The Navy and the Kauai Island Utility Cooperative have signed a lease to develop a 19.3-megawatt direct-current solar facility in conjunction with a 70 megawatt-hour battery energy storage system at the Pacific Missile Range Facility that will benefit the community and missile testing.

The agreement, signed Wednesday, leases 140 acres of Navy land to the utility for development of a solar farm coupled with battery storage.

“The facility will provide renewable power after sunset to help meet KIUC’s members’ electricity needs during peak usage hours,” the Navy said in a release. “The facility will also have the capability of directly supporting PMRF’s mission-critical activities in the event of a short-term or extended grid outage.”

Kauai Mayor Bernard Carvalho Jr. said the community “is blessed to have such forward-thinking partners” in the Kauai Island Utility Cooperative and the Navy’s missile range facility, which is the island’s third-largest employer.

“We will continue to support KIUC however we can as they move us away from fossil fuels and towards an affordable, clean energy future. These projects make sense for our climate, our economy, and our community,” Carvalho said in an email.

The federal government converts alternating-current, or AC, power to about 77 percent of DC, so that would mean just under 15 megawatts of AC power for the project.

In exchange for the use of Navy land, the utility is providing in-kind consideration in the form of an “express” electrical connection to base facilities, which will allow PMRF to operate as a self-supporting micro-grid when necessary, the Navy said. Construction is expected to begin in late 2018.

“This project at PMRF will provide energy security and resiliency that is critical to the base and to Kauai, especially the west side,” PMRF commander Capt. Vinnie Johnson said in the Navy release.

Improving energy efficiency “will ensure our base remains a leader in innovation and at the forefront of the defense of the country. The energy generated and stored will provide a reliable source of backup power for our missions while also contributing to Kauai’s renewable energy portfolio,” Johnson said.

The Navy wants to power up the solar farm in part because ongoing missile testing requires unwavering power for flight tests that process huge amounts of data.

Improved power quality would “reduce the daily need to operate diesel generators in support of current and future mission operations and testing capabilities,” a previous draft environmental assessment stated.

The on-base power supply would supplement “the more vulnerable and lower quality power” from the distant KIUC power plant in Eleele. Not adopting the solar plan would have prolonged the existing “energy security risk” that results from PMRF’s reliance on a single electrical transmission line and backup diesel generators, the environmental report said.

The assessment said 2 megawatts of power are required for day-to-day operations at PMRF; however, “certain missions require significantly higher power for short durations.”

KIUC selected AES Distributed Energy to construct and operate the facility. The bulk of the project costs will be paid upfront by AES, which will then sell energy to KIUC via a 25-year agreement priced at 10.85 cents per kilowatt-hour, according to the Navy.

“KIUC has set an aggressive goal of reaching 70 percent renewable by 2030,” said David Bissell, the utility’s president and chief executive officer. “This project brings us closer to that goal, while also providing greater overall grid stability via the use of battery storage.”

Bissell said the project will displace 2.8 million gallons of diesel annually, can power roughly 6,000 homes and “creates a downward pressure on rates” through the long-term agreement “that is well below the current cost of diesel.”