BAR HARBOR — The 288-panel solar array on the Public Works Building will soon have a battery to go with it, as approved by Town Council in a unanimous vote last month.
The battery will store energy produced by the solar panels, and this energy will be used during periods of high energy demand. For the first five years, savings in the town’s utility costs will go to pay off the battery. Once paid off, the battery is projected to save the town over $7,500 per year in utility costs.
The battery installation was proposed by ReVision Energy, who installed the town’s solar array in 2015. Hans Albee, Professional Engineer for ReVision, told councilors at the June 18 meeting that having a battery to store energy would “continue to reduce cost at the facility.”
Towns and other large consumers of electricity have two parts to their electric bill.
“There’s a charge for the energy, and a charge for how fast you’re using that energy,” Albee said. The latter charge, known as the “demand charge,” can account for up to 50 percent of the electric bill, Albee said.
“A storage system can monitor flow of energy,” Albee said, “and if it gets to a level that triggers the demand charge, power would come from the battery.”
Albee proposed that ReVision would install the battery with no upfront cost to the town.
Money saved on the town’s electric bill, would be paid to ReVision until the cost of the project was paid off. Then ownership of the battery “would be passed over to the town,” Albee said.
Councilor Gary Friedmann, who helped negotiate the solar panel installation project in 2015, said, “When we put these panels on, we knew that [energy storage] was going to be an issue. At the time, the batteries weren’t as attractive economically.”
With advances in lithium-iron batteries, Albee said, the cost has come down. “Energy storage projects like this are just starting to be happening in the state,” he told councilors.
“I love this idea. I don’t see a downside,” said Councilor Judie Noonan.
Councilor Erin Cough asked what maintenance costs the town would incur once the battery is paid off. Albee said costs will include an anticipated replacement of battery cells after 10 years, and an annual service $600 fee for managing the battery. All the expenses have been calculated into the savings estimate, he said.
“Down the road you’ll see some savings, definitely,” said Stan Harmon, the town’s finance director.
The solar panel array installed in 2015 generates electricity for the Public Works departments operations. That year the council approved a 20-year Power Purchase Agreement (PPA) with ReVision and Emera in August.
Under the PPA, the solar array is owned and paid for by ReVision, which supplies electricity to the town at a set rate.
After six years of use, the town has the option to purchase the system at fair market value. That purchase, if it happens, would nullify the PPA.