Renewable Energy Waste Management: Solar Panel Circular Economy

Abstract

This article explores the concept of end-of-life (EoL) solar panels and how a circular economy approach can offer a sustainable solution to this emerging challenge.

The embrace of solar panels has surged in recent years as the global community confronts the pressing issues of climate change and the shift toward renewable energy sources. Solar—or photovoltaic (PV)—panels have emerged as indispensable technologies in our quest to diminish reliance on fossil fuels, combat climate change, and foster sustainable economic growth. Presently, the United States draws 7.21% of its energy from solar, powering approximately 27 million homes, with solar capacity expanding more rapidly than any other renewable source. Notably, in 2023, a staggering 48% of new U.S. electric generation capacity originated from solar, marking a remarkable 36-fold increase from the 4% recorded in 2010.¹

At the same time, clean energy generators’ efficiency, affordability, and versatility have improved, reflecting ongoing trends that propel their development and adoption.¹ Predictions indicate a tripling of solar energy capacity over the next 30 years.² Since 2015, new PV-panel installations have more than doubled, driven by favorable U.S. federal and state policies, coupled with escalating demand for clean energy in both public and private sectors (see Figure 1a and 1b).³ Furthermore, solar module prices continue trending downward due to federal incentives and industry growth despite higher-than-anticipated global demand, supply disruptions, and other challenges. However, the escalating use of solar energy would increase the number of decommissioned solar panels in the next decades, elevating the volume of waste requiring recycling.

Figure 1.

PV-panel trend data (a) cumulative U.S. solar panel installation, (b) changes in deployment growth and unit price from 2009 to 2022, (c) end-of-life estimate by 2050 based on Regular-loss and Early-loss scenarios, and (d) percent mass and value of decommissioned solar panels.^1–4

The Lifespan and Composition of Solar Panels

As the solar panel market continues to grow, so will the quantity of decommissioned panels. Some of the first installed panels are reaching the end of their lifetimes, generally estimated at 25 to 30 years. In many cases, decommissioned PV panels still function, but with reduced efficiency. For example, most operational panels may still achieve 70–80% efficiency at 25–30 years;⁴ however, system owners may replace them with more efficient panels before then. Some installed panels may not last their expected lifetimes due to manufacturing defects, improper installation, and damage from hurricanes, fires, and other natural disasters.

While solar panels generate electricity with minimal maintenance and produce no greenhouse gas emissions, end-of-life (EoL) solar panels pose several challenges to achieving circularity, including insufficient recycling capacity, which could lead to the loss of materials from the supply chain. The most widely cited estimate of EoL PV panels, the IRENA and IEA-PVPS 2016 report, estimates there will be nearly 60 million to 78 million metric tons of EoL PV panels globally by 2050.⁵ The United States is projected to make up the second-largest global share of this estimate, ranging between 7.5 million and 10 million metric tons of PV panels (Figure 1c).⁵ Potential early retirement due to lower prices and improved designs may result in higher waste production than anticipated.⁶ However, it is important to put these volumes in context, as all energy generation technologies generate waste. Although the volumes of solar panel waste will be large, they are dwarfed by wastes from fossil fuel energy generation: coal ash is projected to be between 300–800 times larger than PV module waste if we do not transition to a carbon-free energy economy.⁷

Monocrystalline and polycrystalline solar PV cells (Figure 1d) are composed of silicon (5 wt%); ethylene vinyl acetate (EVA) film (10 wt%), which encapsulates the silicon; 3–5-mm thick tempered glass (76 wt%) that covers the encapsulated silicon; aluminum frame (7%); silver (0.1%), and lead in the form of lead solder (varies). Other types of solar panels may contain potentially toxic metals like cadmium (thin film cadmium telluride [CdTe] panels), while others may contain copper indium gallium selenide (thin film copper indium gallium selenide [CIGS] panels).⁶

End-of-Life Strategies

Sustainable practices in solar panel management contribute to the circular economy, aiming to minimize waste and promote resource longevity. Several strategies support the integration of solar panels into the circular economy. Designing panels with end-of-life considerations facilitates disassembly and recycling. While extending the panel lifespan by 10–20 years can mitigate waste, it may disincentivize technological innovation. Refurbishing and reselling old solar panels extends their lifespan, reducing the demand for new production and conserving resources. Recycling end-of-life PV panels generates environmental benefits like the recovery of valuable materials, a reduction in the need for raw materials, and the conservation of energy. However, it can be difficult to recover small amounts of valuable metals, such as silver, from PV panels, both practically and economically.

As noted above, industry experts expect that large volumes of solar panels will become waste in the coming decades. It currently needs to be determined if the existing infrastructure for recycling can absorb the processing of this bulky waste stream. While landfilling of PV panels is currently prevalent, it should be discouraged since the energy and resources invested in manufacturing solar panels are wasted if they are landfilled instead of recycled.

