we do. they are about the size of a solar panel, look similar and are on some roofs of houses in my area. the ones i’m refering to are not for boiling water, just for preheating so need less energy when it goes back into the [ger: heizungskreislauf]. all the ones i know are older then the current solar panel boom. fun fact, there are even concepts (and implentation, but i can’t find it) for vacuum glas tubes that have a parabolic mirror around a black painted copper pipe, which should be able to generate ~400 °C “process heat”. but they are not wide spread, cause solar is so much cheaper now