GreenVolts, a San Francisco company taking the approach of focusing large amounts of sunlight onto small, high-efficiency solar cells — called concentrating solar photovoltaic (CPV) — has raised a significant $30 million funding from the giant venture firm Oak Investment Partners.

Other recent solar fundings we’ve seen have been much larger, but for notably different technologies. Nanosolar, Ava Solar and SoloPower raised over half a billion dollars combined for thin film, which tries to make low-efficiency cells as cheap as possible. SolarReserve just took $140 million for solar thermal, which uses water or molten salt instead of solar cells. To compete, CPV will have to be at least competitive with those technologies, a fact that’s made some investors wary of it.

CPV takes a nearly opposite approach to thin film, in terms of how it produces energy . Cells that can convert up to 40 percent of the sunlight to electricity — three to seven times more than thin film cells — are placed in the center of an array that focuses more light on them using lenses and mirrors. In GreenVolts’ case, each cell can receive well over 500 “suns” worth of energy, so much that they’d be fried if not for attached cooling arrays.

That setup provides plenty of electricity, but all the extra equipment raises costs, so that most CPV firms have been unable to prove their products are much cheaper than standard solar cells.

However, GreenVolts is working on a big project to prove that it’s viable for utility-scale electricity generation, which would mean that it’s much cheaper than your average solar technology. The GV1 project is a megawatt solar project (enough to power 300 to 500 homes) being built in Pacific Gas & Electric’s territory, which GreenVolts says will be completed later this year.

Notably, this funding is only the second full venture round taken by the company. Provided it can hit its cost targets at GV1, it would be reasonable to expect a much larger follow-on round next year, perhaps even as much as the companies cited above have received.

The largest CPV fundings to date have gone to SolFocus. Other promising companies in the field include Covalent Solar with its concentrating “windows”, Sunrgi with an ultra-focusing model, and Xtreme Energetics, which uses transparent electronics licensed from Hewlett-Packard.