Solar Photovoltaic Technologies: Past, Present and Future

Transcription

1 Solar Photovoltaic Technologies: Past, Present and Future Xihua Wang, Ph.D., P.Eng. Assistant Professor of Electrical & Computer Engineering University of Alberta April 18, 2018

2 Outline History of photovoltaic (PV) technology A review of current PV devices and systems PV industry A bright future: the development of solar technologies 2

3 Photovoltaic (PV) effect The photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light and is a physical and chemical phenomenon. Photons (light) Electrons (electricity) PV technology: solar energy to electricity 3

4 History of PV technology 1839: French scientist Edmond Becquerel discovered the photovoltaic effect while experimenting with an electrolytic cell made up of two metal electrodes placed in an electricity-conducting solution. 1883: Charles Fritts, an American inventor, described the first solar cells made from selenium wafers. 1905: Alberta Einstein published his paper on the photoelectric effect (along with a paper on his theory of relativity). He won the Nobel Prize for this theory in : Photovoltaic technology was born in the United States when Daryl Chapin, Calvin Fuller, and Gerald Pearson developed the silicon PV cell at Bell labs. A one-watt cell cost almost $300 per watt in 1956 while a commercial power plant cost 50 cents a watt to build at that time. 1958: The Vangard I space satellite used a small (less than one watt) array to power its radios. The Explorer VI satellite launched in 1959 contained 9600 PV cells (solar cells). The size was 1 cm x 2 cm each. The history of solar - U.S. Department of Energy 4

5 1964: NASA launched the first Nimbus spacecraft - satellite powered by a 470-watt PV array. Solar cells were used successfully in powering satellites. 1970s: Dr. Elliot Berman, with help from Exxon Corporation, brought price of solar cells down to $20 a watt. Solar cells began to power navigation warning lights and horns and other applications in remote locations. 1973: The University of Delaware built Solar One, one of the world s first PV powered residences. 1977: Total PV manufacturing production exceeded 500 kilowatts NASA s Lewis Research Center installed a 3.5-kilowatt PV system in southern Arizona - the world s first village PV system. 1985: The University of South Wales broke the 20% efficiency barrier for silicon solar cells. 1994: The U.S. National Renewable Energy Lab (NREL) developed multijunction GaInP/GaAs cells exceeding 30% efficiency. The history of solar - U.S. Department of Energy 5

6 My research history of PV technology Boston University (U.S.) Nano-electronics and nano-optics My path to PV (Jan. 2009) Barack Obama U.S. president (Jan to Jan. 2017) Steven Chu, Nobel Prize in Physics in 1997 Secretary of Energy (Jan to Apr. 2013) University of Toronto Quantum dot PV technology 6

7 Solar spectrum Quantum dots with different sizes I was a postdoc in Prof. Ted Sargent s group at the University of Toronto ( ). 7

8 University of Alberta July, 2012 University of Toronto The development of photovoltaic resource maps for Canada 31 st Annual Conference of the Solar Energy Society of Canada. Aug th

9 Outline History of photovoltaic (PV) technology A review of current PV devices and systems: How PV devices (solar cells) work Solar cell: materials and efficiencies From solar cells to PV systems Concentrator photovoltaics (CPV) PV industry A bright future: the development of solar technologies 9

10 How PV devices (solar cells) work (iv) (iii) (ii) hν (i) Light absorber (E g ) (ii) (iii) (iv) Absorb photon energy (hn) > band gap (E g ) (i) electron-hole pair excitation (ii) electron-hole pair separation to charge carriers (iii) carrier transportation (iv) carrier collection by electrodes 10

11 Solar cell: materials and efficiencies First generation solar cells (Crystalline Si cells): Monocrystalline silicon: 1.1 ev, world record efficiency 26.6% Polycrystalline silicon: 1.1 ev, world record efficiency 22.3% Indirect bandgap semiconductor 200 um thick Second generation solar cells (Thin-film technologies): Amorphous silicon thin film: 1.7 ev, world record efficiency 14.0% CdTe thin film: 1.5 ev,, world record efficiency 22.1% CIGS thin film: ev, world record efficiency 22.6% Direct bandgap semiconductors 1-2 um thick Third generation solar cells (Emerging PV): Organic photovoltaics (OPV), world record efficiency 11.5% Dye-sensitized solar cells (DSSC), world record efficiency 11.9% Colloidal quantum dot (CQD), world record efficiency 13.4% Perovskite solar cells, world record efficiency 22.7% 11

