Blog from Jane Marsh: How to Prevent Solar Panels From Having Negative Impacts on Stormwater Runoff

Solar energy has boomed in the United States as more Americans race to cut electricity costs and reduce energy consumption at home. About 4% of U.S. homes are solar-powered, with 13% of homes expected to tap into solar energy by 2030 – nearly triple the amount we’re seeing now.

Of course, this comes as little surprise with the rising utility expenses. According to the U.S. Bureau of Labor Statistics’ (BLS) Consumer Price Index Summary for July 2022, the energy index rose by 32.9% over 12 months.

The U.S. is committed to transitioning to a broader scope of cleaner energy sources. Under an executive order directed by President Biden, federal agencies are deploying 30 gigawatts of offshore wind power by 2030 and a minimum of 25 gigawatts onshore by 2025. Yet, solar energy remains at the front of most people’s minds.

On the surface, there doesn’t seem much to complain about when it comes to solar panels. Federal tax credits and rebates drive down installation costs and homeowners reap the rewards of ample utility savings and clean electricity. However, utility-scale solar projects have uncovered one potential problem with photovoltaic (PV) panel systems: stormwater runoff.

Impervious Surfaces a Risk for Erosion

In April 2022, Virginia’s top environmental official caused waves in the renewable energy sector when he declared a need for regulating solar panels as impervious surfaces. A response from the Virginia Department of Environmental Quality (DEQ) sent further shockwaves two weeks later as the agency indicated there’d be time for solar companies to comply with the state’s potential policy changes for PV solar farms.

Virginia’s environmental director wasn’t wrong, of course – solar panels are, in fact, impervious and can cause issues associated with stormwater runoff.

Utility-scale PV systems discharge stormwater at the panels’ drip line similar to how a gutterless roof directs and accelerates water flow. Rather than stormwater flowing across the panel surface to a dredged field or parking lot, it infiltrates the ground below. As a result, the land becomes susceptible to erosion, sediment accumulation, and contamination.

Overly saturated land poses a concern as stormwater runoff flows downstream toward large water channels – potentially carrying harmful debris to vital drinking water resources for neighboring communities.

The District of Columbia (D.C.) Department of Energy and the Environment highlights the most critical implications of stormwater runoff in the city, including:

• Less drinking water with reduced ground absorption
• Flood damage to residential and commercial properties
• Clogged waterways and damaged aquatic ecosystems and habitats
• Land loss from widened streams
• Trash, debris, and chemicals that pollute water and other natural resources
• Public health and safety risks, including unsafe drinking water and drownings
• Economic consequences for tourism, recreation, and fisheries
• Overpowered stormwater management systems

Although regulations on solar arrays’ impervious surfaces could potentially hinder state efforts to transition to renewable energy fully, it’s impossible to ignore the impacts of stormwater runoff from solar arrays.

Best Practices for Reducing Stormwater Runoff From Solar Panels

The world has made progress in solar technologies over the years. Still, only 2% of the world’s energy comes from solar, which is minimal compared to other energy sources. As such, perfecting the imperfections is critical if the industry and renewable sciences hope to see continual growth.

Developing best practices for reducing stormwater runoff from solar arrays is necessary. Compromising the safety of our natural resources – particularly safe groundwater drinking sources – isn’t permissible.

For starters, site selection for solar farms matters. Topography should be a top consideration when choosing where to implement a large solar project. Additionally, understanding the current natural conditions, such as nearby water channels and soils, will give insight into how runoff flow could harm the neighboring areas if a project is not managed correctly.

Although prospective solar farms undergo regulatory reviews and public forums to discuss how the project might impact the environment, the preliminary grading plans are conceptual at most. This raises the question of whether the construction of drainage areas is even possible.

Implementing new rules for providing analyses and design plans to ensure the construction of dredges and other drainage solutions – and constructing them before installing the PV farms – will save time, money, and runoff problems.

Remedial work around the installed solar farm may also be required. Remediation measures might include planting new vegetation, placing additional piping to redirect runoff to roads and sewers, erosion control blankets and hydroseeding on slopes, and constructing dry and wet retention ponds.

Improving the Science Will Prevent Solar Panel Runoff

Filling in the scientific gaps will help improve solar technologies and best practices in the long run. Marrying renewable energy with natural resource preservation is essential for a cleaner, healthier planet.

About the author: Jane works as an environmental and energy writer. She is also the founder and editor-in-chief of Environment.co