Solar energy is currently the fastest growing and most renewable energy source in the world. The relative decline in the cost of solar energy has made it available to more people than ever before and has led to an exponential growth in its use.
But as the solar energy industry develops, the problem of waste management arises. What will happen to millions of solar panels around the globe at the end of their lifespan?
Why should solar panels be recycled?
Anyone who works in the solar industry is well aware of the benefits that solar energy provides. Clean, renewable energy saves money and fossil fuels, helps reduce greenhouse gas emissions, and requires minimal maintenance and lifetime investment compared to other forms of energy generation. But even many industry professionals don’t know what the pros and cons are for solar modules at the end of their life.
Solar equipment will last for decades, especially if properly maintained. The design life of a solar panel is approximately 20 to 30 years, and most solar panel manufacturers provide a performance guarantee to protect solar system owners. The warranty provides assurance that the solar panels will generate a certain amount of power, except for unexpected cloudy days. Many manufacturers guarantee 90% performance after 10 years and 85% after 25 years.
Solar panels become less efficient over time, and performance guarantees protect consumers in the event of a premature decline in energy production. Most systems installed in the late 1980s and early 90s are still producing a reasonable amount of power. However, the day will come when a reliable infrastructure for their disposal will be required, as a large number of solar systems will be decommissioned.
With more than 400 gigawatts of photovoltaic modules installed in the world today, it is important that they do not become a burden on the environment, but serve the benefit of people and do not cause harm in the future. According to experts, the problem of utilization of “solar waste” will globally face mankind in 2-3 decades, since most of the solar panels that are working today will have exhausted their resource by this time. Moreover, the threat to the environment will be quite high, because there will be an incredibly large amount of waste that is difficult to recycle.
In some cases, photovoltaic modules can be reused or refurbished and given a “second life” to generate electricity. Other components of solar systems can also be handled responsibly. Inverters, for example, can be recycled as electronic waste, and frames, racking equipment can be reused using new technologies or recycled like other metals.
Currently, most countries do not have a reliable infrastructure for recycling solar panels. Since solar energy is a relatively young industry, the annual decommissioning rate of solar energy systems is still low. Most of the solar panels that are disposed of annually have not yet reached their useful life, but are simply damaged or defective.
According to the forecast of the International Renewable Energy Agency (IRENA) , without recycling, by 2050 global waste from the production of photovoltaic panels will increase significantly and amount to approximately 60-80 million tons (cumulative volume). Since all solar cells contain a certain amount of toxic substances, this can be a problem. Solar panels contain heavy metals such as cadmium and lead, which can leach into the environment if not properly recycled. Carelessly discarded solar panels can end up in large landfills, which will lead to negative consequences for the environment. But in addition to protecting the environment, recycling solar panels is also economically beneficial. The natural reserves of some rare elements contained in solar modules (for example, gallium, indium) are depleted over time. They could be saved when recycling solar panels and continue to be used to make new solar panels and other products. According to IRENA experts, by 2050 the recycling of secondary solar modules can generate up to $15 billion in revenue.
Solar panel recycling options
As we said, some of the materials that make up solar panels can be reused: glass, aluminum, copper and semiconductors. For example, in the composition of crystalline silicon batteries, approximately 76-77% glass, 10-12% polymeric materials, about 8-9% aluminum, 5-6% silicon semiconductors , about 1% copper, and there are also other metals – no more than 0.1% (silver, tin, lead, gallium, arsenic, etc.) In thin-film modules, the proportion of glass is much higher – from 88 to 97% in different models . But they often include such toxic compounds as cadmium telluride, as well as indium and copper diselenide. Approximately 85-95% of “solar waste” is recyclable – aluminum frames, racks and racks, glass. The rest of the waste is the PV modules themselves, metal foil, switchboards, connecting wires, terminal boxes, printed circuit boards, lead solder.
