The key to grid integration of solar: visibility

By K Kaufmann

For solar energy to be fully integrated onto the electric grid, it must first be “visible.”

In other words, “you need to have some idea of what every single solar panel is doing,” said Pascal Storck, Global Manager of Energy Services of Vaisala, a firm that provides technology for solar resource assessment and prediction.

Storck, who is also a member of the Solar Electric Power Association’s (SEPA’s) Board of Directors, will be one of the featured speakers at the Solar Integration Workshop being sponsored by the educational nonprofit April 30 in San Diego. Solar visibility is a key focus of the day-long event.

Firms such as Vaisala and some utilities and grid operators have achieved that level of visibility for large-scale solar projects that are directly connected to the grid. The challenge ahead is having the same predictability for rooftop solar and other forms of distributed renewable energy generation, Storck said.

“We don’t know how this is going to shake out in the U.S.,” he said. “There are a lot of people that are not going to want to give a utility access to their generation profiles. The question is — does the utility have the right to ask?

For customers being compensated with net-metered retail rates for excess power they feed into the grid, the anwer to that question is “likely yes,” Storck said. “But what happens when local energy storage is more cost effective than net metering?”

Find out more about SEPA’s Solar Integration Workshop here.

The Sacramento Municipal Utility District (SMUD) in California is one of the utilities now working on solutions to the complex issues — technological, financial and regulatory — that full visibility raises.

SMUD uses “live telemetry” — basically, high-speed dial-in lines — that can provide continuous output data for solar installations of 500 kilowatts (kW) or larger, said David Brown, Principal Distribution System Engineer for the public power utility. But while these commercial and larger-scale projects make up about three-quarters of SMUD’s total solar capacity, he said, in sheer numbers, they are dwarfed by smaller rooftop installations.

Having separate meters measuring output for about 95 percent of those rooftop arrays allows SMUD to collect and archive their production data, said Brown, who will also be speaking at the Solar Integration Workshop.

“We have the ability to reconstruct what’s going on; that gives us a kind of visibility,” he said. “The biggest challenge is when the sun is shining the brightest, when we don’t have load — principally in April and March where we have really good sunlight, lower temperatures and no air conditioning running, no heaters running. What we build our visibility for is to be able to analyze what’s going on on those days.”

Looking for other views on solar integration? Check out some of the ideas submitted for SEPA’s 51st State Initiative here.

Storck said his workshop presentation will provide an update on current research and development initiatives aimed at improving solar visibility.

“One thing we see on the solar side of the business, the variability of the generation has impacts anywhere from a few minutes in advance to days ahead, to weeks and months in advance,” he said.

Brown’s workshop presentation will include case studies of some of SMUD’s efforts aimed at improving solar visibility and grid integration in general.

One example, he said, is the proactive approach the utility is taking on interconnection studies to ensure its local distribution system can handle the increasing numbers of rooftop installations coming online.

If “we see over time we could end up with too many customers producing too much power, we’re trying to preempt and remediate that,” he said. “We give the applicant (options) to change the installation size or have a customer contribute to remediation — putting them on their own transformer, upgrading the conductors that are serving them.”

It’s where utilities talk solar — SEPA’s Utility Solar Conference, April 27-29 in San Diego. Find out more here.

Bob Gibson, SEPA’s Vice President for Education and Outreach, sees the current industry focus on grid integration and solar visibility as yet another sign of how rooftop solar and other forms of distributed renewable power are driving irreversible changes in the energy sector. He expects the upcoming Solar Integration Workshop to be the first of an ongoing series of forums SEPA will offer on these issues.

“Initial concerns about theintegration of solar often focused on whether or not a given distribution line could handle a two-way flow of power,” he said. “The emerging dialog now centers on how and how quickly distributed solar can be managed as part of a reliable, resilient grid.

“And we have to ensure balanced distribution of costs and benefits to all affected parties — utilities, consumers and the ever-growing solar and renewable energy industries,” he said.

“Most of the utilities right now, they are doing the right things at the right time,” said Storck, pointing to industry participation in solar forecasting studies. “Predictability is what they are after, the piece they are missing.”

K Kaufmann is SEPA’s Communications Manager. She can be reached at [email protected].