances to show their theoretical maximum power draw rather than their normal power draw on their labeling.  While you need to leave a bit of ‘headroom’ to allow for occasionally one or another of your appliances peaking up higher to full power, it is acceptable to assume that most of the time, most of them will be using average rather than maximum power.

So how do you work out how much power your appliances are really truly drawing?  Easy.  There are devices that you plug in between the appliance and the wall, and they measure the power consumption of whatever is plugged into them.  Indeed, you don’t need to plug only one appliance into one of these measuring devices – we’ll sometimes plug a power strip into the measuring device, and then connect a bunch of equipment to it.

As you can see, Amazon sell such units for as little as $16.  Although there are some new low price units, we have always bought the only slightly more expensive Kill a Watt brand monitors.  You only need to get one to be able to work your way around your house testing everything.

In addition to showing you the instantaneous power usage, the Kill a Watt unit has another useful function – it can also show you total energy used over time.  When would this be useful?  Think of something that cycles on and off, such as your fridge.  You can measure how much power it uses when it is on, and you can guesstimate how much extra power to allow for when it first starts up, but how much power does it use per day?  Unless you stand over your fridge nonstop, day and night, carefully noting the minutes it is on and the minutes it is off, you’ll have no accurate way of knowing this.  But with the Kill a Watt meter, you simply plug the fridge in, check it is zeroed, then come back in a day or two and note the total hours elapsed and the total kWh used.  How easy is that!

(Note that if you are doing these calculations, you should check for different total energy consumption rates based on hot and cold weather, on opening the fridge a lot or a little, on placing hot foodstuffs into the fridge, and so on.  You’ll find that your daily average usage will vary enormously from some ‘good’ days to some not so good days.

How to Measure the Actual Power Being Provided by Your Generator

Your objective, much of the time, will be to run your generator at about 75% of full power.  At power levels much above this, or at power levels much below 50%, your economy will start to suffer and you’ll be getting fewer kWh of electricity per gallon of gas.

But how do you know how much power you are taking from the generator?  Easy.  Use the same Kill a Watt meter you used to calculate your power draws, and plug it into the generator then plug all power loads into a power strip plugged into the Kill a Watt.  That will tell you exactly the power you use.

You can use this information to know when you can add extra power loads to your generator, and when you are close to maxed out.

Two Notes About Fuel Storage

Many cities and many landlords have restrictions on how much fuel you can store at your residence, and probably also on the types of containers you can store the fuel in.  Sometimes these limits are per address, sometimes they are per building (which might mean you could keep fuel in a garden shed as well as in your garage and as well as in your house, too).

Enforcement of such bylaws is typically done ‘after the fact’ – ie, if you have a fire and it becomes apparent you had a mega-fuel dump in your garage, then you may find yourself being asked some awkward questions, not only by the fire marshal, but quite likely by your insurance company, too.  By the way, it is not always easy to tell, after a fire, exactly how much fuel was stored in each container, particularly if they were all in the one area.  It is probably possible to see how many fuel cans you had, but harder to tell which ones were full, which were half full, and which had only a couple of pints in the bottom.

It might pay to familiarize yourself with these requirements, and if you have a large number of half empty fuel containers, you better be sure you can explain why.

That also points to another benefit of a fuel-efficient low powered inverter/generator.  If you are trying not to trespass too far into ‘forbidden territory’ in terms of the fuel you store, then the more hours you can run your generator on a small amount of fuel, the better.

Secondly, gasoline (and most other liquid fuels) has a surprisingly limited life.  You can store it for three months with no ill effects, but after about six months, you’ll start to encounter problems.  Our article about fuel storage tells you more about these issues and also recommends the best form of fuel life extending chemicals.

Maintaining Your Generator

We hate internal combustion powered equipment, and avoid it wherever we can, particularly for things we only use rarely.  They can be difficult to store and unreliable in operation after extended storage.  Electrically powered items are generally very much better.

But in the case of a generator, you have no effective alternative to some sort of internal combustion powered device, and so you’ll need to be attentive to the manufacturer’s recommendations about periodic maintenance.  Not quite so clearly stated is the need to also be sensitive to the age of your fuel and managing that, so you aren’t running old untreated fuel in your generator.  Also not stated, but in our opinion very important, is to run your generator for several hours, perhaps once a quarter.  Solstices and equinoxes are the trigger dates we use for all sorts of maintenance items (other people use daylight saving start/end dates for things that need maintaining less frequently).

One other thought.  It might be useful to keep a spray can of engine starter fluid as a way of helping your generator come to life if it has been too long since it last ran and it is proving reluctant to start, particularly on a cold day.  Some generators start more readily than others.

Summary

A small, lightweight, and almost silent emergency generator can allow you to keep power on in your normal home, even when the lights are out all around you.  While we have nothing against larger systems that will power your entire home (and have one ourselves), if you’re not ready for a ‘full-on’ system and the costs and complications associated with it, a simple portable inverter/generator will give you enough power to make the difference between great discomfort and only moderate inconvenience.

These small units are also invaluable for apartment dwellers.

May 042014
 
This Avometer advertisement appeared in 1953, and offers the meter for £23.50, twice the average weekly wage at the time.  Similar meters today can cost only $23, closer to the average hourly rate.

This Avometer advertisement appeared in 1953, and offers the meter for £23.50, twice the average weekly wage at the time. Similar meters today can cost only $23, closer to the average hourly rate.

As we imagine and plan for a difficult life in the future, we realize that we will need to learn more skills than we currently have, because when things go wrong, we can’t simply go out and buy a replacement, and might not be able to find anyone conveniently nearby to fix the problem, either.

Hopefully you’ll continue to have at least some electricity at your retreat, and will be able to enjoy the extraordinary benefits that electricity has given to us all.  If you want to get a taste for just how extraordinary, beneficial, and essential those benefits are, treat yourself to a weekend with no electricity.  Turn off the main breaker in your fuse box on Friday night, and don’t cheat by using any batteries.  Go totally electricity-less for a weekend, and do it not when the weather is comfortable outside, but when it is either impossibly hot or impossibly cold.

Okay, now that you’re back reading the article again, and fully convinced about the essential role electricity has in your life (how long did you last before turning the breaker back on?) there’s every chance that at some future point, you’re going to have to become an amateur electrician, and maybe even an amateur electronics repair tech too.

You’ll not be able to repair anything if you can’t first troubleshoot to find out the problem.  Ideally, you’ll also want to be able to test the repair before making the fixed device ‘live’ once more, too.  Now the good news, particularly with electrical (as opposed to electronic) devices, is that many problems can be troubleshooted using that most sophisticated of instruments, the Mark I Human Eyeball.  You’ll spot breaks in cords, blown fuses, burned out plugs, and so on, just by looking.

But whether it is for troubleshooting, or for checking the correctness of repairs before plugging the devices back into your main power circuits, you’ll find everything you do will be immeasurably assisted by what is termed a ‘multi-meter’ – a device that will show you various things about electrical circuits – in particular, both amps and volts for AC and DC circuits, and also ohms for resistance, and with multiple scales ranging from fractions of a volt/amp/ohm up to tens of amps, probably thousands of volts and millions of ohms.

The first ever multimeters came out in 1923, and were the result of a British Post Office technician getting exasperated at having to carry so many individual test meters with him (and back then they were all big, bulky, and heavy, too).  His creation was the Avometer (Avo being an acronym for Amps, Volts, Ohms), and when first released it had seven different functions (three DC voltage ranges, three DC amperage ranges, and one resistance range).  When the Avometer finally and sadly ended production in 2008, it had 28 ranges, also now including AC volts and amps.

