With an eye on spiraling energy prices, the city of Boston is studying its biggest-ever solar energy project designed to harvest rays atop municipal buildings and shave its $26.3-million annual electric bill.
Cambridge-based consultants Zapotec Energy began a study in October of Boston’s 321 municipal and school buildings, including City Hall, to determine which have the most potential for productive rooftop solar arrays. The goal is to generate up to 2 megawatts of photovoltaic energy annually, or over 1 percent of the city’s annual usage.
“The volatility of the electric prices is concerning to businesses and government,” said Brian Swett, the city’s chief of environment, energy and open space. “Obviously this winter is a big spike and the volatility is significant.”
Rates for the National Grid electricity customers in Massachusetts will rise 37 percent beginning this month. NStar, which is Boston’s electric utility, has not filed its rate increase proposal for the year beginning in January, but is expected to seek a similar increase because of rising costs to buy electricity on the wholesale market.
A $40,000 grant from the U.S. Department of Energy paid for the Boston study, expected to be complete in December. The program is part of Boston’s 2011 climate action plan, which seeks to reduce greenhouse gas emissions by 25 percent by 2020.
In addition to solar capacity, Zapotec will look at buildings’ ability to handle the weight of solar arrays and how recently their roofs have been replaced. After Zapotec identifies the buildings with the most potential for solar generation, the city will issue a request for proposals from solar companies.
Two potential business models are being considered. In the first, the city would pay for the up-front installation costs and own the system.
Alternatively, under a power purchase agreement model, the city would agree to buy electricity from the solar installer, which would own and maintain the equipment. Because there would be no up-front costs to the city, a project using that arrangement could start during the current fiscal year running through June 30. The price would be fixed for a period of time, typically 20 to 25 years.
Boston buys its electricity from Holden-based Direct Energy, a third-party retail supplier that uses NStar’s transmission lines and offers discounts to residential and institutional customers. But the rates offered under a solar-based power purchase agreement model would be even lower, city officials predict.
“The volatility of energy prices is as concerning as the actual price,” Swett said. “It’s the drastic changing that makes it very hard to budget, so the value of able to hedge and have some predictable power costs coming in is significant. If we can know what our electricity prices are for the next 20 years, that’s helpful.”
City Hall An Option
Among the large municipal buildings that could be included, officials say, are Madison Park High School in Roxbury and City Hall.
“One of the first questions [Mayor Martin Walsh] asked when we sat down to review our energy efficiency plans was about City Hall,” Swett said. “Taking a look at this building, it’s a nice concrete structure, but there are shadows from 60 State St. and other buildings with significant shading. But there are actually some portions of the City Hall roof that may lend themselves to solar.”
Boston installed its first municipal solar projects in late 2012 at the city archives building in West Roxbury and transportation department building on Frontage Road in South Boston. The two buildings house 95- and 120-kilowatt installations, respectively, and the Frontage Road system supplies back-up battery power to fuel tanks used to fill up city vehicles.
At the same time, Boston is encouraging private property owners to maximize their solar-generating potential, part of the climate action plan’s goal of doubling the city’s solar-generating capacity to 25 megawatts by 2020.
In September, the city launched a website where residential and commercial land owners can enter their addresses and get an estimate of their property’s solar generation capacity and available incentive programs. The data on 127,000 properties is available online at www.mapdwell.com/en/boston.
It’s also launched some quirkier efforts designed to raise public awareness about clean energy, such as partnering with Cambridge-based startup Changing Environments to install solar-powered park benches that include cell phone chargers.
Email: sadams@thewarrengroup.com
