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 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.

Aug 032013
 
This 4WD $11,500 Polaris UTV can carry 1,000lbs and tow another 1,250lbs.

This 4WD $11,500 Polaris electric UTV can carry 1,000lbs and tow another 1,250lbs at speeds of up to 25 mph, and some tens of miles in distance.

We wrote before about the benefits of considering electric vehicles for your future retreat transport needs – see our article ‘Is a Tesla the Best Car for a Prepper‘.

We concluded that some sort of electric vehicle would be excellent in a Level 3 situation, because electricity might be easier to generate/create than other fuel/energy types.  But of course a Tesla is a very expensive vehicle, and not well suited for ‘working’ purposes on a farm.

There is also a much less expensive possibility that would be suitable for many preppers.  Getting an electric ‘golf cart’ type vehicle, sometimes also referred to as a ‘golf car’.  You might initially think of true golf carts and reject the thought of such things having any use at all in a grid down retreat situation, and while it is true that the type of vehicle you’d see on a golf course or in use by a ‘Mall Cop’ would not be a good general purpose vehicle at your retreat, that’s not the type of vehicle we have in mind.

Instead, and as well as the traditional/commonly seen type slow sedate golf cart type vehicles, there are many more types of electric vehicle that might be better suited for off-grid use.

Different Types of Electric Vehicles

We are talking about a probably open vehicle that has seating for two or four people, and some load carrying capacity (up to maybe 1000 lbs) to carry general stuff about the farm and even from your retreat to a local town and back.  It might also be able to tow another 1000 lbs or more, and could even be 4WD.

Some are more like mini-tractors, and can be fitted with various accessories to help you in your farming (and with a snow plow blade too for winter driveway clearing).  Some are fairly slow, others are surprising sporty, with maximum speeds in excess of 25 mph.  These types of vehicles are sometimes termed a ‘utility task vehicle’ or UTV, or perhaps a ‘Side by Side’ vehicle, or a Recreational Off highway Vehicle (ROV).

So the first thing you need to do is define the ‘mission’ of the electric vehicle.  Is it to primarily be used to transport you and trade or shopping goods to/from the local town, or will it be used as a mini-tractor type farm vehicle?  If the former, depending on the type of roads you expect to encounter, especially after a few years of zero maintenance and with no snow removal in winter, you’ll know the sort of traction system you need and the range the vehicle should have.  Maybe a regular golf cart will be fine, maybe you’ll need an off-road type vehicle.  Maybe the range of the vehicle with standard batteries is fine, or maybe you need heavy-duty batteries.

If you want to have a mini-tractor type vehicle, you’ll be needing a very different set of capabilities and design considerations.  If you want a vehicle to carry back deer and other game when you go hunting, then obviously other issues apply, including having a cargo tray.

Pricing

These electric utility vehicles vary widely in price, the same as cars.  But as a round figure, plan to spend more than $10,000 on a new vehicle, depending on the features you want.

Of course, there are much less expensive second-hand ones out there, but if you are buying second-hand, you should probably factor in the cost of a new set of batteries too.  The chances are whoever is selling a used vehicle will claim the batteries are almost brand new, and maybe they even have a recent manufacture date on them, but because lead-acid batteries are very susceptible to mistreatment (particularly being discharged down too far) even a new set of batteries might have a very short remaining life.

Ebay Motors has a UTV section in it with a number of listings at any time for electric type UTVs, and a separate section (under Other Vehicles and Trailers) for Golf Cars.  We’ve sometimes seen them listed on Craigslist, and most medium/larger cities have dealers who specialize in such vehicles.

When buying any sort of electric vehicle, you also need to understand if the charger is included with the vehicle or if that is an additional extra item.

Range

Range is – or should be – measured differently for a UTV than for an electric car, because they use different types of batteries.  A regular car probably uses Li-ion batteries, and they can be discharged pretty much all the way down to zero charge without harming the batteries, so if the car’s range is quoted as ‘how far you can go on a complete charge’ that is a valid measurement to consider.

But a UTV is probably powered by Lead-acid type batteries, and they behave very differently.  The more you discharge a Lead-acid battery, the fewer the number of times that you can recharge it, and the greater the harm you do to the battery.  So when you are being quoted a range for a UTV, you need to understand what percentage of charge depletion is being used to assess the vehicle’s range.  Is it the range to use up half the battery charge, 80% of the charge, or the theoretical maximum 100% charge range which you should never use?

Best practice for Lead-acid batteries is to discharge them only 50% before recharging; some, but not all, of the better ‘deep cycle’ batteries can allow up to an 80% discharge.  We discuss matters to do with caring for and best using Lead-acid batteries here.

There are two more things to consider when assessing range capabilities.  The first is that the range assumes new batteries in best condition, and the second is that the range assumes moderate speeds and good surfaces.  As the batteries age, they will hold less charge each cycle, and your range will therefore drop every time you recharge the batteries.  If you ‘need’ to be able to travel 20 miles on one charge, you ideally should get a vehicle with a 30 or 40 mile range, so that you can continue to get at least 20 miles of travel from the UTV for a long time before needing to replace its batteries.

It is common to see UTVs claiming ranges from about 20 miles up to about 50 miles ‘per charge’ but you’ll need to carefully understand what ‘per charge’ means’.

Batteries and ‘Fuel Economy’

There is no standard battery configuration for UTVs, and so simply understanding the different range capabilities doesn’t directly equate to how much electricity each vehicle requires to travel one mile.  That’s a bit like saying ‘this car gets 200 miles per tank of gas, and that car gets 300 miles’ – unless you know how many gallons of gas in the tank, the range figure doesn’t directly equate to fuel economy.

So you should understand the battery configuration for the UTV.  Generally, UTVs have some number of either 6V, 8V or 12V batteries, and probably all connected in series.

Many vehicles operate on 48V or 72V, but whether this is the result of a series chain of 6V, 8V or 12V batteries varies from brand to brand.

To understand the ‘fuel economy’ of the vehicle, you need to know how many kWhrs of electricity are used to drive how many miles.  Divide the miles traveled by the kWhrs used, and you’ll get miles per kWhr.  Probably this will range from 2 to 5, and noting how electricity will become scarce and expensive in the future, you should pay attention to this number and be willing to pay an up-front premium to get a more efficient/economical vehicle.

We are starting to see some UTVs with range/economy boosting features such as higher efficiency motors (rather than old-fashioned series wound motors) and regenerative breaking (ie, when you press the brake pedal, the motor becomes a generator and starts charging the battery again).  Search out the most efficient UTV you can find, as long as it also provides the other functionality you need as well.

Recharging

Many UTVs will recharge from a regular 110V AC power outlet, and many will also accept direct DC charging too.  Ideally, you’d like a vehicle that will work both ways so as to give you more flexibility for the type of charging equipment you use.

If you live in a sunny area, you might even decide to mount solar cells on the vehicle’s roof (and some models come with a solar roof already installed).  We’re a long way short of being able to have the solar cells power the vehicle real-time, but if you have maybe 200W of solar cells on the roof, then when the sun was shining directly on them, that would give you the equivalent of about a 1 mph speed from solar power alone.  That’s not exactly brilliant, but if you are driving into a town and back again, and if you get five hours of sun, that could give you as much as another kilowatt-hour of power which might give you as much as 5 more miles range on your day’s use of the vehicle.

If you do get an electric UTV, you should of course remember to increase the number of solar panels (or whatever else you’ll use to generate electricity) you have to reflect your increased electricity need and consumption.

Safety Considerations

If you are buying some type of UTV, and plan to take it anywhere other than on perfect road surfaces, you probably should be sure to get a vehicle with a roll cage on it to protect you in case it tips over.  These protective cages also require you to have seat belts fastened, so you want good seat belts in the vehicle too.

