It's not as common as solar photovoltaic panels, but Hawaiian start-up Sopogy thinks small-scale solar thermal makes sense. Photos: Concentrating on solar power in Hawaii
Start-up Sopogy, based in Honolulu, has taken the basic design of large solar thermal power plants and shrunk it down so it can fit on a building's roof.
Demo models of its electricity-generating solar collectors--essentially metal half-pipes with a reflective coating--are now being tested with a Fortune 500 company and a few utility customers, according to company president and CEO Darren Kimura.
To expand, this fall the venture-funded company intends to raise an additional $9 million, which it hopes to secure by the end of the year, he said.
Concentrating solar power, or CSP, uses reflective troughs or dishes to concentrate sunlight to heat a liquid that flows through a pipe above the troughs. That heated liquid, which can be oil or water, is converted into steam to turn an electric turbine.
On Monday, start-up Ausra announced that it has received $40 million in venture funding to finance product development and construction of a large-scale 175-megawatt solar thermal power plant in California.
That's one of many projects, such as Nevada Solar One, now being pursued in desert areas around the world. The customers are utilities, which need to boost the amount of renewable energy they generate to meet government regulations.
But Sopogy's thinking small. Each individual collector produces 500 watts. That's roughly what a house consumes, but strung together in an array on the ground or on a roof, these panels could supply a chunk of a commercial building's needs, for example.
In a project in Hawaii, the company will be connecting several of its MicroCSP units together to generate one megawatt, according to Kimura. That plant, now in the permitting phase, is expected to go online in January of next year and be completed by late summer.
Last month Sopogy signed on Avista Utilities, based in Spokane, Wash., to test the system in northern Idaho scheduled to be operating by next summer.
Coal or natural gas-fired power plants can generate tens or hundreds of megawatts. But utilities are looking at different options for power generation during peak times, such as the middle of a hot day, when the demand--and price--of electricity is highest.
"On balance, CSP has a huge advantage in most cases over say, wind, because it produces power when people need it the most," said Alex Klein, an analyst at Emerging Energy Research. "CSP projects are effectively competitive at higher prices because they are generating electricity at peak times."
Solar systems--both thermal and photovoltaic--also have the advantage of being modular, so as they are scaled up, the price per kilowatt tends to go down, Klein added.
Corporations such as Wal-Mart, which is installing solar systems in Hawaii and California,
Industry experts foresee wider adoption of solar thermal power plants in desert areas because, with government incentives, they approach the cost of power generation from fossil fuels.
The U.S. National Renewable Energy Laboratories estimates that solar thermal technology can supply hundreds of gigawatts of electricity, or more than 10 percent of demand.
Ausra CEO Peter Le Lievre earlier this week said that
By contrast, Sopogy's approach is to generate electricity on-site and in a wide range of environments, not just deserts. Apart from providing ample heat, coming from Hawaii gives the company an excellent test ground, Kimura said.
"Hawaii has a harsh environment. There are earthquakes, storms; there is salt water in the air (which can damage mirrors). Since it's designed to work in Hawaii, it'll work virtually anywhere in the world," he said.
The company is using nanomaterials to coat the reflective troughs to make them more durable, he added.
Commercial customers can use the steam for purposes other than generating electricity, such as heating or cooling through absorption air conditioners.
The cost factor
An important piece of data still needed on Sopogy's demonstration systems is cost per kilowatt in different areas and at different times of the year.
Right now, its system can produce electricity at somewhere between 12 and 16 cents per kilowatt-hour. That's higher than fossil fuel sources of power, but Kimura expects the price to go down if products can be manufactured on a larger scale.
Also, renewable energy sources benefit from incentives. And distributed generation has the advantage of competing with retail electricity prices, which are higher than wholesale prices from power plants.
Emerging Energy Research's Klein said that 16 cents per kilowatt-hour for a small-size CSP system would be compelling, although he's doubtful it can be done now.
At that price, Sopogy's MicroCSP system would be competitive with solar photovoltaic (PV) panels that convert sunlight into electricity, or concentrating solar photovoltaic technology, where lenses focus light on solar cells to boost output.
"It's an interesting model because it does present a competitor for solar PV. But it depends whether they can demonstrate that they can compete on cost and ease of installation," he said.
Another important consideration is the ongoing maintenance costs, noted Reese Tisdale, a senior analyst at Emerging Energy Research. Because there are few moving parts, solar PV installations tend to have a simpler maintenance.
Tisdale said Sopogy appears to have a unique approach in the solar thermal world. But other energy companies have shrunk down large-scale power generation technologies to a smaller scale. For example, Infinia is making a relatively small solar Stirling engine.
"It's another alternative. I definitely think it's worth exploring," Tisdale said.