2019-01-11 / Community

Our Sustainable City

Clean green energy Is solar living up to our expectations?
By Julie Rosenbach
Sustainability Director

South Portland’s one-megawatt solar array at the city’s capped landfill came online in October 2017. It was the first solar array of this size – the largest project allowable under Public Utility Commission rules – on municipal property in Maine, highlighting the city’s commitment to renewable energy. In this column, we will talk about how the solar project came to be, how it is performing and the growing impact of solar energy in Maine.

First, a little background about our solar landfill project. With the goal of transitioning to clean, costeffective, renewable energy, the city hired Portland-based ReVision Energy to install a 2,944 photovoltaic panel array on our 34-acre former landfill, which is behind the city’s transfer station and new Municipal Services Facility. The solar array was projected to generate 1.2 million kilowatt-hours of energy per year, or roughly 12 percent of the electricity used by South Portland’s municipal and school buildings, and result in significant long-term cost savings for the city.

After years of scoping, the project came to fruition as a joint partnership between South Portland, Portland and Revision Energy. City staff members from Portland and South Portland worked closely with the principals of Revision Energy on the proposal, and after considerable work, arrived at financial terms that made moving forward with the project feasible and worthwhile.

Under the contract, the city does not actually own the solar array for the first six years. Instead South Portland purchases the electricity generated by the array from a third party financing partner who owns the project. This is called a Power Purchase Agreement (PPA). By using the PPA model, the city was able to significantly reduce the cost of the overall project by taking advantage of a federal tax credit that would not have applied to us as a nonprofit entity if we owned the project outright.

The PPA set an initial rate approximately 2.5 cents per kWh higher than what the city currently pays for electricity, with an annual escalation. This translates into a $31,000 premium annually for the first six years. Starting in year seven, the city has the option of buying out the system at its market value. Assuming the city executes this option, which is recommended in order to meet the project’s financial projections, the project will become cash positive and begin paying for itself annually because the energy savings will exceed the cost of debt service and operations and maintenance. Based on conservative projections (we hired experts to carefully review our assumptions and to model how changes in energy prices, changes in regulations, equipment performance and other factors would impact the finances of the proposed array), the project is expected to provide a full return on investment in year 11, and over the life of the project, save the city more than $3 million.

So, after its first full year, is the array living up to our expectations? Not surprisingly, yes. The array is performing within 6 percent of projected estimates. Though we can very accurately project out long term average performance, the variable weather within any given year makes production harder to predict, so solar array production within 10 percent of modeled estimates in any given year is excellent. We are right on track and in line with arrays in our surrounding area, which have experienced similar weather conditions over the past year.

Not only is our solar array producing the projected amount of energy, it’s now one of many arrays that are being installed on closed landfills in Maine. Other municipalities including Belfast, Portland and Eliot have capitalized on the sun’s potential for energy.

“Maine has a surprisingly strong solar resource because our latitude is identical to sunny places like northern Spain and the French Riviera. Few people up here are aware that a solar array installed in South Portland will deliver the same annual output as a solar array in Houston, Texas because we have good sunshine and because solar panels perform better in cool, dry climates. Another way to quantify our solar resource is to note that Maine gets just 10 percent less sunshine per year than most of Florida,” said Phil Coupe, co-founder of ReVision Energy, referencing the National Renewable Energy Laboratory’s studies on irradiance levels in the U.S.

These and other arrays across the region are helping us transition the way we use energy.

“Twice in 2018, solar power generation throughout New England caused a massive, historic shift in demand on the grid. On a sunny day in April, the 150,000 solar arrays in the region delivered so much power to the grid that for the first time ever, the 24-hour ‘low demand’ event occurred at 2 p.m. in the afternoon rather than 2 a.m. in morning,” Coupe reported. “Then on Thanksgiving, when it was again sunny and cool, those same solar arrays put so much power on the grid that the normal spike in demand from roasting millions of turkeys in electric ovens disappeared.”

Solar energy is no longer just for the eco few. Over the past several years it has become a smart, cost-effective, mainstream source of energy.

“People who have been thinking about solar should act quickly because Maine’s solar industry is going to be very busy this year,” said Coupe, noting that ReVision has about a six-week backlog of work at present and expects to fill up for the year sometime this summer.

Our Sustainable City is a recurring column in the Sentry intended to provide residents with news and information about sustainability initiatives in South Portland. The Sustainability Office is staffed by a full-time director and parttime program coordinator, and is located on the first floor of City Hall.

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