Cold Desert Water

Except for the costal region of Peru, deserts typically have very low humidity and hence a low greenhouse effect. This means the nights get quite cold as heat is radiated to the 2 degree absolute blackbody of space. To capitalize on that only requires creating a radiator that can be fed heat from an insulated body of water. Of course one can collect heat with the radiator and feed it into a hot water heater.

Insulate a tank of water. Put a heat valve tube through the insulation at the top. Do the same with another insulated tank of water except the tube comes out the bottom. Connect the top of the bottom tube to the bottom of the top tube. At this junction put a big chunk of metal with a hole at its side. In this hole put the end of a heat pipe that also runs down the length of a black body radiator.

During the day, the radiator heats up, hopefully above the temperature of the hot water. The heat pipe delivers heat to the heat valve which takes it to the hot water tank. At night the radiator radiates its heat to the black body of the sky, it cools off, hopefully to below the temperature of the cold water. Heat will then be delivered to the heat pipe via the lower heat valve.

With a sufficient area of radiator and volume of water, enough hot and cold water should be created to climate control relatively large greenhouses. If cold enough, the cold water ought to be able to cause condensation reducing the humidity in the greenhouse with a simple water tower. This would also recover some of the evaporated water and creat temperature differences for air flow.