A vehicle with four-wheel braking would be slightly preferable to one with two-wheel braking.

Maintenance

It is true that an electric UTV doesn’t need some things to be maintained that would otherwise be required in a gas-powered UTV.  Clearly it has no internal combustion engine and all the related things to do with that, but equally clearly, it still has plenty of moving parts plus it has a battery system too.

Whatever vehicle you get will have a detailed owner’s manual with maintenance schedules included.  Our point here is merely to point out that electric vehicles are not maintenance free.  They still need work on their brakes, steering and suspension, for example, and they need regular attention to their batteries, water levels in them if applicable, checks for any corrosion around the batteries, and so on.

Plus, every some years, depending on your usage, you’ll need to replace the batteries themselves.

As an interesting aside, in a normal modern-day living environment, the total costs of ownership as between a gas or electric UTV are similar – some people claim one is better than the other, others claim the opposite.  Certainly, a gas-powered unit that might have 200 miles of range before needing refueling is much more convenient than an electric one which might need some hours of recharging every 30 miles.  But in our case, we’re buying not so much for present convenience as we are for future utility.

Summary

Ideally you want to be able to continue using some forms of powered vehicles in a Level 3 situation.  In a Level 1 or 2 situation, this is easily achieved by simply using the fuel you have stored.  But in an extended Level 3 situation, you need to be able to make your own fuel.  There are a number of different ways of making gasoline or ethanol type fuels, LPG or methane type gas fuels, and diesel, and in addition to that, you’ll of course have some methods of generating electricity too.

The best prepper will have several vehicles, each powered from different fuel sources.  At least one should be electric.

Jul 292013
 
Some people deride coal as being dirty, ugly, and old fashioned.  They are foolish to do so.

Some people deride coal as being dirty, ugly, and old-fashioned. They are short-sighted to do so.

It is only slightly an exaggeration to say that coal has fueled and been a significant enabler of much of the modern world’s development.

But these days, ‘conventional wisdom’ denigrates coal as being dirty, environmentally unfriendly, and generally nasty.  The popular perception (which is completely wrong) is that the US (and possibly world-wide) coal industry is in terminal decline, because it is an obsolete and no longer effective/useful energy source.

Is there actually any continued role for coal in the future – either in our ‘normal’ future or WTSHTF?  Due to the prominence of coal for much of our past, that is a question we need to research and resolve.  So, please keep reading.

Historically, coal has been a long time and low-tech energy source, being reasonably easy to mine, to transport, to store, and to use.  Any low-tech energy source becomes very relevant to us when we consider a future where our high-tech infrastructure may have failed.

Coal has been used for hundreds if not thousands of years in homes, then subsequently as a fuel for stationary boilers in factories, then as a fuel for steam ships and steam locomotives, and as a feedstock for gasworks making city gas supplies, and as an energy source for power stations, and even as a raw source for hydrocarbon products of all sorts.  As recently as the mid 2000s, more than half of our nation’s energy came from coal-fired power stations.

In times of oil scarcity, coal has been used to make ‘artificial’ petrol and other liquid fuels.

Coal is also used in the production of steel, cement, even paper, and many other things.  The US is the world’s second largest coal producer and has the world’s largest reserves – more than 240 years of supply.  So coal would definitely seem to be something all preppers should consider.

As preppers, our major focus on coal would be as an energy source.  The good news is that coal is a very good value source of energy, less than half the cost of most other major energy sources.

There are very many different ways to measure the costs of energy, but the disparity between the cost of coal and other energy sources is so huge as to make it unnecessary to quibble over the last few percents.  If you look at the table on page 3 of this document, you’ll see the following costs per million BTUs of energy for a range of different energy sources (2010 data averaged across the US).

Energy Source Cost ($ per million BTU)
Coal $2.42
Natural Gas $7.41
(note – prices in 2013 are about half this)
Distillate Fuel Oil $20.62
Jet Fuel $16.28
LPG $19.61
Motor Gasoline $21.98
Residual Fuel Oil $11.70
Other $17.97
Average for all Petroleum $20.32
Nuclear $0.62
Wood and waste biomass $3.45
Electric Power Industrial $2.62
Electric Power Retail $28.92
National Average $18.73

 

As you can very clearly see, and based on these wholesale/industrial rates, nuclear power is massively better value than any other power source, but coal comes second, followed closely by wood.  Natural gas is three times the cost of coal, LPG and gasoline are about eight times the cost.

So, in terms of theoretical cost per theoretical unit of energy, coal is massively better than all other energy sources open to us, both now and in the future.

Another interesting point is that one ton of coal can create two barrels of oil.  At the time of writing, this regularly updated coal price report shows coal varies in price from as low as $10.30/ton to as high as $68.25/ton.  To put this number into clear perspective, even after allowing for carbon capture and other ‘best practice’ environmental considerations, it costs less than half as much to convert coal to oil than it does to buy a barrel of oil directly (here’s an interesting report on that topic).

We point this out not to suggest we all create Fischer-Tropsch plants to convert coal into oil in our back yards, but merely to open your eyes to the enormous potential of coal for many different energy applications, both at present and in the future.  It is very wrong to think of coal as ‘old fashioned’ (and as ‘bad’).

If the preceding is even half-true, why don’t we all build massive coal bunkers and store tons of coal?  Sure, it is true that coal is not a very ‘clean burning’ energy source, but who would worry about that after TEOTWAWKI, when all sources of industrial pollution with have been close to zeroed out?  Let’s learn some more about coal.

Different Types of Coal

As you might have noticed from the coal price report linked in the preceding section, the amount of energy you can get from a ton of coal can vary widely, as do other factors such as its sulphur content.  Here’s an interesting chart that sets out the varying amounts of sulphur and energy from coal in different parts of the US.

The wide range of different properties of coal have been categorized into four broad categories (and there are sub-categories within each of these four main categories).  The ‘best’ coal for most purposes is generally anthracite, followed by bituminous, sub-bituminous, and finally lignite type coal.

Anthracite has the highest calorific (energy) value, the highest carbon content, and is the oldest coal.  Each of the three subsequent grades have less energy, less carbon, and are more recent (albeit in geological terms of hundreds of millions of years).

The subbituminous category is of interest, even though it would seem to be the third of the four grades, because it has a low sulphur content.

Using Coal

Coal burns hotter than wood and can create more soot.  If you are going to burn coal in your house, you’ll need to make sure that your fireplace and chimney system can handle the greater heat of coal.

Coal also needs a different type of air flow than does wood.  You need to have coal on a grate with air able to come in from under the great and go through the coal bed for its combustion.  This is fairly critical – a solid bed of coal (as may happen after some hours of burning and a layer of ash being created) will prevent air flow and proper combustion; whereas too porous a bed will also fail to allow for optimum burning.

A well tuned coal fire should generate little smoke, although that depends a bit on the type of coal being burned.  Typically anthracite is preferred for home use and it is a ‘clean’ burning coal.

Coal comes available in different size ranges.  Here’s a list from small to large, and with sizes (which seem to vary from place to place somewhat)

  • #5 (typical size 3/64″ x 100 mesh)
  • #4 (typical size 3/32″ x 3/64″)
  • Barley (Buckwheat #3) (typical size 3/16″ x 3/32″)
  • Rice (Buckwheat #2) (typical size 3-5/16″ x 3/16″)
  • Buckwheat (typical size 9/16″ x 3-5/16″)
  • Pea (typical size 13/16″ x 9/16″)
  • Nut (typical size 1 5/8″ x 13/16″)
  • Stove (typical size 2 7/16″ x 1 5/8″)
  • Egg (typical size 3 1/4″ x 2 7/16″)
  • Broken or lump (typical size 6-8″ x 4″)

We’ve seen people express opinions favoring one size over the other, and others favoring quite the opposite (for example here), and the best size probably depends on the type of stove/furnace and grate you are using.  If you are using an auto-stoker device, then size becomes even more relevant.  Suggestion – experiment to start with, using different sizes until you find the size that works best for you.

