|The old stove on left features a "thermodome" that lowered over the cooking pot after the heat was turned off.|
OK, after our recent experiment, I admit I am obsessed with thermal cookery. Or to be more exact, I have always been obsessed with energy efficiency.
The efficiency of a modern electric cook stove has a thermal efficiency of about 15%, meaning that 85% of the energy is wasted. This is partly because converting fossil fuels to electricity produces an energy efficiency of 20-45%, depending on the power plant.
There is much room for improvement, since this is about the same efficiency of an open fire, a truly ancient technology.
One way we can improve on the efficiency of the cooking process is by using thermal retention which prevents heat loss to the point that food continues cooking without additional energy.
Using thermal retention to cook foods can save up to 80% of the energy required for normal cooking, depending on the thermal cooker and heat source used, and on how long it takes to get the hot pot into the cooker.
An electric stove, when used with a thermal cooker, doubles its efficiency to about 26%, which still is not that good, but much better than the electric stove alone.
|This old stove shows a "thermowell", a built-in thermal cooker. With the pot shown, one could cook three different foods in one pot.|
Around the early 1900s, kitchen stoves were designed with heat retention features, and were called "fireless cookers". Some old stoves had insulated bells that lowered over cooking pots to retain heat (marketed as "thermodomes"). Others had thermal cookers or insulated "wells" built right into the cooktop that pots could be lowered into for thermal cooking.
One such stove boasts of a "New and Improved Thermowell" that does one hour of cooking with only 10 minutes of energy use. Another was sold as the stove "that cooks with the gas turned off".
|A 1950s era electric stove that still featured a built-in thermal cooker.|
As power became more abundant, such efficiencies were lost. The good news is that we can re-introduce this energy saving technology quite easily in our modern kitchens with materials we may already possess.
Sample Cooking Times In A Thermal Cooker
White rice: 5 min on heat, 1-2 hours in cooker
Brown rice: 10-15 min heat, 2 hours in cooker
Potatoes: 5-10 min heat, 1-2 hours in cooker
Creamed soups: 2 min heat, 1 hour in cooker
Dried beans (soaked): 10-15 min, 3-4 hours in cooker
It is hard to imagine a more cost-effective technique to lower energy use than a homemade, DIY thermal cooker. See our post about trying out our first DIY thermal cooker HERE.