In the past, Avometers often cost more than a couple of weeks wages for the technicians using them, so they were hardly a commonplace device that people would have ‘just in case’ they might need it in the future.  But in time, more manufacturers started making similar devices, and with less robust but more automated manufacturing methods and standards, and so prices dropped amazingly.  I remember buying one as a teenager, very many decades ago, and at the time never gave thought to how such devices once cost hundreds of times more than they did then – and today, they are even cheaper still.  You can buy a reasonably multimeter from somewhere like Harbor Freight, or on Amazon or eBay, for under $20, and an excellent one for under $40.  So there’s no reason why you shouldn’t have one.

What To Look For When Choosing a Multimeter

A typical multimeter will be able to test at least five different things – DC and AC volts, DC and AC current, and resistances.  There are differences between meters, however, in terms of the minimum and maximum values it can read for all five of these scales.

Needless to say, you’d like a meter that has the broadest range of scales, but in terms of what you really need, if you are using your meter mainly for testing electrical devices, you probably need to be able to read DC volts from a minimum of maybe one or two volts (ie perhaps a 10V scale) up to a maximum of less than 1000V; DC amps from perhaps a 1A or 0.1A (100 milliamp) scale up to maybe 10A; AC volts from perhaps a 10V up to a 1000V scale; AC amps from perhaps a 1A scale and up as high as possible; and resistances from as sensitive a scale as possible (maybe a max of 10 kOhm on the scale, and showing individual ohms at the low-end of the logarithmic scale) up to showing maybe a 10 MOhm maximum scale).

If you will be using your meter for electronic troubleshooting as well as electrical troubleshooting, you might want to have some additional scales to show lower values for DC volts and DC amps, and probably a lower AC amp scale too.  You might also want to be able to read higher current flows too – this will likely require a specialized device (see below).

If you need other ranges beyond these, you’ll probably know about your special needs already.

A nice feature is a continuity buzzer.  This is useful when you’re doing mundane tasks like checking to see which ends of which wires relate to the other end of the same wires, or checking for breaks in circuits.  Instead of having to watch your meter, you simply touch your probes to things and if there’s a clear connection between the two things you are touching, the meter will buzz or beep.

It helps to understand, for the AC measurements in any meter, what range of frequencies the AC measurements are accurate for, and what types of waveforms it will accurately read.  If you’re just reading mains power type frequencies, then most meters will work well for that, but if you have unusual wave shapes or are wanting to measure audio or radio frequencies as well as mains frequency, then you will need a specialized meter that measures true RMS and higher frequencies.

Some meters have additional functions, including the ability to measure frequency, capacitance, inductance, temperature, diodes and some functions of transistors.  You’ll of course pay extra for such extra features, but if they have value to you, then why not get the ability, particularly because these extra functions don’t necessarily add much more to the price of the meter.

See further discussion in the section on analog or digital meters, particularly for some features that are unique to digital meters.

A meter should have at least one fuse in it to protect its circuitry from overload.  This is particularly essential in analog meters, where the meter’s integrity relies on you, the user, selecting the correct scale to start with whenever you connect the meter to anything.  Old hands know the rule ‘always start with the highest value range setting, and then switch down as needed’ from bitter experience.

Our point here is to identify the type of fuse used and to lay in a small supply of spares.  In the worst case scenario, if you blow the fuse, you can replace the fuse with regular wire or any other sort of fuse as well – the meter will continue to work, but it will no longer be protected, so your next mistake will probably fry it.  We’ve only once ever blown a fuse, so you probably don’t need to have too huge a supply of spares.

Accuracy Issues

Different meters make different claims about their accuracy, and some digital meters display more digits than others – indeed, they’ll probably display a more detailed number than their underlying accuracy allows.  By this we mean a meter that has an accuracy of +/- 3% might have a three or more digit display, so it could in theory show, say, 97.2 volts, whereas the actual voltage could be anywhere from 94.3V up to 100.1V – so what is the sense in telling you about the 0.2V when even the 7 volt part of the reading can vary widely from 4 up to 10.

Don’t get too hung up on accuracy issues.  Most of the time, the required value and tolerance of anything in typical electrical (and electronic) circuits is fine if it is within about +/- 5% of the optimum value, and sometimes you’ll find that +/- 10% is still perfectly acceptable.

Better analog meters will have a mirror on their scale.  This enables you to directly line up the angle between yourself, the needle, and the scale and avoid any parallax errors when reading values from the scale.  The bigger the scale on an analog meter, the more accurate the readings you can get from it.

A possible exception to our suggestion you don’t need a lot of accuracy would be reading the voltage of your input power supply.  Noting that power varies according to the square of the input voltage, if your voltage varies by only 10% from specification, the power available to your device will vary about 20%.  That can lead to not-obvious problems that end up burning out motors and frying electronics, so you probably want a meter that has reasonably good accuracy on whatever scale you’ll use to measure input voltages into devices.

One type of accuracy is important.  Whenever you connect a meter to a circuit, you actually change the nature of the circuit, and so the reading you get from the meter will be influenced by the fact that the meter has been connected to the circuit.  This is not really a worry when working on mains level voltages and multi-amp currents, but it can become significant when working on very low voltage and very low current electronics.  Most digital meters are very much better than most analog meters in this respect; if you are getting an analog meter, make sure it is rated at 20 kOhms/volt or higher (a measure of the impact of the meter on the circuit it is testing).  Digital meters should have an impedance of at least 1 Megaohm, and 10 MΩ would be better.

Analog or Digital Multimeters?

A great value analog meter, the Mastech YX360.

A great value analog meter, the Mastech YX360.

The big question you need to answer is whether you should get an analog or digital meter.  Analog meters have an ‘old fashioned’ dial and needle that moves across it, and digital meters of course have a digital digit display.

For an uncertain future, you should use as low-tech a product as possible.  An analog meter would be the best way to go in such a case, because it has almost no electronics at risk of being ‘fried’ by an EMP, and it does not require any power to read volts and amps (but it will unavoidably need a battery to be able to read resistances, due to the way that resistances are tested).  On the other hand, digital meters are very much nicer and more convenient and flexible, all of which is dangerously tempting!

Talking about batteries, make sure your meter uses a typical/common battery and voltage.  Don’t be tempted to go out and buy a lovely old antique Avometer, for example.  Although we have one ourselves, it is more as a museum/display piece than an everyday part of our test gear, because it uses a unique type of 15V battery that is, for all practical purposes, no longer available.

The higher the meter’s battery voltage, by the way, the better it will be able to measure high values of resistance.

A great value fully functioned digital meter, the Mastech MS8268.

A great value fully functioned digital meter, the Mastech MS8268.

Digital meters of course need power (usually from their battery) for everything they do, but their power needs are very low, and we find that the batteries in our digital meters last years at a time.

Interestingly, whereas analog meters are possibly more electrically and electronically robust, digital meters are more physically robust.  If you drop your analog meter, you might destroy it (the indicator needle is on a very sensitive bearing), but if you drop your digital meter, you are much less likely to harm it.

Digital meters have a lot going for them.  Better ones have auto-ranging, so you don’t have to worry about frying the meter by setting it too sensitively for whatever you are measuring.  They are generally a bit more accurate than analog meters too, but see our comments about accuracy above.  On the other hand, some people like to be able to see the swing of a needle which can sometimes help you better understand exactly what you’re seeing when troubleshooting, and of course this is only possible with an analog meter.

Digital meters usually have auto-polarity, so there’s no need to hassle over connecting the positive lead to the positive side of a circuit, and the negative lead to the negative side.  Better analog meters will have a polarity switch so you can simply slide the switch rather than reverse the leads if you get it wrong.

