Researchers in the USA have demonstrated how microchannel technology could significantly improve the efficiency of solar thermal electricity production.

Pioneered at Oregon State University (OSU), the microchannel technology has been tested at laboratory level and "could open the door to a significant, 15 per cent higher efficiency for solar thermal technology", according to Kevin Drost, a retired OSU associate professor of mechanical engineering.

OSU is leading a research consortium developing the microchannel technology, which uses extremely small channels and a branching distribution system to speed the energy transfer process in solar thermal systems.

The consortium has been awarded a $2.5 million grant by the US Department of Energy’s SunShot Initiative to help bring microchannel technology to a practical field test. It says that the technology will help to make solar thermal systems more cost-competitive with other forms of electricity generation and expand the number of locations able to host a solar thermal plant.

"We’re confident that this work will meet the goals being set by the Department of Energy," Drost said. "With their support we’ll now move it beyond the laboratory toward a technology that could be commercialized."

A feature of OSU’s work is the use of supercritical carbon dioxide for heat transfer, instead of the molten salts used in existing solar thermal power plants. "Solar thermal technology has to work at very high temperatures and very high pressures, which present special challenges," Drost said. "We are demonstrating that microchannel systems, as well as the use of supercritical carbon dioxide as a heat transfer fluid, should meet those challenges."

Supercritical carbon dioxide can operate at 650-720°C, compared to 500°C for molten salt. The use of supercritical carbon dioxide will improve efficiency, use a much smaller turbine, and will help to eliminate the need for water cooling towers, a special concern in some of the sunny, dry locations where such energy plants are likely to be located.

The microchannel receiving panels using the supercritical carbon dioxide are also about four times smaller than existing technology, which reduces cost, loss of thermal energy and weight.

Collaborators on this project include Sandia National Laboratory, Pacific Northwest National Lab, the National Energy Technology Lab, University of California, Davis, and ECOKAP Technologies.