Photovoltaic panels are noted for their ability to convert sunlight into electricity. But for a long time passive solar collectors have been used to provide hot water and heated air to residences and commercial businesses. Now a company in California is using the heat from solar to cool buildings. The company is Cogenra Solar. The product is called SunDeck. A 20 SunDeck modular system recently was installed on the roof of the Southern California Gas Energy Resource Center, a building that accommodates 700 staff and contains office space, workshops, an exhibit hall and conference rooms. The 20 unit installation generates 50.2 Kilowatts producing enough electricity to power the building, and enough heat to drive a single-effect absorption chiller to provide air-conditioning.
Solar panels are effective collectors of heat but not terribly efficient in generating electricity. At best panels convert at a rate of about 20%. But by building co-generation technology into the panels, energy conversion achieves 75% efficiency because the excess heat gets captured and stored as latent energy in liquid. That liquid then gets used to operate the cooling technology which is very similar to traditional absorption chillers except that no additional energy is required to create the cooling effect.
For Southern California Gas the ability to do co-generation using solar gives them a renewable energy solution that can help their customers dramatically reduce fossil fuel energy usage. And that translates to significant operational savings for both the utility and its customers.
Each SunDeck unit generates 10 tons of cooling , enough to cool two normal homes. The units lower greenhouse gas emissions by an estimated 50-60% from traditional photovoltaic systems. Payback ranges from three to five years.