Semiconductors for Efficient Energy Solutions

Transcription

1 Semiconductors for Efficient Energy Solutions B. M. Arora Dept. of Electrical Engineering IIT Bombay Powai, Mumbai NC2E-2014 Pune Univ, 21 Feb

2 OUTLINE OF TALK i) PHOTOVOLTAICS ( PV) Semiconductors Based Electricity Generation Silicon Solar Cells Thin Film Solar Cells I) Amorphous Silicon, ii) Copper Indium Gallium Diselenide, iii) Cadmium Telluride iv) Organic Semiconductors, v) Dye Sensitized Heterojunction Solar Cells Tandem Solar Cells ii) SOLID STATE LIGHTING (SSL) Semiconductors Based Light Sources Blue LEDs with Green and Red Phosphors Blue Green and Red Light Emitting Diodes Organics (OLEDs) 2

3 Indian Power Sector (30 th September, 2013) Power Installed Capacity = 2,28,722 MW 2.09% 12.32% Thermal 17.40% Hydro Nuclear Renwable 68.19% Thermal Hydro Nuclear Renewable 1,55,969 MW 39,788 MW 4,780 MW 28,185 MW 3

4 Renewable Power Capacity (31 st October, 2013) (Grid Connected) 12.8% 7.1% 12.7% Wind Small Hydro Bio Solar 67.4% Wind Small Hydro Bio Solar Total 19,934 MW 3,747 3,776 2,080 29,537 MW MW MW MW (927 MW Off Grid/Captive Power - mostly Waste to Energy, Biomass/Cogeneration, SPV 4

5 ENERGY USAGE IN INDIA About % of Electricity is used for Lighting 5

6 Mission Road Map Application Segment Target for Phase I ( ) Cumulative Target for Phase 2 ( ) Cumulative Target for Phase 3 ( ) Grid solar power (large plants, roof top & distribution grid plants) 1,100 MW 4,000-10,000 MW 20,000 MW Off-grid solar 200 MW 1,000 MW 2,000 MW applications Solar Thermal Collectors (SWHs, 7 million sq. meters 15 million sq. meters 20 million sq meters solar cooking/cooling, Industrial process heat applications etc.) Solar Lighting System 5 million 10 million 20 million 6

7 Potential of Solar Energy in India The daily average solar energy incident varies from 4-7 kwh per square meter. The potential of power generation is MW per square kilometer of land area depending upon the technology and geographical location. It is possible to set up solar power generation capacity of over 1,00,000 MW in India. Potential for solar power is dependent on future developments that might make solar technology cost-competitive for gridinteractive power generation applications. 7

8 ESTIMATE OF ENERGY CONSUMPTION Present World Consumption ~ 15 TW Source : EPIA (EUROPEAN PV Industry Assocn )

9 Kerosene Lantern, Solar Lantern, Solar Hut Off-Grid Solar Power in Rural India A 10 Wp PV module can supply one 7W CFL for 4 hours Kerosene Lantern gives about 30 lumens, consumes about 1-2 litre of Kerosene per week. 9

10 c-si 5 kw Installation at Auroville 10

11 SPV Power Plant at Goshen Drass Kargil (40 kwp) 11

12 5 MWp SPV Plant at Khimsar, Rajasthan 12

13 Semiconductors for Solar Cells and LEDs INORGANIC Materials Elemental Semiconductors : C,Si,Ge Compound Semiconductors III IV V VI GaAs CdTe GaN InGaP CuInSe InGaN CuInGaSe CuZnSnSe AlGaInP ORGANIC Materials : A Whole New World 13

14 Solar Cell Generations Perovskite Solar Cells 14

15 Commercial Solar Cells S Guha, Physics News

16 The Energy We Receive From Sun Earth receives about 100 mw /cm 2 or 1kW /m 2 from sun. Mission Target ~ 20GW Consider 15 % utilization efficiency + Installation Area for harnessing 20 GW ~ 300 km 2 About 75,000 acres Amount of Silicon required include Losses ~ 10Kgm/KW 20 GW requires ~ 200 X 10 6 Kgm 16

17 Mono and Multi-crystalline Silicon Monocrystalline Silicon Multicrystalline Silicon INGOT Brick Silicon Wafers Cell Wafer Cell 17

18 Mono and Multi Crystalline Silicon Solar Cell p-si (~ 200 μm) Single Crystal / Multi-Crystalline Si Loss High Temp High Temp Texturing Process Steps S Guha Talk IIT Bombay Dec

19 Some Typical Solar Cells c-si Solar Cells Flexible 19

20 Standard Solar Spectra 20

21 Illuminated Solar Cell I-V Chracteristics FF= [V MP. I MP ] / [V OC. I SC ], η = P max / P in Quantities of Interest : V OC, I SC, V MP, I MP, P max, Fill Factor(FF), Efficiency( η), Series Resistance R s,shunt Resistance R sh P in requires measurement of input optical power 21

