Hawaii Demonstration Project Still Pumping Solar Thermal Energy

Solar thermal in HawaiiThe Sopogy Consentrating Solar Power Plant, located on the Big Island of Hawaii, produces enough electricity to power the Natural Energy Laboratory of Hawaii Authority and push plenty of power back onto the grid as well.

The 125 kilowatts of power the Concentrating Solar Power plant produces is just a fraction of the 500 kilowatts the solar thermal array could produce, said plant operator Dean Towle. Presently, the generator the plant uses can only produce 125 kilowatts. It's been noted, however, that Sopogy could install three more generators and increase the output.

“This was just intended to be a demonstration project,” Towle stated.

The demonstration was a success and Sopogy, which stands for Solar Power Technology, has been expanding and developing projects in California, Arizona, Mexico, Japan, the United Arab Emirates and other locations around the globe since the Big Island project was successfully completed in 2009.

The project uses cold water pumped from the ocean to chill fresh water and the solar thermal array to superheat an oil mixture that then creates steam.  The steam turns a generator motor and produces power.

“Two hours of running out here, I can heat 9,000 gallons of oil to 220 degrees,” Towle added.

Since the oil stays hot, he can generate power for a few hours whenever he wants it. If Towle were a utility, he might run it after the sun goes down for a few hours to meet peak demand. But since the energy is primarily used to power a nonprofit and everyone goes home at the end of the day, he saves the leftovers for the following morning.

The project was made possible by a $10 million loan from the state of Hawaii. Once the project got legs, investors helped to repay the loan. As a demonstration project, some pieces were experimental. For example, Sterling Engines were initially used to build and pump the steam. While the engines looked neat, they weren’t strong enough for the job and Sopogy had to adapt existing waste heat exchanger technology instead of building its own from scratch.Sterling engines

The generator motor is magnetized and frictionless.

“It makes a tiny little whir when it’s working,” Towle stated. “But it produces electricity pretty darn good.”

He reworked a desalination tank that wasn’t getting the water clear enough to effectively clean the reflective troughs so that it condenses water from the air instead. The pure water is extremely good for keeping the solar thermal mirrors sparkling clean. It also works well for home brewing, he added – something the easy access to extreme hot and cold water on site makes simple.

Sopogy recently moved its headquarters from Oahu to California and has seen continuing growth and international interest in its solar thermal technology.