When we cook we're bringing up food to a certain temp, then maintaining it at that temp till it's done cooking. If we could perfectly insulate it, then it could hold that temp as long as we want without being on the fire. So the only energy input is getting it hot -- after that it's cooking on its own.
So this is trying to approximate that by insulating the pot.
I always sort of assumed that there's a lot of heat 'loss' from food itself heating up -- as in most the cook time is getting the food up to the temp (i.e. when cooking a steak), not waiting for it to cook at the temp. But I suppose that for certain grains and stews and things that thinking is wrong.
There's a few ways to heat food up, the most common of which is to heat the vessel to well above the right temperature and wait for the food to come up to the right temperature. The cooker linked takes advantage of this method since it is fine if the vessel comes down in temperature a little bit, so long as it doesn't get below the food's "done" temperature. You still have to be vigilant about the temperature of the food, to ensure it's not overcooked.
The less common method is to heat the vessel (often water) up to the right temperature, and let the food come to equilibrium. This is basically sous-vide, and would not work with the linked method, since the temperature of water can't go down. You might be able to fudge things a bit by over-heating the water a bit, but then you risk overcooking the food.
Who cares if the perfect turbine could only ever convert 59% of the wind power through it!
"a rocket mass heater consists of an insulated combustion chamber where fuel is burned with high efficiency at high temperature, and a large thermal mass in contact with the exhaust gases which absorbs most of the generated heat before the gases are released to the atmosphere.... "
The stove with one burner dropped down [1] seems more practical, not requiring a separate device/extra step.
[1] https://krisdedecker.typepad.com/.a/6a00e0099229e8883301a3fd...
It is cleaner perhaps and more purpose-built. But I would not call that practical.
https://www.cabelas.com/shop/en/thermos-cook-and-carry-syste...
https://en.m.wikipedia.org/wiki/Dutch_oven https://en.wikipedia.org/wiki/Haybox
But I've just found this and it looks excellent! https://en.m.wikipedia.org/wiki/Thermal_cooking
