“It’s really exciting” that at least eight states are pursuing flexible interconnection of MW-scale solar on distribution grids, said Kate Tohme, director of interconnection policy at renewables developer New Leaf Energy.
Speaking on a panel at a conference hosted by the Coalition for Community Solar Access, Tohme said “interconnection costs are our highest development costs in most scenarios, and flexible interconnection is going to be the most affordable way for us to interconnect and avoid infrastructure upgrades.”
A project owner choosing flexible interconnection agrees to limits on exporting solar power to avoid breaching the thermal limit of substation transformers. But if the level of curtailment is uncertain, financing can be challenging.
Panelist David Golembeski, senior project manager at the Interstate Renewable Energy Council, described two types of flexible interconnection: schedule-based interconnection, as pioneered by California, and dynamic flexible interconnection, in which the utility may use a distributed energy resource management system (DERMS) or other means to curtail export as needed.
Tohme described flexible interconnection progress in seven states besides California:
· Colorado’s Public Utility Commission has ordered utility Xcel to file a flexible interconnection tariff in July.
· New York utilities Avangrid and National Grid have piloted flexible interconnection and are seeking to expand their programs.
· Illinois utility ComEd is collaborating with stakeholders to reach as much as 200 MW of flexible interconnection, with occasional curtailment governed by a DERMS system now being developed.
· A Connecticut working group has filed a proposal for flexible interconnection.
· The Massachusetts Public Utilities Commission is supporting a working group that is expected to propose a flexible interconnection program by year-end.
· Maine regulators have created a forum where flexible interconnection may be discussed.
· In Minnesota, a working group aims to launch flexible interconnection.
Golembeski added that Washington, DC, Oregon and Maryland have implemented phased interconnection, where the utility might allow a 2 MW project to initially interconnect 1 MW of capacity, increasing to the full 2 MW once a grid upgrade to handle the extra capacity is completed.
Tohme noted that with schedule-based interconnection, “we’ll see a huge benefit” of added distributed solar “that can be achieved more quickly, but ultimately we might get less” distributed capacity online than with dynamic flexibility.
She said Colorado is considering an approach that would start with schedule-based interconnection, “but when the DERMS is up and running, it’s going to tell the projects when they can operate more.” With the schedule setting the minimum export amounts and therefore a floor to revenues, “that gives us a benefit for financing.”
For financing projects with dynamic flexible interconnection, Tohme said “the big question is, how can we have a curtailment cap?” And if the cap is breached, “we need to have some recourse.” She said compensation funds for breach of a curtailment cap can come from “shareholders of investor-owned utilities, ratepayers, or if we create some kind of an escrow account that the flexible interconnection projects pay into, and then can also be paid out of. We have to figure it out.”
Panel moderator Vaughan Woodruff, principal of EquinoxDG, drew a comparison to curtailment of rooftop solar production in Hawaii and California through the use of the “volt-watt” inverter setting. Some customers “are curtailed quite a bit from that,” he said, while no “predictable way to mitigate the impacts on those customers” has yet been developed. “That seems challenging to navigate.”
Panelist David Gahl, executive director of the Solar and Storage Industries Association, said that flexible interconnection pilots across the country show that curtailment risk is less than 1%, and in the pilots in upstate New York, the curtailment was five hundredths of 1% of the projects’ total generation.
Looking beyond the U.S., Golembeski noted that Australia is enabling flexible interconnection through the internet, and said “We want to ensure that the cost and timing of deploying these technologies is well considered, that regulators are saying, ‘Okay, we don’t actually have to do full-fledged DERMS. It is really expensive and complex.’ There are other options.”
Gahl said his group is working with many of the people attending the panel discussion to develop language on flexible interconnection that could be inserted into an interconnection agreement, or tariff language that could be inserted into a standard interconnection tariff arrangement.
Gahl also noted a Pacific Northwest National Laboratory study that found flexible interconnection yielded significant revenue benefits for community solar projects and reduced the burden on utility planning departments, while enabling more clean energy on the grid. A study on flexible interconnection in New York, he said, found that it enabled substantially more market opportunity in the upstate and western parts of the state.
Tohme closed the panel by responding to a question about hosting capacity maps, saying that “it’s part of our advocacy, promoting capacity maps, so that you can see where there’s a flexible interconnection opportunity, where you can avoid costly upgrades.”
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