Solar Provides Second Life for Capped Massachusetts Landfills

The Project

GeoPro with Ballasted Foundation on Massachusetts LandfillThe Massachusetts towns of Easton and Ludlow are among the first communities to take advantage of an emerging trend in New England – they’ve transformed their capped landfills into clean energy farms by installing ground mounted solar panels. Over the course of a year, an average landfill PV installation will generate millions of kilowatt hours (kWhs) of power, generating lease revenues and saving the cities in which they’re located hundreds of thousands of dollars.

In March 2012, Borrego Solar Systemsexecuted 20-year power purchase agreements (PPAs) with the towns of Ludlow and Easton. Under these partnerships, Borrego Solar agreed to lease 14 and 8 acres of town landfill plots respectively in order to build solar power installations that would generate clean electricity to feed back into utility grid operated by Western Massachusetts Electric Co. (WMECO) for Ludlow and National Grid for Easton.

“This will save the town $140,000 a year and more than $2 million in savings over the life of the contract,” said Ludlow Energy Committee Chair James P. “Chip” Harrington. “Electricity now costs the town 9 cents per kilowatt hour. Estimates are that the cost will come down to 4 or 5 cents per kilowatt hour.”

Easton Town Administrator David Colton said that the “annual $33,000 lease and lower cost of energy credits will save the town about $225,000 a year…Between the revenue, land reuse and green energy, what’s not to like?”

In April 2012, Borrego Solar retained SunLink to engineer the racking solutions for both sites, a 2.6 megawatt (MW) solar energy system for the town of Ludlow and a 1.9 MW installation for the town of Easton.

The Challenge

SunLink’s GeoPro was originally conceived as a utility-scale post-mounted system, with the company’s smaller Ballasted GMS serving as the most-often-selected product for projects like landfills where penetrating the protective membrane (or ‘cap’) is prohibited, and some amount of topographic settling will occur. However, in this case, the project developers at Borrego Solar desired a utility-scale solution, making GeoPro the right product for the projects. With Borrego Solar’s installation criteria in mind, SunLink’s product engineers set out to develop a ballasted version of GeoPro* which would be optimized for the Massachusetts landfill environments.

*GeoPro with a ballasted foundation has since become a standard product offering.

The Solution

GeoPro Fixed Tilt Racking with Ballasted Foundation on LandfillSunLink product designers customized a GeoPro product for the Ludlow and Easton landfills by focusing on three objectives: a ballast, rather than post-mounted foundation; minimizing the load at each ballast block; and allowing for differential settlements.

As a starting point, Borrego Solar used SunLink’s proprietary boundary layer wind tunnel testing values to design the ballast blocks to be used on each site. The larger surface area of the ballast design was a critical element in making sure that the caps’ integrity would be maintained. SunLink then adapted its post design to incorporate a steel base plate which would be used to attach the system to the ballast blocks.

In order to both minimize the load at each ballast block and allow for differential settlement, the standard continuous-row configuration typical in GeoPro installations was modified to a table solution consisting of five four-module-in-landscape panel assemblies. The foundation locations were also pulled in to optimize the efficiency of the support purlins, creating a double cantilever structure.

To keep installation costs down and speeds up, the Borrego Solar crews set up prefabrication stations between the rows where the modules were “prepanelized” with the racking hardware using SunLink-supplied jigs. In Easton, the panel assemblies were manually lifted into place and fastened to the substructure, while in Ludlow a SunLink-supplied lifting jig was used to install the panel assemblies mechanically. GeoPro was designed to allow either installation method, depending on customer preference.

“SunLink is one of our strategic racking solution partners because they consistently deliver high quality products at competitive prices,” said Aaron Hall, president of Borrego Solar Systems. “We have an internal team of engineers called the Resources Group, whose task is to vet and approve new and existing products available in the marketplace, ensuring we’re always delivering the greatest value to our customers. They have always been impressed with the attention to detail coupled with extensive testing and engineering that goes in to the SunLink product design and manufacturing. In addition, their suite of products can handle pretty much any type of project.”

Together, Making a Difference

The ballasted GeoPro provided the solution that Borrego Solar needed to provide its customers in Easton and Ludlow with the highest possible energy output and most aesthetically pleasing solution for their landfill solar farms.

“As our industry grows so does competition and the availability of top quality products and services. It is increasingly more important for manufacturers to add value in other ways than just low prices and quality products.” Hall said. “SunLink works with our engineers to provide innovative and creative solutions to complex challenges in the field. If we need their help we can count on it. They understand our objectives as well or better than any other suppliers, which allows us to value engineer together almost as if we were one company.”

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