The race is on for energy-technology entrepreneurs who have won federal economic-stimulus grants from a special high-risk technology program—with promises of more money if they can move their inventions closer to market over the next two years.

The Energy Department's ARPA-E agency—modeled on a military program for bankrolling cutting-edge technology, including computer networking that led to today's Internet—has awarded $151 million to 37 companies around the country. Nearly 3,700 companies applied for the money. A complete list of the winners selected by the Advanced Research Projects Agency-Energy can be found here.

The San Francisco Business Times has examined four of those winners in the Bay Area. They offer a glimpse into some of the most promising ideas in energy, including virtual wind-turbine wings, superefficient water filters, new processes for carbon sequestration, and batteries that could dramatically reduce the cost of electric vehicles.

Envia Systems will use its $4 million award to attempt to exponentially increase the energy density of lithium-ion batteries. Lithium-ion batteries, like the ones being used in the Tesla Roadster, cost between $25,000 and $30,000. So a smaller battery that can run longer would bring the costs of electric vehicles down.

“Even the big automakers said, ‘There’s no way we can put cars on the road and be profitable unless the costs come down,’” said Michael Sinkula, director and co-founder of Hayward, California-based Envia. “More battery power in the same space means less costs.”

Envia is attempting to double the energy density of the batteries in two years, based on technology discovered at partner Argonne National Laboratory.

“Historically, energy density increases maybe 5 percent each year,” Sinkula said. “If you’re doubling it, that’s extremely significant.”

The 20-person company plans to hire up to 10 people for the project, including scientists and engineers.

Porifera Inc.’s technology also came out of a national lab, this time Lawrence Livermore National Laboratory. The company, based in Hayward, licensed the technology for carbon nanotubes from the lab after discovering that both gas and water run through carbon nanotubes quickly, which demonstrated that the nanotubes could be used as effective filtering devices.

The company got a grant first from the Defense Advanced Research Projects Agency, known as DARPA, to see if it could use those nanotubes for effective desalination—separating salt from salt water. And now ARPA-E has awarded the company $1.08 million to see if the technology can effectively separate carbon dioxide from polluted air streams. “For carbon sequestration you have to change the rate (of flow),” said Olgica Bakajin, chief technology officer of Porifera and formerly a lab scientist who helped make the discovery about the nanotubes.