Yeah, that's my thought. Think heat exchanger, not heat engine. If you managed to get your input water at 10C from the ground up to 30C, you'd have very little

Yeah, that's my thought. Think heat exchanger, not heat engine. If you managed to get your input water at 10C from the ground up to 30C, you'd have very little left to do before it's usable in a shower. Either way, the thermal mass of the flowing cool water will definitely improve the solar PV efficiency and lifetime.