Sustainable Energy

DOE Attempts to Jump-Start Concentrated Solar

Researchers seek breakthroughs for a technology designed to make solar more efficient.

Conventional solar power remains too inefficient to compete with fossil fuels.

Attempting to jump-start research on novel solar technology, the U.S. Department of Energy’s Advanced Research Projects Agency–Energy (ARPA-E) on Monday announced new funding for concentrated solar photovoltaic projects. Awarded under ARPA-E’s Micro-scale Optimized Solar-cell Arrays with Integrated Concentration (MOSAIC) program, the money will go to 11 projects at 10 organizations, including MIT, Xerox PARC, Texas A&M, and the solar manufacturer Semprius.

Concentrated PV (or CPV), which uses lenses and mirrors to focus the sun’s rays on tiny PV cells, could dramatically increase the efficiency and lower the cost of producing electricity from sunlight. MOSAIC’s goal is to “double the amount of energy each solar panel can produce from the sun, while reducing costs and the space required to generate solar energy.”

During the solar boom of 2005 to 2008, several startups developing CPV systems received federal government support and funding from venture capital firms, only to collapse when low-cost Chinese manufacturers drove down the cost of conventional solar panels (see “One Step Forward, One Step Back for Concentrated PV” and “Will a Breakthrough Solar Technology See the Light of Day?”). Today, CPV remains too expensive and complicated to replace conventional solar installations on a widespread basis.

Although the efficiency of conventional solar PV has increased and costs have fallen dramatically in the last several years, solar power generation remains generally more expensive than producing electricity with low-cost fossil-fuel plants. The efficiency of conventional solar PV panels (in terms of the portion of energy in sunlight converted to electricity) lingers below 20 percent. CPV systems already achieve efficiencies of 30 percent, and promise much higher.

The MOSAIC projects differ from earlier concentrated PV technologies in that the tiny arrays that concentrate the sunlight are built into traditional flat panels. The description of one of the funded projects, at MIT, gives a sense of the complexity of the technology: the system comprises two micro-tracking systems—one that involves a double array of micro-optics, and a second that rotates and tilts the entire apparatus.

One limitation of CPV has been that it traditionally works only in areas of high solar irradiation—i.e., desert regions like the American Southwest—and requires expensive solar tracking mechanisms to keep the arrays pointed directly at the sun. Several of the MOSAIC projects are attempting to overcome those barriers. A team at Caltech, for instance, is developing a technology that it says will offer efficiencies of more than 30 percent and operate in less than ideal locations, without tracking the sun.

“Increasing efficiency by this amount is transformative,” says Harry Atwater, the principal investigator on the Caltech research effort.