REC puts online Hawaii's largest solar plant

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Hawaii has come to be described as a postcard from the future due to its high penetrations of renewable energy on isolated grids. Nowhere is this more true than the island of Kaua’i, where renewable energy is expected to meet 38% of annual demand by the end of 2015.

As part of that 38%, today REC interconnected a 60-acre solar PV project which adds another 12 MW-AC of solar capacity to the island’s grid. This is the largest solar PV project to go online in the state, as well as REC Solar’s largest to date.

The project also incorporates a 6 MW lithium-ion battery, which will REC says will help to smooth the integration of PV on the grid. Due to Kauai’s small size and isolated geography, cloud cover can significantly impact solar PV generation on the island.

REC says that this battery can help to meet demand after the sun goes down, but that this is not its primary purpose. "The main function is frequency and voltage control, which allows (KIUC) to lower its spinning reserves, therefore saving money on fuel," REC Solar Hawaii Regional Manager Drew Bradely told pv magazine.

In addition to REC Solar’s plant, Kaua’i also hosts a 14 MW-DC PV project which SolarCity put online in September 2014 and another 6 MW-DC utility-scale project built by Alexander & Baldwin.

In addition to these SolarCity holds another power purchase agreement with Kauai’s public utility, and plans to build a 13 MW-DC solar project on the island. Like REC’s project the SolarCity plant will also be supported by battery storage, which the company says will allow it to meet evening electric demand.

Altogether, Kauai Island Utility Cooperative (KIUC) estimates that utility-scale and rooftop PV plants on the island already totals more than 50 MW. The island has only 66,000 inhabitants, meaning more than 750 watts of PV for every resident.

REC’s Bradley estimates that solar will now meet 20% of annual demand on Kaua’i, and is peaking at 70% of demand during the day. Due to this high level of daytime solar penetration, KIUC is planning a pilot time-of-use rate program for residential customers which will offer a discount for electricity use from 9 AM to 3 PM.