22 Solar Cell Parameters 22

23 Ideal Transparent Hot carrier Intrinsic loss Usable Eff, % Fundamental losses Single/ Tandem Fundamental factors limiting Efficiency Ideal cell Eff, 100% 100% 90% Unavoidable losses for single gap S/C 28% escapes as hν<e g (1.124eV) 80% 70% Optical Loss can be reduced by tandem cells 60% 50% 100.0% 25% loss as hot-carrier hν>>e g Optical/Electrical Loss can be reduced by tandem cells 40% 30% 20% 10% 72.2% 47.0% 29.8% 29.8% Radiative & Auger limits the usable output to only 29.8% 0% Carrier Loss 23

24 Examples of Silicon Solar Cell Efficiency Characterisctics of a common silicon solar cell under standard illumination( 100 mw /cm 2 ) in commercial solar panel V OC = 600 mv I SC = 35 ma / cm 2 FF = 0.75 η = (V OC. I SC. FF)/ P in = 15.75% Highest efficiency laboratory silicon cells * ( Area ~ 4 cm 2 ) * * Zhao et al, Prog Photovolt Res & Appl 7, 471 (1999) 24

25 Prof Martin Green Univ of New South Wales, Syddney, Australia Pioneering work in Silicon Solar Cells PERT : Passivated Emitter Rear Totally Diffused ; PERL : Passivated Emitter Rear Locally Diffused 25

26 Additional Losses in Real Life Cells Theoretically achievable efficiency is 29.8 %. Where does a 16.2 % cell lose the rest? Optical Losses, Carrier Losses 26

27 Major steps for higher efficiency Minimize back reflection, Texturing & ARC Minimize bulk- recmbination.highest lifetime material Minimize junction recombination ( heavily doped-auger recombination important)-to minimize Auger, use a moderately doped emitter layer. To minimize front surface recomb., use oxide passivation of front surface To minimize back surface recomb., provide a field assist to drive holes away 27

28 NREL REPORT BEST CELLS 28

29 A two junction Solar cell 29

30 Record Laboratory Solar Cell Efficiencies Highest Efficiencies Achieved in Small area Cells in Labs Mono-Si 25 % ( UNSW, 1999) Multi Si 20.4 ( FhG-ISE,2004) a-si:h (Triple Jn ) 16.3 United Solar,2011) a-si:h c-si (HIT) 24.7 ( Sanyo, 2013) CdTe 18.7 ( First Solar, 2013) CIGS 20.4% ( EMPA, 2013) CZTSSe 11.1 % ( IBM, 2013) Organic 11.1% ( 2012) Triple Jn ( one sun) 37.7 % ( Sharp, 2013) Triple Jn ( x 942) 44% ( Solar Jn ) 30

31 Price of Module Factors driving Down Prices 1) Poly-silicon price fell from $ 400/Kg in 2007 to $ 25 /Kg in ) Increasing Cell efficiency Price Rise caused by Silicon shortage 3) Improvements in Manufacturing Technology 4) Economies of scale 5) Intense Competition Rough Prices in Rupees Multi-silicon : Rs 35 per Wp in large quantity (MW) : Installed system ~ Rs 80 per Wp Rs 60 per Wp ( small numbers) 31

32 Cost of Solar Electricity S Guha, Physics News

33 National Centre for PV Research & Education (NCPRE) IIT Bombay Mandate: i) Research and Development : a) High efficiency silicon solar cells (20% efficiency) b) Novel Materials c) Power Control Electronic systems ( ~ 5 kw) d) Characterization and Modeling ( Solar Modules) e) Indian National Users Programme ( INUP) f) Industry Affiliates ii) Education : a) Development of PV courses at IIT Bombay b) Outreach : 1) Short term courses dealing with solar cells, power control electronics etc 2) Educational experimental kits for learning of Solar cells, modules, 33

34 NCPRE requested to do this by MNRE s High Level Task Force for Solar PV Survey done jointly with Solar Energy Centre (SEC)

35 Hot & Dry Zone No. of Sites 1 No. of Modules 7 Cold & Dry Zone No. of Sites 1 No. of Modules 3 Hot & Humid No. of Sites 15 No. of Modules 27 Temperate Zone All 5 Climatic Zones of India covered No. of Sites 1 No. of Modules 2 Composite Zone No. of Sites 2 No. of Modules 16

36 15 year Old PV Module working fine Discoloration & Delamination Discoloration & Cell Cracks (blue lines) Shattered Glass Corrosion, Burn Marks and Discoloration Corrosion & Delamination (Left) and corresponding IR Image showing Hot Spot (Right) White Powder from degraded Back sheet

37 Histogram of calculated Pmax degradation Degradation in Pmax for c-si IV parameter degradation-mono c-si Data Analysis is in Progress IV parameter degradation-mono c-si Pmax degradation in different climatic zones

38 IV Curves Corrections as per IEC procedure 1: STC 1:α,β keeping Rs=0,k=0 STC 2:cosidering all 4 parameters Graphs generated using variable radiance data from IITB modules. From the graphs we can infer that the error in translation is within 10 % for STC 1 method. Survey Report is under preparation and will be submitted to High Level Task Force by end of August.

