Solar cells. Erik Stensrud Marstein IFE/UiO. 25/ Gardermoen

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1 Solar cells Erik Stensrud Marstein IFE/UiO 25/ Gardermoen

2 «Home»

3 The Norwegian Research Centre for Solar Cell Technology Glomfjord Drag Årdal Trondheim Kristiansand Oslo/Kjeller/Askim

4 Agenda The solar resource «What is a solar cell, really?» Solar cell operation Solar cell history Solar cell technology today Solar energy systems The way ahead?

5 The solar resource

6 The solar resource R 6, m V 1, m m 1, X! kg ρ 1, kg/m 3 5, K T surface T interior 13, K sohowww.nascom.nasa.gov

7 SPACE The solar resource ATMOSPHERE EARTH YOU

8 The standard solar spectrum (AM1.5) 1800 Visible light Irradiance ,5 1 1,5 2 2,5 3 3,5 4 4,5 Wavelength [um]

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10 The solar resource final remarks + The biggest (BY FAR!) energy resource we have available + Renewable + Distributed (geographically) - Variable (second, minute, hour, day, month, season) - Distributed (geographically) - Distributed (spectrally) - Accurate prediction of electricity production requires insight

11 What is a solar cell? 200 μm Al kontakt Al BSF Si wafer Ag kontakt 6 Kløw (2013)

12 Solar cell operation E phot = hc/λ > E g - E g V

13 Solar cell operation Direct conversion of sunlight to electricity

14 Solar cell operation The efficiency (η) of a solar cell is defined as the ratio between the maximum electrical power delivered by the cell and the power of the light falling upon it: P sun η = P cell / P sun P cell P cell is given by P cell = I V

15 A word on W p Most people use $/kwh as a measure of electricity prices Challenge: kwh depends on local irradiation Solution: W p The photovoltaic community uses $/W p A 1 W p cell is a cell delivering 1 W at Standard Test Conditions STC = 1 kw per 1 m 2 Solar cell production data are given in W p

16 Solar cell history

17 År Hendelse 1839 Fotovoltaisk effekt i elektrolytt (Becquerel, F) Gårsdagens solceller Wikipedia

18 År Hendelse 1839 Fotovoltaisk effekt i elektrolytt (Becquerel, F) 1883 Solcelle med «stort» areal Se (Fritts, USA) Gårsdagens solceller The current, if not wanted immediately, can be either stored where produced, in storage batteries, or transmitted a distance and there used Fritts

19 År Hendelse Gårsdagens solceller 1839 Fotovoltaisk effekt i elektrolytt (Becquerel, F) 1883 Solcelle med «stort» areal Se (Fritts, USA) % effektiv solcelle av Si (Chapin/Bell Labs, USA) Wikipedia

20 År Hendelse Gårsdagens solceller 1839 Fotovoltaisk effekt i elektrolytt (Becquerel, F) 1883 Solcelle med «stort» areal Se (Fritts, USA) % effektiv solcelle av Si (Chapin/Bell Labs, USA) 1958 Anvendelse Vanguard I første soldrevne satellitt Wikipedia

21 Year Event Solar cell history 1839 Photovoltaic effect in electrolyte (Becquerel, F) 1873 Photovoltaic effect in solid state - Se (Smith, UK) 1883 Large area solar cell thin film Se (Fritts, USA) % Se solar cell self-powered photometer for photography % Si solar cell (Chapin/Bell Lab, USA) % Cu 2 S/CdS solar cell (Reynolds/US Air Force, USA) % GaAs solar cell (Jenny/RCA Lab, USA) 1958 Vanguard I first solar powered satelite 1970 GaAlAs/GaAs heterostructure solar cell (Alferov/Ioffe, SSSR) 1973 Global oil crisis Wikipedia

