Most of the region’s solar arrays are buried beneath mountains of snow this winter, temporarily obscuring their ability to offer big savings on utility bills.
For the city of Boston, a bright spot emerged in the findings of a newly-released study that far exceeded officials’ expectations for the solar-generating potential of municipal buildings including City Hall.
“These are the next best places to continue our push on solar,” said Joseph LaRusso, the city’s energy efficiency and renewable energy finance manager. “We’re hoping to at least triple the amount of installed capacity.”
Boston generates just under a megawatt of electricity from solar farms at the city archives building in West Roxbury and its transportation building on Frontage Road.
Cambridge-based Zapotec Energy analyzed all 321 of the city’s municipal and school buildings and identified a top-25 list capable of generating 3.8 megawatts of electricity annually. That’s nearly twice the goal set out by the city’s Environment Department last year when it commissioned the study using a $40,000 grant from the U.S. Department of Energy.
Community Centers As Shelters
The city designated four community centers as priority sites for solar installations to improve their readiness as emergency shelters.
Using a $1.3-million grant from the state Department of Energy Resources and a $145,000 city contribution, Boston will install battery-powered backup generators at four community centers. LaRusso said.
Those four sites – Roslindale Community Center, Curtis Hall Community Center in Jamaica Plain, Tobin Community Center in Mission Hill and John Shelburne Community Center in Roxbury – could support a combined 181 kilowatts of photovoltaic systems, according to Zapotec.
Boston Mayor Martin Walsh requested that City Hall be listed as another priority site.
The Government Center property has surprisingly good solar potential despite its proximity to skyscrapers in the Financial District that cast shadows on two-thirds of its 1.5-acre roof most of the year, Zapotec President Paul Lyons said. City Hall could support a 43-kilowatt solar array on the corner of the roof closest to the John F. Kennedy Federal Building, Zapotec determined.
“It’s a fairly small array, but it will produce a fair amount of energy in a reasonably efficient manner,” Lyons said.
Zapotec collected information from four city databases on aspects of each building, including its square-footage and how recently the roof was replaced. Only buildings with roofs that are less than 8 years old or are due for imminent replacement were eligible for solar arrays, Lyons said.
The company calculated average daylight sunshine on Dec. 21 – the shortest day of the year – for each property using solar performance software from the National Renewable Energy Laboratory. Buildings that receive full sunshine between 9 a.m. and 3 p.m. during the winter drew the highest ratings, Lyons said. Zapotec also analyzed the capacity of the roofs to support the self-ballasted solar systems, which weigh about eight pounds per square foot.
Properties capable of supporting the most powerful systems were all schools with roofs in the 2-acre range. The top-performing systems would be located at James Hennigan Elementary School, Richard Murphy Elementary School and Brighton High School, the study determined.
Offshoot Of Greenhouse Initiative
In 2007, the city set a goal of reduction greenhouse gas emissions from municipal operations by 25 percent from 2005 levels by 2020. A 2011 update to the climate action plan set the same goals for the entire city, followed by such initiatives as mandatory building energy disclosures for large commercial landlords.
Fiscal savings are another top consideration.
City environment officials expect the solar upgrades could cut the city’s $26 million annual electric bill by hundreds of thousands with no upfront costs through power purchase agreements with solar companies. The city will solicit proposals from solar providers later this year, said Austin Blackmon, who was named the city’s chief of environment and energy in November.
The most common arrangement for municipalities is to grant solar companies permission to install and own photovoltaic systems on city properties. The municipality then agrees to purchase electricity for a fixed rate and time period such as 20 years. Typically, there is no upfront cost.
The final site selection will take place after developers submit containing more detailed information on the properties’ structural capacity and electrical systems, LaRusso said.
Email: sadams@thewarrengroup.com