As with any type of combustion indoors, we’d recommend you have a couple of CO detectors to keep an eye on CO levels, just in case unusual conditions interfere with the normal safe operation of your fireplace/stove.  You should also have a fire extinguisher or two, and perhaps a bucket of sand (or baking soda) as an excellent way of damping down a coal fire if it starts to get out of hand.

We’d also suggest you regularly inspect your flue/chimney setup for any ash accumulation and sweep it clear as needed.  After a while you’ll get a feeling for the needed frequency of maintaining this – failure to do so might interfere with the venting of the fire and cause dangerous gas buildups inside your house, and/or might encourage chimney fires.

Of course, if you change your coal type, you’ll need to ‘recalibrate’ your expectation of how regularly you need to clean your flues.

Real World Costs and Benefits

We were earlier quoting the wholesale costs of different energy sources.  As you can doubtless guess, there’s a world of difference between the ex-mine cost per pound of buying 1,000 tons of coal, and the cost of having one single 50 lb bag of coal delivered to your doorstep.

Here’s a very useful fuel comparison calculator you can use to compare the respective costs of different energy sources for home heating.  It comes with some default numbers that aren’t enormously out of line, but adjust them for the actual costs you’d pay in your area, and you’ll get a clearer view of the actual costs and benefits of different heating sources.

Coal’s benefit reduces somewhat when you’re buying coal in small quantities, but it typically still shows some advantage over most other heating options.

Read More in the Second Part

This was the first part of a two-part article on coal.  Please now click on to read the second part of the article – Practical Issues to Do With Using Coal.

 

Jul 292013
 

We love coal fires and their distinctive appearance and smell.  The fact they are a very efficient and low cost way of heating is a further reason to consider coal as a fuel source.

We love coal fires and their distinctive appearance and smell. The fact they are also a very efficient and low cost way of heating is a further reason to consider coal as a fuel source.

If the concept of coal as a fuel source appeals, you need to shift from the theory to the practicalities of what it will cost to buy the coal, how you will store it, and other related issues and considerations.  Our earlier article, ‘Coal – A Prepper’s Friend of Foe‘ looked at the overall issues to do with coal, this article looks at some further specific things to consider when evaluating coal.

Where the Coal Is and Buying It

Clearly the closer you are to a coal mine, the lower your cost of coal will be, although another factor will be the ease of shipping coal to your location.  Here’s a somewhat dated but still accurate map showing the spread of coal fields across the country, and here’s a link to the latest US Energy Information Annual Report on coal which has details of mines and their production levels and much more.

If you are wanting to buy significant amounts of coal, then you could consider buying full rail wagon or truck loads.  A full truck load is about 24 tons.  But if you are wanting more moderate amounts (especially to start with when you might be experimenting with different sizes and grades of coal to see what works best with your setup), you should find the closest possible coal merchant.  If you can’t find any nearby coal merchants, you could contact the closest coal mines and ask them for referrals.  Of course there are online services such as this and this too (but we’ve yet to see Amazon start selling it complete with free second day delivery included!).

However, please wait a few minutes before rushing to buy some hundreds of tons of coal.  You should read on to the next section.

The Downsides of Coal

There are two major problems (as well as some minor problems) with coal that argue against our broad adoption of a coal strategy for our future energy sources.

The first is that burning coal is harder on our furnaces than burning wood.  The sulphur that is present in coal creates compounds that attack the metal of our stoves, fireplaces, chimneys, and other structures.  This is nothing that can’t be reasonably compensated for when designing and building such structures, but it does accelerate the wear on all such things, compared to burning wood or natural gas or fuel oil.

The second major problem is storing coal.  Now, you might think that a natural unrefined substance such as coal, which has been slowly forming for 300 million years, and which you may also know is fairly hard to set on fire and to keep burning, would last another few million years without any problems after taking it out of the ground, but if you thought that, you’d be surprisingly wrong.

Coal can be a potentially troublesome product to store.  It reacts with air and with water, and the result of the reaction causes a release of heat.

The release of heat does two things.  First, it speeds up the reaction (making for a positive-feedback loop), and secondly, if it builds up sufficiently, it ignites the coal.  So you can have a pile of coal, even in a cool and/or damp environment, that sets itself on fire.  Amazingly, and completely counter-intuitively, spraying a pile of coal with water can increase the chances of it self-combusting.

Coal not only burns spontaneously after it has been mined, it can also do so while still in the ground; indeed, according to this article, thousands of coal fires are burning all around the world, all the time.  Coal fires in China burn through 120 million tons of coal every year, and contribute 2% – 3% of the total annual worldwide CO2 emissions from fossil fuels.

Coal fires in stored coal piles are far from uncommon, and take very little time to start (75% of such fires start within three months of a coal pile being formed, and many of those fires within the first two weeks).  A little known fact about the Titanic is that when it put to sea on its maiden voyage, it had a fire burning in its number six coal bunker.

If you have large-sized piles of coal, you need a way to monitor their core temperatures.  If the core temperatures reach 140°F, then you need to consider preventative measures, and by the time it gets to 150° it is time to break the pile and allow the coal to cool before repiling it.  Coal generally will start to smoke at about 180°, and at that point, it is a bit too late because it is starting to combust.

Note that coal will often steam as water dries off, this is different to smoking.

Large lumps of coal are more resistant to spontaneous combustion than smaller lumps, and anthracite is the least susceptible, while lignite is the most susceptible.

If there is a lot of air flow through the pile, that will keep the coal cool.  If there is no air flow through the pile, that will keep oxygen away from the coal and limit the reaction.  But somewhere in the middle, between ‘no air’ and ‘lots of air’ is a danger zone with enough air to encourage spontaneous combustion.  It can only take a small amount of air flow for this to occur.

So, if you are storing coal, you need to keep the piles small and monitor their core temperatures.

A related issue is that coal deteriorates over time.  It again seems strange that something which is formed so slowly over 200 – 300 million years is so apparently ‘unstable’, but you will definitely start to notice reductions in heat output from coal that has been stored for extended periods of time.

These heat output reductions are probably not profoundly significant, and you can still store coal for many years, even tens of years, and still get valuable energy from it, and when you compare this to storing wood (which might rot) and liquid fuels (which need stabilizer and even then have a maximum storage life of perhaps ten years) it is clear that coal is as suitable for storing long-term as other energy sources.  But it isn’t perfect.

Legal Restrictions on Burning Coal

Another problem might be any clean air regulations in your state/county/city that restrict your ability to burn coal.  The problem is that such laws almost certainly don’t say ‘except in an emergency when you can burn anything you like at any time for any purpose’.  If the law says it is illegal to burn coal today, it will still be illegal to burn coal WTSHTF, and while enforcement might be thin, sooner or later some enterprising person will realize you are burning coal and will use the law as an excuse to legally ‘fine’ you, with the fine perhaps being the forfeiture of your remaining coal or food or anything else they wish it to be.

On the other hand, if your region just has occasional, weather/air quality dependent burning bans, then perhaps, after TSHTF, the authority that rules on such things will no longer function, and/or, the lower level of general industrial activity will reduce the number of times during the year when coal is banned.

Clearly if you plan to rely on coal as a year-round fuel source (eg firing a boiler that then provides heating, hot water, and possibly even electricity generation or a mechanical power source) you need to be sure you can legally use it year round.

How Much Space Does a Ton of Coal Take Up?

So, if you do decide to set aside space to store coal in bulk, how much space will you need?

