Company seeks best way to produce power locally
Peggy Peattie / Union-Tribune
The PowerDish was invented, developed and produced by Infinia Corp of Kennewick, WA. It is a 15.4 ft diameter mirrored dish that concentrates sun energy onto a compact Stirling engine where it is converted into electricity. The PowerDish produces up to 3,000 watts of electricity.
Photo by John Gibbins – Union-Tribune
The Infinia Power Dish, a mirrored 15.4-foot-diameter parabolic concentrator that funnels the sun’s energy into a Stirling engine, is being tried out at an SDG&E maintenance yard in El Cajon.
One looks like a large satellite dish in which sunlight heats an engine humming like a very loud fluorescent light bulb.
The other is like a big pizza box on top of a pole where dozens of thumbnail-sized photovoltaic panels silently convert the sun’s rays into electricity.
Both follow the sun throughout the day and are more powerful than the typical photovoltaic panels on rooftops around town.
Installed recently in an El Cajon maintenance yard, the two systems show technologies that San Diego Gas & Electric Co. is considering as it works to significantly increase the amount of power it gets from the sun.
The idea is to figure out what technology works best in urban areas for generating power without burning fossil fuels.
Big for-profit California utilities will be required to get a third of their power from so-called renewable sources by 2020. And they can’t count the rooftop solar panels installed by their customers.
SDG&E’s requirements are so great, it is looking for the best way to produce power locally, said Jim Avery, the utility’s senior vice president for power supply.
Even with the proposed Sunrise Powerlink, the controversial $1.9 billion transmission line that would link the county to the Imperial Valley, SDG&E can’t import enough of the power from so-called renewable sources.
“We need renewables here in San Diego,” he said.
The company is looking for technologies it can use itself and that can be used by private companies which will build systems and sell the power to the utility.
The big dish on display Wednesday uses a Stirling engine, which converts the sun’s heat into mechanical energy, which then drives a generator.
Developed by Infinia of Kennewick, Wash., the dish collects the sun’s rays and focuses them on an engine that heats up to 1,200 degrees Fahrenheit. The heat expands helium, which drives a piston and then moves into another chamber, where it moves another piston as it cools and contracts.
“You can put this in an urban area,” said Charlie Walker, an Infinia salesman. The concept is similar to that behind a massive solar farm proposed for the Imperial Valley, he said.
The pizza-box like panels were made by SolFocus, of Mountain View. They use curved mirrors to concentrate sunlight on tiny, highly efficient, photovoltaic chips.
The idea is to save money on the most expensive part of a solar panel, the silicon that does the work of turning light to electricity, said Nancy Hartsoch, a SolFocus vice president.
Her company’s product is 50 percent more efficient than traditional photovoltaics, but uses 1,000 times less silicon, she said.
Both companies said their technologies require about 5 acres to make 1 megawatt, or enough power for about 650 homes.
The test installations SDG&E showed off Wednesday are not its first. Last year, the utility installed a test system developed by Pyron Solar of Sorrento Valley that uses floating photovoltaic panels.
By Onell R. Soto, UNION-TRIBUNE STAFF WRITER
Wednesday, June 2, 2010 at 8:27 p.m.