The solar heat pump concept is simple: zeolite in one container, water in another container, containers connected with a pipe, suck out the air which causes the water to boil at ambient temp., the zeolite absorbs a lot of water vapor and heats up; the water cools down. To reset, just heat the zeolite with solar, waste heat, etc, to dry it out. When it’s hot outside distribute the cold from the water. When it’s cold outside distribute the heat from the zeolite.
Zeolite is about $30 US per 100 pounds in 50 pound bags (2011 dollars) ZEOMAX Zeolite Turf Aid 50 lb, more expensive in smaller quantities Kitty Crystals Premium Cat Litter 24 lb. (Probably less directly from a mine.)
Zeolite is safe; it’s used in many applications from soil amendments and deodorizers to health products.
Experimental results show the system provides about 500 BTUs to 1300 BTUs per pound of zeolite depending on the quality of the zeolite, natural is better than synthetic. The typical home in the US requires about 36,000 BTUs per hour (3 ton heat pump) for cooling which is 864,000 BTUs per day. That’s about 1000 pounds of zeolite to cool a typical US home, every day, all day: no CFCs, no carbon footprint, no greenhouse gasses, DIY friendly, safe and relatively inexpensive, very low electrical energy for the vacuum pump (solar friendly). Its use for refrigeration in underdeveloped places is obvious.
It’s safe, simple, inexpensive, eco-friendly and can be a major component of off grid systems. So why haven’t we heard about the zeolite heat pump? The truth is that the information is obscure, buried amid so much clutter that few have ever heard of it in relation to solar energy. Even Wikipedia only mentions it in passing for solar panels, its use in heating and refrigeration or solar air conditioning. When you do a search on zeolite you get inundated with health supplement links. (Evidently some people believe it cures cancer, prevents bone loss and detoxifies.) There is very little on the Internet about how to use it as a heat pump. Following are 3 of the best links:
I plan on doing some tinkering with it in the not so distant future. Below are some technical data that may help you with your tinkering.
Water boils at 70F at 3.75 psi, 60F at 3.5 psi, 50F at 3.25 psi, 40F at 3 psi (approx values)
Zeolite Density (about the same as water): 0.9-1.1 grams per cubic centimeter
Temperature required to dry zeolite: 300F (150C) (minimum, 250F (120C))
Recommended operating pressure: 1-2 psi (about 1/10th atmospheric pressure)