Some digital meters will have added functions such as ‘hold’ which locks in the display the value when you pressed the hold key.  That way if you forget it, you don’t need to remeasure because it is still on the display.  Sometimes you might also see the ability to capture minimum and maximum values, too.  This can be helpful, particularly if you are not staring nonstop at the meter, and have a problem you think might be due to occasional spikes or drops in power.

An auto-off feature is really nice – it saves you if you forget to turn the meter off; you don’t have to worry about running your battery dead.

If you are getting a digital meter, make sure it has a light switch on it so you can turn on a backlight and read the LCD display if you are somewhere with low ambient light.

So, yes, there are lots of benefits to getting a digital meter.  Our suggestion, noting how inexpensive both digital and analog meters are these days, would be to get one of each.  That also allows for the adage that a well prepared prepper has at least two of everything essential and important.

Which One to Buy?

Here’s a listing of analog multimeters from Amazon.  We’d probably choose the Mastech YX360 as a great value analog meter.  It seems to also be sold under different names by other companies, too, but generally at a slightly higher price.

Here’s a listing of digital multimeters, also from Amazon (of course).  You’ll see some units for under $10, but we’d probably splurge and spend not quite $30 to get this truly impressive Mastech MS8268 meter.  Indeed, although we have a shelf full of meters already, we liked this meter so much that we went out and bought one while writing this article!

High Current Ammeters and Clamp Meters

The Mastech $45 AC and DC clamp meter.

The Mastech $45 AC and DC clamp meter.

A problem that is common to most analog multimeters is that they have difficult reading high amp values, because they are built around a meter that is very sensitive, rather than one which is very insensitive, to current flows.

An inconvenience that is also common to all regular meters, is that to read the current flow – the amps – in a circuit, you need to cut the circuit open and connect the ammeter in series with the circuit.  When testing volts, you simply place the voltmeter in parallel across the circuit, which is usually a much easier thing to do.  (Oh yes, as for testing resistances, that can be the biggest hassle of all, because you have to isolate the thing you are testing from everything else before you can get an accurate reading.)

There are of course solutions to these issues.  You can get dedicated high-current reading ammeters and connect those in series in such circuits.  Or, in the case of AC current in particular, you can get a ‘clampmeter’ which is a device that you simply place around one of the wires.  The clampmeter senses the magnetic field created by the flowing AC current in the wire, and so displays the measured current in the wire without you needing to penetrate/cut the wire at all.

Due to the way they work, they are not so good at measuring small amounts of current (ie under one amp) but they are excellent for measuring large currents, potentially up to several hundred amps.  They are also inexpensive, and of the ones listed on Amazon at present, we think this one is probably the best buy (ie just under $30, and with scales all the way up to 600A) for most people and purposes at present.  There are other meters costing very much more, but offering not much extra in the way of useful features for most of us.

There is one feature which some of the more expensive clamp meters offer.  That is the ability to read DC current as well as AC current through the clamp.  If you might find this worth paying only a little extra for, something like this Mastech meter is probably a good choice, and still costing less than $45.

These are wonderful devices, but note they only work when placed around one of the wires in what is usually a two and sometimes three or four wire circuit.  If you place it around both wires in a typical AC power lead, the magnetic field from one of the wires is essentially cancelled out by the field from the other wire, so you will need to somehow separate the wiring to put the clampmeter around one of them.  You might find a very short extension cord where you’ve opened up the wiring between the male and female ends, allowing you to then clamp around whichever wire you wish, will be helpful in such cases.  (In theory, of course, you’ll get the same current reading from either the phase or the neutral wire, and hopefully you’ll get absolutely no current reading at all from the ground wire.)

There is another approach to this – there are wonderful line splitter devices such as this one on Amazon that not only split the line for you, but also have an extra section of line where the current signal is amplified ten-fold, enabling your clamp meter to pick up and display lower currents (for example, a 0.1 amp current would then read as 1.0 amps on the clamp meter).  At a cost of less than $15, this is a very useful thing when testing AC power around your retreat.

Summary

We suggest all preppers should have at least one multimeter as part of their tech/troubleshooting supplies.  If you are buying only one meter, and primarily for electrical purposes, perhaps buying a simple analog meter will not only save you money but also give you the most ‘future proof’ device.  But if you want vastly more capabilities, then you’ll probably choose to treat yourself to a digital meter as well.  And don’t forget a clamp meter too.

May 022014
 
A diagram showing how a fuel cell works.

A diagram showing how a fuel cell works.

This is a further part of our series on solar energy.  Please also visit our sections on energy in general and solar energy in particular for more related articles.

Chances are you’ve not even thought about hydrogen powered fuel cells as part of your retreat energy strategies.  For most purposes, fuel cells would indeed not be a good choice, but there’s one special scenario where they might be of relevance – as part of a way to store energy.

But, before you rush off to your local fuel cell store to buy a dozen (as if such a place exists!), you might want to read through this article and in particular, appreciate that whatever the advantages of fuel cells may be, there’s one also a disadvantage.  The technology for a ’roundtrip’ transfer of energy from electricity to hydrogen and back to electricity is expensive and not very efficient (on the other hand, it is not necessary any worse than other alternatives open to you).

You could be excused for stopping reading at this point, and we write the rest of this article mainly to provide a reference point you can track from.  We are sure that the technologies involved will improve over time, and you can match new products with the information here to see how much closer to practical affordability things are progressing.  Of course, if you do come across a relevant new improvement, please let us know so we can update the information here.

We’ll explain a bit about fuel cells in this article, and look at the plus and minus issues associated with storing your surplus energy (should you be so fortunate as to have any, of course!) in hydrogen and then converting it back to electricity via fuel cells.

What Fuel Cells and Hydrogen Energy Storage Involves

A fuel cell can be thought of as using the opposite process to that which causes the electrolysis of water.  When you electrolyze water, you use electrical energy to separate the water into its component hydrogen and oxygen.  When you use a fuel cell, you combine hydrogen and oxygen to create water and you get electrical energy produced as part of the process.  Other materials can also be combined, but hydrogen and oxygen is the most common, particularly because this means you only need to store the hydrogen, obtaining the oxygen from the air all around us.

Note that you could also run an internal combustion engine on hydrogen fuel, but this is nothing like a fuel cell.  A fuel cell has no moving parts and generates little heat and almost no noise, an internal combustion engine takes chemical potential energy, converts it to heat, and then converts the heat to motion, and then converts the motion to electricity.

Ecologists like fuel cells because the byproduct of running a fuel cell is simply water.  No noxious/toxic nitrogen or sulfur products, and no carbon releases.  What’s not to like about that (or so the ecologists ask/tell themselves).  But, as with most things, there’s a lot more to fuel cell technology than simply ‘burning’ hydrogen and oxygen and getting water and electricity as a result.

Fuel cell technology is both old and new.  It has been around in experimental form for a long time – the first were invented in 1838.  More recently, fuel cells have been used to generate power on the space station, and in experimental fuel-cell or sometimes termed ‘hydrogen powered” vehicles.  Fuel cells, in miniature form, are even used in portable electronics.

Not all fuel cells use hydrogen.  There are other chemical processes that can also be used (if the fuel cell is designed for it of course), but we are focusing on hydrogen fuel cells here because on balance, the ’roundtrip’ to generate hydrogen, store it, then use it in a fuel cell is probably the easiest and best for prepper purposes.

Although based on old technologies, fuel cells are also more in an experimental than a commercial state of being at present.  This is because there are issues with cost and efficiency that currently make them impractical for any type of regular normal use, but while the efficiency levels are very low, the promise of boosting efficiency holds out an exciting hope that fuel cells may become more commercially viable in the future.

