Been revisiting one of my older ideas regarding energy independence. It is basically a very large(room sized) heat engine designed for very long uptimes and durability. Think decades. It would use a low temperature differential and have abysmal efficiency, but it could be built and maintained with off-the-shelf parts. All it needs is hot water. Heating water with solar thermal is debatably cheaper than photovoltaics, but even if it’s not, the goal is a low tech solution.