Landfills can be great sites for solar, as long as attention is given to certain considerations unique to these projects.
Location
One of the first considerations in developing a solar project is to find a suitable location. Several basic land-related requirements must be satisfied, including:
• Low development cost real estate
• Sufficient sun exposure
• Accessible utility and distribution infrastructure
A copious yet under-utilized resource that can accommodate all three basic requirements is a capped landfill. A typical landfill spans five to 50 acres and is situated along a developed transportation route at the outskirts of an urban or suburban area. The space is relatively clear and open. Many offer a robust grid infrastructure, as power is used to process waste or, often, the local power plant reclaims and uses the landfill gases to generate new power. Once a landfill has served its purpose, it is formally capped and then, too often, becomes a vacant lot with few development options. Recently, however, investors and developers have begun to see the potential in these sites for solar projects.
Design
Developing a solar project on a landfill, however, poses a new set of challenges for system designers. Beneath the surface, landfills can produce flammable gas as part of the decomposition process. Most landfills are aged to the point where the excess gas is minimal, but there is always a presence of gas and developers must be mindful of this fact in their system designs. To prevent the contents beneath the surface from contaminating the surrounding environment, the landfill cap cannot be penetrated. This makes racking and wire management difficult, as a typical ground-mount solar project would drive foundation posts deep into the soil. Similarly, the landfill cap cannot support heavy weight over a small area. Heavy, dense system design elements, like transformers and concrete foundations, require careful application. Finally, the landfill cap cannot be graded, so the PV system must follow the existing contours of the land.
These complex factors have a major impact on inverter selection. The inverter is the interconnection between the array and the grid, and the type of inverter used will be critical for success in landfill projects. There are two routes: central inverters or string inverters. Mechanical construction constraints as well as the electrical system design may dictate which to use.
As manufacturers advance inverter designs and can offer greater flexibility and higher system performance, landfill solar projects will become more attractive—and make good use of otherwise inoperative land.
By: Efrem Tagliamonte of Advanced Energy
Want more? Try these articles:
Solar Speaks: Considerations For Landfill Solar
Webinar – Landfill Solar: How To Mount On Moving Ground And Take Part In A Growing Trend
Tell Us What You Think!