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.
If giant solar thermal power plants spread across the desert are like a mainframe, Sopogy is making the equivalent of a personal computer.
The Hawaii-based company on Tuesday at the Intersolar 2008 conference will show off the latest version of its MicroCSP--essentially a shrunk-down version of concentrating solar power (CSP) equipment used in power plants.
The SopaNova 4.0, a "micro concentrated solar power" trough, has been redesigned to be longer and use less material.
(Credit: Sopogy)It's a trough with a reflective coating that focuses sunlight onto a pipe that carries an oil. That heated liquid goes through an organic Rankine cycle engine to convert it into electricity.
The conventional thinking in solar these days is to think big. Proposals for concentrating solar power plants call for hundreds of rows of troughs or mirrors to make steam to drive an electricity turbine. The output of these proposed plants will be hundreds of megawatts, approaching the size of traditional power plants.
Sopogy's product, called SopaNova 4.0, is aimed at utilities as well, but for smaller-scale projects, in the range of 250 kilowatts to 25 megawatts. The latest edition is longer--between 12 feet and 18 feet long--than previous editions because of a new manufacturing process.
"On cost per watt, we're cheaper than PV (photovoltaics)," said CEO Darren Kimura. "But that's not what really matters. We can do more production. We actually get more sun energy every day."
With a higher output, the payback on an initial investment comes quicker, he argued. The troughs can be used by corporate customers as well for on-site power generation.
In terms of the efficiency of converting sunlight to electricity, the SopaNova is between 20 percent and 30 percent, he said. That's lower than its larger CSP cousins, which operate at higher temperatures, but better than most solar photovoltaic cells.
Unlike flat solar photovoltaic panels, solar thermal systems have storage today. In practice, Sopogy's trough systems can store a few hours worth of electricity, which can be used when electricity is more expensive or when there isn't light.
Sopogy is thinking relatively small when it comes to its own capital needs.
The company raised $9 million in venture funding earlier this year and got a $35 million special-purpose bond from the state of Hawaii.
Later this year, Sopogy will look to raise another round of equity, which will be more than its past round but far less than the huge deals--some topping $100 million--announced by traditional CSP companies.
"We're trying to demonstrate that you can do solar technology but still be capex (capital expenditure)-light," Kimura said.
Ultimately, the company intends to go public. "The goal in solar is to become a really big company and the market space allows for that. If you don't, you'll get acquired," Kimura said.
The company has about 20 customers now. The Natural Energy Laboratory of Hawaii recently broke ground on a project to install thousands of the troughs to ultimately make one megawatt of electricity.
The troughs can also be used to generate process heat, which can be used in a variety of applications, Kimura said.
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