Furthermore, if money is not a constraint, then the ability to store hydrogen for extended times with little loss is a huge plus.  Most other energy storage systems are not as practical as hydrogen if you want to store the energy not just for a day or two but for many months.

Hydrogen Related Issues

Even if fuel cells themselves become more efficient, there’s another step in the process that needs a lot of additional optimization – collecting/creating hydrogen and then distributing it to refueling points.

It is important to realize that while hydrogen is the most abundant element on the planet, and oxygen is all around us, that does not mean the cost to power a fuel cell is negligible.  Most of the hydrogen out there is currently ‘locked up’ in water (which is, as you doubtless already know, H2O) and extracting the hydrogen from water (or from natural gas – another rich source – CH4) – is expensive, as can also be the technologies to store and transport hydrogen.

On the other hand, as long as you have hydrogen stored in a leakproof container (slightly harder than it sounds!), it will keep forever.  This is the same as propane, but quite unlike petrol or diesel (see our discussion about storing liquid fuels), and also quite unlike other energy storage methods such as batteries or accumulated reservoirs of water for hydro power.  This is clearly a good thing.

The relevance of hydrogen storage and fuel cells for us preppers is as another way of storing energy.  If you are preparing for only a level 1 or low-grade level 2 event, maybe you’ll cover your energy needs by simply buying a generator and laying in an adequate supply of fuel for it, and possibly stick a couple of solar panels on your roof as well.  That’s a fine way to proceed, and it allows you to reasonably closely match your power needs as they vary during each day and night with the supply of power from the generator.  In such cases, however, you’ll not really ever find yourself in a situation with ‘too much’ power and wanting to find some good use for it.

But most of us, no matter what outcomes we are preparing for, will choose to use primarily renewable energy sources (ie wind and solar) for much/most/all our energy needs.  The huge problem with these energy sources is that their output varies widely, with the weather, and in an unpredictable manner.  As we discuss in articles such as ‘How Much Solar Power Generating Capacity Do You Need‘ and ‘How Much Extra Emergency/Reserve Capacity Does Your Solar Power System Need‘, it is necessary to develop more powerful than necessary generating systems so that they will provide close to sufficient power, even with very little sunlight (or wind).

The happy flipside of this is when the wind is blowing in its sweetspot speed zone, and the sun is shining brightly onto your solar panels in a cloudless sky.  All of a sudden, your power generation is providing you with two, five, maybe even ten or twenty times the power and energy you need.

There’s no such thing as ‘too much power’ of course, and there’s no problem or harm to your system if you simply choose to ignore the extra power that is coming from your generating system and ‘waste’ it.  But maybe you might also look at the downside of sometimes being very short of energy, and seek a way to capture and save/store some of this spare energy to then use when your system is struggling to provide the energy you need.  There are a number of ways you can do this, and the simplest is to go out and buy some more storage batteries.  But maybe you feel the need to shun simple, and prefer to seek out complex solutions!  Or, more seriously, maybe you want to spread your risk by having multiple technologies for every part of your retreat and its mission critical systems, and in such a case, a second method of power storage in addition to batteries might be worthy of some more investigation.

It would be possible to use this extra power to store hydrogen, and then when you need to use the stored energy, run the hydrogen through a fuel cell to regain the electricity.  That’s the simple theory of it, anyway.  Let’s look a bit more now at how it would actually work, and what problems you could run into.

Let’s think about this in three steps.  The first is how to ‘get’ hydrogen.  The second is how to store it.  And the third is using the fuel cell(s) to convert it back to electricity.

1.  Getting Hydrogen

There are two possible and somewhat practical ways of getting hydrogen.  The first involves the electrolysis of water, the second involves steam reforming of natural gas (ie methane); this latter method works well for large plants, but not so well for smaller domestic production.

So, if you look at electrolysis, while you could build your own electrolysis plant, perhaps you’ll simply choose a turnkey unit.  Ebay sells hydrogen generators, and we saw a listing for one that requires a maximum of 400W of power to generate up to 5L of hydrogen a minute.  In other words, if we believe its specifications, 1kWh of power would generate 750L of hydrogen.  Ebay has this unit listed for $12,000, and it is being sold by a Chinese supplier.

But, be warned.  Anything that talks about ‘up to’ has immediately given itself an enormous ‘loophole’ to invalidate its claim.  Up to 5L a minute includes all numbers less than that, doesn’t it.  We just do not believe, for an instant, this unit will consistently create 5L of hydrogen while consuming electricity at a rate of only 400W – if it was to do this, it would be unbelievably efficient, and several times more efficient than leading branded products with more credible specifications.  You’ll doubtless be shocked and horrified to learn that you need to tread cautiously when trusting the word of Chinese suppliers selling products through eBay!

Before we move on, let’s just point out one other thing about this unit.  It only draws up to 400W of power.  You are likely to have several kW of spare power capacity at good times that you want to divert and store.  So you might conceivably spend $36,000 for three of the units, and that still only gives you a way to divert 1.2 kW of power.  If you wanted to be able to divert 5 kW, then you’re looking at $144,000 for enough of these units, and clearly that’s no longer a sensible approach.

Let’s now look at another product with more believable specifications.  A Hydrogenics HyLyzer unit.  These will product either 1 or 2 Nm3/hr of hydrogen – that’s basically a fancy way of saying 1000 or 2000 liters.

The key part of the specifications given here is the disclosure that the unit consumes electricity at a rate of 6.7 kWh per 1000 liters of hydrogen created.  So a single unit would soak up your spare power at a rate of 6.7 kW.  To put that another way, each kWh of electricity creates about 150 liters of hydrogen.  Units can usually be run at maximum production rate (to use up the maximum spare power) or at lower rates (if you have less spare power).

Heavier duty larger capacity units (of a size probably impractical for us to consider) can be somewhat more efficient, perhaps requiring only 5 kWh per 1000 liters of hydrogen.

We understand but have not been able to get confirmation from Hydrogenics that these units cost in the order of $40,000.  Here are some apparently not quite so good units and their prices.

2.  Storing Hydrogen

The good news is that hydrogen is very light.  Indeed, the weight of the hydrogen you store will be only a very small fraction of the weight of the tanks you have to store it in.

You can choose from various different sizes and strengths of gas tanks.  They can weigh as much as 300 lbs each (for a typical ultra high-pressure steel ‘6K’ tank with a 42.48L storage capacity) and can store hydrogen at pressures of up to 10,000 psi (700 Bar).  At 700 Bar, you are storing just under 38 gm of Hydrogen per liter of tank space, at 200 Bar, you are storing about 14 gm per liter (and about 7 gm/L at 100 Bar).  In addition to heavy bulky steel ‘bottles’ (sometimes with side walls an inch thick) there are more modern containers with high tensile carbon fibres wrapped around the inner bottle, allowing for smaller lighter containers with the same strength as steel.

We prefer medium rather than ultra high pressures – less energy is required to compress the hydrogen to store it and there is less risk of tanks exploding and less stress on adapters and intermediate pressure regulators.  On the other hand, the less the compression, the greater the number of tanks you need.

A possible compromise would be tanks weighing about 150lb each and holding about 7250 liters of hydrogen.  Each of these tanks has enough hydrogen for about 9 kWh of electricity, and costs in the order of $400.  Depending on your perspective, that’s either a lot, or very little.  To put it in perspective, a 12 kWh storage battery, that would be suitable for about 9 kWh of actual power, costs $3000.  So the cost of tanks to store hydrogen is massively less than the cost of batteries, and furthermore, whereas batteries have a finite life and need ongoing trickle charging to maintain their charge, once you’ve filled your gas bottle full of hydrogen, you can pretty much forget about it for a long time into the future.  And you could empty and refill it very many times before it became unreliable (even though we don’t anticipate you doing this much more than once or twice a year).

