Simple Solar Heat Pump, Heating and Cooling

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.

Small scale experiment here and here. (You’ll need to scroll down a bit.)

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:

Scientific Paper on Developing it for Solar (PDF, good data and technical details)
It’s use as a Beer Keg Chiller (click on the products tab or zeolite technology tab)
An Experiment at an Eco-Village

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)

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7 Responses to Simple Solar Heat Pump, Heating and Cooling

  1. JC says:

    Great idea. What do you use for your vacuum pump.
    Also I wanted to mention what a nice job you did on your WordPress page. Any tips on how to get it to look so cool?
    John.

    • genecurtis says:

      I haven’t tried the experiment yet, but I plan on using an old modified air compressor, reversed to work as a vacuum pump. Just about anything that can draw the system down to 1 psi should work.

      Thanks for the compliment on the blog site. I used the 2010 theme and uploaded the book cover header from art I created. (Books I’ve written or compiled.)

  2. Poodle Head Mikey says:

    I have been pondering that “simple solar heat pump” link/drawing that somebody posted. Can you explain it to me? Because I have some questions.

    Stated and drawn:

    Water in one container.
    Zeolite in another container.
    The containers are connected to each other and to a vacuum pump.
    The vacuum sucks out the air which causes the water to boil at ambient temp.

    I’m OK to that point.

    But the: “the zeolite absorbs a lot of water vapor and heats up; the water cools down” part seems to be plain wrong. How does the zeolite absorb any water vapor? The same vacuum pump evacuation which boils the water would pull the water out of the zeolite just the same way. Wouldn’t it? That’s one.

    Another is: how would any water vapor even access the zeolite? Wouldn’t it all be pulled out through the vacuum pump?

    And finally: if we are boiling off the water under vacuum – don’t we fairly quickly run out of water? Doesn’t the water just vaporize, get removed through the vacuum pump, and so be lost to our process?

    What am I missing here?

    • genecurtis says:

      The system pressure is pulled down until the water starts to boil and then the vacuum is closed off. The zeolite locks the water into its crystal structure and is released by heating, not by the vacuum.

  3. Poodle Head Mikey says:

    That doesn’t make sense to me. If the vacuum pump is turned off – what maintains the vacuum? With water continually boiling off vapor into the low pressure area above it, without the vacuum pump running the pressure will immediately rise. Won’t it?

    PHM
    ——–

  4. J Ahmad says:

    well, Poodle head.
    this experiment is based on proven theory and facts.
    this is known as adsorption cooling.
    It is being used for large scale solar airconditioning projects.

    • Poodle Head Mikey says:

      I don’t dispute that the experiment is based on true facts. All I am asking is to have the physics of the project explained in a cohesive and logical way. I am very familiar with refrigeration theory and design, including adsorption cooling. But based on what I know and on what you have said; I cannot see how the energy required will accomplish what you stated that it will. All I am asking is that it be explained in some reason-filled way.

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