38kg is just over 10 gal. Of course, that's the approximate expected daily output for a 1kW source of heat. You may be able to get a lot more solar heat than that. A typical average solar energy input is around 280 W/m2
. If you're in some sunny desert you may get more. If your gathering area is comparable to your pool area (~100m2
), then you could get around 30kW. That would get you around 300 gal/day.
Depending on what your scarcest resources are (start-up money, land, salt water, ...) you may be able to do better. The thermodynamic limit is certainly a lot better, because when you let the input solar energy just heat up water you throw out quite a lot of its free energy, the parts due to its frequency spectrum and to its narrow range of directions. There are ways of harnessing those parts (photovoltaic cells, solar concentrators via mirrors) to use the solar power to generate electricity. That electricity can then be used to drive a heat pump, heating up your salt water and cooling the metal baffle. So long as the waste heat of the electrical generation process is used to also heat the saltwater, you'd get more water out per amount of land used, although with higher initial capital costs.
(published on 02/12/12)