A suitable compressor is likely to cost in the order of $5000.  Add another thousand or two for miscellaneous piping, regulators, and other incidentals.

In addition to storing compressed hydrogen, it is also possible to store it mixed in with other chemicals (metallic hydrides), or in liquid form.  The former method is complicated but allows for dense storage of hydrogen, the latter method is massively more ‘costly’ in terms of energy needed to liquify and cool it.  We like the simplicity of just compressing the gas.  Less to go wrong, which has to be a major consideration when planning for any sort of emergency backup scenario.

Is Hydrogen Dangerous?

Talking about things going wrong, some people are unnecessarily alarmed at the thought of storing hydrogen.  They have this mental image of the airship Hindenburg in flames, and that colors their perception of hydrogen as a safe fuel.

In actual fact, the most spectacular part of the Hindenburg’s fire and demise was not the hydrogen burning, at all.  It was the very reactive and flammable outside skin of the airship, and also the diesel fuel stored on board.  Yes, the hydrogen did burn, but quickly and relatively harmlessly compared to these other two fire sources.  The Hindenburg would have burned almost identically even if it was full of ‘safe’ helium (the fire is believed to have been started by lightning igniting its outside skin).

Hydrogen is actually less flammable than regular petrol.  Gasoline will burn when it reaches a temperature of 536°F, hydrogen requires a higher temperature of 932°F.

The best thing about hydrogen is that it is very much lighter than air (about 15 times lighter).  If any hydrogen ‘spills’ or leaks or otherwise escapes, it simply shoots upwards, like a cork held at the bottom of a tub of water and then released.  As long as the release of hydrogen is either outdoors or in a structure with venting that allows the lighter than air hydrogen to escape to the outside atmosphere, there will be no problem.

3.  Fuel Cells

Fuel cells have a lot going for them.

They are easily twice as efficient than internal combustion engines, because they directly ‘convert’ hydrogen to electricity, whereas an internal combustion engine converts hydrogen (or any other fuel) first to heat and then to mechanical energy and then from that to electrical energy (that’s three conversions instead of one, each with issues and inefficiencies).

They are quiet, compact, and have no moving parts, making them potentially very reliable.  Indeed, these fuel cells talk about needing maintenance only once every five years.  On the other hand, there is a wide variation in cells as between ones designed for occasional/intermittent/light use, and those designed for heavy-duty ongoing use, and we sense that many fuel cells are still only one or two steps away from experimental and possibly not yet ready for a long hard life ‘in the field’.

It seems that fuel cells commonly consume about 800 liters of hydrogen per kWh of power generated.  Some can go down to the low/mid 700s, and we’ve seen others climb up over 1000 L/kWh.  Compare that to creating 150 liters of hydrogen per kWh of power consumed, and you’ll see that you are getting little more than one sixth of the power back that you used in the first place.

Furthermore, you need to allow for minor other power losses in the total process from solar cell to hydrogen to fuel cell to a/c power in your retreat.  For example, these efficiency ratings are the best possible, assuming the units are running in their ‘sweet spot’ – if you reduce their loads, then their efficiency may drop off.

No allowance is included for the energy cost to compress the hydrogen, for any leaks and losses during transporting the hydrogen from electrolyzer to fuel cell and storing it, nor is any allowance included for other things like energy for cooling systems, and other inputs such as electrolyte and coolant.  We’re also not allowing for more energy loss when the DC power out of the fuel cell is converted to AC power.

Here are some fuel cell systems and their prices.  Here’s another one, slightly less efficient.

Hydrogen Storage – Costs, Costs, and Benefits

So, to summarize, it seems that a hydrogen storage system will cost you in excess of $40,000 for a hydrolizer, another $20,000 for a fuel cell, and let’s say $40,000 for compressors, storage tanks, and everything else.  In other words, you have about a $100,000 cost to get a reasonably sized system established.

This is expensive, and it is also inefficient – you get back about 1 kWh for every five or six you use in the first place, and you’re using a system that can only use power at a rate of about 6.7kW; you’d need to add another $40,000 to your installation cost to be able to recover power at twice the rate.  On the other hand, does efficiency really matter if the energy is otherwise being wasted?

The 6.7kW rate is interesting, it coincidentally means that for every hour you are capturing energy at this rate, you get a net of about 1 kWh of energy for reuse in the future.  Let’s say that in the summer, you have four hours of ‘bonus’ power each day for 150 days, that means you’ve managed to harvest a usable 600 kWh of energy to use during the winter.

That’s actually not as insignificant or disappointing an outcome as you might at first think.

You would need almost 500,000 liters of hydrogen stored in this example so as to get the 600 kWh of output (or, if you prefer, 40 kg).  On the basis of tanks weighing about 150lb each and holding about 7250 liters of hydrogen, this would be a tank farm of about 70 tanks.  Compare that to a comparable battery setup with a similar number of batteries – there’s probably not a huge difference in size (and, in case it matters, the batteries are heavier).  The big difference is in total system cost.  Whereas the hydrogen system has a high cost to get started, it has a low variable cost as you increase its storage.  The battery system has a low-cost to get started, and a high variable cost for each extra battery.  You’re looking at the better part of a $250,000 system to store the same amount of power in batteries as you could with a $100,000 hydrogen system.

So, yes, a $100,000 investment would get you a setup that could store 600 kWh of energy.  Add another $40,000 for more hydrogen generation capability, and more for additional storage as your budget would stretch – perhaps another $80,000 to have 1.2 MWh of energy that is stored over the summer and available over the winter ($180,000 for hydrogen compared to perhaps $450,000 for batteries).  Now the benefits of a hydrogen system start to become very apparent.

There’s another point in favor of hydrogen storage too.  If you were to have an enormous 600 kWh battery storage resource, you might find it ‘costing’ you as much as 6 kWh a day, every day, in trickle charging, to keep the batteries maintained and in good condition.  That’s not a problem in summer, hopefully, but in winter, that is power you can ill afford.  To put that in perspective, you want your 600 kWh of power to last you for 150 days of winter, but during those 150 days, you’ll need 900 kWh of power just to maintain the batteries.  That doesn’t work, does it!

Batteries are the best solution for storing relatively moderate amounts of energy for relatively short periods of time – a day or two up to a week or two.  But for large amounts of energy, and longer periods of time, they start to become less appropriate, as we just saw in the above example.

One further comment.  If we were to invest in a hydrogen system, we would definitely want to make sure we had redundancy – both plenty of spares and ideally two hydrolyzers and two fuel cells.  So either buy two smaller units, or increase your investment still further by having additional larger units as part of the system.

UPDATE March 2018 :  Costs for battery storage have dropped, and probably now using a Li-ion bank of batteries would allow for lower trickle charging needs too.  Without redoing the math, we do note that all major commercial installations for storing surplus energy seem to be moving to battery solutions rather than hydrogen solutions.

Battery technology has improved substantially in the four years since this was written, and promises to continue improving, with the potential for major stunning breakthroughs at any time.  On the other hand, hydrogen and fuel cell technology is more mature and is limited by inviolable physical and chemical constraints that mean there is no perceived potential for similar improvements in hydrogen technology.  We suspect that hydrogen as a way of storing/banking electricity is a technology that has come and gone, never to return.

Summary

If you want to store less than, say, 100 kWh of energy, and for a relatively short amount of time (say, less than a month), then probably batteries are your best choice.  But for large amounts of energy storage – indeed, for almost unlimited amounts, and for long-term storage, a hydrogen based storage system comes into its own.