39 SPIRE Solar Simulator 300 nm 1100 nm Spectrum considering trend towards High Efficiency Modules Class A+A+A+ 2 m x 1.3 m Modules PV Module Monitoring Station DAYSTAR Multi-IV Tracer (16 Channels, 3200W) 5 Different PV Module Technologies Continuous Monitoring of Performance Environmental Chamber Temperature Cycling Test Damp Heat Test Humidity Freeze Test PID Test Other Equipments: Electroluminescence Camera Infra-Red Camera High Voltage Tester Purchase of Solar Simulator, Environmental Chamber, EL Camera, IR Camera & High Voltage Tester is in the process

40 SOLID STATE LIGHTING (SSL) Semiconductors Based Light Sources Blue LEDs with Green and Red Phosphors Blue Green and Red Light Emitting Diodes Organics (OLEDs) 40

41 Lighting with Electricity Low Pressure Sodium Vapor Lamp High Pressure Sodium Vapor Lamp 41

42 Two Approaches for Producing White Light LEDs Red + Green + Blue LED (RGB) White Light can be produced in different ways U S Dept of Energy April 2013 Blue LED + Red Phospher + Green Phosphor LED (PC) 42

43 O Large Savings in Electricity, to the tune of 10,000 MW or more, are expected by replacing inefficient lamps with LED lamps 43

44 White GaN-based LEDs in outdoor lighting 44 Pedestrian bridge across Rhine river harbour, Duisburg, Germany

45 Performance (lumens/watt) Progress in LED brightness Fluorescent Lamp Incandescent Lamp Edison s 1st bulb GaP:Zn,O red red/orange AlGaInP/GaP red/orange AlGaInP/GaAs red/orange AlGaAs/GaAs red GaAsP:N red/yellow GaP:N green Alq 3 AlGaInP/GaP >100 lm/w OLED green 31lm/W InGaN green 25lm/W InGaN blue 25lm/W GaAsP red PPV SiC blue Year Nitrides and organic materials are overtaking conventional III-V s in brightness and opening new wavelengths

46 Efficiency & Efficacy of Various Light Sources Type of Light Source Efficiency Efficacy (%) (lm/w) Incandescent light bulb 5 15 Long fluorescent tube Compact fluorescent lamp (CFL) High-power white LEDs Low-power white LEDs Sodium lamp (high-pressure)

47 Advantages of LEDs over CFL LEDs are Environmentally Friendly Compared to CFL 47

48 Solid State Lighting Long Life Incandescent Lamp CFL Linear Fluorescent Lamp LED Prices ~ 1000hrs ~ hrs ~ hrs ~ hrs Table U S Dept of Energy April

49 Eye Sensitivity Quality of LED Lighting i) Lighting Requires White Light ii) White light : Red + Green + Blue iii) White Light can be Cool White Or Warm White depending on the amount of Red component 49

50 Quality of Light and Light Sources Colour Rendering Index ( CRI) : depends on spectral content of lamp and reflectance of object ( 8 StandardTest Colours) CRI is a measure of ability of Light Source to render color CRI of 90 or above indicates excellent color rendering. CRI of 80 or above recommended for interior lighting. Warm white LEDs have CRI of 80 and above. Correlated Colour Temperature ( CCT): Warm White (Yellowish) Sources have Colour Temp K and are used for Interior Lighting Neutral white sources have colour temperature K Cool white ( Bluish) sources have higher colour temp. 50

51 Price Comparison Of Sources U S Dept of Energy April

52 Prices of LEDs U S Dept of Energy April

53 Red Green Phosphors Based GaN White LED Δλ (440) = 24 nm, Δλ (538) = 75 nm, Δλ (615) = 95 nm, Gen Blue Power : 0.73 W Output Blue Power : 0.036W White Light Green Phosphor Red Phosphor Output Green Power : W Output Red Power : W Total Light Power Out : W Possibilities of Much Higher Efficiency (> 50% ) and Efficacy ( 400 lm /W) outlined. State of the art in 2009 : Input Electrical Power : 3.2 V x 0.7 A ~ 2.2 W Total Lumens : 129 lm, ~ 59 lm/w Blue LED Efficiency : 0.73/ 2.2 = 0.33 Power Conversion Efficiency : 0.403/0.73 = 0.55 Overall Efficiency : 14 % Spectral Efficiency : = 0.78 Jeffrey Y. Tsao et al Proceedings of the IEEE Vol. 98, No. 7, July

54 OUTLOOK Semiconductors offer tremendous opportunities for devising efficient means of generating of electricity using Solar Energy. There are equally great opportunities for efficient utilization of energy, particularly for Lighting. Much greater effort is needed to harness these opportunities 54

55 Thank you! 55