Photovoltaics in our Energy Future

Transcription

1 Photovoltaics in our Energy Future Marc Landry National Center for Photovoltaics Presented to IEEE May 17, 2008 The opinions expressed are those of Marc Landry and do not represent the opinions of the NCPV, NREL, or the DOE.

2 World s Consumable Resources Quads BBoO TW-yrs Breeder Reactors U 235 Crude Oil Natural Gas Coal Oil Shale Tar Sands 0 0 Hydrates on Ocean Floor Conventional Future

3 Sustainable Resource Potential World energy consumption ~ 14 TW-yr Resource Limit Practical Potential 70 TW > 100 TW TW Oceans Hydro Biomass Geothermal Wind Solar

4 How Does the Sun Stack Up? Hours What are these units of time of sunlight hitting the earth? Breeder Reactors U 235 Crude Oil Natural Gas Coal Oil Shale Tar Sands Conventional Future TW-yrs

5 All Path s Lead to Solar Pure Economist s Path: Use what s cheapest, no environmental concern tar sands coal Solar shal e gas oil All Other Renewables Low CO2 Path: Invest in the future now ta r coal oil sa nd s Solar gas All Other Renewables

6 Photovoltiacs Basics Think of PV as a solar battery.

7 Making Semiconductors n or p

8 Photovoltaic Cell Structure Cover (e.g.,glass) Transparent adhesive Antireflection coating Front contact Current Back contact and cover n-type semiconductor p-type semiconductor Power out (W) x 100% Solar cell efficiency (%) = Area (m 2 ) x 1000 W/m 2 10% efficiency = 100 W/m 2 or 10 W/ft 2

9 Photovoltaic Building Blocks System Cell Module Includes storage, voltage regulation, inverters, etc. Array

10 Photovoltaic System Types Grid Connected System (Line Tie or Utility Interface) DC System

11 Why So Many PV Technologies? Part of the reason is the sun doesn t shine at one wavelength. ASTM G Reference Spectra 40 Different materials are used to capture various portions of the solar spectra. ev Also. manufacturing cost vary site resource varies installation priorities materials utilization Efficiency (%) Ge AM0 Black-body limit Si GaAs InP Cu(In,Ga)Se 2 CuInSe 2 CdTe Cu(In,Ga)(S,Se) a-si:h 2 CuInS 2 Cu 2 S CuGaSe AM1.5 CdS

12 PV Technologies Generation Crystalline silicon 1 Flat plates Thin films 2 New technologies 3 Concentrators Silicon 1 2 Multijunctions (III-Vs)

13 World PV Cell/Module Production 2007 = 3.8 GW Thin-Films

14 Crystalline Silicon Single Crystal Si Ribbons Wafering String Ribbon Si Multicrystalline Si Wafering Edge-Defined Film-Fed Fed Growth (EFG) Si

15 c-si Status and Direction Efficiencies Best Laboratory: > 24% Commercial Modules: 10-19% depending on technology Advantages Si 2 nd most abundant element in earth s crust Si most studied element on the periodic table leverage IC industry knowledge base large industrial base allows for some factory standardization Issues material losses due to sawing energy intensive processes (1410 C) wafer 5-10 X thicker than it needs to be (40% module cost) to go well beyond 13% modules need better V oc & FF via improved fundamental understanding most cells designs need to be cool and direct sun

16 Thin-Film Amorphous Silicon United Solar Ovonic

17 a-si Status and Direction Efficiencies Best Laboratory: > 13% Commercial Modules: 5-9% Advantages uses abundant Si very thin, < 1 micron very low energy processing works well in low light and hot environments Issues low efficiency too high a bandgap (need to get the red in) instability with illumination best materials made at the lowest deposition rates

18 Thin-Film CdTe GRAIN BOUNDARY 4 µ ~1 µ

19 CdTe Status and Direction Efficiencies Best Laboratory: > 16% Commercial Modules: 10-11% Advantages good CdTe grown at high deposition rates high efficiency for a thin-film Issues Cd = heavy metal perception problem Te could be a resource limit better CdS, TCO + Glass will increase J sc to go well beyond 13% modules need better V oc & FF via improved fundamental understanding