If you’re seriously considering such a system, check the current pricing and the best models out there.  Our sense is that values and capacities are slowly evolving and improving, making the appeal of these systems become greater and greater over time.

Apr 252014
 
A lot of energy is wasted when hot water goes down your shower drain.

A lot of energy is wasted when hot water goes down your shower drain.

There are lots of devices out there at present to make one’s life more energy-efficient.  The problem that most of them face is that few of them are cost-effective when we’re paying so little for reliable ever-present energy.

But if – when – energy prices skyrocket, and/or if/when energy becomes scarce and unreliable, all these devices will come into their own and become valuable and essential.  Needless to say, as we prepare for ‘discontinuities’ in society, one of the biggest discontinuities we have to consider is an interruption to our energy supplies, and so it behooves us to consider all such energy-saving devices, not so much for their present benefit today, as for their future benefit, subsequent to TEOTWAWKI.

Here’s an interesting article that profiles three similar but different approaches to recycling some of the heat from your shower’s waste water.  The concepts are immediately and intuitively sensible, and the savings apparently quite substantial – reducing the energy cost of the hot water used in the shower by up to 60%.  Depending on how often you shower and how many gallons of water you use each time, this can reduce your daily energy consumption by 4 – 6 kWh a day.  That might not sound like a lot, but when you consider that the average household uses 30 kWh each day, and your retreat will definitely use much less, this becomes a significant reduction in your total daily needs.

While water heating may not be a fully mission-critical part of your retreat’s energy planning (we are assuming you’ll fit a solar water heater to supplement any other water heating strategies you have) there’s no harm and potentially some benefit in recycling every possible watt-hour of energy you possibly can, and these three approaches all seem reasonably low-tech and low-maintenance and sensible.

Whether you buy the equipment from one of the three companies, or simply create your own similar system, it is definitely something to consider.

In case the linked article should disappear, here are direct links to the three companies and their products :

Heatback :  http://www.heatback.co.nz/home

CINTEP :  http://www.recyclingshower.com.au/

Recoh-vert :  http://www.recohvert.com.au/

All three companies come from NZ or Australia, probably because the magazine is published in Australia.

Nov 202013
 
This 'power meter' actually measures energy, while visually displaying the rate of power being provided.  Confused?  Please read the article and hopefully all will be explained.

This ‘power meter’ actually measures energy, while visually displaying the rate of power being provided. Confused? Please read the article and hopefully all will be explained.

One of the most important parts of planning and managing your retreat is to optimize its power and energy requirements.

The two terms – power and energy – are often used, in normal casual conversation, as meaning the same thing (for example, sometimes you’ll see references to electric power and sometimes to electric energy, although both terms probably are referring to the same thing), and we’ll wager that if we carefully read through the half million words of content already published on this site, we’d find some cases where we too have used one term while meaning the other, so we will try to be scrupulously correct in this article.

Most of the time, there is little harm and no misunderstanding caused when a person is talking, generally, about things to do with power/energy, and when they use the word power or energy in the wrong context.  But, when it comes to ‘doing the sums’ and understanding exactly what your power and energy needs are, you do need to exactly understand the difference between the two concepts, and make sure you are using the correct units (and also making sure that the specifications for the equipment you’re considering are also correct, and/or being able to work through their assumptions to understand exactly what it is you are being sold).

To make things more complicated, both power and energy can be measured in several different types of units.  You are probably already familiar with some of the measurement systems and their names, and some other terms you know of you perhaps didn’t even realize were measuring power or energy.  These would be terms such as horsepower, btu, therm, watt, kilowatthour, joule, erg, calorie, foot pounds, newton meters, and various other terms too.

Power – The Watt

For the purpose of this explanation, we’ll talk about two simple units of measurement – the watt, as a measure of power, and the watt hour as a measure of energy.  First, let’s understand the terms, then we’ll explain what they mean, their differences, and how to convert between them.

In the US system of measurements, the watt is a common measure of power.  You are probably familiar with its use to measure electrical power, and other systems can be used to measure power too – for example, in Europe, the power of a vehicle is usually measured in watts rather than in horsepower.

The abbreviation for the watt is the letter W (an upper case W) – yes, this can be confusing.  If you are using the word, you typically use lower case when writing it, but if using the abbreviation, you should use upper case.

It can also come in smaller units – milliwatts, microwatts, and potentially even smaller numbers.  You will occasionally see things such as small portable appliances have their power requirement described in milliwatts (mW).  A milliwatt is one thousandth of a watt, and is abbreviated with a small letter m and a capital W.  It is very important you do this, because if you write it MW, that means megawatt, which is a totally different number entirely!  You are unlikely to come across measurements in microwatts or smaller, these are quantities that normally only appear in scientific calculations and not in domestic appliances.

Going the other way, to larger quantities than a few watts, you will commonly find kilowatts (kW), megawatts (MW), and sometimes larger quantities such as gigawatts (GW) and even terawatts (TW).  If this sounds sort of familiar, it might be because you see similar suffixes for measuring computer storage, and so you probably already know that kilo means one thousand, mega means one million, giga means a billion, and tera means a trillion.

Note that kilowatts are written as kW, whereas megawatts (and other larger quantities) are written MW, etc. Watts can of course be converted to other units of power.  For example, 1000 watts (ie 1 kW) equals 1.34 horsepower, so your car with 300 hp can also be described as having 224 kW of power.

We’ll stick with watts for this discussion rather than muddy the waters unnecessarily with other terms.  But if you do need to do conversions, you’ll find websites such as this to be helpful.

Power

So, what is a watt?  It is a measure of power, and we’ll give you some examples of what we mean by power.

The first example is to think of a simple electrical heater.  Maybe it is an old-fashioned one with two or three ‘bars’ in it, and you can choose to have one, two or all three of the bars turned on.  Perhaps with one bar turned on, the heater is rated at 500 W, with two it is a 1000 W (or 1 kW) heater, and with three, it is giving you 1.5 kW of power.

Think also of light bulbs.  The more watts the light bulb consumes, the brighter the light, right?  If you think back to the now old-fashioned incandescent bulbs, you would probably be using 60 W or 75 W or maybe even 100 W and sometimes more powerful bulbs to light your rooms.  More watts means more power means more light (with a light bulb) or more heat (with a heater).

Now let’s think of an analogy, which we’ll use to explain the difference between power and energy. Think of a garden hose.  Turn it on a bit, and water will trickle out of the hose, and you can’t squirt it very far.  You would describe that as not very powerful, right?  Turn it on full, and more water will come out, and you can squirt it further.  The flow of water is now more powerful. You can think of electricity and power in general in similar terms to water flow, and whereas we measure water flow in things like gallons per minute, we measure electricity flow and power in general in watts.

Okay, so hopefully now you understand what power is.  Next, we will explain energy.

Energy

Let’s keep thinking about the flow of water through the hose.  The faster it goes, the more power it gives us, right?  And, also, the faster it goes, the more gallons of water it uses.  This is sort of totally obvious.  We can short of think of the total gallons of water used as a measure of the total energy consumed, and the flow as being the rate at which the energy is consumed.

If we had, for example, 100 gallons of water, that could flow through a hose in 10 minutes at a rate of 10 gallons per minute, or it could take 50 minutes at a rate of 2 gallons per minute.

And, there in a nutshell, is the relationship between power and energy.  Energy is like the total store of water, and power is the rate at which the energy is being consumed.

