Life Cycle Assessment and eco-efficiency of prospective, flexible, tandem organic photovoltaic module
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Organic photovoltaic technology has reached a sufficient maturity to enable commercially viable products for integration into buildings with power conversion efficiencies up to about 5%, for example, using a roll- to-roll (R2R) processing of single bulk heterojunction devices technology. This paper reports on a Life Cycle Assessment (LCA) and eco-efficiency analysis of prospective tandem organic photovoltaic (OPV) modules which have been manufactured to the most part in pilot environments. To realistically model the LCA and eco-efficiency a power conversion efficiency of both 10% and a more modest 8% were used with lifespan scenarios of 15 and 20 years. The tandem OPV modules modelled in this study have: a cell stack consisting of new advanced materials such as nano-sized zinc oxide, nano-sized silver, and semiconductor polymers; a light management structure; and new flexible PET based encapsulation with organic and inorganic barriers. This tandem technology was modelled assuming an industrialized production based on real and estimated resource consumption and pollution data from an existing roll-to-roll pilot OPV plant and from material suppliers together with projected costs. Established multi-silicon (multi-Si) and cadmium-telluride (CdTe) photovoltaics were taken to benchmark the environmental impacts in produc- tion and the expected levelized costs of electricity. The results of the modelling show that the production of 1 m 2 tandem OPV module represents only approximately 3–10% of the impacts of 1 m 2 of the bench- mark multi-Si or CdTe modules when the global warming potential (GWP), cumulative energy demand (CED), eco-toxicity, and metal depletion environmental impacts are considered. The results also show the energy payback time of a tandem OPV at facade is only 18–55% of that of the benchmarks, and the GWP is just 12–60% of that of the benchmarks. An eco-efficiency comparison indicates that, for applica- tions where photovoltaic modules cannot be optimally oriented towards the sun, a flexible tandem OPV might be a superior alternative to multi-Si and CdTe modules.