Editor’s note: This story has been edited since its original posting to clarify the technology planned for use.
Boasting both a state Solar Initiative and a New Solar Homes Partnership, California has become prime real estate for solar developers.
Florida-based cleantech company GDT Tek announced on March 1 that it had purchased 109 acres in Desert Hot Springs, Calif., in order to develop a 20-megawatt (MW) commercial-scale solar photovoltaic (PV) system. That will take up 100 acres of the site. The other nine acres? That will be used to build what the company calls “a pilot thermal solar system” that combines concentrating solar power with a waste-heat technology. That system, the company said, could be 40 percent more efficient than current PV technology.
Heat to electricity technology is not completely new, especially to GDT Tek. Its 50 percent-owned subsidiary, Steriwave-GDT Tek, a JV company with Steriwave Hungary, specializes in creating heat capturing devices (like the one pictured above) that reuse the heat to create electricity. Steriwave-GDT Tek even has a patent pending for underwater technology that captures methane hydrates from undersea reserves to be resued for electricity generation.
For California, the installation is another step toward a statewide goal of reaching 1,940 MW of installed solar capacity by 2016. The California Solar Inititative (CSI)—run by the California Pubic Utilities Commission (CPUC) and with a total budget of $2 billion over the next 10 years—set the goal and provides cash back incentives for solar systems.
CSP plants can work in a few different ways, but are always based on the concept of heating a liquid, which is why they are often also called solar thermal plants. One common system, called power tower, uses big mirrors—heliostats—to direct sunlight at the top of a tower several hundred feet high. The energy is received by the tower and used to heat water, generating steam and then power. There are plants like this already operating in Europe, and several are either under construction or planned for construction in the United States, including some that use molten salts to store the heat that’s been gathered so it can be used to produce power long after the sun goes down. Parabolic reflector systems use curved mirrors that direct the heat toward receiver tubes positioned along the focal line of each parabolic mirror.
It’s unclear exactly how the solar thermal aspect of the GDT Tek system will work. In a statement, company president Bo Linton says it will use a “new solar thermal style panel that the GDT Tek waste heat to electricity system employs.”
“Waste-heat” typically refers to systems that capture heat lost from operating motors—like this system in Alberta that we reported on last November. And in materials and a video describing its technology GDT Tek references harnessing heat from a gas-powered engine.
But in this case, it appears that GDT Tek intends to use solar heat—captured by its “new solar thermal style panel”—as the heat source in an organic Rankine cycle system. This is a process in which, first, heat is captured and used to heat a fluid that has a much lower vaporization temperature than water. This fluid—now a hot vapor under high pressure—is then employed to spin a turbine connected to a generator, producing electricity. According to the National Renewable Energy Laboratory, these systems are often paired with parabolic trough collectors.
“Our CTO, Ralf Horn, has estimated that our system will prove to be 40 percent more cost efficient and productive than current PV technology,” Linton said. “Once we build it side by side the proof will show right on the meters for the entire world to see. It’s our goal to become the frontrunner in solar farm technology and this site is a major step in getting us recognized as what we believe to be the best solar farm technology on the planet.”