Our first comment is to remind you of the problems outlined in the preceding section to do with coal’s propensity to spontaneously self-combust.  It is better to have a number of smaller piles/bunkers/whatevers of coal than one large one.  If nothing else, we’d want to be sure that nowhere in our fuel pile was more than four feet from the outside.  That might sound like a restrictively small size, but you could get as much as 6 tons of coal in such a pile.

This is a very conservative suggestion, but better safe than sorry.  Back in the 1920s, the Railroad Administration suggested piling coal for railroad storage not over twelve to fifteen feet in height when the track is placed on top of the coal pile, and not over twenty feet when a locomotive crane is used.  The Home Insurance Company advised against piling in excess of twelve feet, or more than 1500 tons in any pile, and suggested trimming the piles so that no point in the interior was more than ten feet from an air-cooled surface.

Coal is dense, but due to its irregular size and shape, it doesn’t pack efficiently.  In general, you can expect to get from about 43lbs to 59 lbs of coal per cubic foot.  Because coal is heavier than water, wet coal takes up more space for a given amount of weight than does dry coal.  Older coal (ie bituminous or anthracite) will have a greater weight of coal per unit of volume than does newer coal.

So, back to our suggestion you keep a coal supply in piles measuring 8′ x 8′ on their base and 4′ high – a total of 256 cu ft.  If you work on say an average of 50 lbs of coal per cu ft, that would be about 12,800 lbs of coal, or 6.4 short tons per pile.  You are using 10 sq ft of floor space to store a ton of coal.

Summary

This was the second part of a two-part article about coal.  If you’ve not already done so, you might choose to now read our first part, ‘Coal – A Prepper’s Friend or Foe‘.

Coal is usually the second cheapest energy source in the US today.

The two cheapest sources of energy in this country are strangely the two which ‘greenies’ hate the most – coal and nuclear.  On the other hand, arguably the ‘cleanest’ source of energy is also the most expensive (electricity) and being as how almost half of all electricity comes from coal fueled power stations (and most of the rest from stations burning either natural gas or oil) the ‘cleanness’ of electricity relates only to what you see coming out of the wall rather than the total process of generating the power in the first place!  But it isn’t our place, here, to get into a discussion on the illogic that surrounds too much environmentalism….

Suffice it simply to say that while it is of course entirely impractical to consider building your own personal nuclear power plant; depending on where you are, where you could source coal from (and at what cost) and any local restrictions on burning coal, you might find coal to be a surprisingly cost-effective and good solution for much of your future energy requirements.

If you do choose a coal based approach to some of your energy needs, you are well advised to choose specific stoves/furnaces that are designed and optimized for the different burning characteristics of coal (compared to wood).

We’d recommend you research the issues to do with using coal at your retreat.  You might be surprised at how positive a coal based energy approach could be.

Here’s an interesting reader forum type website that could be a good resource for preppers wanting to find out more about buying, storing, and using coal.

Jun 252013
 
The stunning Tesla S has a best-case range of over 300 miles between battery charges.

The stunning Tesla S has a best-case range of over 300 miles between battery charges.

One of the big problems we all have to consider is what sort of motorized transportation we can use in a Level 2/3 situation.

The problem is that modern-day fuels – gasoline, diesel, liquid propane and compressed natural gas – are all vulnerable to disruptions in supply, processing and distribution such as would occur in any sort of emergency situation, and so we’ll largely be forced to rely on such stored fuel as we may have, and when that runs out, our options become difficult.

Sure, you could look at ways to make your own bio-diesel, and that might become a necessary option.  You could also look at modifying a vehicle to run on wood gas.  And some people, by choice or necessity, will allow themselves to settle for horses or oxen.

But there’s another option worthy of consideration, especially in Level 2 and early Level 3 scenarios.  An electric vehicle that you can recharge from solar or wind power.

This is of course not a cheap option, because the first thing you need to do is buy an electric vehicle.  But if you have the budget to consider such things, and depending on the amount of surplus renewable electricity you expect to be generating each day, it might be your best option.

How Much Electricity Does an Electric Vehicle Use

Just as with any other powered vehicle, the range you get depends on your speed, driving style, and the terrain.

There are some major differences in how battery mileage is tested in the US, Japan and Europe, so we’re generally using US EPA quoted figures, which may or may not be exactly realistic, but which tend to give the lowest claimed ranges, so they are probably better than the other tested range claims.  If you are evaluating electric car ranges, make sure you understand how the range figure was established – the latest US EPA test is a ‘five cycle’ test and more complete than its earlier two-cycle testing.

Their range also depends on how much of the battery’s full charge is used.  Generally it seems to be considered best practice not to 100% deplete the batteries.

  •  A Tesla Model S has either 60 kWhr or 85 kWhr batteries, and can get you 350 miles or more on a single charge in optimum conditions.  We are not certain how much of the total stored charge is used.
  • A 2013 Chevrolet Volt has a 16.5 kWhr battery and a 38 mile range, during the course of which it depletes 10.3 kWhr of its total battery capacity.
  • A Nissan Leaf with a 24 kWhr battery gets 84 miles on a full battery charge, or 75 miles on an unstated lesser amount of charge.
  • AA Ford Focus Electric with a 23 kWhr battery gets 76 miles per EPA figures.

Looking at these and other numbers, it seems fair to say that each mile driven in an electric vehicle takes somewhere in the order of 250 – 300 Whr of electric energy.

To translate that to other terms, you could run a 20 watt LED/CFL lightbulb for 12 – 15 hours with the same amount of power required for an electric vehicle to drive one mile.  You could run a 1600 watt heater for 10 minutes with the same power that takes the electric vehicle one mile.

More Electricity is Required to Charge the Car

Say you have a solar panel setup that gives you 5000 W of power when the sun is shining on them.  You might think that you can connect the solar panels up to your electric vehicle, and if the vehicle has, say, a 20 Whr battery, then a simple calculation suggests that you just need to charge it for four hours and you’ve put 20 kWhrs of charge into it.

Unfortunately, that’s an over-simplification.  You need to adjust for the various inefficiencies and conversion losses you’ll experience from when the power comes out of the solar panels until when it ends up stored in the vehicle battery.  You should figure on as much as 30% of the power from your solar cells being lost in the process of taking them from the original low voltage DC solar cell output to a high voltage input (often in AC) to the charger unit for the vehicle, and through that and in to the batteries themselves.

It would probably be prudent for you to talk to the car manufacturer about a direct DC input to the vehicle’s charging system.  If you can go straight from DC to DC, this might give you a considerable improvement in efficiency, but depending on the vehicle and its DC charge voltage (which could be very high), this might not be feasible.

There is another electricity need as well.  You can’t leave a car with a dead battery.  You need to keep the battery with a certain minimum amount of charge, and because the batteries self-discharge at a slow rate, you need to be topping the vehicle up every week or so whether you are using it or not.

One more thing to consider is that charging your vehicle will probably take considerable time.  If you can provide, say, 5 kW of power, then you’re looking at probably a full sunny day of solar power for a Leaf or Focus to be charged, and two or three days of this to charge a large capacity battery (but longer range) Tesla.

And if you thought you’d pack a portable solar kit in the back of the vehicle and charge it at your destination prior to returning home, that is probably impractical.  If you had a 200 W solar array (uncommon, but here’s a site selling 150 W and 300 W portable panels), then it would take about two hours of charging for each mile of range added to the car.  If there were 8 – 10 hours of sun in a day, that would give you 4 – 5 miles of extra range.

What is the Service Life of a Battery Powered Car

Unlike the lead-acid starter battery in a regular vehicle which works until, one day, it no longer works; electric vehicle batteries don’t usually catastrophically fail.  Instead, they slowly but surely degrade, meaning they hold less and less charge with each successive discharge/recharge cycle.

