Sustainability of Solar Panels

Photovoltaics (PV) are a renewable energy technology, but they have not been proven to be sustainable as of yet.  They often include rare and toxic materials, and there is currently no regulation on recycling in the US. It is imperative that we fully examine and implement recycling capabilities for solar panels as the installed solar panel capacity has been rising steadily with an 18% increase in 2008 in the US alone.  

The most common solar cells are made from single crystalline silicon in a very energy intensive production process.  It takes 2 years of a panel’s solar energy conversion to produce the same amount of energy used to produce that panel. Large material losses occur when the Si is sliced into thin wafers because the cutting blade is approximately the same thickness as the final wafer. Also, the etchants used in the production process tend to be greenhouse gas emitters, such as SF6. Recently, this has been replaced with NF3 because it has a better greenhouse gas profile; however, because NF3 is not as strong an etchant, the process uses more water, exemplifying a common sustainability issue.  Advanced solar panels are being constructed from cadmium telluride (CdTe) and have only a 1 year energy payback timeline. Cadmium is on the EPA list of toxic materials and is known to be carcinogenic. Tellurium is a rare material and is a by-product of copper and lead production. These are just some of the possible environmental issues that are faced in the production of solar panels.  

There has been some movement by manufacturers to ensure that their solar panels are recycled. In Europe, a consortium of solar panel manufacturers has been formed, known as PV Cycle, in which all signatories agree to sharing the costs of having their solar panels recycled. They have found that this minimizes the total expense of collection and recycling. First Solar has implemented the first manufacturer-based recycling program in the US. They will collect and recycle any of their solar panels and have found that they can reuse up to 90% of the materials in future modules.

The Idea Behind the Blog

The idea behind this blog is to deepen my own, and possibly other's, understanding of sustainability and how it relates to the materials that surround us.  This is quite a comprehensive subject as the idea of sustainability is complicated one, and involves many different viewpoints, and there are too many materials and composites out there to enumerate.  Sustainability, at its most basic, asserts that the rate of growth or production of a material is greater than or equal to the rate of use or decline of that material.  For example, forestry can be a sustainable production method if the rate of tree growth or plantings is greater than the rate of logging or cutting.  If, however, new trees were not planted to make up for the removal of other trees, it would no longer be a sustainable system. 

          
The way that this relates to the sustainability of materials themselves can be looked at in a variety of ways.  In the forestry example, the trees are the material and the sustainability equation is quite simple.  In some cases though, sustainable materials are those that can be taken from the land without causing irreparable harm to the surrounding ecology.  Mining is an example of a production method in which a material can be labeled either sustainable or non-sustainable depending on whether the producers have taken into account the ecology of the land around them and the environmental impact of the process.  A product can be deemed sustainable if it uses less materials than its predecessors tended to, whether the material is sustainable or not.  What happens to the material after a product’s life cycle is complete can also affect its sustainability.  The point here is that sustainability and sustainable materials have a host of definitions, and this blog is going to try to sort those out one material and one definition at a time.