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

The Wonderbag – something you can also easily make yourself – gives you a low energy way to make a high quality meal.

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

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

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

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

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

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

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

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

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

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

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

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

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

A Low Energy Slow Cooking Solution

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

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

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

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

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

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

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

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

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


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

  4 Responses to “An Energy Saving Approach to Cooking”

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  1. What they are talking about is a haybox. This was very common in the 1700 1800’s.

    I do this with a laundry basket and some towels. Get your food hot/boiling. Put a towel in the bottom of the basket, wrap with more towels, cover with towels and leave for 8 hours or whatever. Doesn’t cost a thing.

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