Solar Cooling – using solar heat to cool our buildings!
By Solar Oregon Board Member Bruce Barney
Most of us would say that it is really hard to make solar thermal panels work for space heating in most of Oregon; after all, when we need the heat is when the days are the shortest and the sun is at it’s lowest point in the sky….But what about using solar thermal panels to cool your house in the very sunny summer months in Oregon?
Recent advances in absorption chiller technology are starting to make solar cooling (i.e. solar air conditioning) become economically feasible. How does it work? Well, it is easy to chill water with a regular refrigeration cycle and distribute the cold water through a bulding’s air handlers to provide cooling, but absorption chillers do this with an input of heat. (Have you ever seen a propane powered refrigerator in an RV or remote cabin? – same idea.) The technology has been known for a long time, but it has never made economic sense to use it because it used so much energy to generate the heat. That, in concert with low efficiencies and high costs, led absorption chillers to be rarely used, and then typically only in applications with a source of ‘free’ heat.
All that is starting to change with the increase in the cost of energy and new technologies in absorption and in solar thermal collectors. The bottom line is that solar thermal energy is starting to make sense as a source of air conditioning! What a great way to use our solar resource! There are even a few firms making solar coolers for residential applications. It seems the typical system uses evacuated tube collectors to generate the hottest temperatures possible, (which makes the absorption process more effective/efficient). The hot fluid can be sent right to the absorption device or can even be stored to allow air conditioning when the sun is not shining.
A little research will show that solar absorption cooling is already being explored aggressively in Europe, so it won’t be long before we start hearing a lot more about it. As the world’s population continues to grow and develop, the need for air conditioning will only increase. Perhaps the solution to the problem will once more be solar energy!
Here’s an interesting home brewed ice maker that discusses some of the theory of solar cooling in an easy to understand way: http://web.archive.org/web/20011116075625/http://www.humboldt1.com/~michael.welch/extras/solarice.pdf