20 Thin-Film CuInGaSe 2 (CIGS)

21 CIGS Status and Direction Efficiencies Best Laboratory: > 19% Commercial Modules: 9-12% Advantages highest efficiency for a thin-film stochiometry somewhat self assembling architecturally aesthetic (dark films) works well in red end of spectrum Issues has proven difficult to manufacture (4 elements in large area) In could be a resource limit best materials grown at low deposition rates best cells grown with a wet CdS process

22 23

23 III-V Concentrators

24 III-V Status and Direction Efficiencies Best Laboratory: > 40% (under concentration) Commercial Modules: >30% Advantages by far highest efficiency technology stable with illumination and gamma rays (space) efficiency goes up with concentration (peak ~ 300 suns) Issues highly toxic gases involved in fabrication too expensive for terrestrial applications without concentrators concentrators require direct sun concentrators require tracking and robust optics

25 Next Generation and Novel PV Nanoparticulate CIGS precursor materials Mo Glass Drivers - ultra low cost - ultra high efficiencies - new materials - new device physics Candidates - Nanoparticle precursors - Exciton cells (dye, polymer, organic, small molecules ) - Quantum dots, hot-carrier, impurity band cells Other - New TCO s - Thermophotovoltaics Prediction is very difficult, especially about the future. - Niels Bohr

26 Any questions? THANK YOU!!!!

27 Efficiency (%) Progress of Best Laboratory Cells RCA Multijunction Concentrators Three-junction (2-terminal, monolithic) Two-junction (2-terminal, monolithic) Crystalline Si Cells Single crystal Multicrystalline Thin Film Technologies Cu(In,Ga)Se 2 CdTe Amorphous Si:H (stabilized) Emerging PV Dye cells Organic cells Matsushita (various technologies) Monosolar Boeing Boeing 1980 Kodak University of Maine RCA RCA RCA RCA Westinghouse ARCO No. Carolina State University RCA Kodak Boeing RCA Best lab cells shown Modules typically ~ 60% of best lab cells Solarex Spire 1985 Solarex Kodak* Stanford ARCO Varian AMETEK Boeing Spire UNSW Georgia Tech University So. Florida Photon Energy 1990 Boeing University of Lausanne *Not NREL-confirmed NREL UNSW Sharp United Solar NREL Euro-CIS Japan Energy UNSW 1995 UNSW Georgia Tech UCSB* NREL UNSW NREL/ Spectrolab Spectrolab NREL Cu(In,Ga)Se 2 UNSW 14x concentration NREL NREL NREL University of Lausanne NREL United Solar Cambridge* 2000 Spectrolab NREL NREL Groningen Siemens Princeton* NREL University Linz University Berkeley* Linz* NREL

28 Commercial Flat Panel PV From Citigroup Global Markets, equityresearch, Applied Materials,Inc, (AMT), 19 Feb

29 Photovoltaics History 1932 Audobert and Stora discover the photovoltaic effect in cadmium sulfide Photovoltaic technology is born in the United States when Daryl Chapin, Calvin Fuller, and Gerald Pearson develop the silicon photovoltaic (or PV) cell at Bell Labs the first solar cell capable of generating enough power from the sun to run everyday electrical equipment NASA launches the first Nimbus spacecraft a satellite powered by a 470-watt photovoltaic array The University of Delaware builds "Solar One," a PV/thermal hybrid system David Carlson and Christopher Wronski of RCA Laboratories produce the first amorphous silicon photovoltaic cells, which could be less expensive to manufacture than crystalline silicon devices In July, the U.S. Energy Research and Development Administration, a predecessor of the U.S. Department of Energy, launches the Solar Energy Research Institute (today's National Renewable Energy Laboratory), a federal facility dedicated to finding and improving ways to harness and use energy from the sun President George Bush announces that the U.S. Department of Energy's Solar Energy Research Institute has been designated the National Renewable Energy Laboratory.