There are two main ways to recycle panels. This is the so-called “fine” when almost all elements are removed from the used panels for processing, and the second option is “rough processing”, when only basic materials (aluminum, plastic, glass) are removed. In “fine processing”, the modules are pre-treated, the laminating coating is removed, glass and metals are removed.
But since there is relatively little solar waste today, it is mostly recycled in factories to recycle glass and metal. In effect, what is happening is “rough recycling” in which valuable and environmentally hazardous metals are not properly recovered and disposed of. Therefore, many companies are thinking about how to make the process of recycling solar panels the most optimal and environmentally friendly.
The further rapid development of the solar industry will also lead to an increase in the number of solar panels that need to be recycled or disposed of in the coming years. Therefore, in some countries, manufacturers of solar panels are required to comply with the requirements and disposal standards at the legislative level. For example, in Europe today, up to 70% of the materials that make up solar modules are recovered for reuse.
But every year more panels reach their end of life, and even now old solar panels are slowly becoming a problem. Recycling is still at a very early stage of development, but as the market continues to grow, it will play an important role in the solar industry. For an industry that prides itself on sustainability, it needs to focus on end-of-life recycling of solar panels so they don’t end up in landfills.
From a regulatory point of view, PV panel waste still falls under the general waste classification. The only exception exists at the EU level, where photovoltaic panels are defined as e-waste in the relevant documents . Therefore, the common belief that solar panels are not recyclable is a myth. This is a process that needs time to be widely adopted, as well as further research, to fully unlock the potential for adequate recycling of all solar cell components. For this reason, it is essential that the design and processing departments of enterprises work closely together to ensure optimal disposal.
Given the lifetime of solar panels , a surge in solar panel recycling can be expected as early as the early 2030s. It is important that these panels are recycled, otherwise valuable resources that could be used to produce more solar panels will end up in landfills and, worse, toxic compounds will be released into the environment.
How are solar panels disposed of?
Like any other product, solar panels can be recycled. For example, a crystalline module includes primary materials such as glass, plastic, aluminum. All three of these materials can be disposed of using the normal recycling process.
Although silicon wafers themselves are not recyclable like glass and plastic, some specialized recycling companies can reuse silicon cells by melting them down and recovering silicon and various metals.
The difficulty in recycling solar panels is not that the materials they are made of are difficult to recycle; rather, they are made up of many elements that are used together in a single product. Separating these materials and recycling them is a complex, time-consuming and costly process. For this purpose, processors use modern equipment.
The solar panel recycling market is gradually growing. The main reason why this is happening at such a slow pace is that the number of solar panels that can be recycled is still limited. However, recycling facilities and divisions are developing infrastructure to increase their own capacity.
The process of recycling different types of panels – details
There are two main types of solar panels that require different approaches to recycling – silicon-based and thin-film. Both of these types of panels can be recycled using various industrial processes. At present, silicon-based panels are more common, although this does not mean that there is less value in thin film-based cell materials.
Research carried out on the subject of solar panel recycling has led to the emergence of numerous technologies. Some of them even achieve astonishing recycling efficiencies of up to 96% , but the goal is to raise the bar even higher in the future. While the modules can be reused, the material separation process can be complex and require advanced equipment.
silicon solar panels
The recycling process for silicon-based photovoltaic panels begins with the disassembly of the product itself to separate the aluminum and glass parts. Nearly all glass (about 95%) is recyclable and all external metal parts are for re-molding cell frameworks. The rest of the materials are processed at 500°C in a heat treatment unit to facilitate bonding between cell elements. Due to the intense heat, the encapsulating plastic evaporates, leaving the silicon cells ready for further processing. Supportive technology ensures that even this plastic is not wasted, so it is reused as a heat source for further heat treatment.
After heat treatment, everything that is separated can be easily reused by 80%, while the remaining 20% is still further purified. The silicon particles in the bonding layer of the wafers are etched away with acid. Deformed and spent wafers are melted down to be reused in the production of new silicon modules, resulting in 85% silicon recycling .
