How Can We Make the Life Cycle of Solar Panels Greener?
Disposal and recycling of photovoltaic (PV) modules are of key importance for a successful growth of environmental sustainability. The WEEE (waste of electric and electronic equipment) directive has been updated to make the life cycle of solar panels greener. All the related operations to achieve these goals are currently undertaken by various non-profit organizations and companies.
Two Methods: Thermal and Mechanical
So far, two different methods, thermal and mechanical, are used to ensure the correct procedure to recover and put back into the production cycle all the materials solar panels are made of. The application of the first or the second one depends on the presence of silicon in the solar panel modules.
If silicon is absent, the entire panel will be thermally dismantled by means of chemical baths. The mechanical process instead will separate each part (the aluminium frame; the glass that covers the module; the silicon and the metals, such as silver, that make up the solar cells; the copper of the electrical connections between the cells) through two phases. First, a specific machine,which takes about ten seconds, is used to detach the module from the upper glass. Then, the glass is ground and resold. At this point, the solar cells have to be unglued from the plastic material that protects them. Therefore, copper, silicon powder, and plastic materials are what at the end of the whole process remains.
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Efficiency of the Methods
Thermal and mechanical recycling approaches are generally characterized by an efficiency up to 98%. This means that 19.6kg of materials can be extracted from a PV module of 20-kg-weight, and they can be used for supporting the production of new PV modules or other productions. Silicon powder is useful in cast iron foundries but it cannot be reused for the construction of new photovoltaic cells as it still contains a certain percentage of glass. Moreover, a research is being carried out in order to elaborate a process for succeeding in extracting silver from the silicon powder itself. The metal, in paste form, covers the cells up to more than 4%. However, then the extraction process will be useful to cover the considerable costs of the collection of the exhausted modules.
Finally, the plastic that is recovered is recycled to make containers and vessels. Concerning the investments necessary to develop unique technologies, construct and run the plants, European companies spent about half a million Euros, but they estimate to write off expenses in more or less four years. They made it possible to treat about one ton of complete modules per hour, as to say a little more than 50 modules. For a single module the electrical consumption is about half a kilowatt hour, an extremely limited quantity of energy. Nevertheless, the issues related to the recycling of the modules are different. Each system requires a specific evaluation to establish a range of consistent costs, but in conclusion it is always worth investing in photovoltaics because of the well-known pros which they entail.
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