Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.
Talk:Solar thermal energy
There's one fairly obvious approach to solar thermal I've never read about, presumably because it's considered impracticable.
In a hot desert with land to spare, you could bury water pipes near the surface in two adjacent plots of land. Horizontal insulation (mineral wool?) panels would be moved at dawn and dusk so as to create permanently hot and cold plots; constructing the panels is likely to be the most difficult aspect to realise.
The arrangement could be suitable for space cooling, water distillation and driving a heat pump. The warm water might boost the yield of a relatively small concentrating-solar heater. Possibly, a small heat pump would be sufficient for moving the water around.
Perhaps this idea could be used for space heating in high altitude places with high winter insolation, for example much of Armenia.