Little nitpick: the title is "The Fireless Cooker that Feeds Low-tech Magazine", as in "this is the fireless cooker we use".

Explaining this just to make sure I get it.

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.

A longer article that was cited, https://www.lowtechmagazine.com/2014/07/cooking-pot-insulati...

It's a very large teapot cosy, in other words. Seems reasonable, though obviously you still need some way to bring the pot up to temp (for that cast iron, induction would be efficient if not low-tech).

There's a few commercial versions of this idea that combine some sort of insulation with a vacuum container, which increases the efficiency.

https://www.cabelas.com/shop/en/thermos-cook-and-carry-syste...

When cooking, the rate of heat needed to maintain the same temperature is exactly the rate at which the food is cooling. So heating up a pot and insulating it is roughly equivalent to heating up a pot and continually heating it to maintain the same temperature. If we changed the culture of cooking to recognize this, we could save a lot of energy.

And this is why the instant pot is such a good value. It's very insulated and incredibly efficient

We used to cook up a stew or a joint in a casserole dish with a lid (like a dutch oven), and put it in a haybox for the day so we had a hot hearty meal at the end of a day outdoors.

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

TL;DR: It's just a good amount of insulation around a vessel (like a crockpot) that's been heated up in some other way.

A great way to cook rice when electronic assistance is unavailable.

Styrofoam is stable upto 79 C / 175 F. But is it completely safe, especially from offgassing?

These have existed for years in Asia. Just search for “thermal cooker”.

What problem is this trying to solve exactly

so, styrofoam is not technology?