12 Crystalline Si Solar cells There are no natural mineral deposits of Si, as it is too reactive. 1. Starting material is ultrapure sand (SiO 2 ) 2. Sand is reduced by carbon at high temperature to produce 98% pure metallurgical grade silicon or MGS 3. MGS is converted to gaseous trichlorosilane (bp 32 o C) 4. Trichlorosilane is purified by distillation (difference in boiling points of impurity compounds) 5. Trichlorosilane converted back to Si by decomposition, yielding electronic grade silicon or EGS Saga, NPG Asia Materials (2010). 12

13 Thin-film solar cells Thickness of light absorbing layer in Si solar cells is around 200 um. Thickness of light absorbing layer in thin-film solar cells is 1-2um

14 From solar cells to PV systems DC ~ 0.6 V AC 110 or 220 V 14

15 SunPower Corporation 15

16 Various PV systems Grid-tie (with or without battery) systems Stand-alone systems Inverter

17 Concentrating photovoltaics (CPV) Cheap optics + expensive but highefficiency multi-junction solar cells. 17

18 Outline History of photovoltaic (PV) technology A review of current PV devices and systems PV industry: production and price trend A bright future: the development of solar technologies 18

19 Energy pay-back time of Rooftop PV systems in Germany Photovoltaics Report, Fraunhofer, ISE, Freiburg, 26 February2018; 19

20 Photovoltaics Report, Fraunhofer, ISE, Freiburg, 26 February2018; 20

21 Global PV industry production by region ( ) Global cumulative PV installation until 2016 (includes off-grid) Photovoltaics Report, Fraunhofer, ISE, Freiburg, 26 February2018; 21

22 Price for PV systems in Germany Photovoltaics Report, Fraunhofer, ISE, Freiburg, 26 February2018; 22

23 U.S. PV system cost benchmark summary (inflation adjusted), U.S. Solar Photovoltaic System Cost Benchmark, August

24 Evolution of PV module efficiency Photovoltaics Report, Fraunhofer, ISE, Freiburg, 26 February2018; Commercial silicon module efficiency Prog. Photovolt: Res. Appl. 13, 447 (2005) 24

25 Photovoltaics Report, Fraunhofer, ISE, Freiburg, 26 February2018; 25

26 Outline History of photovoltaic (PV) technology A review of current PV devices and systems PV industry A bright future: the development of solar technologies Emerging PV technologies New concept: artificial photosynthesis New development: Luminescent solar concentrators 26

27 Emerging PV technologies Research Cell Efficiency Records (Nov 2017) Perovskite cells: Solution-processed light-absorbing materials, earth-abundant elements; Compatible to roll-to-roll printing process (compared to solar cells by vacuum deposition and crystal growth), record-efficiency 22.7%. 27

28 Perovskite solar cells Solution-processed (CH 3 NH 3 )PbI 3 organic/inorganic hybrid materials that have the same crystalline structure as perovskite (CaTiO 3 mineral ). Nature Energy 1, (2016) Nature Reviews Materials 3, (2018) 28

29 New concept: artificial photosynthesis Photosynthesis in plants ChemPhotoChem 2, 148 (2018) Inspired by nature, solar-to-chemical energy: CO 2 reduction Water splitting (H 2 generation) 29

30 Photoelectrochemical/photocatalytic water splitting: Photoelectrochemical/photocatalytic CO 2 reduction: Science 334, 645 (2011) Advanced Science 5, (2018) Nature Reviews Materials 2, (2017) 30

31 New development: Luminescent solar concentrators for building integrated photovoltaics (BIPV) Traditional concentrating photovoltaics require tracking systems. Luminescent solar concentrators for building windows and parking coverages. Nature Reviews Materials 2, (2017) 31

32 Absorption and emission spectra of organic dye based luminescent solar concentrators. Xihua Wang Research Group at the University of Alberta works on quantum dot based luminescent solar concentrators. Absorption and emission spectra of quantum dot based luminescent solar concentrators. 32

33 In 2002, global energy consumption rate is ~ 13.5 TW (10 12 watts). In 2050, expected global energy consumption rate is ~ 30 TW. Nocera, Daedalus 112 (2006) Future of solar electricity Solar energy: 1.5 x 10 5 TW at Earth surface 0.05% (Earth surface) x 20% (efficiency) = 15 TW 33