Solar air conditioners to chill California utility

Southern California Gas company is testing how well the sun can cool buildings.

The Los Angeles-based utility said on Tuesday that it has chosen two solar concentrators to measure how effective they are at cooling. The units will be installed on the roof of its Energy Resource Center (ERC) in Downey, Calif.

Both products--one from Hawaiian start-up Sopogy and another from HelioDynamics in the U.K.--reflect and concentrate incoming sunlight onto a pipe to heat water. That heated water is used in place of gas or electricity to power an industrial absorption chiller, which creates cold air using a heat exchanger and compressor.

(Credit: Sopogy)

Using the sun for cooling has long been considered an excellent application for solar energy because the air conditioning load corresponds with daylight hours Concentrators can be more efficient and take less space than photovoltaic panels which make electricity, according to Southern California Gas.

Sopogy's MicroCSP is essentially a shrunk-down version of the parabolic troughs used in giant solar power plants. HelioDynamics' concentrators can produce both heat and electricity.

Southern California Gas chose these concentrators because they are small enough to fit on an office building roof and are modular, said Hal Synder, vice president of customer solutions. Each unit is capable of providing enough cool air for three average-size homes. Air conditioning can be half of a commercial building's electricity use.

The utility plans to test these concentrators for two years and will add electricity production to the site in a year.

There are already a handful of companies developing concentrators for cooling. Chromasun, started by one of the founders of concentrating solar company Ausra, has developed a solar collector designed for commercial and industrial customers which can reduce energy bills significantly by cutting peak-time usage.

Meanwhile, there is already a solar cooler in operation. Late last year, famed piano maker Steinway & Sons installed a solar cooling system that uses reflective troughs. Like the SoCal Gas systems, the heat feeds an absorption chiller to provide cool air and dehumidify Steinway's buildings. In the winter, it provides heat.

[NocturnalCT]

Interesting. Using waste heat or solar power sounds promising, as long as the machinery is cheap enough that it saves more power in its life time than what it cost to produce and maintain it. I'm not familiar with absorption chillers so I found this Wikipedia article that may be worth reading: http://en.wikipedia.org/wiki/Absorption_chiller .<br /><br />http://www.absorptionchillers.com/ has some no-nonsense application criteria as well:<br />------<br />Absorption Chillers may be worth considering if your site requires cooling, and if at least one of the following applies:<br /><br /> *<br /><br /> You have a combined heat and power CHP) unit and cannot use all of the available heat, or if you are considering a new CHP plant<br /> *<br /><br /> Waste heat is available<br /> *<br /><br /> A low-cost source of fuels is available<br /> *<br /><br /> Your boiler efficiency is low due to a poor load factor<br /> *<br /><br /> Your site has an electrical load limit that will be expensive to upgrade<br /> *<br /><br /> Your site needs more cooling, but has an electrical load limitation that is expensive to overcome, and you have an adequate supply of heat. <br />------<br /><br />This seems to suggest it may not be feasible to install these units if there's sufficient electrical power available at the site, something that's unlikely at Steinway. Then again solar heat definitely qualifies as for the 'waste heat is available' check mark.<br /><br />Thanks for posting!

[zyxxy]

These would provide nice supplemental cooling during the warmest part of the day, while the sun is shining. I can see having a hybrid system with traditional electric powered chillers sized for the 24/7 load and then having supplemental solar powered absorption chillers to combat solar heat gain during the day.<br /><br />I think if you measure the efficiency of direct solar heat driven absorption cooling to an indirect solar to electric to traditional electric cooling, that the conversion losses from the indirect method are very high.

[mgpc]

These units are definitely not the first in the United States. There is at least one installed in Florida, and Maryland Green Power Co is installing one in Washington, D.C.<br /><br />The construction, however, is different. Maryland Green Power's system uses vacuum tube solar collectors to concentrate heat.<br /><br />Why reinvent the wheel? The solar thermal technology to accomplish solar air conditioning is already being mass-produced.<br /><br />Also, it is very tiring when other companies put a tiny solar panel on a roof and use it to feed a d.c. compressor. That is a very poor, linear application of technology.<br /><br />More information on solar air conditioning on MGPC's blog:<br /><br />http://www.marylandgreenpower.com/greenpower/

[americanmicrosolar]

my company have an evacuated tube thermosyphon unit being certified in the US at this time that is far less expensive than the solar concentrators mentioned in the story. It is capable of boiling up to 90 gallons of water with no pumps or electricity needed. just mains water supply. Alternatively another medium can be used for much higher temperatures. It seams sometimes we try to re invent the wheel rather than admit others may already have a good design Allan