Photovoltaic (PV) solar components are designed to produce renewable and clean energy for approximately three decades. The first substantial PV installations happened in the early 1990s, and since early 2000s solar power generation has proliferated. Global installed PV capacity reached around 400 GW at the end of 2017 and is expected to rise further to 4500 GW by 2050. As a result of the increase in the global market for PV energy, the volume of modules that reach the end of their life will grow at the same rate in the near future. At the end of 2016, the cumulative global PV waste accumulated 250,000 metric tons, while it is expected that the figures will be increasing to 5.5–6 million tons by 2050. Currently, the majority of PV waste ends up in landfill sites worldwide. Therefore, the disposal of PV panels will become a pertinent environmental issue in the next decades. End-of-life management of PV panels is also essential to protect the environment and human health from any negative impacts resulting from the uncontrolled release of the materials that comprise PV systems. Furthermore, valuable metals like aluminium, silver and copper are also present in the modules, which represents a valuable opportunity if they can be adequately recovered. The landfill option creates additional costs to the public and government, and it does not retrieve the intrinsic values of the materials present in the dumped PV modules
- Crystalline silicon technology
Crystalline Si (c-Si) technologies dominate the current market share of PV modules (more than 90%), and the aluminium back surface field is the current industry-standard technology. There are different cell structures for crystalline silicon-based PV cells. The cells are electrically interconnected (with tabbing), creating a string of cells in series and assembled into modules to generate electricity. A typical crystalline silicon (c-Si) PV module contains approximately 75% of the total weight is from the module surface (glass), 10% polymer (encapsulant and back sheet foil), 8% aluminium (mostly the frame), 5% silicon (solar cells), 1% copper (interconnectors) and less than 0.1% silver (contact lines) and other metals (mostly tin and lead). The rest of the components have a small percentage of the total module weight.
- Thin-film technologies
Thin-films represent less than 10% of the entire PV industry. The currently dominant thin-film technologies are cadmium telluride (CdTe), copper indium gallium selenide (CIGS) and amorphous silicon (a-Si) . Thin-film solar cells were developed with the aim of providing low cost and flexible geometries, using relatively small material quantities. CdTe is the most widely used thin-film technology. It contains significant amounts of cadmium. A-Si has low toxicity and cost but also low durability, and it is less efficient compared with the other thin-film technologies, and CIGS has a very high optical absorption coefficient because it is a direct bandgap material.
Photovoltaic panel recycling methodologies
PV modules are mostly recyclable. Materials such as glass, aluminium and semiconductors can theoretically, be recovered and reused. Nowadays, Japan, Europe and the US are focused on research and development related to solar module recycling. Most efforts related to solar panel recycling concentrate on Si panels and aim to recover and recycle the most important parts. The most common methods for recycling c-Si PV modules are based on mechanical, thermal and chemical processes. Although thin-film solar cells use far less material than c-Si cells, there are concerns about the toxicity of materials such as tellurium (Te), indium (In), and cadmium (Cd). In the recycling process, panels are primarily dismantled by removing the surrounded Al frame, as well as the junction-boxes and embedded cables. The panel’s aluminium framing is the second-largest portion of the materials can be recovered from the PV panel. The aluminium frame will be removed manually from the panel before shredding Once the aluminium frame was removed entirely, the panel lost its rigidity causing the remaining layers to slightly fold in on themselves similar to a rolled piece of paper. This loss of rigidity proved useful for fitting the panel into the hopper of the shredder. The glass panel will be the most considerable component portion recovered during the panel recycling process. Silicon-based panel and thin-film solar panel glass recycling is a more thorough process, involving shredding. The shredded glass panel is recyclable and can be reused in the production of new products, such as glass bottles. There is no known dedicated PV panel recovery and reliable technology operating on a commercial scale in Australia at present. Once the panel was processed through the shredder, the material will be collected for the further chemical recycling process.
Currently, many of the chemical methods have been the subject of laboratory-based research, there are limited commercially available treatments for PV panel recycling. The US-based solar manufacturer First Solar applies both mechanical and chemical treatment methods to thin-film solar panels. On the other hand, c-Si solar-panel modules have been recycled by a company in Germany. Australia has limited facilities for panel separation recycling PV panel. Similarly, other countries have problems in applying recycling technologies. In Australia, it has been identified that the increasing volumes of end-of-life PV system components and the lack of dedicated recycling capacity. PV panel disposal to a recycler is considered expensive and cost-prohibitive. The cost and handling requirements for current disposal to recyclers is a barrier to provide free or nominal cost service to the customer. Without adequate government support, local recyclers will not be able to operate a sustainable business model in PV recycling industry.