Their rate of deterioration depends on various things, with the two major issues being the simple passing of time, and the number of cycles of charge/discharge they experience.

Chevrolet warrant their Volt batteries for 100,000 miles or 8 years and estimate that the battery will have lost 20% of its ability to hold a charge by the end of that time.  Its battery warranty is a slightly complex consideration though because the vehicle is dual-fuel; it will be running on its gasoline engine for an unknown percentage of the warranty period, as well as sometimes off its batteries.

Tesla warrant their batteries for eight years and unlimited miles, and will replace them if their capacity diminishes by 30% during that time.

So it seems that we can expect probably ten or more useful years from a battery pack, no matter how much we do or do not use it.  That’s both good and bad – what say TEOTWAWKI occurs just a month or two before you were planning on (needing to) replace your battery pack?  As long as you have a reasonably new battery pack, you’re good for up to ten more years of battery life, but otherwise, you’re going to have a much shorter useful remaining life, and because the batteries slowly decay even if sitting unused, you couldn’t keep a supply of spare batteries to extend the total life of the vehicle.

Needless to say, there’s no way you’ll be able to build your own high-tech lithium ion battery.  Once the one in the car is no longer functional, that’s it until – if/when – the high-tech world we luxuriate in  is restored again.

Uses For an Electric Car

So why would you even want to consider an electric car in a Level 2/3 situation?  After all (at least per our standard definitions) a Level 2 situation is all about living off stored resources until such time as normalcy returns, and a Level 3 situation assumes normalcy won’t return any time in the foreseeable future and requires you to fully transform to a sustainable ongoing lifestyle.

In a Level 2 situation, you’d simply run normal vehicles off stored fuel.  In a Level 3 situation, you’d be reliant on animal power or a low tech type of wood gas burning car – maybe even a steam-powered car.  (Yes, we’ll write about both these concepts in future articles.)

But there may still be room for an alternate technology in both situations.  An electric car reduces your reliance on stored fuel while you still have any (a Chevrolet Volt type solution – a vehicle that will run on either battery or gasoline would be ideal), and in a Level 3 situation, an electric car gives you additional capabilities that animals don’t have – the ability to travel an extended distance at speed, at least for as long as there are passable roads, and to the limit of your battery range.

Unless you spend a lot of money on a Tesla, the present selection of electric vehicles all have limited range – about 30 – 70 miles, depending on driving conditions.  There’ll be no recharging stations for you en route WTSHTF but if your retreat is within 10 or so miles of a local community, making roundtrips between retreat and community possible on a single charge, then in a future Level 2/3 situation, the electric vehicle can be useful.

Clearly, it is not an essential item that you must have as part of your basic core prepping supplies, but if budget and circumstance allows, it might be a valuable additional option.

A Warning Note About Range Claims

It goes without saying that ‘your mileage may vary’ in terms of the actual range you get out of your vehicle.

In addition to all the usual range-affecting factors that you are familiar with when driving a regular gas-powered vehicle, an electric vehicle’s range also varies significantly if you need to use its heater or a/c unit (headlights don’t make such a big difference).

But there’s another factor to also keep in mind.  Every time you discharge and recharge the lithium ion batteries, their capacity diminishes slightly – maybe by less than one tenth of one percent, which sounds like nothing until you think forward to what happens after the 100th or 1000th charging cycle and then all those tiny reductions in storage capacity have become significant.

The chances are that the useful life of your vehicle’s battery system will be determined not by its sudden complete failure, but by its gradual reduction in driving range below the point that you need.  For example, if your retreat is 12 miles from the nearest town, and you have a vehicle with a 35 mile range, you start off, with a brand new battery, needing to drive 24 miles with a 35 mile charge.  That’s easy.

But after some years, the batteries have lost 20% of their storage capacity and you now have to drive 24 miles on a battery that holds a 28 mile charge.  That’s getting to be ‘touch and go’, isn’t it.

Then, in another year or two or three, the batteries reduce down to having the same range as you need to drive, and what happens then?  Remember where we commented, above, that recharging the vehicle away from a heavy-duty high current source of power will take almost literally forever.  In other words, the vehicle has essentially become functionally useless, unless you can arrange for some source of recharging in the local township you make your roundtrip visits to.

Our points here are three-fold.

First, take all range claims with a grain of salt.  They’re probably not as inaccurate as some of the claims made for regular vehicles that you drive ‘normally’, and in the future, you’ll almost definitely drive an electric vehicle as super-economically as possible, but even so, allow yourself a margin of error between the claimed range and the actual range you might get.

Second, if your typical roundtrip distance will be close to the claimed range capability of the electric vehicle when new, you’ll only have a limited life before the vehicle’s range has reduced below that you need.

Third, because the effective life of the vehicle will most likely be limited by its gradually reducing range, the longer the range it has when new, the longer its effective life will be before that range has diminished down to useless.

Benefits of an Electric Car

An electric car offers several benefits compared to regular gasoline powered vehicles.

The first benefit is that, as surprising as it may seem, an electric car should be more reliable than a regular internal combustion engine powered vehicle.  It has many fewer moving parts, and many fewer stressed parts.  With the local dealership no longer being available to fix your vehicle any time it develops a problem, a reliable vehicle becomes much more essential.

The second benefit is that electricity is an easier fuel source to create and replenish than petrol.  This might also seem counter-intuitive, but the chances are your retreat will have multiple ways of generating electricity but no ways of making petrol.  At a stretch, you could come up with a bio-diesel or a wood gas type system, but complexity issues start to increase in such cases.

The third benefit is that it is quite likely you will simultaneously be desperately short of energy in general, but also have occasional surpluses of electricity.  An electric car provides a way for you to store and use any surplus electricity you are generating, rather than have it go to waste.

What About the Prius and Other Hybrid Vehicles?

Do not buy a Prius or other hybrid electric vehicle.  These cars essentially have no ‘stand alone’ or independent electric power capacity.  They are designed to recover, store, and re-use power from the vehicle when it brakes, so their batteries have very limited capacity and their electric motors are primarily boost or assist motors, capable of powering the vehicle only at low speeds.

These are great cars, for sure, but they are best thought of as super-efficient gasoline powered cars.  Without available petrol, they are useless; indeed, most of them have no provision for external charging.  They also have very low capacity batteries – a typical Prius has about a 1 kWhr battery, of which only about half is available for use in powering the vehicle.  This is a perfectly sensible design for its prime purpose – recovering and reusing energy that would otherwise be lost every time the vehicle brakes, but it is clearly totally insufficient to allow for fully electric-powered travel for more than a mile or so.

The plug-in version of the Prius has a larger battery – 4.4 kWhr – which gives it about an 11 mile range.  This is great when you have gasoline in the tank to fall back on as soon as the 11 mile range has been used up, but not so great as a purely electric vehicle in a future scenario where gas is no longer available.

Electric Car Models

There are quite a few different models of electric cars out there, although most sell at best only a few thousand units each year, so you’re not likely to find one on the local used car lot any time soon.

Furthermore, it is our sense that the technology is steadily evolving, and with the batteries having a finite life, there are definite costs associated with buying a second-hand electric vehicle.  It is good to delay buying an electric vehicle as long as possible – but if you decide you can afford one and can justify one, be careful of this strategy.  You might find you leave it too late!

Rather than list the vehicles currently available – a list which risks being incomplete and quickly going out of date, we suggest you look at these two Wikipedia pages – a list of electric cars currently available and a list of production battery electric vehicles, to see whatever is currently out there.

Most of the electric vehicles are solely electrically powered.  But there are a few (most notably the Volt) which combined both a regular petrol engine with a battery/electric motor, and while these might have shorter electric ranges, they open up an interesting possibility for the future.

