Groton — The Naval Submarine Base moved another step closer to having a 7.4-megawatt fuel cell park on its grounds, which officials say will enhance the base's military value by reducing energy costs and making it more energy resilient.

Those involved marked the progress with a groundbreaking ceremony Wednesday at the future site of the fuel cell park, which is not much bigger than a tennis court, adjacent to the base's power substation.

Construction of the multimillion-dollar project is expected to start in September. When complete, it will supply electric power to the base and the local power grid.

The project is happening through the Navy’s Enhanced Use Leasing Program, in which construction or renovations on underused federal property is funded by a private developer leasing property, with rent paid by the developer in the form of cash or in-kind service such as power and equipment upgrades.

Fuel cells, in this case manufactured in Torrington, use an electrochemical process and natural gas to produce electricity. They also produce as byproducts heat and water that can be used for other purposes.

"It is designed to compete with the grid, and be better than grid power, but it's also about resiliency and the reliability of having power locally on base," said Tony Rauseo, senior vice president and chief operating officer of Danbury-based FuelCell Energy, which is designing, manufacturing and overseeing the installation of the fuel cell park.

FuelCell Energy then will sell the power generated by the fuel cells to the Connecticut Municipal Electric Energy Cooperative, or CMEEC, which oversees the local grid and has entered into a 20-year purchase power agreement with the Navy.

The fuel cell park will produce about 64 million kilowatt hours of electricity annually, according to Drew Rankin, executive director of CMEEC. By comparison, a typical house in Connecticut will consume about 600 kilowatt hours of electricity a month or 7,200 kilowatt hours a year, Rankin said.

The amount of electricity that will be produced from the fuel cells is about 5 percent of the CMEEC's total supply demand. Its member municipalities include Groton, Norwich, Jewett City, Bozrah and Norwalk. In the event of a regional blackout, the base could tap into the fuel cell park's output, and it would meet all of the base's critical load demand, according to Rankin.

Based on an estimate of 7.5 cents per kilowatt, the fuel cells will allow CMEEC to save between $1 million and $2.5 million per year for the next 20 years, he said.

The project, which is expected to be complete by the end of May 2019, is part of an overall Navy goal to reduce energy consumption and reliance on foreign sources of oil and rely more on the use of alternative sources of energy. Energy is the single largest cost for Navy installations, according to Capt. Paul Whitescarver, commanding officer of the base, which spends more than $10 million in energy costs per year, about 25 percent of its annual operating budget.

Energy costs were a huge factor in determining military value during the 2005 Base Realignment and Closure, or BRAC, process, during which the base narrowly escaped closure.

Reducing energy costs frees up money for other purposes, such as operations and improving tactical performance, Whitescarver said.

The project was years in the making, said Bob Ross, executive director of the state's Office of Military Affairs, starting with Capt. Marc Denno, base commander from June 2009 until May 2013, then Capt. Carl Lahti, now an admiral, who took over from Denno, then Whitescarver, who chimed in, "but I'm finishing it."

The initial idea, Ross said, was to build two diesel generators to provide emergency backup power to the base. He called Wednesday's event a "big step in a big idea."