22 Year Event Solar cell history 1839 Photovoltaic effect in electrolyte (Becquerel, F) 1873 Photovoltaic effect in solid state - Se (Smith, UK) 1883 Large area solar cell thin film Se (Fritts, USA) % Se solar cell self-powered photometer for photography % Si solar cell (Chapin/Bell Lab, USA) % Cu 2 S/CdS solar cell (Reynolds/US Air Force, USA) % GaAs solar cell (Jenny/RCA Lab, USA) 1958 Vanguard I first solar powered satelite 1970 GaAlAs/GaAs heterostructure solar cell (Alferov/Ioffe, SSSR) 1973 Global oil crisis 1994 ScanWafer AS established

23 Gårsdagens solceller Global solar power installations [MW p ] Mostly harmless EPIA (2014)

24 Dagens solceller Global solar power installations [MW p ] 1 GW p 10 GW p 100 GW p EPIA (2014)

25 Bloomberg NEF

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38 What do the numbers mean? MW p /y ~ km 2 /y 10+ billion solar cells/y ~ 1 unit/production line/second(-ish) MW p /y ~ 75 TWh/y ~ 1.5 Denmark/y

39 W p Most people use $/kwh as a measure of energy costs Solar cell output depends on local irradiation The photovoltaic community uses $/W p A 1 W p cell is a cell delivering 1 W at STC STC = 1 kw per 1 m 2 Solar cell production data are given in W p Current price of solar modules: < 1 $/W p

40 Dagens solceller Fraunhofer ISE, BNEF, ITRPV

41 13% 16% 49% Module Cell Wafer Silicon (poly) System 22% ITRPV (2013)

42 Year Event Solar cell history 1839 Photovoltaic effect in electrolyte (Becquerel, F) 1873 Photovoltaic effect in solid state - Se (Smith, UK) 1883 Large area solar cell thin film Se (Fritts, USA) % Se solar cell self-powered photometer for photography % Si solar cell (Chapin/Bell Lab, USA) % Cu 2 S/CdS solar cell (Reynolds/US Air Force, USA) % GaAs solar cell (Jenny/RCA Lab, USA) 1958 Vanguard I first solar powered satelite 1970 GaAlAs/GaAs heterostructure solar cell (Alferov/Ioffe, SSSR) 1973 Global oil crisis 1994 ScanWafer AS established 2012 ~100 GW p solar cells installed, ~40 GW p production capacity 2012 REC Wafer closes all production in Norway

43 Solar cell history? Phase 1: Vision/concept Phase 2: Competitive troublemaker Phase 3: Smart solar

44 Solar cell history final remarks Reasons to celebrate Solar cells CAN deliver Solar electricity is competitive Solar energy is available where people live The solar cell industry is becoming large ~ i 2011 Reasons to worry Fast development Subsidies/policies Infrastructure Variability Storage Geographic compensation Eastward shift of the industry

45 Solar cell technology today

46 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % Technology shares Solar cell technology shares Other R&S Si mc-si sc-si Photon Int l (2012)

47 Technology shares Solar cell technology shares 100 % 95 % 90 % 85 % Other CIGS CdTe a-si R&S Si mc-si sc-si 80 % Photon Int l (2012)

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50 Efficiency Final remarks Efficiency matters! Efficiencies still continue to increase Key route to solar electricity cost reduction Much room to improve Shockley Queisser limit (Si): ~29% Theoretical limit: ~80%+++

51 Large scale process plants REC REC

52 Solar modules The photovoltage of one solar cell is small (~0.5 V). Several solar cells are connected in series in a solar module in order to obtain useful output voltages. The output voltage of a string within a module equals the sum of the individual cell output voltages. The output current of a module is the sum of the individual string output currents

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54 Solar cell technology today final remarks Crystalline silicon solar cells completely dominate the market Industrial solar cell efficiencies on the rise Several concepts hold the potential of increasing efficiency significantly Solar electricity prices are perhaps better understood by considering solar modules as mass produced electronic devices Learning curves Important effect of large market and large scale production facilities

55 Solar cells final remarks Solar cells are now increasingly mainstream Solar electricity costs make it competive in many markets Subsidies have been crucial Sufficiently large markets Predictable price development Smart phasing out put pressure on producers Solar cell impose a new electricity market structure Power plants are often small and privately funded Increased awareness among customers Variable electricity prices Solar electricity might become our largest electricity producer

56 Thank you for your attention!