First, their shorter range (ie about 35 miles for a Volt) might be sufficient for short runs between your retreat and the nearest township.  And, second, you might be able to modify the petrol powered engine to run on wood gas.

This would require considerable effort on your part, of course, but by making a hybrid electric/wood gas vehicle, that would seem to give you the best of both worlds for the future.

Summary

In our wonderful modern world, with gasoline prices amazingly low (even $4.50 a gallon is ‘low’ compared to the true replacement/alternate technology costs of energy) and petrol freely available at gas stations open 24/7 just about everywhere in the country, electric cars make no sense for most of us.

While it is true you save money in per mile fuel costs when running on electricity; overall, and for most of us, the up-front extra cost of the electric car outweighs the per mile savings.  Even if there is an eventual saving to be had, the inconvenience of the range limitations of electric vehicles, and the time it takes to recharge them, reduces the use of electric cars to essentially around-town runabouts.

But in the future, when gas disappears from the gas stations, and other liquid fuel replacements become massively more expensive than petrol even at its highest current prices, electric cars may become much more useful for shorter range transportation.  Most of us will find it easier to generate electricity (to power a vehicle) than to create petrol or diesel.

Jun 042013
 
When the grid goes down, we will not only need to generate our own electricity but we'll need to store it too.

When the grid goes down, we will not only need to generate our own electricity but we’ll need to store it too.

In our amazing modern life, we seldom pause to consider all the ‘behind the scenes’ miracles that are being worked for our benefit – all the things which could fail, might fail, and probably will fail in a Level 2/3 scenario.

Of all these blessings that we take for granted, perhaps none is greater than the miracle of electricity.  For most of us, nearly all the time, we can plug anything into any wall socket in our house and it will operate, and we can turn on any or all of our appliances and enjoy their normal operation, at any hour of the day or night.

Electricity from our local utility company is always available and amazingly inexpensive and probably has been the greatest lifestyle enhancer of the last 100 years.

You mightn’t think electricity to be amazingly inexpensive when seeing your monthly bill, but try going without electricity for a week or two then ask yourself ‘how much would I pay to get my electricity back?’ and then you’ll appreciate its value.  Or cost out other ways of creating the electricity – for example, electricity from a high-efficiency diesel generator will probably cost 40c per kWhr, compared to a typical cost of about 10c for mains provided electricity.

When the grid goes down and you have to generate your own electricity, you’ll quickly build an even greater appreciation of how amazing our present electricity supply is.  No part of generating electricity in the future will be easy, and because you’ll be using a different way of generating much/most/all of your electricity, one issue deserves particular mention – something you’ve never needed to think about in normal life (although in actuality, it is something the utility companies are very sensitive to).

The chances are you’ll make use of photo-voltaic cells – PV cells or solar cells – for at least some of your energy needs.  Maybe you might use of wind power, too.  These are great energy sources, but there’s an associated problem.  This is the start of a four-part series of articles that considers this problem, and offers ways to optimize your work-arounds and solutions.

The Need to Match Electricity Demand to Electricity Supply

The problem relates to a major limitation of both your likely future energy sources.  In the case of PV cells, you know they only work when there’s reasonably bright sunlight.  So, you never get any power at night, and on short winter days that are overcast, you get very little power even in the middle of the day.

In the case of wind power, the wind turbine only generates power when there is ‘good’ wind – nice steady smooth wind blowing in a reasonably consistent direction at a reasonably consistent speed (wind gusts can destroy a turbine) that is neither too fast (at high speeds, turbines stop working to prevent damage) nor too slow (turbines have a minimum speed below which they no longer generate useful amounts of power).

The problem with both PV cells and wind turbines is that you can’t match their power generation to meet your requirements.  A diesel generator simply starts working harder (and burning more fuel) when its load increases, and if you have a micro-hydro station, you can vary the amount of water driving the turbine, but there’s no way you can make the wind blow more strongly or the sun shine more brightly.

The typical solution is to have a PV/wind system that provides enough power during a realistic typical sort of day of working to both cover your power needs during the period of operation, plus surplus power which can be transferred into some sort of electricity storage system.  Then, when the power being generated becomes insufficient to meet your requirements, you can switch to the stored power and use that until such time as the primary power source can start meeting your needs again.

Hence the need to store electricity.

Storing Electricity is Not Always the Best Solution

In addition to whatever method of storing electricity you might choose to match with your renewable electricity generation program, there is another way of storing electricity which has a huge plus but also a huge minus.

We are talking about simply keeping a large supply of diesel or propane for a generator.  Each gallon of diesel can give you about 10 kWhrs of electricity, and with a typical house using about 1000 kWhr of electricity a month (depending on design, size, and climate of course) at present (with plentiful energy, low-cost, and no need to fanatically conserve energy) this suggests a diesel generator would consume about 100 gallons of diesel a month to give you all the electricity you need.  A few tweaks to your retreat design, some more insulation, and some alternative heat and energy supplements, and you could easily halve this to 500 kWhr of supplementary electricity per month – a mere 50 gallons.

If you have 1,000 of diesel stored, that could see you through 20 months of power needs, which would cover all Level 1 and most Level 2 scenarios.  Those 1,000 gallons of diesel represent something well under $10,000 to purchase, to stabilize with fuel stabilizer for many years, and to store in good quality long life tanks.

As a comparison, if you wanted to have a battery based electricity storage capacity of say 75 kWhr, you’re looking at an investment in batteries and control circuitry of $20,000 or more, and you’ll want to significantly expand the power output of your solar or wind setup so it has sufficient extra capacity not just to meet your regular needs but also to charge up the storage banks – maybe something like an extra 5 kW – 10 kW of power generating capacity – figure on another $10,000 or so for that.

So for solutions extending out a year, two, maybe even three or four, you might decide not to overcomplicate things (and add to the cost as well) and have a system that provides renewable energy during the day and relies on a diesel generator at night.

But, having said that, a key part of preparing includes planning not just for Level 2 situations, but also for ultimate Level 3 situations, and if you base your electricity generation on diesel, you know that, sooner or later, you’ll run out of diesel.  So if you wish to be best prepared for the future, you’ll recognize that electricity storage, while not necessarily the most economical solution for Level 2 events, is essential for Level 3 preparedness.

Any type of preparing of course ideally involves multiple solutions to each single problem, so as to have redundant approaches, and for this reason too, it makes sense, even in planning for shorter term problems, to have at least some way of storing some electricity.

How to Store Electricity

It is difficult to store electricity, with the only ‘true’ form of electrical energy storage being a device known as a capacitor.  While capacitors are remarkable and very useful in some applications, they are sadly not really well suited for storing the large amounts of energy we wish to store, and for the lengths of time we wish to store it.

We’ll spare you the science, but suffice it to say that all other forms of energy storage involve using the electricity to create a different form of energy which can be conveniently stored and converted back to electricity again in the future.  Even a battery, which might seem to be a pure store of electricity, actually converts the electricity to a chemical form of energy.

In considering an electricity storage method, you need to consider a number of factors :

  • System efficiency – for every kWhr of energy you put into the system, how much do you get back again when you convert it back to electricity again?  In the broader scheme of things, efficiency is of course important, but in this application, where you’re essentially storing spare/surplus power, it isn’t quite as important as it would be, for example, for a utility company that is paying for all the electricity it generates and seeking a way to cover the ups and downs of daily demand.
  • Storage losses – does the stored energy slowly – or quickly – dissipate over time, or does it stay unchanging for long periods of time?  In our case, we will have a mix of requirements – some energy needs only be stored for 15 hours or so (ie from when PV cells stop providing power around sun-down until they start again shortly after the next dawn).  But you will want to be able to store some energy for a longer term in case of extended periods of insufficient power supply during the day.  Storage losses are an important factor.
  • Size and other requirements – is anything special needed?  Does the storage thing take up a lot of space?
  • Maintenance and useful life – how many times can electricity be transferred in and out of the storage system?  What types of ongoing maintenance are required, and how easily can the system be maintained in a future situation where you’ll not have high-tech equipment, and sooner or later will run out of replacement spare parts?  How many years until it fails entirely and needs to be replaced?  Clearly these are very important issues for us.
  • Capacity – how much electricity can be stored in the system?  Are there limits to its ability to grow?  Of course we need to have adequate capacity – that goes without saying, and if there’s a low tech way we can grow the system in the future, so much the better.
  • Cost – what are the costs of storing electricity in the system?  Do we need to comment on the fact that, as preppers, we are always confronted with too many different high priority ways to invest our money and insufficient money to invest!

