Achates Power received a $2 million Department of Energy grant to create a highly efficient opposed-piston engine for hybrid vehicles. Achates, based in Sorrento Valley, will work with the University of Michigan and Nissan Motor Co. Ltd. on the project, it said in a statement March 6.

The new design will be a unique single-cylinder opposed-piston (OP) engine. In an opposed-piston engine, combustion at the center of a cylinder drives pistons at either end of a cylinder.

“The project builds on the successful development of the OP engine and expands our research and development into the hybrid and range-extender market,” said Fabien Redon, chief technical officer for Achates Power, in a prepared statement. “The inherent balance and power characteristics of the OP engine make it an ideal powertrain in a hybrid solution, providing vehicle manufacturers a cost-effective solution to improve vehicle fuel efficiency and reduce carbon dioxide (CO2) emissions.”

The federal grant came from the energy department’s R&D office, the Advanced Research Projects Agency-Energy.

Achates is funded by venture capital firms and the Oil and Gas Climate Initiative. The latter represents major oil companies’ investment in low-emission technologies. Achates designs its opposed-piston engines mainly for trucks or heavier vehicles.