Absorption chillers have been around for over 150 years. This is not a new technology. They are still used today. If you have an RV then you may have an LPG driven absorption refrigerator. You can even purchase an absorption refrigerator/freezer combo unit for your home today. I am sure many are in use in off-grid homes today. The question I have is, Can one use the hot water from a solar hot water heater to drive an absorption chiller?

First, what is an absorption chiller? Absorption chiller uses the process of evaporation and condensation to cool. I am not going to try to fully describe it, but I will point you to a good link or two. Basically, you use heat to generate cold. The heat we want to use is from a solar hot water heater.

Herein lies the problem, efficient absorption chillers require water of at least 190 °F (88 °C). How can I get that kind of heat from a typical solar thermal collector? So I started Goggling. And what should I happen to find. A company that makes solar absorption air conditioners. When I first looked at them I thought it was the same old PV driven air conditioners. No sir, it was indeed what I was looking for.  They do use an evacuated tube thermal collector. This will give you high water temperatures. So it can be done. But you need a cooling tower. Nobody wants a cooling tower next to their house. Too much maintenance. I would want a “Normal” A/C radiator unit outside my house to reject heat. That, and the smallest unit is 10 tons. That would cool your house off in a hurry.

I am sure it can be done. I have seen on the internet smaller chiller units. One could setup a more normal external cooling tower. Since most new chillers are double effect, at least the BTUs you put in is what you get out. Since summer time gives you the most BTUs, I think some day it will be worth another look.

I leave you with this link. Low Firing Temperature Absorption Chiller System A student, ,KEVIN A. GOODHEART, submitted this paper toward completion of his MS ME. A nice piece of work that I will have to read fully at a later time.