Although there are very many different ways to store electricity (perhaps better to say ‘to store energy’ because the thing we are storing is not actually electricity, but something else which can be converted into electricity), in our case there are only one or two which are practical to the size, scale, budget, and other requirements we are likely to have.

The most obvious storage system involves batteries – probably some sort of lead-acid batteries.  A less obvious form is to store energy in a rapidly spinning flywheel, and a third approach, which may work well for some people but not well for others, is to store energy in the form of pumping water up to a higher elevation, and then to reclaim it as needed by having the water flow down through a micro-hydro power generator.

Continued in Part Two

Please now click on to read part two of this series, ‘Using Batteries to Store Electricity‘, and then continue on to parts three and four (Other Energy Storage Methods and Strategies to Reduce Your Need to Store Electricity).

We also have other articles on the general topic of Energy.

Jun 042013
 
A cutaway view of a typical lead-acid battery.

A cutaway view of a typical lead-acid battery.

This is the second part of a four-part article series about how to store electricity (better thought of as storing energy rather than electricity per se).  If you arrived directly here from a link or search engine, you might wish to start from the first part of the series here, then read on sequentially through this article and the balance of the series.

Lead-acid batteries use a technology that has been around since the mid 1800s.  The relatively recent Lithium-ion technology is showing some signs of promise as a possible replacement to lead-acid, but that is still a way off, and for now, for our purposes, lead-acid batteries, while far from innovative, remain probably the best general purpose way to store electricity in circumstances that typical preppers are likely to encounter.

Batteries offer between about a 50% and a 85% efficient means of storing electricity, making them neither particularly better nor particularly worse than most other forms of storing electricity.  They have acceptably low storage losses, typically losing somewhere between 2% – 15% of their charge each month.

As old-fashioned as they may be, the generic concept of lead-acid batteries masks the fact that there are many different types of lead-acid batteries, designed for different purposes, and with greatly varying suitability for our requirements.

They also have a surprisingly complex series of requirements for how to charge and maintain them so as to get the optimum life out of the batteries – to prolong the amount of electricity they will store, to maximize the number of charge/discharge cycles they can withstand, and to protect against sudden failure.  For optimum use, it is important to be sensitive to many aspects of their care and conditioning that we never consider with our car battery – and the proof of the need to look after our storage batteries should be evident when you consider how quickly car batteries fail!

Lead-acid batteries fall within three general families when it comes to how they are made.  The oldest technology is the ‘wet’ or flooded type battery, then there are gelled batteries and AGM (Absorbed Glass Mat) batteries.  Flooded batteries typically have removable caps and you should occasionally check the level of the liquid inside the cells, adding distilled water as necessary, although some now have ‘fully sealed’ cells (which actually aren’t fully sealed).  AGM and gel batteries are always sealed and in theory need no maintenance.

Some people view gel cells as a transitional technology and suggest you avoid them, preferring either AGM or wet cells.  Gel cells require different charging procedures and voltages than regular and AGM batteries, and are more prone to degradation or failure if not treated optimally.  AGM cells are very low maintenance, but more expensive for the same amount of capacity as wet cells.

The most common measure of a battery’s storage capacity is how many amp-hours of charge it can give.  However, it is important to appreciate that the amp-hour capacity of a battery is dependent on how fast it is being discharged.  The slower the rate of discharge, the more total charge the battery will give you.  For example, a battery that is discharged evenly over 20 hours will typically give 10% less charge than a battery discharged over 100 hours.  A battery that is discharge over 8 hours will typically give almost 20% less charge than one discharged over 20 hours.

Our point is that it is important to understand whether a battery’s capacity is being measured on the basis of a 100, 20 or 8 hour discharge rate.

The lead-acid battery that most people are most familiar with is a car starting battery.  This is designed to store a small amount of charge which can be provided at a very high rate of current for a short period of time, for the purpose of starting the engine.

It has a secondary purpose to power the car’s various electrical loads for a moderately short amount of time while the vehicle is stopped and the engine switched off.

But these batteries are not designed to give up all their charge over a slow gradual period; indeed, they’re not designed to give up all their charge at all.  They are not ‘deep cycle’ type batteries.  Perhaps because of this, they are typically not even rated in terms of amp-hours of storage, but rather quote a ‘cold cranking amp’ current rating – the amount of current it can supply when being called upon to turn a vehicle’s starter motor.

Don’t use car batteries as storage batteries.  They are not designed for deep discharging and don’t last long.

No lead-acid battery should be fully discharged before recharging it again.  The greater the amount of discharge before recharging, the more the battery is stressed and the shorter its future life will be, in terms of additional charge/discharge cycles and capacity of charge that can be stored per cycle.

Deep cycle batteries are designed to allow for the greatest amount of charge depletion per cycle.  Typically these types of batteries (sometimes referred to as ‘golf cart’ or even as ‘forklift’ batteries) are designed to give up perhaps 70% of their capacity per discharge without suffering any severe consequences.  Some batteries allow for an 80% discharge, but it is probably better to go easy on them and not go all the way down to 80%.

Depending on the exact battery design, discharging to 50% is considered the ideal compromise, and you should avoid discharging beyond about 70% of capacity.

You can measure the state of charge of a battery either by testing the specific gravity of its liquid, or by testing the voltage it puts out.  The specific gravity measurement is slightly more accurate, but with so many batteries either sealed or AGM, these days most people use voltage readings as a measure of charge instead.  The voltage steadily declines as the battery discharges, starting from 12.6V when fully charged.  Am offload reading of 12.3V shows about a 50% charge, and a 12V reading (offload) more or less corresponds to a 75% discharged state.

Battery life also depends on other factors such as even ambient temperature (cooler is better than warmer).

Modern batteries such as these or these claim to give up to 2000 or so cycles, with discharge all the way to 80% each time.  That’s almost six years of daily discharging (or twelve if two-daily discharging, and so on for extended cycles).

In terms of actual elapsed time, these types of batteries seem to be talking of lifetimes in the 10 – 20 year range, if the number of cycles isn’t exceeded in a sooner time frame.  That’s starting to become a viable life.

Other highly respected battery suppliers include Concorde/Lifeline and Rolls/Surrette.

If you are building a high-capacity battery, there are several ways to do this to best effect.

The first is not to use a 6V or 12V based system.  Increase your voltage (by connecting batteries in series) to 24V or 48V.  This has several benefits, including reducing the electrical losses through your wiring and/or reducing the need for ridiculously oversized wiring to carry your battery current.

The second is of course to connect multiple batteries in parallel, but this needs to be done with caution.  The more batteries in parallel, the greater the chance that a ‘bad cell’ in one battery unit will bring down the entire set of batteries.  What happens is the battery with the higher voltage then starts ‘charging’ the battery with the lower voltage, and bleeds away its power into the weaker battery.

For this reason, it is always important to match batteries with like batteries, whether connecting in parallel or serial – batteries of similar capacity and similar state of life.

It is best to arrange for each individual battery in your battery array to be of as large a capacity as possible.

