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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.

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David Spero[suffusion-the-author display='description']

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