Intriguing, but wouldn't it be even more efficient to just paint something black and let the sun heat it directly?

At the cost of very efficiently radiating that heat back out into space at night.

Making electricity and then using that electricity to heat something elsewhere lets you insulate, effectively allowing you to create a box that heat energy can only pass one way.

You'd need some kind of storage for the heat, something with a large thermal mass that doesn't readily give up it's heat to the surroundings. Sand or water or even big rocks or a thick slab of concrete.

depends how hot you want to get something