The Navy wants to power up what could be one of the largest solar farms in the state at the Pacific Missile Range Facility on Kauai, where ongoing missile testing requires unwavering power for flight tests that process huge amounts of data.

The solar photovoltaic system with battery storage could generate up to 44 megawatts of direct-current, or DC, power, according to a draft environmental assessment for the project.

Among the benefits would be improved power quality “to reduce the daily need to operate diesel generators in support of current and future mission operations and testing capabilities,” according to the report.

The on-base power supply would supplement “the more vulnerable and lower quality power” from the distant Kauai Island Utility Cooperative power plant in Eleele. Not adopting the solar plan “would prolong 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.”

Typically, the system would charge the batteries during the day, and then the batteries would discharge at night to provide power to the community grid, according to the plan.

The proposal suggests up to 44 megawatts of DC power.

“However, the actual size of the project will take into consideration the amount of capacity the utility can accept,” the Navy said in an email. “This may be much less than 44 MW.”

The environmental report said the project could be constructed in phases, with up to 21 megawatts of DC power on 87 acres in the first phase and up to 23 megawatts on 94 additional acres in the second phase.

The federal government converts alternating-current, or AC, power to about 77 percent of DC, so that would mean just under 34 megawatts of AC power for the full project.

The 27.6-megawatt AC power Waianae Solar Project on 200 acres — Hawaii’s largest photovoltaic effort — recently began operation. Hawaiian Electric said developer Eurus Energy America would sell it power at a rate of about 14.5 cents per kilowatt-hour, making it one of the state’s lowest-cost renewable-energy projects.

The Navy proposes to lease up to 181 acres of PMRF land to a developer for the construction and operation of the PV array and battery system. Asked at what cost the solar power would be sold to KIUC, the Navy said, “Specifics of the project are still being determined. However, should the project move forward, any (power purchase agreements) would be between the developer and the utility.”

The Navy said the specifics of the battery system to be used are still being determined. “The intent is that the (batteries) will be designed to provide power to the installation during contingency situations when the KIUC grid supply is not reliable,” the draft environmental assessment said.

Construction is anticipated to start no sooner than December.

PMRF is home to about 1,000 employees, including 100 sailors, more than 100 civilian employees and about 750 contractors and tenants, the Navy said. During a missile test the number of base personnel can swell by 100 to 400 additional people.

PMRF remains central to many of the nation’s missile tests as threats increase around the world, meanwhile.

The U.S. Missile Defense Agency and Navy in December tested the versatility of the SM-6 missile with two of the rockets fired at a ballistic missile target in the “terminal,” or final, phase of flight.

The Pearl Harbor destroyer USS John Paul Jones fired the defensive missiles after a target missile was launched from PMRF. The target missile represented a medium- range ballistic missile — something the U.S. military is increasingly concerned about.

The SM-6 Dual 1 missile is considered a “triple threat” in that it can be used for increasingly lethal cruise missiles that come in low; for ballistic missile defense; and for anti-surface warfare against ships.

A next-generation guided missile known as the SM-3 Block IIA developed by the United States and Japan was flown in its first target intercept test off Kauai earlier this month. The bigger SM-3 Block IIA has more than twice the range of the current SM-3 Block IA and IB interceptors deployed on 33 U.S. Aegis ballistic missile defense ships, according to the nonprofit Missile Defense Advocacy Alliance.

Additionally, the Navy and Raytheon in June installed an AN/SPY-6 radar, also known as the Air and Missile Defense Radar, at PMRF for air and surface targeting tests. Raytheon said the radar, to be installed on the Navy’s Flight III destroyers, can see a target half the size and twice the distance of today’s radar.