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Five Research Grants Totaling $1.5 Million Seek to Lower Costs and Improve Implementation of Large Solar Energy Installations

September 18, 2011
Stanford University

The environmental benefits of utilities getting energy from large solar power plants could be tremendous, but hurdles remain for significant penetration. The TomKat Center for Sustainable Energy chose a group of Stanford researchers in a competitive process to tackle the problem from several angles.

BY MARK GOLDEN

Stanford University’s TomKat Center for Sustainable Energy is backing five university research projects to help make large solar power installations more cost competitive and efficient, and to help deal with solar energy’s hard-to-predict output. Under the center’s new thematic research approach, researchers will also look at such plants’ impacts on land and water.

"We chose to look at large-scale solar power because it could help us get to an energy system that supports a sustainable future, but there are very complex, very important barriers to overcome," said TomKat Center Director Stacey Bent, professor of chemical engineering. “Any of these research projects individually may provide a big push in the right direction. Taken together, they may truly shift our thinking about how to tackle the barriers toward significant penetration of large scale solar power.”

Most of the research results could apply both to large arrays of photovoltaic cells, which get their energy from sunlight, and to concentrating solar power installations, which convert the sun’s heat into electricity usually via a turbine. Some of the research could also help with other intermittent renewable energy sources, such as wind. The seed grants fund faculty research with potential for high impact. These “proof of concept” awards enable researchers to move from theory to early experiments and analysis.

The TomKat Center is taking a new and creative approach this year with its “Research Portfolio” program, which might help improve interdisciplinary research methods generally. The program brings together experts from different disciplines to work on different aspects of a major problem, in this case greater deployment of large-scale solar power. Researchers receive an individual seed grant in one of four areas of expertise: generation and conversion; transmission and distribution; energy storage; and land and water use. In addition, the researchers will communicate and collaborate in the larger portfolio project activities.

“The strategy is intended to allow for research advances in the individual contributing disciplines while at the same time broadening the potential impact of the work through cross-interaction with researchers from other disciplines,” said Bent.
The Department of Materials Science and Engineering’s Jennifer Dionne and Michael McGehee won the grant in the area of generation and conversion. They will try to boost the efficiency of thin-film solar cells by adding upconverters, which allow more light from the sun to be absorbed by the solar cell. Dionne and McGehee hope to show that bimolecular upconverters could help the new generation of solar cells eventually surpass the 20% efficiency milestone. Thin-film cells offer great promise because they are inexpensive to manufacture, but they haven’t yet been shown to convert sunlight into electricity at efficiencies competitive with traditional crystalline silicon solar cells. The Stanford researchers will develop an inexpensive upconverting material and add that to dye-sensitized solar cells to prove their concept, but they expect that the technology could be applied to other kinds of photovoltaic cells.

In the area of transmission and distribution, TomKat will fund a study by Ram Rajagopal, civil and environmental engineering, to better manage the inherent variability of solar power. Unexpected cloud cover frequently cuts solar supplies, requiring reserve generating capacity with high financial and environmental costs. Instead, Rajagopal hopes to demonstrate a better way by matching solar power generators with large consumers who can ramp usage up or down in sync with somewhat random supplies. He will design a variable-reliability contracting mechanism that requires no reserves, as well as a system to identify firms that can benefit most from variable power supplies and then value their flexibility. Working with Pramod Vishwanath, visiting professor in electrical engineering, Rajagopal will also investigate the communication platforms necessary between generators and consumers for such arrangements.

Another way to deal with the intermittent nature of solar power is by storing some of it for use when output drops. The Department of Chemical Engineering’s Thomas Jaramillo and Curtis Frank plan to develop a type of fuel cell that can store electricity by producing hydrogen and oxygen from water and later produce power when the molecules are allowed to recombine to make water. High costs and low performance have kept such devices from commercialization for two decades, but the researchers hope to develop an alkaline-based device using a new membrane material and new catalysts not made from precious metals. If they succeed, they will create the first prototype of this kind of device.

A team led by Michael Lepech, civil and environmental engineering, will develop a new accounting method to value the preservation, use and enhancement of the natural ecosystems owned by large solar generating facilities. New solar power plants are difficult to finance in part because they often compete in a market against old power plants burning fossil fuels. New solar plants have much higher depreciation expenses, resulting in an investment disadvantage due to accounting. Lepech and his team will develop new methods to more appropriately value the natural ecosystem preserved by a solar generator as an asset. A rigorous, market-based valuation of ecosystem services for competitive large-scale solar power generation could counter the depreciation disadvantage and lead to lower capital costs.

“Ultimately, we see this operationalizing the lofty goals of sustainable development through traditional corporate accounting and finance practices,” said Lepech, who is joined in this project by David Freyberg, civil and environmental engineering; John Weyant, management science and engineering; and Stefan Reichelstein, Graduate School of Business.

The Department of Environmental and Earth System Science’s Chris Field, Noah Diffenbaugh and David Lobell will study the effects of large solar plants on land and water resources in the US Southwest. Some of the world’s highest agricultural yields come from irrigated systems in deserts, which are also attractive sites for large solar power stations. Managing multiple demands on water and land in these areas is, the researchers wrote, “perhaps the core challenge facing the future of the Southwest.” Specifically, they will investigate the consequences of solar projects for local precipitation, the opportunities for integrating agriculture and solar infrastructure in desert regions, and the consequences of climate change and disturbance of soil for dust accumulating on solar panels.

The TomKat Center was created in 2009 with a $40 million gift made by Stanford alumni and husband-and-wife team Tom Steyer and Kat Taylor. Its goal is to harness the skills and creativity of Stanford's leading science, technology and policy experts to transform the world's energy systems for a sustainable future.

The grants examining land and water impacts are being co-supported by the Precourt Institute for Energy, and gifts from the Schmidt Family Foundation and the Stinehart/Reed Donor Advised Fund.

Mark Golden is communications/energy writer for the Precourt Institute for Energy, which includes The TomKat Center for Sustainable Energy.