Landfill of the Rising Sun

Best practices for landfill solar installations.

Back in 2009, solar electric generation systems installed on previously assumed-to-be unusable landfills were few and far between. Only a handful of projects had actually been completed, like at the Republic Services-owned Tessman Road Landfill in San Antonio. But by 2010, the idea had gained traction as more town managers and landfill directors were attracted by the idea of converting their brownfields into greenfields while producing clean, renewable energy capable of either eliminating energy needs on site or creating energy for neighboring communities and power grids. These projects essentially amount to more money in a municipality’s general fund, or operation budget, and also can be seen as an additional source of revenue from a property that was previously written off.

In 2010, Rhone Resch, president and CEO of the Solar Energy Industries Association, reported that the compound annual growth rate for grid-tied photovoltaics (PV) from 2000-2009 was 69 percent. In 2009 alone, grid-tied PV grew 38 percent in the wake of an economic recovery, alongside a 40 percent decline in PV module prices. Regardless of the evidence supporting solar electricity hitting its biggest strides in the past five years, a common concern the industry still faces is finding appropriate locations to capture the maximum amount of sun while causing minimal impact on the environment. In the Southwestern deserts of Arizona, California and Nevada, sunshine is plentiful, but the lack of proximity to a power grid (point of interconnection) can be an issue that makes these projects financially unattractive. This is in addition to potential adverse effects a solar farm could have on some of the local endangered flora and fauna.

Rooftop installations in the center of major metropolitan areas have their own drawbacks: shading from foliage, pollution, adjacent properties, limited space, building code compliances and weight/load issues on structures with roofs that weren’t originally built to take on the additional 7 to 10 pounds per square foot.

These issues are what make landfills so attractive for solar projects. In our experience, the average landfill has at least five acres and often up to 80 acres of land suitable for solar. This leads to a potential of 1-16 megawatts (MW) of power on each given landfill, of which there are approximately 100,000 sites (either decommissioned or operational) across the country. By installing solar power arrays on even a quarter of America’s landfills, we can produce approximately 212 gigawatts (GW) of clean energy, which was nearly 500 times the solar energy produced in the United States in 2009 (425 MW). The environmental benefits of offsetting a portion of a municipality’s energy needs with clean energy combined with the cost savings involved are a win-win for tax payers and also serve as a great tool for meeting a state’s renewable portfolio standard (RPS), which requires that a certain amount of the state’s energy come from renewable sources by a specified period of time.

Despite these benefits, not every project is low hanging fruit. Site location, project timing and land specifications are the main considerations project developers analyze to determine which landfill projects are ripe for the picking and which need to be left on the vine. A good grasp of available financial incentives is important as well.

Site Location

Proximity to environmentally protected land parcels like wetlands, marshes, swamps, riverfront areas, flood plains or even land located within a buffer zone (usually within 100 feet of protected land) can handicap a project from day one. That’s why a good understanding of the properties adjacent to a prospective site can save you time and money.

In some states, like Massachusetts, a developer might need to file an Environmental Notification Form if the proposed renewable energy installation will generate 25 or more megawatt hours of electricity, or if the construction of the solar project will require the alteration of one or more acres of bordering vegetated land. Protected lands can sometimes require permission from conservation commissions that could take up to six months to obtain.

An experienced solar consultant or developer with a good understanding of the usual permitting costs and scheduling setbacks can help ease this part of the process. Moreover, when researching the feasibility of a solar project on your landfill, make sure you have access to a description of all existing utilities, site plans, site assignment limits and abutting properties within a 500-foot radius.

Aside from the need to pull permits and file notices with the local authorities having jurisdiction (AHJ), the closer your property is to a three-phase electric power line (13.8 kV line is common) the better. In some rural areas that are predominantly residential, there might only be a single-phase power line, which will most likely not have the capacity for a larger solar installation. One good rule of thumb is to know whether there are any large commercial electricity users in the immediate vicinity, because their circuits are more likely to have the necessary capacity requirements.

Anytime you have to trench and run conduit a lengthy distance to reach your point of interconnection to the grid, the cost of the installation is going to increase. Additionally, the more land your solar installation touches, the more potential there is for additional permits that need to be pulled, which can slow the project down. That’s not to say that excess land use can be prohibitive. Landfill operators who have a mile run from the solar array to the point of interconnection have still seen the economics work out. Nevertheless, any reduction in land use will increase your return on investment.

Project Timing

The cliché “timing is everything” certainly applies to landfill solar installations. When trying to avoid disruption to, or penetration of, a protective capping system, it’s often best to pursue ballasted solar technologies that will sit on top of the fill. But in order for the installation to stay in place and resist wind loads and other environmental conditions, a certain amount of settling of the fill must first take place.

It’s important to know when the cap was put in place, because the majority of settling occurs in the first 10 years. If the site is young, there might be some erosion and contiguous settling concerns. Conversely, the site shouldn’t be too old because caps put in place before a certain date (15-20 years) might require a preliminary third-party environmental assessment and updated closure measures that will cost more money up front. Make sure to review your landfill closure/cap design plan at the beginning of the development process.

In some cases, you will want to check with the landfill engineering firm that decommissioned the site, because both the interconnection applications and approval process, and the DEP and local permitting process can take up to six months. Thus, it’s important to understand the project timeline and start these processes as early as possible.

Land Specifications

The ideal setting for a landfill solar power installation is a site that is flat and large enough to host at least a one MW direct current (DC) array or larger. To avoid any potential sliding of a ballasted array, dome- or bowl-shaped fills will require landscaping to terrace any sloped land, and the solar panels will have to be spaced to avoid shading from adjacent panels. That will add to the upfront costs. In general, there should be at least five flat acres of space to utilize per MW of energy to install.

A good understanding of what kind of waste is in the fill also is crucial during the permitting process. If the waste is in any way toxic, additional precautions may need to be taken by the solar photovoltaic panel installers during the construction phase of the project. There’s also the potential that additional permits need to be pulled just to work on the site.

Financial Incentives

In addition to everything else, it’s important to understand what state and federal incentives are available to you. Some states offer upfront cash rebates based on the size of the system to be installed, while others spread rebates out over a five-year period based on your system’s actual energy production. With more and more states creating renewable portfolio standards that incentivize solar power, a market has sprung up to trade solar renewable energy credits (SRECs). SRECs are valued differently in each state and utility zone, but the hope is that their value will rise over time, which will increase the savings to customers who go solar, who are typically the owners of the solar installation or the owners of the meter the installation is feeding the grid through. In certain states, like Massachusetts, the energy off-taker can be designated to other electricity meters within the same utility zone, so the benefits of the SRECS can be spread a little further.

Joseph Harrison is project developer for Borrego Solar Systems Inc., a San Diego-based solar photovoltaic energy financing and contracting company.

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