AES Corp. has completed a solar power plant on Kauai that can do something most renewable projects can’t: deliver power when it’s most needed.

The 28-megawatt solar farm on the south shore of the Garden Isle includes a first-of-its-kind design that transfers power from the sun to batteries and onto the power grid more efficiently than other existing storage systems, AES Chief Executive Officer Andres Gluski said Tuesday in an interview. That allows the Lawai Solar and Energy Storage Project to supply energy more consistently than typical wind or solar farms.

“We’ve passed the 50-yard line, and the end zone is in sight,” Kauai Island Utility Cooperative President and CEO David Bissell said as the cooperative and its renewable energy partner AES unveiled the state’s largest solar-plus-utility-­scale-storage power facility.

AES owns and operates the Lawai project, which will supply electricity to KIUC. It will eliminate the need for about 3.7 million gallons of diesel annually and supply about 11 percent of Kauai’s electricity, making the island more than 50 percent powered by renewables, according to a KIUC statement.

More than 100 people attended the blessing and had a close-up look at the solar panels and batteries that are now operational.

“Now that the Lawai project is online, as much as 40 percent of our evening peak power will be supplied by stored solar energy,” Bissell said. “I think it’s safe to say this is a unique achievement in the nation and possibly the world.”

The project includes a bank of batteries that can deliver power for as long as five hours, to a maximum of 100 megawatt-hours, Arlington, Va.-based AES said in a statement.

Besides supplying local utilities, this type of system could be used at military installations that want to reduce fuel deliveries or remote mines far from power grids.

AES expects to build more of them.

“The big problem with solar is that it peaks when demand does not peak,” Gluski said. With batteries, “that energy is much more useful for the grid and for consumers.”

Solar panels create direct-­current electricity that must be converted into alternating current before it’s sent over the grid. The AES design uses a more efficient conversion process that makes it faster and cheaper, said Woody Rubin, president of AES Distributed Energy.

“You really are combining speed and flexibility there,” Rubin said. “The plant ramps to provide true capacity faster than any thermal ramping resource on the island.”

Star-Advertiser staff contributed to this report.