Coming out of the shadows

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DOE grant supports solar energy innovations

By Roger Snodgrass

Two more allotments of what is mainly stimulus funding have been made available to Los Alamos National Laboratory in recent days.

Energy Secretary Steven Chu announced that up to  $87 million with $50 million of that from the American Recovery and Reinvestment Act, would be available nationally. He made the announcement last week on opening day of the  annual Solar Decathlon competition sponsored by the Department of Energy on the National Mall.

“Today’s awards are among the many investments made to create new jobs and a clean energy future with solar power, Chu said, as he designated several potential projects for accelerating the use of solar energy and offered to invest in “technologies of the future.”

One of two grants for LANL that could amount to about $1 million apiece went to Stephen Obrey, a staff scientist in the lab’s Chemistry Division for one of the least favored areas of alternative energy research in recent years.

“As far as alternative energy is concerned, solar thermal has been largely ignored,” said Obrey in an interview Wednesday. “This is one of the first calls in years where people have actually addressed the issue.”

While the other main branch of solar energy, solar photovoltaic has been the primary object of attention, the other branch, known as Concentrated Solar Power (CSP) or thermal solar, has been somewhat relegated to the sideline.

Photovoltaics depend on arrays of cells with a material for converting solar radiation into direct current. Thermal solar energy is produced by using mirrors or reflective lenses to heat a fluid in a pipe-like container that can be used to run steam through a turbine to produce electricity.

“The design of a solar thermal power plant and coal-fired power plant are very similar, the only thing that changes is the source of heat.”

 “The end goal as we perceive it is to make solar thermal electrical production competitive with coal,” said Obrey, “but with the expectation that solar thermal production will not have the heavy carbon dioxide emissions that coal fired produces.”

Obrey’s contribution is to design a new heat transfer fluid that will make CSP more economically viable.

“Current technology is based on working fluids that only allow operating temperatures up to 400 degrees Celsius,” he said. “The new technology would allow temperatures closer to 600 degrees, which will improve the efficiency of the heat conversion by 50 percent.”

An additional advantage of the higher temperatures, comes from the ability to store the solar heated energy after the sun goes down, extending the useful life of the solar energy beyond those periods when the sun is shining, including into the night. This potential is an advantage over photovoltaic systems, that are largely dependent on immediately available sunshine.

Both solar technologies have advantages, depending on geographical variables, and both would work well in New Mexico and the greater southwest where there are vast areas of open land and plenty of sunlight.

“One of the major limitations of solar thermal in the past, is that nobody has looked at the smaller idiosyncracies associated with developing this technology to its fullest potential,” Obrey said.

A second grant to LANL would be used in a project to assess the cost-savings potential of using silicon nanowire architecture in photovoltaic applications.

Altogether 15 solar energy projects at DOE national laboratories would receive up to $17 million for research and development.