The solar power farm sits on top of the city’s enclosed Sunset Reservoir – an area the size of twelve football fields. It’s a big solar farm for an urban area.

“What’s exciting about this project is also that we’re generating clean electricity that can be delivered right where it’s going to be used,” said Arno Harris. Harris is CEO of Recurrent Energy, the San Francisco company that built the array.

Harris says there’s a growing market for projects like this ā€“ what’s known as mid-scale solar. Traditionally, there are two kinds of solar projects: huge solar farms that cover hundreds of acres and small rooftop installations on houses. Both have run into problems.

“With those large projects, the size of the land that you need forces you to go out into pristine wilderness. What you run into is that they take a really long time to deliver and there are all sorts of ‘gotchas’ along the way,” says Harris.

Those “gotchas” have to do with a complex permitting process in California. Large solar farms go through a gauntlet of state and local agencies. It’s an even longer process if the land is home to sensitive species like desert tortoises.

With residential rooftops on the other hand, the problem is installation costs. “You got a lot of trips up the ladder and you’re not putting a lot of panels up there,” says Harris.

A mid-sized project, like the 5 MW array at Sunset Reservoir, avoids those problems. Installation costs are cheaper, thanks to economies of scale. And it’s able to obtain permits faster than a large solar farm.

“What we think really is the sweet spot is this place in the middle.”

That is, to Harris, the ideal solar project is a little like Goldilocks ā€“ not too big, not too small, just right.

Transmission Challenges

Julie Fitch of the California Public Utilities Commission agrees there’s a lot of potential in mid-scale solar. When the state first passed its goal of reaching 20% renewable energy by 2010, utilities raced to sign contracts.

“Most of the focus has been on those large, centralized plants – that also have implications for transmission because it takes a transmission line to deliver that large chunk of power to where people use it.”

Chris Johns, President of PG&E Co., says the transmission process can be very challenging. “Many of the projects are taking years and within that time frame, the construction piece is just a small percentage of that time.”

Mid-size solar projects avoid the need to build new transmission lines, says Johns, since they can often plug into existing power lines. PG&E will still need large-scale solar, he says, to meet the state’s renewable energy goals. But mid-size solar is on the rise, thanks also to falling prices on solar panels.

“Quite frankly, right now, the smaller scale stuff is a little more affordable.”

Julie Fitch says the CPUC has launched a program to develop 1000 megawatts of these smaller projects.

While a large renewable project can take five or six years, these projects will have an 18-month deadline to get online. “The idea is: if you’re not fast, your advantage is not as great as you’ve told us. So let’s try somebody else,” says Fitch.

Fitch says she’s hopeful these projects will help utilities reach the goal of 33% renewable energy by 2020. But mid-sized solar isn’t just for utilities.

source: kqed