Beyond that, rather than to create one huge battery with maybe six individual batteries paralleled together, it is much better to create two three battery units, or even three battery units, each with two paralleled batteries.  That means you can better rotate your batteries in and out of service, alternately charging and discharging each battery in sequence, and stretching out the overall life of all the batteries.

Continued in Part Three

Please now click on to read part three of this series, ‘Other Energy Storage Methods‘, and then continue on to part four ‘Strategies to Reduce Your Need to Store Electricity‘.  If you’ve not yet done so, you might wish to also read the first part of the series, ‘Storing Electricity‘.

We also have other articles on the general topic of Energy.

Jun 042013
 
The fickleness of wind and other renewable energy sources means you need to store power as best you can when it is available, for future use when it is not available.

The fickleness of wind and other renewable energy sources means you need to store power as best you can when it is available, for future use when it is not available.

This is the third part of a four-part article series about how to store electricity (better thought of as storing energy rather than electricity per se).  If you arrived directly here from a link or search engine, you might wish to start from the first part of the series here, then read on sequentially through the balance of the series.

Flowing Water Uphill and Other Gravitational Energy Stores

Another interesting approach to storing electricity is by pumping water uphill.

If you have a hill on your property and sufficient water, you can use surplus energy to pump water up to a large reservoir on the top of the hill, and then when you need electricity, you run the water down the hill and to a hydro-electric plant at the bottom.

This can store energy for a longer term – the only storage loss being evaporation – but involves potentially massive amounts of water and as much vertical rise/fall as possible.  If you double the height differential, you halve the amount of water you need, and vice versa.

Although this might seem like an unusual and strange technology, 93% of all stored power, world-wide, is stored this way.

To put the amount of water needed into perspective, if you wanted to store enough water to be able to generate 5kW for 100 hours – a good reserve for emergencies) you could either have an efficient diesel generator and about 50 gallons of diesel, or if you were able to store water somewhere 100 ft higher than ground level, you’d want to have about three million gallons of water in the reservoir.  That is about 400,000 cu ft of water, so think of a pond measuring perhaps 200 ft by 200 ft and 10 ft deep.  You’d also need another storage area at the bottom to hold the water prior to pumping it back uphill again.

This is of course not impossible, assuming you have a way to get the vertical rise that is necessary, and a source of water to replenish losses from evaporation.

The concept can be extended and slightly modified, indeed, it is merely an extension of the concept found on many cuckoo clocks, where a weight slowly descends, driving the clock mechanism, then is ‘rewound’ when you use energy to pull the weight back up again.  Anything that uses gravity as a way of storing energy can work.

There is a project currently being developed in California that uses rail boxcars loaded with heavy gravel.  Electric locomotives use spare grid power to haul the boxcars up a length of steeply inclined track, and then when the electricity is needed to be returned to the grid, the boxcars are allowed to push the loco down the track, and the loco now acts as a generator feeding power back into the grid.

Such a system can be 80% or more efficient, and will store energy indefinitely with no storage loss.  The boxcar example requires more power to push the boxcars uphill than would be available from a typical private power source, but this could of course be modified (lighter boxcars and/or less steep grade).

These types of systems can require a fair measure of space.  In the water example, if the water reservoirs at top and bottom are ten feet deep, you need almost 2 acres of space just to store the water, plus more space for the pipes and generator/pump.

But their biggest requirement is the height differential.  If you’ve got a fully flat property, you’re either going to have to create a raised portion, which would involve a prohibitive amount of earth working, or else look for other alternatives, which presently tend to invariably circle back to batteries.

Using a Flywheel to Store Electricity

Flywheel technology is becoming more practical, although still a technology that is equal parts experimental and/or not ideally suited for our applications.

With a flywheel, spare electrical energy is used to spin up the flywheel – a huge heavy massive device that spins rapidly – and then when electrical energy is needed, the flywheel is used to run a generator.

Flywheels can store surprisingly large amounts of power, and if in a near vacuum and with magnetic bearings, are slow to lose their energy (by ‘slow’ we mean the energy loss rate is acceptable for a device that charges during the day and discharges at night, but not quite so acceptable if you want to be able to store energy for several days).  They can provide a reasonably efficient means of storing power.

They are also fairly low maintenance, especially if kept in a semi-sealed environment.  But they are also large heavy devices, potentially weighing 5 – 10 tons or more, and require very precise balancing and bearings due to the speeds they spin at.

Flywheels are best suited for applications that require large amounts of sudden energy and/or applications that have large amounts of energy suddenly surplus.  That’s not to say they’re not potentially good for our sorts of applications too, and the good news is that the growth in renewable energy generation is feeding growth in related issues, particularly energy storage.

We expect to see small-sized flywheel installations continue to be developed to a point where they may become practical for storing energy for short-term overnight use, but we’ve not encountered a flywheel that is quite ready for prime time just yet, alas, although there are some hopeful developments underway at present.

There are many other technologies that are either in a development stage, or which are not suited for our sort of scale of energy storage – for example, compressed air.

How Much Electricity Storage Do You Need

Storing electricity is a somewhat wasteful and somewhat expensive process, although it could be convincingly argued that having extra spare electricity being unused at certain times of day to also be wasteful too!

Some electricity storage is both prudent and essential.  The question becomes – how much.

If your only renewable energy source is PV, then you need enough for two purposes :

First, you need enough to get you through a typical night from when the energy flow from the cells diminishes as the sun gets low until such time as the energy flow restarts when the sun rises the next morning.

Second, you need additional ‘spare’ capacity to cover times when the weather is bad, the sky is full of clouds, and the PV cells aren’t generating enough electricity during a normal day to replenish the store for the next night.  Indeed, in a worst case scenario, the PV cells might not even provide enough power to cover the normal needs during the day.

You can of course control this to a certain extent by increasing the capacity of your bank of solar cells.  If you need 20 kWhrs of electricity a day – 10 kWhr for daytime use and 10 kWhr to store for the night, then you’re less likely to run into shortage with a setup that is rated to provide 40 kWhr per typical day than with a setup that is rated to provide only 20 kWhr per typical day.

So the greater your surplus during a typical day, the less an amount of reserve storage you need.  If even a cloudy day sees your PV installation providing enough power for the day and the night, all you would seem to need is a single night’s worth of power to be stored.

We’d still like to increase that capacity to allow for mishaps and emergencies.  What happens if something fails in the solar setup and it takes you a day or more to repair/replace it?  Also, if you only need to recharge your batteries every other day rather than every day, clearly you’ll get twice the life from them, and if you are normally only discharging your batteries down to 50% full, you’ll again get much longer life than if every night you are discharging them down to 20% full.

If you are only using wind power, the first thing we’d recommend would be to rush out and buy some solar cells!  Some days there might be no wind, but some sun (and vice versa); by spreading your electricity generation between two different sources, you are reducing your risks and increasing your resilience.

Beyond that, it becomes harder to predict how much wind power you can expect.  You need to look at detailed wind logs for your location, and approximating the above ground height your turbine will be situated at, so as to get a feeling for average, best case and worst case daily and nightly power generation.

Using a process a bit like that we recommend for working out your water needs, you can proceed to calculate some likely pessimistic scenarios about the amount of wind power you might get, and from that, you can then work out how much stored electricity you’ll need.  Don’t forget to allow for an unexpected several day outage occurring at exactly the worst possible moment, too!

But, wait – before you do these sums, you should first re-examine the question of how much electricity you will need and use, and reduce this amount as much as possible.  The next three sections cover this concept.

Continued in Part Four

Please now click on to read the final part of this series, ‘Strategies to Reduce Your Need to Store Electricity‘.  If you’ve not yet read them, you might also want to read the first two parts of the series too – Storing Electricity and Using Batteries to Store Electricity.

We also have other articles on the general topic of Energy.