30 20 TW of PV: Needed & Possible 1.3 x W used by mankind annually 6.46 x 10 9 number of people in the world ~ 2 kw used by each person x 10 x 10 9 projected sustainable world population (2100) * ~ 20 TW Power Needed 1.65 x W solar power hitting the earth x 0.67 portion not reflected back 2.55 x m 2 = half of earth s surface area (sunny side) ~ 650 W/m 2 average solar flux at earth s surface x 2 x m 2 of land (0.14%) to use for PV * x 0.15 average efficiency of future modules ~ 20 TW Solar Power Possible Lewis: 20 TW using 6 x 100 km x 100 km, 33% 1 kw/m 2 * values of greatest uncertainty

31 Required PV Coverage is Possible Structure / Material m 2 mile 2 % land PV needed for 20 TW 2.06e11 79, Nate Lewis calculation 6.00e10 23, Paved roads in the world * 1.94e11 74, All roads in the world * 3.23e11 125, Annual glass production 50 years to 20 TW at 4.1 Bm 2 /yr 4.10e9 1, world railways = 1.12e9 m a 5 m wide PV cover 2.7% 5.60e9 2, * Based on miles of roads in the world from the CIA s World Fact Book and assuming 100 km of road at 10 m width = 1 km 2

32 Energy Payback of PV

33 Element Si H D S C Cu Li Ga Th U Ge In Cd Se Te Abundance of Energy Elements rank mg/kg a-si 86.8% 10.0% 7.2% CIGS 0.8% 19.7% 19.7% 19.7% 0.8% 39.3% CdTe 10.0% 50.0% 40.0% ranking and mg/kg are in earth s crust ** U 0.72% for conventional nuclear (CWR) ** U 99.27% for breeders (FNR) c-si 100% CWR ** FNR test ** Fusion 25% 75%

34 Thin-Films Use Less SC Material Volume of Absorber (cm 3 ) Mass of Absorber (g) c-si CIGS CdTe a-si:h Amount of material needed for 1 kw output (more area for less efficiency).

35 PV Hurdles to the TW Challenge Existing PV Manufacturing costs too much, coming down, but still ~ 5x too high still a small fish in huge pond, but growing rapidly Perception (politics) the solar resource isn t big enough to be a big player because it s not yet significant, it won t ever be existing paradigm = centralized power, PV is distributed high initial investment vs. short term savings Intermittent Resource storage for night and rainy days transmission from sunny to dark areas Not a transportation or a (good) space heating fuel

36 Electricity Research Priorities Improve performance extremely low cost products, e.g., paints or plastics lower cost materials without sacrificing efficiency or durability significantly improved efficiency devices new common materials, TCO s, thermal management, etc. improved solar thermal (thermoelectric) systems New storage systems batteries: Li, Al-air, Zn-air, etc. superconducting technologies New transmission systems long distance transmission (superconductors?) mini-grids space-based solar PV (beaming power to earth) See Lewis, N.S., Crabtree, G., et al., "Basic Research Needs for Solar Energy Utilization

37 Fuels/Heat Research Priorities Efficient solar conversion into chemical fuels photoelectrolysis splitting water into H 2 and O 2 photosynthesis-inspired chemical reactions reverse fuel cell: CO 2 & H 2 O CH 3 OH bio-inspired molecular self assembly solar thermochemical fuel production Thermal Storage improved water systems improved thermal storage materials See Lewis, N.S., Crabtree, G., et al., "Basic Research Needs for Solar Energy Utilization

38 Life-Style & Business Changes Energy Use Changes shift energy intensive work to sunny times (day time) maximize use of daylighting maximize use of passive solar Transportation Changes live closer to work electric cars electric (and extensive) public transit, street cars save fossil fuels (bio-fuels) for flying and construction equipment? See Lewis, N.S., Crabtree, G., et al., "Basic Research Needs for Solar Energy Utilization

39 PV: Existing to Long-Term Benefits Modular (kw to TW) Perfect for peak shaving Disaster relief Clean Few moving parts Quiet Local Jobs Reliable Abundant resource Indigenous resource Energy Security

40 Jobs: Maintenance Installation Sales Manufacturing Engineering Product Development Science Basic Science Applied Science