Photovoltaic Stormwater Management Research and Testing (PV-SMaRT): Best Practices

Have you ever wondered what happens when rainwater falls directly onto ground-mounted solar PV installations? What comes next?  

The PV-SMaRT (Photovoltaic Stormwater Management Research and Testing) project addresses these questions. Published through the Office of Scientific and Technical Information (OSTI), this technical report refines models to estimate rainwater flow in solar projects, offering insights into best practices for stormwater management and the challenges of solar innovation.

And here's a teaser: The difficulties in solar panel design, such as inconsistent guidelines and regulatory variations, will significantly impact the approval process for your solar project designs. Keep reading and you will get to know how.  

Get Introduced to the Purpose & Stakeholders of this Study

The PV-SMaRT project aims to provide valuable insights for solar projects. It focuses on studying rainwater drainage at ground-mounted PV solar sites and identifying optimal management practices. The goal is to address challenges related to rainwater and water quality at solar sites across various locations by enhancing models used to estimate rainwater flow.  

The project involves several key stakeholders, including public and private organizations responsible for stormwater management decisions, which affect the cost and feasibility of PV installations. These stakeholders include:  

1. Authorities Having Jurisdiction (AHJs) for water quality permitting

2. Hydrologic engineers  

3. Solar developers

4. Landowners

5. Water quality stakeholder groups

6. State and local agencies administering stormwater/water quality programs

7. Solar energy purchasers

Additionally, the project collaborated with stakeholders to share best practices, analyze stormwater runoff coefficients, and distribute tools for managing stormwater and water quality at ground-mounted PV sites. Though focused primarily on the United States, the findings may have broader applicability.

A Straightforward Research Approach

The scholars in this report take a comprehensive approach to studying stormwater management strategies for photovoltaic systems. They prioritize stakeholder engagement and education through the following strategies:

1. Establishing a Water Quality Task Force (WQTF) for expert review

2. Conducting field research on stormwater infiltration and runoff at ground-mounted PV sites to inform scientific models.  

3. Validating the collected data with a 3D hydrologic model, to predict water runoff and generate stormwater runoff coefficients for various site conditions and PV designs.

4. Creating a best practices guidebook for stormwater management and water quality.

5. Conducting outreach and education regarding results, and best practices for stormwater management and water quality at ground-mounted PV facilities.  

More specifically, the project tasks and milestones included these aspects:

• Recruiting a minimum of 10 WQTF members and holding quarterly meetings to offer technical guidance on field research, model development, best practices, and outreach efforts.

• Installing instrumentation in 2 ground-mounted PV facilities in 2 states and in 5 facilities across 5 emerging states.

• Calibrating and validating a 3D hydrologic model and presenting it to the WQTF committee for review.

• Documenting permitting barriers for ground-mounted PV development and presenting stormwater management best practices.

• Engaging local and state regulators, industry, experts, and stakeholders through presentations, webinars, and coordination with national associations, professional organizations, and committees such as WQTF and ASTRO (Agriculture and Solar Together: Research Opportunities).

As you noticed, the researchers involved experts and educated people about the findings. By doing so, this project is helping solar efforts in new areas grow better, ensuring their environmental viability. However, they also uncovered certain challenges in the process, which are detailed in the following section.

The 4 Stormwater Issues in Solar Development

The PV-SMaRT team analyzed stormwater and water quality permitting in 12 states, revealing national regulatory variations. Collaborating with stakeholders, they identified four barriers in water quality permitting, as outlined by the Great Plains Institute in 2021;

1. There is a lack of consistent, data-driven best practices concerning array design, layout, and site standards that can minimize water quality risks and maximize benefits: We don't have enough reliable guidelines, backed by data, for designing solar arrays to protect water quality and get the most benefits. How one designs the solar systems affects how rainwater flows. But the people establishing the rules and the ones building solar projects do not have enough information. This creates uncertainty in designing solar setups, complicating the efforts to manage water runoff effectively and assess associated costs. ‍

2. Divergent post-construction and construction stormwater permit goals may result in suboptimal water quality outcomes: Conflicting objectives between obtaining stormwater permits and site setup may hinder widespread acceptance of solar projects. Solar developers struggle to quantify how green stormwater systems, eco-friendly development, and vegetation cover contribute to water quality. Difficulty arises when evaluating the benefits of perennial plants and pollinators in this context, impacting the market acceptance of solar projects. ‍

3. Solar projects encounter varying expectations and standards across jurisdictions, both state and local: Solar projects encounter varying regulations across different jurisdictions, resulting in distinct permit standards and practices. These differences influence solar design approaches and escalate stormwater management costs, even for similar projects. This complexity and increased expense pose challenges for setting up solar projects across multiple locations.

4. Existing water quality standards and best practices were not specifically designed or tested for solar installations: The regulations established for conventional buildings often overlook the dynamics of solar systems. Consequently, applying these regulations to solar projects can result in inaccurate stormwater estimates. This poses a significant concern as it may impact water management around solar panels and potentially increase the costs.

Findings & Takeaways

Looking into the broader perspectives, The PV-SMaRT project had crucial findings regarding rainwater management and water quality at ground-mounted PV facilities:

• Guidelines for safeguarding water quality with solar arrays require improvement.

• PV system design influences rainwater flow, but current information is inadequate for informed decisions.

• Computer models used by regulators and developers may not consider all technical design features.

• The researchers installed tools at 5 solar sites and gathered 3 years of data to enhance rainwater management and cleanliness.

• A practical guidebook for best practices in stormwater management and water quality has been created.

• Engaging local authorities facilitated the sharing of best practices, rainwater coefficients, and similar tools.

Here are 5 Crucial Recommendations from the Study

The PV-SMaRT project report doesn't explicitly dictate the next steps, but offers several helpful suggestions based on our findings aforementioned;

• Make New Rules: The insights obtained from the project could inform the development of specialized regulations for rainwater management at solar sites, resulting in more tailored and efficient guidelines.

• Talk to Everyone Involved: Continued communication with local governments, regulatory bodies, industry experts, and water quality specialists is crucial. This enables the dissemination of optimal rainwater management practices for widespread adoption.

• Keep Checking In: Establishing regular inspections at solar sites to assess the effectiveness of rainwater strategies and monitor water quality could be a beneficial initiative. This ensures ongoing compliance with regulations and promotes environmental stewardship.

• Continual Education: Since managing rainwater at solar sites is challenging, it is vital to gather more data and undertake further research. It will help create the models and best practices for handling rainwater even better.

• Teach and Train: Continuous education and training should be provided to all stakeholders, including regulatory authorities (AHJs), solar project construction teams (EPCs), and solar energy consumers (residential or commercial PV owners). This ensures widespread awareness and adoption of the best practices and tools identified in the PV-SMaRT project.

Through collaboration, innovation, and education, the PV-SMaRT project paves the way for more effective and sustainable practices in the solar energy industry, ultimately contributing to a cleaner and greener future!