User:KaylaCarleton/Cadmium telluride photovoltaics

Recycling
Photovoltaic modules can last anywhere from 25 – 30 years. Improper disposal of PV modules can release toxic materials into the environment. Only three methods of high value recycling are industrially available for thin-film PV modules, as of 2013. SENSE (Sustainability EvaluatioN of Solar Energy systems) and RESOLVED (REcovery of SOLar Valuable materials, Enrichment and Decontamination) are European funded procedures. SENSE relies on mechanical, chemical and thermal treatments. RESOLVED relies on mainly mechanical treatments. The final method, First Solar, relies on mechanical and chemical processes. Mechanical methods of recycling are more environmentally friendly as they do not rely on the use of chemicals.

Materials that can be recovered in the recycling process include metals, mounts, glass, and, in high value cases, the whole PV module.

As of 2013 the recycling costs for CdTe modules are higher than the re-sale of recycled materials. However, possible future recycling methods may decrease in cost through reduction of expensive and environmentally unfriendly processes. Promising future recycling methods include vulcanization-vacuum distillation and the Double Green Process. Vulcanization-vacuum distillation has been suggested as a possible recycling process to obtain Te and can recover Te with purities up to 99.92%. The Double Green Process consists of almost entirely mechanical processes.

Environmental Impact
Photovoltaics can assist in reducing toxic emissions and pollution caused by fossil fuels. Emissions from fossil fuels that impact global climates such as Nitrogen Oxide (NOx), Carbon Dioxide (CO2) and Sulfur Dioxide (SO2) are not emitted from PV. A single gigawatt-hour of electricity produced from PV would decrease the emissions of SO2 by 10 tons, NOx by 4 tons and CO2 by 1000 tons when compared to coal.

CdTe cells are considered to be both toxic and carcinogenic when inhaled or ingested as Cd is a toxic compound by the US Occupational Safety and Health Administration. Workers in processing facilities may be exposed to, and inhale, fine particles or fumes of Cd.

CdTe production facilities may cause environmental issues when there are accidents in high efficiency production or from by-product exhaust in less efficient production methods.

During a module’s lifespan it will not release any particles or vapors if used as intended. The only way for a completed module to release dust or vapor is by being lit aflame or ground into fine dust. When exposed to temperatures of approximately 1100 °C in lab tests around 0.4% to 0.6% of the Cd content was released.

The overall Cd air emission estimates can range from 0.02 to 0.5 grams per gigawatt-hour.

Early CdTe modules failed elution tests, however more recent models can pass some elution tests. Despite the small amounts of Cd that may leach out, CdTe modules have low overall leachability as the hazardous materials within them are encased within two layers of glass. Despite their low leachability, CdTe modules have very poor biodegradability.