Thick sheets of plastic have been used for years to cover closed, solid waste landfills. Called geomembranes, the plastic sheets keep rain water out and odors contained within the waste mass. Besides the potential recovery of beneficial methane gas, the capped area is virtually useless.
That was true until 2009 when Republic Services, one of the country’s largest waste management companies, made a technological breakthrough. It installed a geomembrane and covered it with -inch-thick photovoltaic collection strips. In doing so, Republic installed the first solar-membrane landfill cover of its kind, a 134-kilowatt pilot project at the Tessman Road Landfill in San Antonio.
“The system at the Texas landfill has held up quite nicely since it was installed. Durability was one of our prime concerns, but it’s performing well,” said Tony Walker, project manager at Republic.
Now a new approach is being scaled up to a 1-megawatt system at the Hickory Ridge Landfill in Atlanta, using improved solar-membrane technology that makes system construction faster and that reduces labor costs. At the Texas project, Republic Services laid down and trenched in place the geomembrane before the solar strips were affixed and connected together on-site. At the Hickory Ridge Landfill, Republic is installing a Spectro PowerCap made by Carlisle Energy Systems. This new dual-purpose landfill closure system laminates solar cells onto a 60 mil thermoplastic polyolefin (TPO) geomembrane at the factory.
“It’s basically just like unrolling carpet,” Walker said. “It comes in dark green rolls in sheets 12 foot wide by 200 feet long. It really speeds up the construction time and saves on labor. At the factory, they daisy chain the solar strips together, so all we have to do is thermoseal them together and run a main line down to the combiner boxes.”
Hickory Ridge will cover approximately 10 acres with solar cells on the south slope of the landfill. It is 50 percent complete and scheduled to go online in June. Electricity generated from the project will be sold to Georgia Power under a long-term power-purchase agreement.
“When completed, it will be the largest solar project of any kind in Georgia,” Walker said.
Membranes laminated with low-profile photovoltaics also have broad applications as roofing material, but there is growing interest from landfills across the country. In late March, Carlisle Energy Services signed a memorandum of understanding with the New Jersey Meadowlands Commission to study the feasibility of using geomembrane solar covers at the Meadowlands’ Erie Landfill. And, although, the number of landfills in the United States has dropped from approximately 8,000 in 1988 to 2,000 in 2009—there’s still a lot of land that could be covered to create clean electricity.