Ex-ante environmental and economic evaluation of polymer photovoltaics (PV) Lex Roes Martin Patel Erik Alsema Utrecht University Heidelberglaan 2, 3584 CS, Utrecht, The Netherlands E-mail: a.l.roes@uu.nl 3 rd international conference on Life Cycle Management Zürich, August 27 th 2007 Copernicus Institute Research Institute for Sustainable Development and Innovation
Contents • Introduction • Environmental assessment (LCA) • Economic assessment • Discussion and sensitivity analysis • Conclusions Copernicus Institute Research Institute for Sustainable Development and Innovation
Research goal What are the environmental impacts and costs of ‘polymer PV’ compared to (conventional) ‘silicon PV’? (In addition: comparison with thin film PV and with grid electricity) Copernicus Institute Research Institute for Sustainable Development and Innovation
What is polymer PV? Polymer PV uses (organic) semi conducting polymers , for conversion of light to electricity. Copernicus Institute Research Institute for Sustainable Development and Innovation
Composition of a polymer solar cell - - + + PVDC/PET Back Foil PVDC/PET Back Foil LiF/Al Back Electrode LiF/Al Back Electrode P3HT/PCBM P3HT/PCBM PEDOT:PSS PEDOT:PSS ITO ITO Glass Glass PVDC : Polyvinylidenchloride, PET : Polyethylene terephthalate, LiF : Lithium fluoride, Al : Aluminum, P3HT : Poly(3-hexylthiophene-2,5-diyl), PCBM : [6,6]-phenyl C 61 -butyric acid methyl ester, PEDOT : Poly(3,4-ethylene dioxythiophene, PSS : Polystyrene sulfonate, ITO : Indium tin oxide Copernicus Institute Research Institute for Sustainable Development and Innovation
Environmental assessment: LCA Functional unit: 25 years of electricity production by PV modules with a performance of 1 watt-peak (W p ) (= 31.9 kWh) Copernicus Institute Research Institute for Sustainable Development and Innovation
Characteristics of polymer and silicon PV Efficiency Surface Reference (cm 2 /W p ) (%) Polymer PV module 5 200 Konarka (2004) Multicrystalline-silicon 13.2 76 De Wild-Scholten PV module and Alsema (2005) Copernicus Institute Research Institute for Sustainable Development and Innovation
Material requirements for 1 W p polymer solar cell Area (cm 2 ) Thickness layer a (cm) Density (g/cm 3 ) Material Weight (g) 222 Glass 0.3 2.579 171.9 222 ITO 1.60E-05 7.2 0.0256 222 1 PEDOT:PSS 1.00E-05 0.002 222 1 P3HT/PCBM 1.00E-05 0.002 222 LiF 1.00E-07 2.64 0.00006 222 Al 1.00E-05 2.7 0.006 200 PVDC 0.008 1.68 2.56 200 PET 0.01 1.33 2.56 10% material losses assumed Copernicus Institute Research Institute for Sustainable Development and Innovation
Problem with polymer PV • Lifetime of polymer solar cell is only a few months with present technology. • Lifetime of silicon solar cell is >25 years. • Therefore we also estimate the minimum required lifetime of polymer PV to have benefits over silicon PV. Copernicus Institute Research Institute for Sustainable Development and Innovation
LCA results Minimum Results for 1 photovoltaic device required (1 W p ) lifetime Environmental Polymer PV multi-crystalline polymer PV impact Unit module silicon PV module category (years) module NREU MJ 11.9 26.2 11 Climate change g CO 2 -eq 727 1425 13 Abiotic g Sb eq 5.0 11.1 11 depletion Ozone layer g CFC-11-eq 0.0000413 0.000125 8 depletion Photochemical g ethene 0.22 0.29 19 oxidant formation Acidification g SO 2 -eq 4.69 5.51 21 3- -eq Eutrophication g PO 4 0.36 0.58 16 Copernicus Institute Research Institute for Sustainable Development and Innovation
Comparison with other PV (per watt-peak) Polymer mc-silicon Thin film CdTe CIS Silicon Dye-sensitised 11.9 26.2 11.9 36.6 20.6 11.7 NREU (MJ/W p ) 727 1425 784 2429 1338 473 Climate change (g CO 2 -eq/W p ) 0.93 2.05 0.93 2.87 1.62 0.92 Energy payback time (yrs) Copernicus Institute Research Institute for Sustainable Development and Innovation
Contribution of production steps to NREU Solar glass 21% Framing 29% ITO sputtering 9% Substrate cleaning 4% PCBM 1% Annealing 1% Lamination 30% Al/ LiF evaporation 4% Copernicus Institute Research Institute for Sustainable Development and Innovation
