What would be cool is to be able to harness waste heat better. For example, using the exhaust from my air conditioning to supplement the hot water heater.
It's just an expansion of how car heaters work. Unless you drive an electric, when the car is moving, heat is free. This is because waste heat is diverted from the radiator to heat the cabin. It's heat that would be generated anyway.
@TranimeGirl just read something about harnessing the cold of space. And there is the girl that did the science project where she created a flashlight that operated on the heat of her hand. Has to do with peltier tiles. Just needs a temperature difference.
https://inhabitat.com/15-year-old-develops-hollow-flashlight-powered-by-body-heat/
@TranimeGirl they are definitely different from photovoltaics. But there are certainly passive solar like pool heaters and such, but certainly adding a pentier panel to one side might harness some waste heat.
@Absinthe I'd like to see peltier technology improve. Solar panels are great and all, but I bet we could get more power by the sun making things hot on one side. This wouldn't work well in all climates, but in places that are fall like most the year, this might work very well