JUNE 2011

Bright idea – solar power over landfills Click to Enlarge
E-mail the author

Last year the United States Environmental Protection Agency (EPA) and the Department of Energy’s National Renewable Energy Laboratory announced that they are evaluating the feasibility of developing renewable energy production on superfund, brownfield, and former landfill or mining sites. They identified more than 11,000 sites that are good for renewable energy.

While the federal government evaluates, private investors, private and public landfill owners are on the prowl to generate more income or reduce expenses on their vast expanses of denuded real estate. Putting photovoltaic cells (PV) on closed landfills, whether in the form of flexible solar-geomembrane technology or conventional panel arrays, is beginning to emerge as a practical solution.

Today, there are fewer than 10 solar installations on United States landfills – a mix of flexible membrane covers utilizing thin-film PV cells and more traditional glass-faced panels. Most are considered in the demonstration phase, but Republic Services, one of the country’s largest solid waste handling companies, has gone beyond the pilot stage and is currently installing a one megawatt solar-geomembrane system in Atlanta, Georgia. 

Meanwhile, environmentally progressive states like Massachusetts are beginning to issue permits for solar projects on closed landfills. Some are already starting construction.

When completed, Republic’s 1 MW system will be the largest in Georgia.

The logic of installing solar arrays on closed landfills is compelling. A September, 2009 study commissioned by the EPA entitled Solar Power Installations on Closed Landfills: Technical and Regulatory Considerations illuminated the potential, “Since 1988 the number of municipal solid waste (MSW) landfills in the United States has decreased from 7,924 to 1,754. Accordingly, at least 6,170 landfills have closed over the past 2 decades. Estimates for the total number of closed landfills in the United States are as high as 100,000. This roughly estimated number of landfills represents hundreds of thousands of acres of real property.”

Accordingly, the EPA is encouraging the reuse of contaminated lands, including properties with closed landfills to site clean, renewable energy projects. Through the Re-Powering America’s Lands Initiative, EPA’s Office of Solid Waste and Emergency Response (OSWER) has identified several important reasons for siting renewable energy facilities on contaminated lands such as landfills, including:

  • Thousands of acres of open space in areas where solar installations may be less likely to involve community concerns over aesthetics.
  • Lower transaction costs compared to greenfield real estate.
  • Contaminated lands have environmental conditions not well suited for commercial or residential zoning and are in low demand by real estate developers.
  • Electricity generated from renewable energy projects on contaminated or remediated lands can be used onsite or sold or credited for offsite use.

Naturally, doing anything new at landfills is fraught with engineering, permitting, regulatory and construction obstacles.

Nevertheless, with leadership provided by MassDEP, Borrego Solar, a private developer of commercial solar projects, has signed a contract with the City of Easthampton to build a 2.3 megawatt DC solar plant on the city’s closed 12 acre landfill. Under a 10 year Utility Credit Purchase Agreement (UCPA) with East Hampton, Borrego will design, build and maintain the system that will produce approximately 2,774,823 kilowatt hours of electricity per year. The in-house financing arm of Borrego, Green Lake Capital, is handling the UCPA with the city.

“Easthampton is the only landfill project involving a signed contract. This project is in the design and permitting phase and will begin construction this summer,” said Joe Harrison, Borrego’s project developer. “We have also been awarded contracts for other Massachusetts solar projects on landfills in Lancaster, Dartmouth, Kingston and Methuen. When we say “awarded” it means we were selected through the request for proposal (RFP) process and are now negotiating the utility credit purchase agreements (UCPA) with the municipalities.”

Borrego is also short-listed as a bidder on five other solar landfill projects in Massachusetts.

Installing a large-scale PV array at Easthampton without penetrating the top soil cap will be accomplished with a ballasted-racking system. Racks of PV panels will be anchored to a series of 5,000 lb. reinforced concrete blocks, or ballasts, that sit atop the cap. Ballasts can be pre-formed off site and placed on a landfill, but in the case of Easthampton they will be poured in place because the site was capped over 20 years ago and most settling has occurred. One of the challenges of installing solar on capped sites is the limitation on the weight of equipment that can work on the landfill.

“Most experts say that the majority of settling occurs in the first 10 years and varies depending of what is in the landfill. We are designing a ballasted system that can withstand a few feet of further settling over the 20 year life of the solar system,” said Harrison. “Easthampton is excellent for a ballasted system. It’s relatively flat with a gentle 3 percent grade to the south.”

DC solar power will be inverted to AC by 4, 500 kilowatt inverters, each located in a metal building next to the landfill. As part of the deal, Borrego will upgrade a mile of transmission line to three-phase power to handle the load.

“We are scheduled to break ground on the site in June and finish construction by fall. Then there will be a couple of months testing and commissioning. The system should come on line in February, 2012. This will be the largest project of its type to be built on a landfill in Massachusetts,” Harrison noted.

Over the 10 year agreement, the city of Easthampton expects a cumulative cash flow of $1,777,868. During that time, Borrego is fully responsible for operating and maintaining the system. At the end of 10 years the city can purchase the system at fair market value, have it removed by Borrego Solar with the site restored to its original condition, or renew the agreement with Borrego for 2 5-year terms.

According to Harrison, MassDEP is extremely supportive of putting solar on landfills and has streamlined the permitting process. “They have an initiative to get solar on landfills. Everyone is aligned in terms of brownfield and landfills because it is a great application. There’s only so much you can do with landfills and here’s a way to generate money for the town and save taxpayers money. The two main concerns are – don’t penetrate the cap and have a good stormwater runoff plan that deals with the solar installation.”

“I think that the future is extremely bright for every landfill that is relatively flat and in close proximity to a three-phase transmissions line. In Massachusetts we have already identified 25 landfills that have been closed for more than 20 years that the size is large enough. There’s another 150 where we don’t have all of the information but we know they have potential. We are just at the tip of the iceberg, so to speak, as far as market potential is concerned,” Harrison concluded.

In 2009, Republic Services installed the first solar-geomembrane landfill closure system at its Tessman Road Landfill in San Antonio, Texas. According to Tony Walker, project manager at Republic, the pilot project has proved successful to date.

Now Republic has scaled up the concept and is in the midst of building the largest PV installation in all of Georgia –not conventional PV, rather a one megawatt solar-geomembrane at the company’s Hickory Ridge Landfill in Atlanta. And, Republic is using a new and improved Spectro PowerCap made by Carlisle Energy Services.

At the first Texas project, the geomembrane and the solar cells were laid down separately. Now the solar cells and the membrane are integrated at the Carlisle factory, come in green rolls 12 feet wide by 200 feet long, ready to be rolled out.

“Carlisle bonds a 60 mil. Thermoplastic Polyolefin (TPO) to the solar strips at the factory. Now all we have to do is thermo seal them together on site and run lines down to the combiner boxes. It really saves on time and labor,” says Walker.

Spectro PowerCap will cover roughly 10 acres on the south slope of the Hickory Ridge Landfill and is scheduled to go online this June. Under a Power Purchase Agreement, electricity will be sold to Georgia Power

For landfill closings, solar-geomembranes are likely to spread across America. In March, the New Jersey Meadowlands Commission signed a memo of understanding with Carlisle to study the feasibility of using Spectro PowerCap at their Erie Landfill.

Putting solar on closed landfills is a great use of space that is otherwise non-productive, especially realized with the economies of scale of over one megawatt production. With municipal budget strains, they will likely be a welcomed source of income. As these early projects prove their value and as standard engineering solutions are accepted by state regulators, mating landfills and solar is looking like a very bright idea.