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Landfill cover promotes new energy source

Case Studies | August 1, 2009 | By:

Energy and waste-disposal companies today recognize that landfills aren’t just burial sites for garbage, but reactors where gases produced by decomposing waste can be used for energy production.

A great example of this technology is at the Tessman Road Landfill in San Antonio, Texas, where Republic Services Inc. is incorporating a biogas-to-energy recovery system into one of its 213 landfills. But the Tessman Road project is taking energy recovery to a new level, including installation of a geomembrane landfill cover that includes flexible solar technology that will help power a sustainable energy park.

By combining a first-of-its-kind solar technology with an existing biogas-to-energy system, the company is turning its Tessman Road Landfill into a sustainable energy park. This green energy venture covers portions of the closed areas of active landfills with flexible, laminate-type photovoltaic (PV) solar collection strips (Photo 1). Photo 1| Flexible, laminate-type photovoltaic solar collection strips are configured on the geomembrane cap to maximize hours of sunlight throughout the year. Photo courtesy of CPS Energy.

The flexible solar laminates, which capture the sun’s rays for conversion into electricity, are adhered directly to the synthetic, green-colored geomembrane (Photo 2) used to cover and close landfill cells as they reach capacity. Photo 2 | The flexible solar laminates are adhered directly to the geomembrane. Photo courtesy of Republic Services Inc. Unlike traditional rigid solar panels, which are bulky and frequently cost-prohibitive to install, this system uses flexible, nonreflective collection strips less than 0.25in. thick. The flexible solar strips can be configured to maximize the hours of sunlight exposure throughout the year, depending upon a landfill’s design and site contours.

For its demonstration project at the Tessman Road Landfill, Republic Services is partnering with CPS Energy, Greater San Antonio’s electric and natural gas provider, to deploy 5.6 acres of the 680-acre landfill with the solar energy cover, attaching more than 1,000 flexible solar strips to the landfill’s south-facing sideslope. Republic and CPS Energy will study and document the results of this solar demonstration project for use in the deployment of solar energy covers on other landfills throughout the country.

Construction on the Tessman Road project, approved by the Texas Commission on Environmental Quality (TCEQ), began in December 2008 and became fully operational in March 2009.

“As the nation’s largest municipally-owned gas and electric company, we’re proud that our customers’ energy bills are among the lowest in the country,” said Milton Lee, CPS’s general manager and CEO. “We are able to do this by providing a diverse mix of fuels and renewable energy sources that combined offer reliable, cost-competitive electric service. Working together with Republic and the Texas Commission of Environmental Quality, we are at the forefront of yet another useful way to tap the energy resources of landfills for the benefit of our customers.”

Republic says it will cover closed landfill cells with the solar collection strips, adhered directly on the geomembrane cap. The solar strips are configured to maximize hours of sunlight throughout the year. The new solar cover will complement the landfill’s existing biogas-to-energy system, in operation since 2002.

The system collects and processes biogas, which is produced naturally at the landfill through the decomposition of waste. The solar strips, which have flexible photovoltaic silicon cells that convert sunlight directly into electricity, will complement the amount of renewable energy provided by the landfill.

With more than 300 days of sunlight per year in San Antonio, Republic estimates that the energy produced by the two fully-operational systems, will continuously create about nine megawatts of power—enough to power 5,500 area homes.

“As part of our commitment to creating cleaner, greener communities, we’re continually researching, developing and implementing innovative technologies to help us preserve and conserve our natural resources,” said Ted Neura, senior director of sustainable business planning and development for Republic Services.

“The solar energy [geomembrane] cover is easier to inspect, maintain, and repair than a traditional clay cap, and is technically superior in terms of odor control and stormwater management,” said Tony Walker, project manager for Republic.

“Geomembrane covers are already in use across the country, but [we are] the first to integrate flexible solar cell technology to create an energy-producing cover system. We look forward to working with state regulators across the country to capitalize on the opportunities provided by landfills and, specifically, our efforts to further the country’s energy independence movement through new sources of solar power,” said Walker.

Republic has 213 operating landfills in 40 states. The company’s research suggests that as much as 2,350 acres could be covered with solar energy geomembrane covers, depending on regulatory approvals. That could translate into enough solar energy to power up to 47,000 homes per year. Combining that with existing biogas-to-energy technology, and there is the potential to generate enough green electricity to power 300,000 homes.

Sources: Republic Services Inc., PRNewswire

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