Hi Laurina and welcome to the BrickWood forum!
Sorry for the slow reply—I’ve been off the boards for a few days.
Your suggestion is intriguing, and personally I’ve not seen any examples of that kind of recapture in this particular application. But it sounds viable as long as you plan ahead.
This would be similar to methods used in ordinary hot water heating systems. In New England many of my neighbors still depend on oil-fired furnaces for their winter heat, though that’s starting to fade away as we bring more solar and wind-generation technology online. One common setup for heating domestic hot water is to run a fluid coil into the furnace, flash-heating the fluid and then circulating it to an insulated hot water tank. There it heats the water, loses energy, and is returned to the furnace to repeat the cycle.
Solar hot water systems were also common 25 years ago, before solar energy panels displaced them. Same idea.
The principle there depends on capturing energy that would otherwise go unused, or is being expended specifically for the purpose.
I’m not sure you’d apply it to a wood fired oven like these designs. Two things come to mind:
- The oven is heavily insulated so that heat is captured, stored and refracted back into the oven cavity. That’s how it achieves the temperatures needed for this kind of cooking. You wouldn’t be capturing “surplus” heat, but rather what is needed for the oven to do its job.
- In practice the oven might be fired, at most, 3 times a week (and blessings on the folks who are doing it more often!). It would be such an intermittent and irregular source of alternative energy that it might not be worth the expense.
So I’d suggest it’s not at all impractical, but you might want to talk it out a little more.
Hope this helps!