OK, here is an idea for do it yourself solar heat...

You get an ordinary small refrigerator.

You get 5 to 10 one gallon containers of ordinary water.

Paint the continers black if you like.

Build a small glass enclosure outside that you place the containers
full of water so the sun can warm them but they are isolated from the
cold air. By the end of the day they are warmed to say 70 deg F.

At night, you bring the containers of water inside and place them in
the freezer section of the fridge. The fridge proceeds to pump the
heat out of them and into your home. After say 8 hours they will
freeze and you will have extraced the specif heat as well as the
latent heat of fusion by freezing the water.

The next morning, you place the containers now full of ice back out in
the sun to thaw and re-heat.

So the beauty of the system is that it uses freezing water which is a
good carrier of heat energy (due to the latent heat of fusion) and at
a good temperature for extracting heat out of the sunlight (32 def F)
and an ordinary refridgerator is a good machine for freezing water.