What happens to a solar PV module after its expected 25-year operational life? With around 2 TW of rooftop and utility-scale PV already deployed worldwide, and a large number of them being retired before operating for 15 years, the amount of PV modules being discarded is growing every year. As PV modules are becoming cheaper by the day, and with the constant improvement in PV module efficiencies, many utility-scale PV power plants are starting to be repowered even before they reach their expected 25 years of operation. Many of these modules are still performing well. Can they be deployed for a second life to provide solar electricity for a few more years?
A PV system built with reused panels
Image: Ricardo Ruther/ISES
The International Energy Agency (IEA) forecast in 2020 that the global cumulative installed capacity of photovoltaics would exceed 1 TWp by 2025 (PVPS TASK, 2020). However, before the end of 2024, this figure will have doubled to more than 2 TW. Recent energy production forecasts indicate that a large increase is necessary, with a target of 75 TW of global PV capacity by 2050 to limit global temperature rise to 1.5 C and mitigate the impacts of climate change.
It is widely acknowledged that solar photovoltaics (together with large-scale onshore wind) is the most sustainable and lowest-cost energy conversion technology. Global solar deployment must grow about 40 times larger than today to fully decarbonize the world. This will be accomplished in the year 2042 if the current growth rate of 20% per year continues.
The growth of PV generation on a global scale will inevitably result in a significant amount of waste from PV modules in the future. On the other hand, solar PV avoids the emission of carbon dioxide. Each kg of solar panel generates about 0.9 MWh over its lifetime, which allows avoidance of about 900 kg of carbon dioxide from coal burning – a ratio of 900:1. This calculation assumes future PV module mass of 25 W/kg (excluding frame), a capacity factor of 16%, and module lifetime of 25 years.
If we assume that 10 billion people require 100 TW of solar PV (10 kW each) for global decarbonization, then 400 W/person of solar modules will retire each year. This amounts to 16 kg of solar module waste per person per year, most of which is glass with a small amount of plastic, silicon and metals. The current glass waste stream in the USA is about 11 million tonnes or 32 kg per person. Thus, solar PV adds 50% to the existing waste stream while avoiding the emission of 900 times greater mass of carbon dioxide. The future solar module waste of 16 kg per person per year is only 2% of the 800 kg per person per year of annual solid waste in the USA.
In summary, solar module waste is a minor issue. However, is there an alternative to sending solar panels to landfill? After retirement, do PV modules still have useful power generation capabilities? There are studies underway that propose a circular life cycle for solar modules. The efficiency loss in a photovoltaic module can range from 0.4% to 5% per year, depending on the climate and materials used.
Manufacturing technology, aimed at increasing PV module power, is advancing rapidly. Panels are increasing in size and cell efficiency is also increasing. Between 1980 and 2020, a 76% reduction in the weight-to-power ratio of PV modules was achieved. This means that new panels can be mounted on existing support structures or trackers to produce much more power.
Currently, the predominant technology in the global market is single crystalline silicon with an approximate module power ranging from 550 W to 750 W, compared with 350 W in 2019, less than 200 W in 2010, and below 100 W before 2000. Large amounts of PV modules are being discarded, and there is a lack of clarity regarding the technical, economic, and social feasibility of reusing them in a second life instead of directing them straight to recycling. Additionally, there is a lack of policies, standards, and methodologies guiding whether the equipment can be reused (second life) or should be recycled. Legislation, such as the WEEE Directive in Europe, presents a challenge for the reuse market.
Circular economy: reuse and recycle
PV CYCLE is a not-for-profit, member-based organization founded in 2007 by the PV industry to manage a broad range of electrical and electronic equipment including PV modules, batteries, packaging and industrial waste. It offers waste management and legal compliance services for companies and waste holders and has representatives around the world. One such member in Brazil grew 160 times in the last four years, processing 13 tons (430 PV modules = 0.2 MW) in 2020 when the company started collecting discarded PV modules, to 2800 tons (more than 91 thousand PV modules = 45 MW) so far in 2024. This growth is projected to reach 4500 tons = 75 MW by the end of 2024; close to 80% of these modules are coming from utility-scale PV power plants. Around 10% of the discarded PV modules are coming from distributors (brand new, damaged during transportation and handling), and the remaining 10% are from smaller system integrators. SunR is now expanding to the whole of Latin America, also targeting the large-scale PV power plants that were put in operation less than 10 years ago.
In 1999, Universidade Federal de Santa Catarina (UFSC) replaced a diesel generator on a small satellite island (Ratones Grande island) off the main island of Florianopolis, Brazil, with a 5 kW off-grid PV system shown in the images below. The 10% efficient polycrystalline silicon PV modules operated continuously until 2022, when it was decided to replace them with new modules more than twice as efficient to double the installed capacity in the same area at that space-constrained location. After more than 20 years of operating in this offshore environment, most of the 76 PV modules still have an output of about 80% of the original nameplate rating and, instead of being discarded/recycled, they were reinstalled at the UFSC solar energy research laboratory and are being monitored in a second-life, PV module reuse project. Social housing programs in Brazil and elsewhere can benefit from very low-cost, second-life PV modules, provided their performance and safety can be guaranteed after manufacturer warranties are no longer valid. Despite not being yet a common practice, there are several research groups and companies in Europe, the USA and Australia, where reuse and second-life activities are being developed.
The circular economy of PV modules could include reuse and a second life, before final recycling to recover materials for the production of new PV modules. However, with state-of-the-art PV modules with 25-30-year warranties below $ 0.10/W, as we have today, the economics of second-life PV modules is a tough bet.
Authors: Prof. Ricardo Rüther (UFSC), Prof. Andrew Blakers /ANU
Andrew.blakers@anu.edu.au
rruther@gmail.com
ISES, the International Solar Energy Society is a UN-accredited membership NGO founded in 1954 working towards a world with 100% renewable energy for all, used efficiently and wisely.
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