3 ms·

We have a rather dumb slow-cooker left by a previous tennant. 170W on High, with some lower value on Low and Warm. 95% of the heat added once it reaches tempe

We have a rather dumb slow-cooker left by a previous tennant. 170W on High, with some lower value on Low and Warm. 95% of the heat added once it reaches temperature is lost the environment. Lame! Low Tech Magazine has a nice article on the topic [1] of 'Fireless Cookers' which while a bit bulky look like they could cut a lot of energy waste, esp. if there is a mini heating element to top-up heating losses. Thermos also make a 4.5L vacuum cooker ("Shuttle Chef") which looks ideal but it for some reason is eye-wateringly expensive and apparently only made in or for Japan. [1] https://www.lowtechmagazine.com/2014/07/cooking-pot-insulation-key-to-sustainable-cooking.html https://www.lowtechmagazine.com/2014/07/cooking-pot-insulati...

com2kid 5y ago
From your article: > the thermal efficiency varies from 13% for electric hobs to 23% for gas hobs They also have a graph showing induction as being less efficient than gas. Everything I have read recently says the exact opposite, that gas spews most of its energy into your house and very little into the pot, while a good flat top electric gets a large % into the pot and induction gets 100% of generated heat into the cooking vessel. (Though I don't know what efficiency induction operates on, obviously electric stoves are nearly 1W of energy in, 1W of heat out!) Unfortunately most articles comparing gas and electric compare energy costs to the consumer, not thermal efficiency, but I do come across papers such as https://www.aceee.org/files/proceedings/2014/data/papers/9-702.pdf https://www.aceee.org/files/proceedings/2014/data/papers/9-7... that are basically the exact opposite of what the site you linked says. Digging further, it looks like lowtechmagazine based their findings on https://mb.cision.com/Public/MigratedWpy/91653/9014629/ae07e9093116fbad.pdf https://mb.cision.com/Public/MigratedWpy/91653/9014629/ae07e... which is measuring losses due to grid transmission which seems to put electric at a distinct disadvantage. That paper does show the massive amount of heat gas stoves dump into the surrounding air, which depending on climate may then have to be removed, likely by an electric air conditioner, taking that into account gas shoots way up in energy costs. And of course that paper is from 2010, as the grid becomes renewable electric starts winning out in every possible direction.
- verytrivial 5y ago
  Yeah, I was mainly talking about the heat once coupled to the pot. If "23%" means 77% of the heat goes straight past the pot, I'm still wondering if this is a heat 'delta' or quiescent heat flow required to keep a pot at a temperature. Taking a spherical-cow approach, exactly how much energy would be required to (pressure?) cook 1kg of meat in an utterly lossless container? I'm picture stove-top pots more akin to helicopters that hot air balloons -- you're paying a lot of energy to keep the pot at a given temperature only because most of the heat is convecting and radiating out even after it manages to couple into the pot at some low factor. A tiny, tiny bit actually goes into changing the chemical state of the food. So, an electically heated pressure + vacuum pot would surely be the most efficient (at making probably entirely untasty food.)
  - com2kid 5y ago
    My instapot is not burning hot while I am cooking with it, so there is some insulation there for sure. Heck my rice cooker seems reasonably well insulated.
- wahern 5y ago
  > Everything I have read recently says the exact opposite, that gas spews most of its energy into your house and very little into the pot That graph is showing thermal efficiency end-to-end, at least when assuming fossil fuel-based power plants. That's made clear in the article, where they also point out that gas burners are horribly poor at heat transfer--but not poor enough in their model to make them worse than electric stoves, induction or resistive.

com2kid 5y ago

From your article: > the thermal efficiency varies from 13% for electric hobs to 23% for gas hobs They also have a graph showing induction as being less efficient than gas. Everything I have read recently says the exact opposite, that gas spews most of its energy into your house and very little into the pot, while a good flat top electric gets a large % into the pot and induction gets 100% of generated heat into the cooking vessel. (Though I don't know what efficiency induction operates on, obviously electric stoves are nearly 1W of energy in, 1W of heat out!) Unfortunately most articles comparing gas and electric compare energy costs to the consumer, not thermal efficiency, but I do come across papers such as https://www.aceee.org/files/proceedings/2014/data/papers/9-702.pdf https://www.aceee.org/files/proceedings/2014/data/papers/9-7... that are basically the exact opposite of what the site you linked says. Digging further, it looks like lowtechmagazine based their findings on https://mb.cision.com/Public/MigratedWpy/91653/9014629/ae07e9093116fbad.pdf https://mb.cision.com/Public/MigratedWpy/91653/9014629/ae07e... which is measuring losses due to grid transmission which seems to put electric at a distinct disadvantage. That paper does show the massive amount of heat gas stoves dump into the surrounding air, which depending on climate may then have to be removed, likely by an electric air conditioner, taking that into account gas shoots way up in energy costs. And of course that paper is from 2010, as the grid becomes renewable electric starts winning out in every possible direction.

verytrivial 5y ago
Yeah, I was mainly talking about the heat once coupled to the pot. If "23%" means 77% of the heat goes straight past the pot, I'm still wondering if this is a heat 'delta' or quiescent heat flow required to keep a pot at a temperature. Taking a spherical-cow approach, exactly how much energy would be required to (pressure?) cook 1kg of meat in an utterly lossless container? I'm picture stove-top pots more akin to helicopters that hot air balloons -- you're paying a lot of energy to keep the pot at a given temperature only because most of the heat is convecting and radiating out even after it manages to couple into the pot at some low factor. A tiny, tiny bit actually goes into changing the chemical state of the food. So, an electically heated pressure + vacuum pot would surely be the most efficient (at making probably entirely untasty food.)
- com2kid 5y ago
  My instapot is not burning hot while I am cooking with it, so there is some insulation there for sure. Heck my rice cooker seems reasonably well insulated.
wahern 5y ago
> Everything I have read recently says the exact opposite, that gas spews most of its energy into your house and very little into the pot That graph is showing thermal efficiency end-to-end, at least when assuming fossil fuel-based power plants. That's made clear in the article, where they also point out that gas burners are horribly poor at heat transfer--but not poor enough in their model to make them worse than electric stoves, induction or resistive.