Solar Power Partners said Friday it plans to raise a $100 million fund for developing more solar projects at places such as hospitals, schools and corporate campuses.

The new fund would follow two previous funds raised by the Mill Valley, Calif. company for designing, installing and operating solar power systems. Solar Power Partners previously raised a $75 million fund and a $35 million fund to finance their projects.

Founded in mid-2006, the startup has already completed 17 projects totaling 5.3 megawatts in California and Hawaii. By the end of the year, the company expects to complete an additional 23 projects totaling about 10 megawatts, said Alexander Welczeck, CEO of Solar Power Partners. (See this map for locations of completed and pending projects).

“Our customers are interested in saving costs, having predicable energy prices and being green,” Welczeck said. “Every project we have completed is producing at or above the expected output.”

The company develops, owns and operates solar power systems for customers, who in return sign a 15- to 25-year agreement to pay for the electricity generated from the systems. The solar power systems are located on the customers’ properties, where the electricity would be used.

This power-purchase-agreement model has grown in popularity because the cost of developing a project, including buying equipment, designing the power system, getting permits and installing the solar panels, can be expensive. A 1-megawatt project, for example, could cost $7 million to $7.5 million, Welczeck said.

Many customers don’t have that kind of money available upfront, but this model allows them to pay it back over time, as a cut of their electricity savings.

Companies such as SunEdison and MMA Renewable Ventures have used the PPA model to carry out large-scale projects for utilities and other businesses. In fact, SunEdison, based in Beltsville, M.D., said this week it snagged a deal to develop a 10-megawatt project for the Florida Municipal Power Agency.

Solar Power Partners focuses on developing smaller solar projects – between 200 kilowatts and 2 megawatts – for commercial customers and public agencies. Earlier this month, the company said it would install a 1-megawatt project at Roche Palo Alto, a research center for the Swiss pharmaceutical giant Roche.

Other projects under development include those at the University of California at San Diego, the California Institute of Technology, the West County Water District in Richmond, Calif. and Safeway stores.

Solar Power Partners this month announced the completion of a 2-megawatt installation at the Fresno Yosemite International Airport in central California. The power plant is the largest airport solar project in the country, Welczeck said. Other completed projects include the Redwood Valley Water District in northern California, the Maui Economic Development Board in Hawaii and the Placer County Juvenile Detention Center in northern California.

Welczeck said his company is lining up projects despite the uncertainty over the fate of a federal tax-investment credit for renewable-energy projects. The tax credit, which pays for 30 percent of a project cost, will expire by the end of this year. Repeated efforts to extend it have failed so far (see Senate Blocks Renewable Incentives Bill).

Many solar power developers have said they might have to suspend projects if Congress doesn’t renew the tax credit (see No Tax Credit, No Solar Power). And power-purchase companies are particularly vulnerable, according to AltaTerra partner Jon Guice, who co-authored a Greentech Media report on these types of financing models (see Power-Purchase Agreements Could Lose Market Share).

But Welczeck remains optimistic. “What we expect is there will be an extension of the investment tax credit this year,” he said.” If not, we are very confident that there will be an extension in the new year, with any new government.