DIY doesn't come with those asterisks, and DIY with only-thermal power use & energy storage is on the simple side of things. "Help me heat in the winter" is ba

DIY doesn't come with those asterisks, and DIY with only-thermal power use & energy storage is on the simple side of things. "Help me heat in the winter" is basically the simplest use-case, because you can accomplish it with a south-facing solar fence and some resistors [or an inverter + space heater, or whatever]. Personally I like the idea of a three-season thermal mass store, a big tank of water or pile of sand that you dump heat into when it's sunny, and extract it at will the rest of the day/week.