Solar Cooling
Residential/ Small Commercial Scale Solar Cooling
Spanish company Rotartica has put together a residential scale AC system that runs off of hot water (at temperatures between 90 and 120 degrees C).
Indian company Thermax, on the other hand, has absorption chillers that run at only 75 degrees C – much easier and more efficient to produce out of a flat plate collector. But its low temperature units only run a single-effect cycle – essentially negating the efficiency boosts of taking in low-temp water.
Rotartica’s system is superior in many ways, in that it is compact and self contained (it looks like a normal residential air handler), and uses a rotary heat pump design that significantly decreases the amount of space required to operate the system. Moreover, Rotartica’s smaller systems can be run without any sort of cooling tower – which is a major point in their favor. Rotartica’s main unit does about 4 kW of real cooling work (according to the DOE and Oak Ridge National Laboratories), equivalent to about 1.15 tons of chilling. But their high-temp systems really require evacuated-tube based collectors, which are more costly, and often less efficient, than flat-plate collectors. Still, with the savings realized from not needing a cooling tower…
The third solar cooling company I’m investigating right now, and the one I’m growing quite fond of in this market sector, is ClimateWell. Their systems (which come in 10 and 20 kW models that in reality only produce about 5-6 kW of real cooling per 10 kW of claimed capacity) are designed to run off of flat-plate collectors, and seem well designed, mature, and sleek. That, and they have a sweet web page with lots of technical drawings and specifications posted, which I really like. Navigate to their specs using the “Documentation” tab in the lower row of buttons on their page, or go to their “How It Works” section for an illustrated absorption chilling walkthrough that doesn’t take an engineering degree to understand. A particularly cool whitepaper in this section details their “Three phase” system, which simultaneously utilizes the heat storage capacity of solid salts while still making use of the high charge and discharge capacities of fluid salts. They explain it better than I possibly could.
Two more companies with interesting, high quality products have also recently come to my attention: SonnenKlima, whose 10 kW (2.85 ton) LiBr chiller seems to be the most efficient in the business, and SolarNext, who manufacture and ditribute what might be the most diverse selection of small scale absorption and adsorption chillers on the market. They have some of the most efficient small scale silica-bed chillers out there, which makes them quite attractive from the standpoint of not having to deal with hazardous chemicals.
The Wikipedia page on solar AC is also well worth a look if one is unfamiliar with certain aspects of the industry or want a refresher One of the things it covers is the difference between AB-soprtion and AD-sorption, which is crucial if one wishes to understand the various phrases being batted aroud on many of these websites and reviewer’s panels.
US company Coolerado, while not really solar based, is producing highly efficient evaporative AC units that are ideally suited for hot, dry environments, like the US Southwest and California, or Spain, Southern France, etc. Unfortunately, in North Carolina, where I live, and much of the East Coast, the humidity simply makes such systems nonviable. But their systems are really efficient, made of high quality materials, and designed to be recyclable. Cradle to cradle makes me smile, so I thought they were worth a mention.
Finally, there’s one other cool technology worthy of mention: The Ice Bear, an interesting technology that stores grid energy in (you guessed it) ice at night, to be used in assisting cooling loads in the heat of the day. By using the energy at night and making use of it in the day, it increases off peak power usage, delivers more overall energy efficiency, produces less carbon emissions because of less peak power usage (peak production is most often supplemented with coal and/or natural gas power plants), and is generally a pretty clever technology, especially in the world’s drier climates, where lower night temperatures make this technology more feasible than in the muggy, high humidity eastern seaboard where temperatures stay high all night. This is a mature technology that is being widely implemented in the US right now, and well worth a look.
That’s it for now – more will be upcoming as the research goes on. Feel free to comment, and let me know if there are any systems or companies missing from this list. Thanks!
