Photovoltaic Stormwater Management Research and Testing

A suite of sensors sits on the ground at the base of a solar panel array.

PV-SMaRT field-testing equipment monitoring underground soil moisture at a New York PV facility. Photo courtesy of Scott McArt, Cornell University

A diagram lists the 5 steps of the PV-SMaRT program: One – Establish water quality task force; Two - Conduct field research on stormwater quality; Three - Calibrate and validate hydrologic model; Four - Develop PV-specific stormwater management best practices; Five - Provide outreach and education to stakeholders.

The Photovoltaic Stormwater Management Research and Testing (PV-SMaRT) project is developing and disseminating research-based, PV-specific tools and best practices for stormwater management and water quality at ground-mounted PV sites.

To achieve PV-SMaRT's goal, NREL is partnering with the University of Minnesota, Great Plains Institute, and Fresh Energy.

Research and Analysis Approach

The PV-SMaRT project will:

  • Work with an advisory water quality task force
  • Conduct field research on stormwater infiltration and runoff at five ground-mounted PV sites in five states: Minnesota, New York, Oregon, Colorado, and Georgia
  • Validate models to predict stormwater runoff for a range of site conditions and PV designs
  • Develop best practices for stormwater management and water quality at ground-mounted PV sites, based on research findings
  • Engage with local jurisdictions and other stakeholders to disseminate best practices, findings from stormwater models, and other resources
  • Provide information to reduce balance-of-system soft costs associated with stormwater infrastructure requirements
  • Improve water quality by developing and disseminating research-based resources.

Best practices will be published based on field research results.

Background on Stormwater Management for PV Facilities

Many jurisdictions treat ground-mounted PV facilities as predominantly impervious surfaces or surfaces that do not allow water to soak into the ground. However, rather than acting like a paved surface, rainwater can generally infiltrate under elevated PV arrays.

Because current stormwater runoff models used by local and state jurisdictions were not designed for ground-mounted PV, the stormwater permitting process can impose costly additional stormwater infrastructure requirements. Often additional land must be leased or purchased for stormwater mitigation measures, such as detention ponds. The current permitting process also often lacks accuracy and leaves many unanswered questions for jurisdictions when they attempt to evaluate applications for risks and opportunities associated with ground-mounted PV facilities.

Through its research and analysis, the PV-SMaRT project aims to address the stormwater and water quality challenges facing PV facilities in most jurisdictions.

Water Quality Task Force

The PV-SMaRT water quality task force works closely with the project team to provide feedback and guidance on the technical analysis, modeling, validation, and creation of water quality best practices. The task force is made up of individuals who represent a variety of views and stakeholder groups, including water quality experts, stormwater professionals, and solar industry representatives. Task force members understand the landscape of technical, strategic, permitting, and ground-mounted PV site development issues to meeting water quality goals.

Task force members include:

  • Jason Bernagros, U.S. Environmental Protection Agency (EPA) Office of Research and Development
  • Seth Brown, National Municipal Stormwater Association
  • Veronica Craw, Georgia Department of Natural Resources
  • Dave Gasper, New York Department of Environmental Conservation
  • Robert Goo, EPA Office of Wetlands, Watersheds
  • Britta Hansen, Emmons Olivier Resources
  • Greg Hoffman, Center for Watershed Protection
  • Jake Janski, Minnesota Native Landscapes
  • Gavin Chase Meinschein, Engie North America
  • David Morley, American Planning Association
  • Andrew Nelson, Westwood Professional Services
  • Peter Parkinson, AES Distributed Energy
  • Sybil Sharvelle, Colorado State InTERFEWS Director.

PV Field Research Sites

The PV-SMaRT project is using five existing ground-mounted PV sites in the United States to study stormwater infiltration and runoff. These sites represent a range of elevations, slopes, soil types, and geographical locations. The unique conditions at each site are being characterized, and measurements are being taken of soil infiltration, runoff, site vegetation density, speciation and rooting depth, precipitation, wind speed, and wind direction.

Minnesota

Minnesota's site has a 4.5-megawatt (MW) DC, fixed-mount, two-in-portrait PV array. It has sandy soil with a pollinator mix dominated by black-eyed Susan daisies and receives 37 in. of annual rainfall. Equipment was installed in June 2020 and will operate for 2 years.

New York

New York's site has an 18-MW DC, fixed-mount, two-in-portrait PV array. It has loamy soil with a tall grass and clover mix, is ungrazed or grazed by sheep, and receives 49 in. of annual rainfall. Equipment was installed in June 2020 and will operate for 2 years.

Oregon

Oregon's site has a 13-MW DC, tracking, two-in-portrait PV array. It's a flat site with clay soil, a diverse pollinator seed mix, and 16 in. of annual rainfall. Equipment was installed in August 2020 and will operate for 2 years.

Colorado

Colorado's site has a 1-MW DC, tracking, one-in-portrait PV array. It has clay soil and pollinator-friendly vegetation, is grazed by goats, and receives 16 in. of annual rainfall. Equipment was installed in September 2020 and will operate for 2 years.

Georgia

Georgia's site has a 1.3-MW DC, tracking, one-in-portrait PV array. It's a flat site with sandy clay soil, mowed cover crops, a high-diversity pollinator mix, and 49 in. of annual rainfall. Equipment was installed in September 2020 and will operate for 2 years.

Related Resources

Modeling the ecosystem services of native vegetation management practices at solar energy facilities in the Midwestern United States, Ecosystem Services (2021)

PV-SMaRT: Barriers and Best Practices, Great Plains Institute (2021)

PV-SMaRT: Potential Stormwater Barriers and Opportunities, Great Plains Institute (2021)

Stormwater Management in Solar Projects: Barriers and Best Practices, Great Plains Institute (2021)

Effects of Revegetation on Soil Physical and Chemical Properties in Solar Photovoltaic Infrastructure, Frontiers in Environmental Science (2020)

Power and Pollinators: Pollinator-Friendly Landscapes for Solar Facilities Webinar, EPA (2020)

SolSmart Issue Brief: Land Use Considerations for Large-Scale Solar, SolSmart and Electric Power Research Institute (2020)

Beneath Solar Panels, the Seeds of Opportunity Sprout, NREL News (2019)

InSPIRE: Innovative Site Preparation and Impact Reductions on the Environment website, OpenEI

Contact

Jennifer Daw

Senior Researcher

Jennifer.Daw@nrel.gov
303-275-4678