Solar energy without panels

I think Harold Hay should get credit for this invention. A solar system operated without any electricity or rather call it Passive Solar Technology. Hay's basic concept was to make use of a roof-pond or an area of water-bags to mainain consistent temperatures indoors during summer and winter. During summer, the roof pond is covered,heat is kept out and you feel cool indoors during the day. At night, the roof pond gets exposed and radiates heat out into the air, still keeping you cool. During winter, the roof pond absorbs heat during the day and the covered roof at night maintains the heat indoor using this "absorbed" heat".

This makes use of water's ability to absorb heat.