Conclusions LCA • Per Watt-peak module, polymer PV has lowest impacts and lowest energy payback time ! • ITO coated glass production, lamination and framing together contribute 89% of NREU. • Production of layer materials has very small impacts. • BUT: R&D challenge is to improve the lifetime! Copernicus Institute Research Institute for Sustainable Development and Innovation
Economic assessment • Direct manufacturing costs of polymer PV • We compare 1 watt-peak modules Copernicus Institute Research Institute for Sustainable Development and Innovation
Cost results per watt-peak Material/process Costs (€/W p ) ITO Coated glass 0.22 PEDOT:PSS 0.00 P3HT/PCBM 0.09 Inkjet printing 0.01 LiF 0.00 Aluminum 0.00 Evaporation 0.03 Module assembly 2.46 Total polymer PV 2.80 Total mc-silicon PV 2.50 (Sinke et al. 2006) Copernicus Institute Research Institute for Sustainable Development and Innovation
Conclusions economic assessment • Per watt-peak, polymer PV has 12% higher costs than silicon PV. • Main contributor to costs is – Module assembly (could be reduced, if efficiency increases: � smaller area) Copernicus Institute Research Institute for Sustainable Development and Innovation
Changing the substrate Different substrate: PET instead of glass • Lower impact? • Cheaper? Copernicus Institute Research Institute for Sustainable Development and Innovation
However: • PET substrate is very thin (50 μ m) • Therefore extra reinforcement might be needed for outdoor use! • We studied: – PET/Aluminum alloy – PET/Medium density fiberboard – PET/Steel – PET/reinforced polypropylene – PET without reinforcement Copernicus Institute Research Institute for Sustainable Development and Innovation
Costs versus NREU of PET with reinforcement (per watt-peak module: 200 cm 2 ) 3.50 3.00 Reference module Costs (€/Wp) PET w ith aluminum alloy PET w ith MDF 2.50 PET w ith steel PET w ith reinforced polypropylene 2.00 PET w ithout reinforcement MDF: medium-density fiberboard 1.50 5 7 9 11 13 NREU (MJ-eq/Wp) Copernicus Institute Research Institute for Sustainable Development and Innovation
Assuming a higher efficiency • Recently 6% efficiency has been achieved (Wake Forest University, 2007) • Predicted future efficiency is 11% ! (Koster et al. 2006) • Environmental impacts and costs will decrease by > factor 2 at 11% efficiency! Copernicus Institute Research Institute for Sustainable Development and Innovation
Comparison with grid electricity Lifetime Electricity yield Costs (€-ct/kWh) (yrs) (kWh/Wp) Polymer Reference module 5 6.38 44.0 PV 15 19.1 14.7 25 31.9 8.8 PET without 5 6.38 36.9 reinforcement 15 19.1 12.3 25 31.9 7.4 Electricity Industrial consumers 11.4 EU27, 2005-2007 avg. Domestic consumers 15.2 (Eurostat) Copernicus Institute Research Institute for Sustainable Development and Innovation
Main uncertainties in this study • Impacts of lamination are assumed to be proportional to surface of the module • Rough assumptions for ‘substrate cleaning’ and ‘annealing’ (but: contribution is low) • Uncertainty whether lifetime and performance remain the same with PET as a substrate Copernicus Institute Research Institute for Sustainable Development and Innovation
Overall conclusions • Per watt-peak, environmental impacts of polymer PV are clearly lower than of silicon PV • Per watt-peak, costs of polymer PV are only 12% higher than of silicon PV • Replacing the glass substrate by PET can bring down costs (from 2.80 to 2.35 €/Wp) Copernicus Institute Research Institute for Sustainable Development and Innovation
Final remark Provided that the lifetime is increased, polymer PV has the potential to become a clean, low-cost alternative for silicon PV. Copernicus Institute Research Institute for Sustainable Development and Innovation
Thank you for your attention! Questions/Remarks ? Copernicus Institute Research Institute for Sustainable Development and Innovation
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