Ex-ante environmental and economic evaluation of polymer - - PowerPoint PPT Presentation

Copernicus Institute Research Institute for Sustainable Development and Innovation

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

3rd international conference on Life Cycle Management

Zürich, August 27th 2007

Copernicus Institute Research Institute for Sustainable Development and Innovation

Contents

• Introduction
• Environmental assessment (LCA)
• Economic assessment
• Discussion and sensitivity analysis
• Conclusions

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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)

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What is polymer PV?

Polymer PV uses (organic) semi conducting polymers, for conversion of light to electricity.

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Composition of a polymer solar cell

ITO Glass PEDOT:PSS P3HT/PCBM LiF/Al Back Electrode PVDC/PET Back Foil

• +

ITO Glass PEDOT:PSS P3HT/PCBM LiF/Al Back Electrode PVDC/PET Back Foil

• +

PVDC: Polyvinylidenchloride, PET: Polyethylene terephthalate, LiF: Lithium fluoride, Al: Aluminum, P3HT: Poly(3-hexylthiophene-2,5-diyl), PCBM: [6,6]-phenyl C61-butyric acid methyl ester, PEDOT: Poly(3,4-ethylene dioxythiophene, PSS: Polystyrene sulfonate, ITO: Indium tin oxide

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Environmental assessment: LCA

Functional unit:

25 years of electricity production by PV modules with a performance of 1 watt-peak (Wp) (= 31.9 kWh)

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Characteristics of polymer and silicon PV

Efficiency (%) Surface (cm2/Wp) Reference Polymer PV module 5 200 Konarka (2004) Multicrystalline-silicon PV module 13.2 76 De Wild-Scholten and Alsema (2005)

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Material Area (cm2) Thickness layera (cm) Density (g/cm3) Weight (g) Glass 222 0.3 2.579 171.9 ITO 222 1.60E-05 7.2 0.0256 PEDOT:PSS 222 1.00E-05 1 0.002 P3HT/PCBM 222 1.00E-05 1 0.002 LiF 222 1.00E-07 2.64 0.00006 Al 222 1.00E-05 2.7 0.006 PVDC 200 0.008 1.68 2.56 PET 200 0.01 1.33 2.56

Material requirements for 1 Wp polymer solar cell

10% material losses assumed

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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.

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Results for 1 photovoltaic device (1 Wp) Environmental impact category Unit Polymer PV module multi-crystalline silicon PV module Minimum required lifetime polymer PV module (years) NREU MJ 11.9 26.2 11 Climate change g CO2-eq 727 1425 13 Abiotic depletion g Sb eq 5.0 11.1 11 Ozone layer depletion g CFC-11-eq 0.0000413 0.000125 8 Photochemical

• xidant

formation g ethene 0.22 0.29 19 Acidification g SO2-eq 4.69 5.51 21 Eutrophication g PO4

3--eq

0.36 0.58 16

LCA results

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Thin film Polymer mc-silicon CdTe CIS Silicon Dye-sensitised NREU (MJ/Wp) 11.9 26.2 11.9 36.6 20.6 11.7 Climate change (g CO2-eq/Wp) 727 1425 784 2429 1338 473 Energy payback time (yrs) 0.93 2.05 0.93 2.87 1.62 0.92

Comparison with other PV (per watt-peak)

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Solar glass 21% ITO sputtering 9% Substrate cleaning 4% PCBM 1% Annealing 1% Lamination 30% Framing 29% Al/ LiF evaporation 4%

Contribution of production steps to NREU

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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!

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Economic assessment

• Direct manufacturing costs of polymer PV
• We compare 1 watt-peak modules

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Cost results per watt-peak

Material/process Costs (€/Wp) 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)

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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)

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Changing the substrate

Different substrate: PET instead of glass

• Lower impact?
• Cheaper?

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However:

• PET substrate is very thin (50 μm)
• Therefore extra reinforcement might be needed for
• utdoor use!
• We studied:

– PET/Aluminum alloy – PET/Medium density fiberboard – PET/Steel – PET/reinforced polypropylene – PET without reinforcement

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1.50 2.00 2.50 3.00 3.50 5 7 9 11 13

NREU (MJ-eq/Wp)

Costs (€/Wp)

Reference module PET w ith aluminum alloy PET w ith MDF PET w ith steel PET w ith reinforced polypropylene PET w ithout reinforcement

Costs versus NREU of PET with reinforcement (per watt-peak module: 200 cm2)

MDF: medium-density fiberboard

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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!

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Lifetime (yrs) Electricity yield (kWh/Wp) Costs (€-ct/kWh) 5 6.38 44.0 15 19.1 14.7 Reference module 25 31.9 8.8 5 6.38 36.9 15 19.1 12.3 Polymer PV PET without reinforcement 25 31.9 7.4 Industrial consumers 11.4 Electricity EU27, 2005-2007 avg. (Eurostat) Domestic consumers 15.2

Comparison with grid electricity

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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

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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)

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Final remark

Provided that the lifetime is increased, polymer PV has the potential to become a clean, low-cost alternative for silicon PV.

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Thank you for your attention!

Questions/Remarks ?