Same principle, but the systems use tubes of water vs. tanks. The tubes are heated and cycled to the hot water storage tank. There's some nifty ways the modern systems trap and concentrate the heat (glycol solutions, evacuated tubes, reflective parabolas, etc), but at their core they're simple systems. Not much to break, and quite efficient.
Although most applications are for domestic hot water use, you can supply a heating system as well which some folks do, such as with radiant floor heating. It might not be enough during the winter to heat the water fully to heat the whole house, but it can boost the water temp from 50 degrees to something higher than that, which saves energy.
Typing too fast. I meant the WATER in the tubes is heated...