Since I'm planning to go off-grid in the next few years, learning what I can about low-energy cooking seems important. I'm planning to build an experimental solar cooker, a solar dehydrator, and a rocket stove, but haven't gotten around to any of these projects yet. But there's one technique I can easily play with right now--since I don't need to build anything first--and that's thermos cooking.
Thermos cooking uses retained heat to cook foods. Instead of needing to fuel a stove for two hours to cook a pot of beans, you fuel the stove only long enough to achieve a boil and then cook the beans for five minutes. After that, the beans and water are sealed into an insulated thermos and allowed to finish cooking using just the retained heat. This obviously takes much longer, but with a little planning it's an excellent method. It conserves fuel, requires little tending once the food is in the thermos, and retains more nutrients than higher-temperature cooking.
In the past week I've done my first experiments using this method. First, I made a batch of wheat berries. One of my favorite bread recipes uses a cup and a half of cooked whole wheat berries--the yield I get when I start with a half a cup of dried wheat berries--and since I was planning to make bread anyway this seemed like a good place to start. I put a half a cup of dried wheat berries into my thermos (actually what I have is an insulated carafe, not a thermos) and added boiling water to cover them and completely fill the thermos. I left the thermos alone overnight and in the morning I had perfectly cooked wheat berries ready to go into my next loaf of bread.
My other experiment was with pinto beans. I wanted to try a relatively large bean, since I've read online that beans can be difficult to fully cook using this method. I figured if I could get it to work with the largest beans, it would work with almost anything. Wednesday night I soaked the beans as I normally would, then in the morning I put them in a pot of water on the stove, brought the water to a boil, and allowed the beans to simmer for five minutes. Then using a funnel, I poured the beans and boiling water into my thermos, filling all the way to the top. I sealed the thermos and left it to cook. From what I've read online, some people have found their thermoses (is that the plural of thermos?) lose too much heat during the long cooking time that beans require, so at some point they need to drain the cooled water and add a fresh batch of boiling water. I checked my thermos before I went to bed last night and the water was still piping hot. The beans weren't done yet, so I let it continue with the original water throughout the night. This morning when I got up, the water was still hot, and the beans were perfectly done.
I'm really excited about this method. It'll be great for all of my grains--wheat berries, oats, rice, etc.--and beans, and I've read that people have used thermos cooking for even more adventurous things, like stews. I definitely have some more experimenting to do! If this is something you want to try, and you don't already have a thermos handy, I've read that Stanley Aladdin and Nissan thermoses are best at retaining heat. You'll also want one with a wide-enough mouth for scooping out whatever you cook--gloppy or sticky things like oats or rice might require getting a utensil of some sort in there--and if you think you'll do a lot of thermos cooking, then find a thermos for which you can get replacement gaskets.
I lucked out because I already had my carafe on hand. It turned out to be superbly well-insulated. The only bad thing is it's a no-name brand, so there'll be no replacement parts if the gasket ever wears out.