The Fireless Cooker That Feeds | Hacker News Reader

The Fireless Cooker That Feeds

notechmagazine.com

45 pointsrudenoise42 comments

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

Thanks for this. I was quite confused by the title. It appears as "The Fireless Cooker That Feeds" for me. I thought, "Isn't any sort of cooker supposed to feed?"

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.

You're not wrong - once the food is at the right temperature, it's done. You can hold food at the "right" temperature for a long time, but if you go above it, it'll over-cook.

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.

Not all food is done once it reaches the desired temperature. A lot of food, e.g. tough meats, need to stay above a certain temperature for a long time until they're done.

And to further that, there's a lot of state change happening at those temps, often why things hold at exact temps for a bit (eg boiling), so they can take plenty of energy to go up a tiny amount. Biscuit for instance has "the rest" at around 165-175. It also sweats a lot and cools itself off unless you wrap it.

Boiling something is more about pulling water out than it is finishing the food. But it's definitely one of the corner cases - for the reason you mention: the temperature increases are small.

But temperature for boiled things is still important - see candy for example. The temperature directly indicates the amount of water left in the mixture.

All that said, resting is a distinct step from heating that is often required for a food to end up as you expect it to. IWO, yeah, food isn't always ready to eat after heating.

Ugh spell check corrected Brisket to Biscuit. Not quite the same thing.

Well, kinda? For example: smoking. You cook it for a long time at a low heat, but that's more about heating it up slowly as opposed to bringing it to a temperature and holding it there. And ultimately you (well, you're supposed to) gauge its doneness by its temperature; smokers still follow the "the vessel is hotter than your target heat" rule.

I would think a slow cooker is a good example of sustained temperature making a big difference.

Or dry beans. Imagine if you just brought those up to temperature and skipped simmering for ~1-2 hours.

Or pasta. You don't bring the water to a boil and then immediately drain.

Or rice, similar to pasta.

Or some tougher leafy greens. Collard greens need to be simmered ~30-60 minutes.

Or caramelized onions. You are doing chemical reactions (browning sugar, etc.) that take time.

Yep. It’s all just physics and chemistry.

There is a gradient of temperature from the surface to the inside of the food. Depending on the composition, it will take more or less time for the thermal energy to propagate.

In addition, cooking involves chemical reactions. Now, I’m not a biochemist, but if I had to guess, most cooking chemical reactions are probably endothermic (short of setting your food on fire), in which case the chemical reaction comes f cooking will remove thermal energy from your cooking medium (e.g. water or oil) and your cooking medium will cool down even if you had perfect insulation.

counterpoint: sous vide

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

Everything related to heat transfer is still relevant and very, very interesting, but I love how dated the assumption of non renewable energy is now in that method of calculating thermal efficiency.

Who cares if the perfect turbine could only ever convert 59% of the wind power through it!

Also mentions the Rocket Stove (new to me), which looks well-worth getting to know about. [https://en.wikipedia.org/wiki/Rocket_mass_heater] (Wiki article describes several designs as well.)

"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.... "

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).

Yeah, when I think of a cooker, I think of something that heats something up, not just keeps it going.

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...

less oven space, need to replace entire stove, made in a factory and not at home.

It is cleaner perhaps and more purpose-built. But I would not call that practical.

I wonder if you couldn't get similar efficiencies by insulating the walls and lid of the pot itself though (and that would work on any stove, not just one that had a sunken burner of a fixed diameter). Choosing a good material for high-temp insulation might be tricky (without making the wall thickness high) but I for one would be happy to have an nice Ti + aerogel pan... (Ti does work on induction too!)

They do mention that in the article "doubles the efficiency of any cooking device because it shortens the time on the fire"

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...

There was also an infomercial[1] for a product called "AirCore" in the US a couple decades ago for something similar.

[1] https://www.youtube.com/watch?v=SIIWBvgyvmI

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.

The pot in this "cooker" is dropping in temperature. Slowly but surely, since no insulation method is perfect against heat transfer.

True. But if the rate of heat loss is low enough, then it doesn't much matter.

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

As well as easy-to-use, safe and consistent

I have a different brand, but I use my electric pressure cooker many times a week. It's a great time saver for cooking real food from scratch.

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

Cooking when/where energy is scarce. Very useful to save on fuel while camping, for example. Also, I suppose, next time the electric grid is down and you want to cook on battery.

Another benefit is that it reduces the heat transferred to the living environment during cooking. Might be useful in a small living space like an RV or tiny house.

It technically just prolongs the amount of time that the heat is transferred right?

That would still be useful if you're in a small space and the heat loss of the space is greater than the heat loss of the insulated pot.

Yes, you're right. It slows the rate of heat transfer.

lol, clearly we're not living in the same climate :D

A lot of people out in the country don't actually have a gas line to their house, and cook using bottled gas. I lived in a situation like that at one point - the cost of the gas saved by the device wasn't really important to me, but it was the burden of making a half day trip to the city to replace the bottle that pushed me to conserve gas.

so, styrofoam is not technology?

Reply on news.ycombinator.com