Dive Brief:

The Kauai Island Utility Cooperative (KIUC) obtained 90% or more of its electricity from renewables on four occasions in January. In addition to its baseload capacities of 8% biomass, 7% hydroelectric and ramping diesel generation, KIUC achieved up to 77% solar in its power mix, the most solar ever integrated by a U.S. utility, according to Hawaii News Now.

KIUC’s annual energy mix in 2015 was 38% renewables and 62% diesel fuel generation. Its rooftop solar penetration is growing and it has two utility-scale solar installations, five hydroelectric facilities and a newly operational biomass plant that burns albizia wood chips.

The 77% solar that drove the renewables total over 90% was only achieved for short intervals, the longest being 61 minutes on January 13, KIUC Spokesperson Jim Kelly told Utility Dive. On an average day in January, solar was about 62% of the utility’s generation, making renewables 77% of its power.

Dive Insight:

The recently-added biomass plant was critical to integrating the high levels of solar, Kelly said. “It gives us renewable generation that is firm power.”

To integrate high levels of solar, KIUC also upgraded its conventional diesel generators so they can be more responsive to solar variability, Kelly explained. Air permits were modified to allow generators to run at below 50% loads. Generator governors were tuned to ramp faster. Relay protection and load shed schemes were redesigned. Solar inverters and battery inverters were adjusted to ride through wider frequency and voltage excursions.

“Being an engineer in the control room is a lot more challenging than it was six months ago,” Kelly told Utility Dive. “There are things happening constantly and it is a real team effort to keep it in balance.”

KIUC grid operators have no choice but to push the envelope, he added. “Outside of solar, there are few other alternatives to the high price of oil generation.”

The co-op is on pace to get 50% of its power from renewable resources in seven years, according to Hawaii News Now.

Renewables accounted for 90% or more of the KIUC fuel mix four times in January, according to spokesperson Jim Kelly:

Jan. 13: Total of 61 minutes at or above 90% renewables with 59 MW of demand and an average resource mix of 71% solar, 8% hydro, 11% biomass, 10% diesel;

Jan. 16: Total of 34 minutes at or above 90% renewables with 57 MW of demand and an average resource mix of 73% solar, 8% hydro, 9% biomass, 10% diesel;

Jan. 17: Total of 34 minutes at or above 90% renewables with 53 MW of demand and an average resource mix of 72% solar, 8% hydro, 10% biomass and 10% diesel;

Jan. 18: Total of 5 minutes at or above 90% renewables with 58 MW of demand and an average resource mix of 77% solar, 6% hydro, 7% biomass and 10% diesel.