Briefly, the main stages of silicon module utilization can be expressed as follows:
- removal of the aluminum frame (100% reusable);
- glass separation along the conveyor belt (95% reusable);
- heat treatment at 500℃ (helps to separate solar cells from plastic components);
- separation of silicon wafers;
- etching of the connecting layer of silicon wafers;
- the subsequent processing of silicon itself is its remelting into reusable slabs (85% reusable), which are then used to produce new panels.
Thin film solar panels
Thin-film panels are recycled more radically, and the technology for their disposal was developed in the late 90s in the United States, and today it is used in a number of European countries. All dismantled elements of solar panels are processed here in a single cycle.
First they are placed in a coarse mechanical grinder. Then, with the help of a hammer mill, a waste fraction is obtained, the pieces of which have a size of no more than 4–5 mm. It is at such dimensions that the connecting bonds of materials are destroyed, which makes it possible to separate them. Unlike silicon-based panels, the remaining substance consists of solid and liquid components. For their separation (separation of liquid and solid waste), a rotating stainless steel drum is used, which mainly keeps the solid parts rotating inside it, while the liquid flows into a special container. With the help of leaching, the semiconductor layer is separated, and solid materials (glass and plastic) are separated from the liquid. Next, the resulting solution – a liquid – is precipitated and purified in order to completely separate the various semiconductor materials. The last step depends on the actual technology used in the production of the panels. However, on average, about 95% of the semiconductor material is not only usable, but also reusable.
The separated solid waste is usually contaminated with so-called interlayer materials, which have a lower mass and can be removed through a vibrating surface. After that, the material is washed. What remains as pure glass yields savings of up to 90% when re-manufacturing glass elements.
Solar Panel Recycling Options
Solar panels are traditionally processed in general glass recycling facilities, where the metal frames and glass parts are recycled and the rest of the parts are disposed of or incinerated. There are currently several global organizations around the world working to make solar panel recycling as complete as possible.
In Europe, the solar market is quite developed, with many European countries installing more powerful photovoltaic systems as early as the 1990s. Therefore, the market for recycling solar photovoltaic modules is constantly developing here. The European Union’s Waste Electrical and Electronic Equipment (WEEE) Directive helped establish the PV Cycle Association to recycle used solar modules and promote and implement global best practices in recycling.
According to government regulations, solar panel owners in Europe must dispose of their panels after they use them. This has created a market for commercial panel recyclers, such as Veolia (France), one of the largest water treatment, supply and waste disposal companies in Europe. It partners with the non-profit organization PV Cycle to collect and recycle solar panels. In 2018, Veolia opened Europe’s first solar panel recycling plant in Rousset, southern France. At this high-tech facility, robots separate glass, silicon, plastics and metals from spent or damaged solar panels.
The US Solar Energy Association – SEIA – also has several recycling partners, and this partnership benefits its members. An example of a SEIA recycling partner is Cleanlites in Cincinnati, which operates a number of facilities that recycle panels and other solar equipment.
Manufacturers are also making efforts to recycle solar energy. For example, companies such as SunPower and First Solar are implementing global recycling programs for their customers. It provides that owners of solar systems who are customers of these brands can return old, spent solar panels to manufacturers for recycling or repurposing.
Much attention is paid to the problem of utilization and recycling of solar panels in Japan and other developed countries. Programs are being developed at the state level to put more pressure on manufacturers to create and implement recycling programs.
In Ukraine, Russia and the CIS countries, the solar battery market is still developing. Accordingly, the problem of their disposal and processing is also in the future. So far, only those who are seriously engaged in solar energy are thinking about this more and more. After all, the faster the solar energy market grows, the more solar systems will fail. All of them will require disposal, and this is a matter of the coming decades. That is why it is important to develop and implement recycling technologies for photovoltaic solar waste already today in order to maximize the environmental and economic benefits of solar energy.