Solar PV Can Be Game-Changer

Solar photovoltaic (PV) power has the potential to be a game-changer with regard to interconnection matters, Charlie Smith, executive director, Utility Variable-Generation Integration Group, said Dec. 5.

During his presentation at TransmissionHub’s TransForum East in Arlington, Va., Smith noted that in Germany, while it took 30 years to develop 30 GW of wind, it took only five years to develop that same amount of solar.

Utilities in Germany were unprepared in terms of interconnection requirements for that amount of generation in that short period of time, he told TransmissionHub after the presentation.

A similar situation could occur in the United States, he said, adding, “There would have to be a massive retrofit of some sort to prevent a destabilizing system event caused by inadequately thought through interconnection requirements for PV.”

Smith said the potential for that occurring faster is greatest in the western United States, such as in California, whose renewable portfolio standard calls for 33% renewable energy by 2020.

“Many people don’t realize that you still need transmission when you put in a lot of distributed generation because you can’t use all that energy – if you have a really high penetration in some area, you’re going to be exporting that energy out of your areas,” he said. “That will go back up through the distribution system, through the transformer, back onto the transmission system to flow out to some other region in the system. You find that transmission quickly becomes a limiting factor if you have a high penetration of PV and you haven’t thought about where it’s all going to go.”

Transmission is the key factor for high penetration of PV, he said, adding that interconnection requirements are also helpful.

“This is the complete opposite of the way we’ve always planned and designed the system,” Smith said. “We’ve always planned and designed for large central stations where the power pretty much flows out of the transmission system into the distribution system and meet the loads. Now, we’re tipping that on its head and we’re talking about generation on the distribution system that’s meeting the load in some region and flowing back up on the transmission system and going out to other regions to meet the load, so it’s really a paradigm shift.”

He continued: “So, some transmission planning, interconnection requirements, I think are critical, the large markets for the balancing. … [F]or a given amount of energy from solar, you carry about twice the variability as you do with wind because the capacity factor is about half [that of] wind. I think wind has kind of led the way with a lot of the system impacts as far as market design, [for instance].”

Smith said: “We’ve done a large series of wind integration studies over the last 10 years to kind of help us understand and think through the long-term consequences. We haven’t really done that for solar yet, so we need to do some more integration studies for solar, and solar and wind, industry-wide, to see what the impact is on the system and what other things we need to think about changing.”

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