Photovoltaic panels mounted on the roof of part of the Bar Harbor Public Works building complex are arrayed east-west, rather than facing south. The town is buying the electricity they generate from ReVision in a power purchase agreement. PHOTO COURTESY OF REVISION ENERGY

Array producing electricity

BAR HARBOR — The solar array on the roof of the Public Works building here has been fully operational since Jan. 19, producing energy for operations.

For the year to date, overall production is 11 percent below original estimates.

The system was built and is owned by ReVision Energy, a Maine corporation specializing in solar power. Under a power purchase agreement (PPA) approved by the Town Council in August 2015, all the power from the solar array is credited to the town’s account with Emera Maine. The town pays Emera a bit less every billing cycle, but the town pays ReVision an agreed-upon flat rate per kilowatt-hour for that power. This year, that rate is 10.259 cents.

“The town is going to make more or less money depending on what the price of electricity does,” Town Council Vice Chair Gary Friedman said.

Voters at the 2015 town meeting approved a warrant article allowing the town to enter into the necessary long-term lease agreement. Under the agreement, the town has the option to purchase the system from ReVision in 2021. It’s the first municipal photovoltaic system in Emera Maine’s service area, officials said at a dedication event in October.

Real-time and historical production levels for the system may be viewed online.

In April and May of this year, the panels produced 9.21 and 9.75 megawatt-hours, respectively, above the target of 8.2 set by the system’s designers at ReVision energy. Production in February and March was below the targets, which are different for each month of the year based on overall expected weather, ReVision engineer Hans Albee said.

The town is buying only the amount of power actually produced; the production targets are not part of the financial agreement.

“We primarily use the tool for seeing what the system is doing,” Albee said. “The targets represent the average production we expect for a day in a given month. In the next six years, we’ll have a much better idea, for this specific array for this specific site, what the production looks like.”

Albee said the east-west array should do a good job at providing power for demand that’s spread over the workday.

“If you look at the graph of daily production, east-west arrays make a wide, flat curve. Production ramps up faster in the morning and lasts longer in the evening. The graph for a south-facing array would be narrower and taller.”

Friedman said Emera also is interested in data from this system.

“Right now, they don’t know how solar installations are affecting the grid locally. They only know what’s going on monthly.”

The power company wants to know how much power is going out into the grid at peak and off-peak demand times. “They’re installing meters at the site to be able to gather this kind of data,” Friedman said.

Liz Graves

Liz Graves

Reporter at Mount Desert Islander
Former Islander reporter and editor Liz Graves grew up in California and came to Maine as a schooner sailor.

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