Let’s go back to thinking about our light bulbs and heater, and see how much energy they consume.  We know that the power used by, eg, a light bulb is maybe 100 W which means that is the rate at which electricity is going through the bulb.  If the bulb is on for an hour, then it will have used 100 watt hours of energy.  If it is on for 30 minutes (ie half an hour) it will have used 50 watt hours of energy (or, if you prefer, 3000 watt minutes or 3 kilowatt minutes).

And so on for any other scenario – you are simply multiplying the rate of power usage (as measured in watts) by the time the power is being used.

Watt Hours – Energy

We normally measure energy in watt hours, or kilowatt hours, and so on.  Sure, you could also measure in watt minutes, in watt seconds, or in watt days, but normally you’ll see this expressed in terms of hours.  The abbreviation for a watt hour is Wh or W h (with a space), and of course the abbreviation for other quantities would be, for example, kWh for kilowatt hour and so on.  We generally prefer to omit the space, just to more obviously tie in the h to the W.

If you are starting to get the hang of this, you will realize that a gallon of petrol contains energy (and could be measured in Wh), and the speed at which it is consumed is described as the power of the thing consuming the petrol (and could be measured in watts).  A more powerful thing (eg a car driving faster) will use the energy (the gallon of gas) more quickly than a less powerful thing (a car driving more slowly, perhaps).

Other types of energy measures also exist, of course.  For example, if you consume natural gas, you might see that your gas consumption is measured in Therms or BTUs rather than in watt hours (1 Therm = 29.31 kWh; 1 Btu = 0.293 Wh, and therefore, 1 Therm = 100,000 Btus).

Power is the rate at which we consume energy.  For example, it might take a certain amount of energy to heat your house from 50° to 60° – let’s say it will require 20 kWh of energy to do this.  That means (ignoring heat losses, etc) you could turn on a 1 kW heater and wait 20 hours for it to heat up your house, or you could turn on five 1 kW heaters and wait four hours, or you could turn on your furnace that, for this example, we’ll say uses 10 kW of power, and wait only two hours.

In all cases, you use the same amount of energy and get the same outcome, but you use it at different rates/speeds.

We Pay for Energy, Not Power

Now for the next thing, which hopefully logically flows from the house heating example above.  In most cases with most utilities, we are charged for the energy we use, not for the rate at which we use the energy (there are exceptions to this, particularly for commercial users that sometimes have high power draws, where they get charged for both the energy they use and also the amount of power available to them to draw from).

In the previous example, we will pay for the 20kWh to heat our house, no matter if we use it quickly or slowly.  In case you wondered, you can see on your utility bill the rate you pay for your electricity, and the chances are you’re probably paying 10c – 15c per kWh, so you’d be paying maybe $2 – $3 for the 20kWh.

Both Energy and Power Calculations are Necessary for a Retreat

When you are planning your retreat, you want to of course minimize its total energy requirement.  But you also want to consider its maximum and typical power requirements, too.

The typical US house (if there is such a thing!) consumes an average of 30 kWh of energy a day.  Hopefully, a well designed retreat can get by with much less than that.  Here’s an interesting table showing how energy is typically consumed in an average home.

The good news part of this table is that your greatest energy requirements – for home heating, cooling, and water heating (which between them comprise 60% of your total energy needs) can be greatly reduced by good insulation and home design, and may also be provided, at least in part, through alternate energy sources such as fires for heating and solar for water heating.  You don’t need electrical energy for all your retreat’s energy requirements.

It is important to understand your home/retreat’s total energy needs (and where/how you will source the energy for these requirements).  But you also need to think about the power requirement.  In the most simple sense, think of buying a generator to power your home.  If you consume 30 kWh of energy per day, that sort of seems like you are using 30/24 = 1.25kW of power, and so if you get a 1250 watt generator, you should be in good shape.  Right?

Wrong.  Sure, your house might use in total 30 kWh of energy for a typical 24 hour period, but it does not use this in a steady even flow.  At some times, for example 4am, maybe it is using no power at all.  But at 4pm, maybe it is using energy at a rate that sometimes peaks upwards of 15 kW, because you have some lights on, the stove top on, the vacuum cleaner running, the fridge compressor cycled on, and so on.  Your 1250 watt portable generator isn’t going to be any use to you at all, because any time you turn your stove on, you are needing way more than 1250 watts of power.

You need to understand both the total energy requirements for your retreat, and also the peak power requirements at which the energy will be needed.

Actually, the calculation needs to be fine-tuned even more.  Your retreat will most likely use more energy in the winter months than in the summer months (more heating, more lighting), and so you need to consider not only the typical average daily energy needs, but also the ‘worst case’ peak daily energy needs, and then translate those into the associated power rates needed.

Appliance Power Ratings and Energy Consumption

Most home appliances have a power rating in watts or kilowatts.  Some may also make some sort of vague claim about how much energy they consume a year – perhaps in the form of an Energy Star rating that compares it to other similar products.

The energy an appliance consumes each year depends on its ‘duty cycle’ – how much time each year it is actually turned on and working.  Think, for example, of a fridge or freezer.  Although it is plugged in and switched on 24/7, it actually is only working for perhaps one-third, maybe less, of the time.  Its compressor will turn on, cool the unit down to a certain temperature, then will switch off and wait until the temperature slowly drifts up from the ‘cold enough to stop cooling’ setting to the ‘hot enough to start cooling again’ setting, at which point in will then repeat the cycle.  It is the same for your furnace or your water heater or your oven or stove top element – these things cycle on and off, all the time, probably with you not even noticing.

So it is difficult to translate from a power rating to a total energy consumption, unless you know how many hours a day/week/month/year the device will be operating.  Energy Star ratings can give you some guesstimates, but these numbers, which are typically self-assessed by the manufacturers, are sometimes massively understated, so consider them as indicative best case scenarios rather than as the gospel truth.

The power ratings are useful when working out what your peak power requirements will be.  Simply add together the wattages of everything that you think might be on at the same time.

There’s one more issue to consider, when considering your peak power requirement.  Many appliances draw more power when they first switch on than they then consume while running.  This can be thought of as the extra power to spin their motor up to speed, as compared to the lesser power required to keep it turning once it is at normal speed.  For a couple of seconds, some appliances will draw two or even three times their rated power.

So, potentially, you need to not only plan for a ‘worst case’ scenario with all appliances running simultaneously (or, alternatively, plan your system so this is not possible) but you also need to plan for a scenario where all the appliances start at the same time, too.

We discuss ways to minimize these issues in other parts of this series.

Summary

Watts measure the rate at which something consumes (or creates) power.  There are other ways of measuring power, too, with different names and units, and there are simple conversion tables to convert any unit of power to any other unit of power.

Anything that provides or consumes power can have its power input/output measured in watts – even open fires.

Watt hours measure the total amount of energy something has consumed (or created) over a certain period of time.  There are, again, other measurements of energy in addition to watt hours, and they can of course be converted between the different measuring systems if needed.

It is convenient for us to consider everything in the same units, and we suggest we stick to watts and watt hours.

The most important thing for us as preppers is to understand the total amount of energy we need per day or week or month, and then to understand the rate at which we need the energy provided (the amount of maximum power we need).

Explaining the Power Meter Picture

Finally, in case it remains still unclear to you, an explanation of the ‘power’ meter we showed at the top of this article.  The rotating disk shows the rate of power flow – the faster it turns, the more power is flowing into your house.  The dials are counting up the total energy supplied, and it is the dial reading each month or two which establishes the total energy you have consumed.

Jul 132013
 
This is a wonderful portable generator, costing only $135 and providing both 12V and 110-120V power.

This is a wonderful portable generator, costing only $135 and providing both 12V and 110-120V power.

We previously wrote a detailed four part series about storing electricity which assumed you wanted to live off-grid, long-term, and needed a high-capacity and very long-lived energy storage solution for such a scenario.