The Circular Economy Approach

Most of the research and development on PV-panel technologies focuses on improving the forward flow supply chain’s affordability, value, and performance. However, current research in the PV industry and the National Renewable Energy Laboratory (NERL) are looking at solutions for the EoL of PV panels and ways of recapturing module materials such as glass, silicon, and aluminum at the end of their use life.⁸ Adopting a circular economy approach is helpful to address the growing concern of solar panel waste. The circular economy based on reusing, reducing, recycling, and recovering can help the PV value chain and mitigate life-cycle environmental burdens. The manufacturer can then use these materials to produce new panels, reducing the reliance on virgin resources and curbing the environmental impact of mining and production. Figure 2 shows the schematic diagram of the circular economy approach for managing end-of-life solar panels.

Figure 2.

Life cycle of PV panels and opportunities for circular economy.

Circular PV economy affords valuable materials for new solar panels and prevents panels from ending up in landfills, and models used to predict the flow of panels could be a helpful planning tool.⁶ Economic strategies and innovative recycling technologies should be developed to overcome these issues, such as designing panels for easy material recovery. The implementation of comprehensive regulations and policies that encourage recycling practices and responsible disposal could encourage a sustainable and eco-friendly strategy for the entire lifecycle of solar panels.^1,9,10

This approach encourages the development of efficient collection and recycling systems to ensure that old panels are not discarded as waste, but transformed into valuable sources for new solar panel production, reducing the demand for virgin resources and reducing the environmental impact.⁸ However, implementing a circular economy approach for EoL solar panels faces several hurdles. Key among these challenges is the need to develop low-cost technologies, infrastructure, and processes capable of extracting valuable materials from the panels while minimizing environmental impacts. Besides establishing cost-effective processes and scaling up recycling infrastructure to extract economic value from EoL PV panels, there is a pressing need for policies to encourage recycling practices and responsible disposal.

As the solar industry grows and an increasing number of panels reach the end of their life, advancing and optimizing technologies for managing the end-of-life phase becomes imperative to establish a sustainable and environmentally responsible approach for dealing with retired solar panels.

State Legislation and Federal Regulations for Sustainable EoL Management

Effective policies and funding are crucial for encouraging the development of a circular economy, especially for PV equipment, ensuring its safe handling, storage, transport, reuse, recycling, and disposal. Several regions have established regulations and guidelines for properly disposing of and recycling PV panels. However, the regulatory standards differ from one region to another. The U.S. Environmental Protection Agency (EPA) created the Universal Waste Regulations as part of the Resource Conservation and Recovery Act (RCRA) to streamline the management and disposal of specific hazardous wastes, aiming to encourage recycling and proper disposal while reducing the burden on the regulated community.¹¹

In October 2023, EPA announced a new rulemaking effort to develop a proposed Universal Waste Rule to streamline the management of end-of-life PV panels.^11,12 The Universal Waste regulations will make it easier for generators to collect, store, and transport end-of-life PV panels for recycling or disposal. Additionally, some jurisdictions are adopting extended producer responsibility (EPR) programs, where manufacturers manage their products at the end of their life cycle, including establishing pre-paid recycling or take-back programs.¹³ The U.S. Department of Energy has a program that funds solar panel recycling technologies.¹⁴ This multifaceted approach underscores a commitment to efficient waste management, recycling initiatives, and reducing the environmental impact within the solar panel industry.

Conclusion

The United States’ efforts to achieve decarbonization involve expanding renewable energy strategies, including scaling manufacturing, responsible material sourcing, end-of-life management, and infrastructure development to support manufacturing and end-of-life management. EPA and NERL studies recommend implementing circular pathways for PV-panel systems, extending module lifetimes, and promoting recycling.^2,6 Extending module life reduces the need for additional materials to make new panels, enhancing the energy values produced over a PV system’s lifetime. Solar panels generate a direct current that needs to be converted to an alternating current we use in the electric grid. Extending the lifetime of PV panels and various devices enhances PV system reliability, improves efficiency, and lowers the system cost. We can extend the lifespan of PV modules through reliability and resilience improvements, accelerated testing, quality control, predictive modeling, and efficiency and material enhancements. Some of these approaches currently include improving power electronics that are critical gateways between the PV panel and the grid.

Increasing manufacturing scrap recovery aligns with demand and aids EoL recovery methods. Improving reliability, resilience, efficiency, and material enhancements can extend PV modules’ lifespans. Modest closed-loop recycling rates (>30%) present opportunities to reduce material demands and waste, emphasizing the importance of recovering valuable PV materials.² However, current barriers, mainly economic, partly due to insufficient volume for economies of scale, may change in the next 10–20 years, assuming increasing EoL PV panel projections. Integrating solar panel recycling into a circular economy requires industry-wide collaboration from manufacturers to recyclers. It will also demand ongoing research, stakeholder collaboration, and clear regulatory frameworks. Achieving these objectives will contribute to the sustainability of solar energy as a clean power source.