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.
http://minds.wisconsin.edu/handle/1793/7644
7 comments
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January 18, 2009 at 7:14 am
greenhomesamerica
Great question–and it’s being worked on. Evacuated tube technology holds an edge here on the collector size since it generates higher temperatures. When this scales down to residential size, it will allow us to increase size of the systems for winter collection and help solve the summer excess heat issue (while giving us “coolth” to boot!). But no need to wait. Solar hot water makes sense for homes right now–even in cold cloudy climates like the Northeast. Check out http://greenhomesamerica.wordpress.com/2008/09/12/shedding-light-on-solar-hot-water/
May 21, 2009 at 11:53 pm
Chuck
I am managing construction of a new green building in San Diego, CA–the Friends Center. I am working with a team of mechanical engineering students from the Jacobs School of Engineering at UCSD. We are seeking to model a system that can use conventional (not vacuum tube) solar collectors coupled with a lithium bromide absorbsion chiller. While very expensive systems using 10 ton chillers and vacuum tube collectors have been built (see L.A. Audubon Center) this technology needs to be made more accessible to the general public to make a difference. I believe this technology holds great promise.
July 1, 2009 at 3:21 pm
captbilly
There are certainly absorbtion chillers out there that will do the job, but in most cases the cost is very high for a residential sized unit. The cost per “ton” of cooling goes way down as the size of the absorption chiller goes up, so most absorption chillers are large commercial units.
As to the cooling tower issue. No chiller requires a cooling tower, but all A/C systems do require some way to reject the heat that is being removed from the building plus the waste heat due to inefficiency of the system. There is a small absorption chiller made in Spain that comes with or without a liquid to air heat exchanger. THe heat exchanger in this unit is similar in size and construction to the A/C condensing units that any home with central air already has. The other option for many homes is to use the swimming pool/spa as the heat rejection device. When using a pool, spa or pond as the heat sink you get the added benefit of essentially free pool heating.
An absorption chiller is more efficient if it can be powered by a higher temperature source, so evacuated and concentrating collectors work best, but the temperature requirements for many of the chillers is only in the 70C- 99C range, which can be achieved by many flat panels in summer time.
October 10, 2009 at 10:12 am
Adam Grant
What is the company in Spain that makes a smaller an absorbtion chiller unit?
I would like to contact them…!
October 11, 2009 at 9:17 pm
indianasolar
Your guess is as good as mine? I don’t know if Google works well for you in Spain but it does great hear in the USA. Give it a try.
October 24, 2009 at 2:03 am
K P Unnikrishna Panicker
I would like to know more about solar powered airconditioning system.
October 24, 2009 at 1:37 pm
indianasolar
As would I. Have you looked at the links in the blog.