That is of course a valid need, and there’s a lot of good information in that series about all aspects of storing electricity – when time allows, you should read it. 🙂

This article, however, is about one special type of energy storage application – a need to have a short-term emergency supply of power when the mains supply fails.  If the failure is a simple short-term thing such as high winds blowing over power lines, then you just need a little bit of electricity ‘to get by’ until the mains power is restored.  These are Level 1 type situations.

If the failure is caused by a major disruption that will escalate to a Level 2 or 3 scenario, you might need some power for a short while to operate radios to communicate and co-ordinate with other members of your group, prior to bugging out to your retreat location.

There are many different ways you can have an emergency power source always on hand, with many different amounts of electrical storage capacity, complexity, and cost. This article considers two approaches.  There are others, but these two are the simplest, and being the simplest is, for our purposes, an essential consideration – simple things are easier to deploy and less likely to fail.

Portable Generators

For almost any non-trivial amount of electrical power, your best solution will always be a generator.

While they are typically heavy, noisy and expensive, you can also get smaller, lightweight, affordable and very quiet generators that would be suitable for use pretty much anywhere – including for apartment dwellers, too.

For example, here’s a portable generator for only $135 on Amazon (pictured above).  This unit is quiet, lightweight, and runs for 8.5 hours on each 1.2 gallon tank of fuel, providing about 400W – 500W of 120V power during that time.  That’s a great value, and with a five gallon container of fuel and running the generator sparingly rather than 24/7, you’ve enough power for maybe three days.

The above generator is a two-stroke generator.  A similar four-stroke generator generates twice as much power using almost the same amount of fuel (four-stroke engines are more efficient than two-stroke), and is similarly quiet, while weighing an extra 10lbs (54lbs instead of 44 lbs) and being slightly bulkier.  It costs just a hair less than $200.

Amazon has plenty of other portable generators, albeit more expensive than these two, as well. Here’s a listing of some of the nicer modelsthat would be excellent as portable, use anywhere, low-sound type generators.

Four quick comments about generators.

First, no matter what generator you might choose, you must operate it outside, due to all the exhaust gases it produces.

Second, you should run your generator once every few months to be sure it is still in good order and condition, and be sure to stabilize your fuel so it doesn’t ‘go off’ while sitting in the generator or fuel can.  There are several types of fuel stabilizer available, the best is PRI.  Don’t settle for any other brand, use only PRI.

Third, these low power generators are very limited in what they can handle (because of their low power output) and you’ll need to be very careful to match the current drains with the generator capacity.  Using a Kill A Watt meter is an easy way to monitor the power being drawn from the generator, and be very careful of peak loads – when motors first start up, they draw a great deal more current than when they are running at normal speed.   These peak loads can fry your generator if you don’t plan carefully for not just average but also peak loads.

Fourth, keep the cords from the generator to the devices using the power as short as possible, and as heavy-duty as possible.  Short heavy-duty cables will waste less power and provide a better voltage level than would be otherwise the case with lighter and/or longer cables.

Lead-Acid Battery and Trickle Charger

The $135 portable generator we linked to at the start of the previous section is probably the least expensive solution for most people, and when you match that with a single five gallon tank of gas, you’ve got the equivalent of about 15 kWhrs of power, and/or about 35 hours of running time.  If that’s not enough, you can simply store as much extra fuel as you need and are legally allowed to have, and/or get a higher capacity generator.

But if you’re in a situation where either you can’t run a generator – maybe you’re in an apartment with no balcony or outside space to operate the generator, or if you’re in a situation where you need a guaranteed, absolutely-must-work source of power for a short but essential period of time, there’s another solution to consider.

Buy a 12V ‘golf cart’ or other ‘deep cycle’ battery (or two 6V batteries that you’d connect in series).  Note that these are very different to auto starting batteries – do not get a regular car battery.

You also will need a trickle charger to maintain it (them) at full charge.  If the mains power fails, the fully charged battery becomes a source of 12V DC power, and if you connect an inverter, you can get 120V AC power from it too.

This is a clean, totally silent and reasonably compact form of electricity generation and storage.  There is almost no maintenance you need to do – you can just set it up and then forget about it for several years before then testing the battery, perhaps once every six months after that, until you note its capacity has diminished to an unacceptable level.

There might be restrictions on how much fuel you can store in an apartment (either from the landlord or the fire department) and there might be restrictions on running a generator, and you might not want to attract attention to yourself and your generator, either; but none of these constraints apply to batteries and battery power.  They don’t need to be stored outside, and modern non-gassing batteries are perfectly fine indoors to store, to charge, and to use as a power source, especially when connected to an intelligent charger.

If you need a lot of standby power, we’d suggest batteries such as these or these.  Other highly respected battery suppliers include Concorde/Lifeline and Rolls/Surrette.

If you don’t need such an expensive high-capacity battery, then a Trojan U1-AGM is a good entry-level battery, probably costing about $125 or thereabouts.  Trojan make other batteries with successively greater capacities, too.

You then need some sort of trickle charger to keep the battery charged.  We consider the NOCO Genius products to be the very best, and you’ll probably find either the G750 or G1100 to be adequate for your needs.  Neither is very expensive, and because your need is more to maintain a charge rather than to recharge the battery, you don’t need a higher current capacity unit.

If you want your battery to run 110-120V appliances, you’ll need an inverter as well.  Get the lowest powered inverter you need, and use it with caution, because any/all 120V appliances will use up your 12V battery very quickly.  We’d suggest you consider getting whatever emergency appliances you need that are designed to operate off 12V DC (and which are designed to be ultra-efficient, too).  That way you don’t ‘waste’ some of your energy by converting it to 120V and then using it in a device that does not have energy efficiency as its main design criteria.  Many appliances designed for sail boats are high-efficiency 12V units, and you can get many different sorts of 12V LED lighting that provide the most energy efficient source of emergency light.

You could also consider getting a set of solar panels to recharge your battery if you were planning for an extended period of needing the battery, but this would likely only give you a very little bit of top up charge each day, unless you had large panels, and then you’re moving beyond the scope of this article (and should read our full four-part series on storing electricity).  Here’s a single panel system that claims to provide 100W of power, and complete with the necessary charge controller unit too; this is about as good a simple choice as possible before needing to move into complicated bulky and fixed installations.  In reality, we expect you’re more likely to get 50W rather than 100W of charging power from the cells, but if you’ve no other way of recharging your battery, this could give you up to as much as 500 W hrs of extra power each day during the period of your power outage.

If you do get a solar panel system like this, you should trial it to understand how it works and how much power to realistically expect, then carefully put it away and not touch it again until you need to start recharging your battery during your power outage.

One more thing to add to your setup.  A 12V to USB charger/connector – a device that will enable you to recharge all your electronic things that can be charged from a USB port.  These devices typically come in the form of a cigarette lighter type adapter for a motor vehicle – they are perfectly good in that form; although you will then either need to solder leads to the adapter or else get a matching socket to connect to your battery.

Make sure that any such USB power supplies are high current (ie more than 2 Amps) so as to be able to recharge tablets as well as phones and other low current devices.

Summary

Many of us have our homes wired up with heavy-duty generators and transfer switches, and many of us have extensive other power storage facilities of various sorts too.

But sometimes these requirements are overkill.  Sometimes we just need a small amount of power, for a short term solution.  Perhaps it is a relatively benign brief power outage, or perhaps it is such a severe event that we’re forced to get out of Dodge just as quickly as we can rendezvous with the other members of our group.

In such cases, a simple small portable generator, or a fully charged golf cart type battery can give us everything we need, and for under $200.