Landfill Solar Development

August 8, 2022

Based on the latest US EPA Landfill Technical data, there are currently 1,300 closed landfill sites within the United States1. As the number of active landfills declines, this land has been successfully converted into golf courses, parks, and nature preserves, and in recent years, solar development projects. These locations are ideal for solar development given their openness and exposure to direct sunlight, and provide an excellent opportunity for government authorities to capitalize on repurposing these lands to meet the ever-growing need for green energy.

A unique solution for each site

While a great opportunity to further green energy initiatives, installing solar projects on landfills is a complex process that involves consideration of several important elements including engineering, permitting, construction, and maintenance. Every solution is unique and tailored for each landfill site and requires design aspects different from a typical ground-mount solar installation.
When evaluating a landfill’s suitability during the engineering phase, there are quite a few characteristics that need to be assessed including:

• Landfill slope and slope orientation;
• Thickness of the cap, depth to specific cap components, and cap component function;
• Post-closure monitoring, maintenance, and use requirements.

Steeper slopes require lightweight arrays and heavier foundations to secure and stabilize the system. This limits the design of the photovoltaic (PV) systems, which can increase the loading and affect side-slope stability. This also affects inter-row shading in the array. The ideal site would be one with slopes less than 8%, but development on steeper slopes can be achieved.

Cap depth and cap components affect the PV design as well. Foundation designs are limited to non-penetrating structure systems. PV system wire management is also limited to above-ground conduits and trays, and not in underground trenches.

When it comes to the type of mounting system to be used, fixed-tilt mounting systems are the preferred option. These systems are typically oriented due south and tilted at an angle that is optimized for best performance. Single- and dual-axis tracker systems are avoided for several reasons. First, single-axis trackers are typically designed with a driven-pile or post and pier foundations which are rarely used in landfill applications; while dual-axis trackers typically require large concrete foundations that are too heavy to use on landfills and require penetration into the ground. Second, settlement in a landfill cap may result in tracker systems going out of alignment which could potentially have significant negative impacts on energy production and cause damage to the structural members.

In addition, the selection of electrical components requires an iterative design review. There are a wide variety of modules to choose from, requiring a decision-making process that achieves maximum energy yield for a particular site. Currently, the most viable options are the bi-facial modules which offer many more advantages over traditional panels. These modules produce output from both sides of the module, and therefore, increase total energy production to generate more power but with a smaller array footprint. Both sides of this panel are UV resistant making them more durable than the traditional options.

A need for proactive, experienced partners

Starting early and teaming with experienced partners is critical to landfill solar development projects especially when considering permit needs. A list of permits typically required- but not limited to – for a landfill solar facility are as follows:

• General Stormwater Discharge Permit
• Special Use Permit (applies if solar is not mentioned in the local zoning code)
• Brownfield Change of Use Plan Approval
• Local Site Plan Approval and Building Permit
• Air Permits
• Pollutant Discharge Elimination Systems Permit

Following the successful installation of the PV project, it is necessary to integrate the landfill post-closure maintenance requirements with the PV system monitoring and maintenance requirements. For example, washing panels to remove dust and silt deposits may be required to increase their performance. However, in landfill applications, cleaning fluids containing harmful chemicals are not allowed, as these chemicals could potentially leach beneath the landfill cover. If water-based cleaning is desired, and no on-site water source is available, the weight of the water trucks must be evaluated to ensure no damage to the landfill cover.

The Fisher Difference

Development of solar energy sites continue to increase at an exponential rate in the United States to meet our aggressive green energy goals. Finding suitable open space sites is a challenge that closed landfills alleviates albeit with additional challenges not faced with clean open space sites such as farmland. Fisher Associates understands these challenges and can help you navigate the planning, design, permitting and maintenance of your landfill solar project. Fisher’s renewable energy team will make your project a success, ensuring that the old adage “one man’s trash is another man’s treasure” rings true.

Contact Fisher Associates’ Interim Director of Energy, Lisa Oliver, P.E. at loliver@fisherassoc.com to learn more and help you prepare for your next solar project.