1 00:00:05,400 --> 00:00:10,980 In this block I will give a quick overview of the development of solar energy technology. 2 00:00:11,130 --> 00:00:15,680 Note, that this overview will be far from complete. 3 00:00:15,680 --> 00:00:20,860 If you are interested in a more detailed overview, I advise you to search on the internet, 4 00:00:20,860 --> 00:00:25,830 where you will find many good historic overviews. 5 00:00:25,830 --> 00:00:32,570 As early as the 7th century before Christ, humans have used the first solar technology. 6 00:00:32,570 --> 00:00:37,110 They used magnifying glasses to make fire. 7 00:00:37,110 --> 00:00:43,370 Later, the Romans and Greeks used concentrating mirrors for the same purpose as well. 8 00:00:43,370 --> 00:00:50,100 In the 18th century Horace de Saussure built heat traps, which are a kind of miniature 9 00:00:50,100 --> 00:00:51,640 green houses. 10 00:00:51,640 --> 00:00:57,630 He constructed hot boxes, consisting of a glass box, within another bigger glass box, 11 00:00:57,630 --> 00:01:00,210 up to even five boxes. 12 00:01:00,210 --> 00:01:07,210 When exposed to direct solar irradiation, the temperature in the inner bottom box rose 13 00:01:07,360 --> 00:01:13,890 up to 108 degrees Celsius, warm enough to boil water and cook food. 14 00:01:13,890 --> 00:01:20,890 These boxes can be considered as the world's first solar collectors. 15 00:01:21,650 --> 00:01:30,030 In 1839, the scientist Edmond Becquerel, at an age of 19 years, discovered the photovoltaic effect. 16 00:01:30,110 --> 00:01:36,930 The photovoltaic effect is the generation of voltage or current in a material when exposed to light. 17 00:01:37,490 --> 00:01:42,280 He observed this effect in an electrolytic cell. 18 00:01:42,280 --> 00:01:49,200 The cell was made out of two platinum electrodes, placed in an electrolyte. 19 00:01:49,200 --> 00:01:55,159 An electrolyte is an electrically conducting solution, and in this case he used silver 20 00:01:55,159 --> 00:01:59,440 chloride placed in an acidic solution. 21 00:01:59,440 --> 00:02:04,960 By shining light on it, he observed that the current in the cell was enhanced. 22 00:02:04,960 --> 00:02:12,060 In the sixties and seventies of the 19th century the French physicist Augustin Mouchot 23 00:02:12,060 --> 00:02:15,050 was developing solar powered steam engines. 24 00:02:15,569 --> 00:02:19,629 He believed that the coal resources were limited. 25 00:02:19,629 --> 00:02:24,599 He developed the first parabolic trough solar collector. 26 00:02:24,599 --> 00:02:30,019 As coal became cheaper, the French government decided that solar energy was too expensive 27 00:02:30,019 --> 00:02:35,239 and stopped funding Mouchot's research. 28 00:02:35,239 --> 00:02:43,739 William Grylls Adams and Richard Evans Day demonstrated in 1876 that a junction based on platinum 29 00:02:43,749 --> 00:02:48,879 and the semiconductor selenium shows the photovoltaic effect. 30 00:02:48,879 --> 00:02:53,310 However, the performance of the device was too poor. 31 00:02:53,310 --> 00:02:58,159 Seven years later, Charles Fritts managed to make a PV-device based on a gold-selenium 32 00:02:58,159 --> 00:03:05,159 junction with a light-to-electricity conversion efficiency of 1%. 33 00:03:06,749 --> 00:03:12,769 In 1887 Hertz discovered the photoelectric effect, which is the effect that some charged 34 00:03:12,769 --> 00:03:19,569 objects when exposed to ultraviolet light lose their charge faster. 35 00:03:19,569 --> 00:03:25,989 In 1905 Albert Einstein published a paper in which he explained the photoelectric effect 36 00:03:25,989 --> 00:03:32,150 with assuming that light energy is being carried with quantized package of energy. 37 00:03:32,150 --> 00:03:39,150 Nowadays, we call these packages photons, which we will discuss later this week in great detail. 38 00:03:39,639 --> 00:03:44,590 For this paper Einstein received the Nobel Prize in 1921. 39 00:03:45,090 --> 00:03:54,259 In 1918 the Polish scientist Jan Czochralski developed a way to grow single crystal silicon 40 00:03:54,269 --> 00:04:01,269 a technique of great importance for the solar cell technology based on c-Si wafers, 41 00:04:01,449 --> 00:04:05,559 which has been developed in the second half of the 20th century. 42 00:04:05,559 --> 00:04:10,739 In week 4, we will come back to this processing method. 43 00:04:10,739 --> 00:04:16,799 In 1932 the photovoltaic effect was discovered in the II-VI semiconductor material: 44 00:04:16,799 --> 00:04:21,160 cadmium sulfide by Audobert and Stora. 45 00:04:21,160 --> 00:04:26,699 In week 5 we will come back to solar cells based on II-VI materials. 46 00:04:26,699 --> 00:04:33,400 It took up to 1953 for the potential performance of solar cells made of various materials with 47 00:04:33,400 --> 00:04:35,819 various band gaps to be estimated. 48 00:04:35,819 --> 00:04:43,419 Dr. Dan Trivich of the Wayne State University performed theoretical calculations in reference 49 00:04:43,419 --> 00:04:45,240 to the solar spectrum. 50 00:04:45,240 --> 00:04:49,690 In week 3 of this course we will come back to such estimations. 51 00:04:49,690 --> 00:04:55,890 The real development of modern photovoltaic devices, as we know them today, 52 00:04:55,890 --> 00:04:58,290 started at Bell Labs. 53 00:04:58,500 --> 00:05:05,500 In 1954 Bell Telephone Laboratories produced a silicon solar cell with a light-to-electricity 54 00:05:05,900 --> 00:05:12,100 conversion efficiency of 4% , and they later achieved 11%. 55 00:05:12,300 --> 00:05:18,800 In the mid and late fifties various companies and labs among US, Signal Corps Laboratories, 56 00:05:19,229 --> 00:05:27,429 RCA Lab and Hoffman Electronics developed silicon based solar cells to power orbiting earth satellites. 57 00:05:28,280 --> 00:05:34,740 From 1958 and in the sixties, the progress in PV technology was driven by the energy 58 00:05:34,740 --> 00:05:37,900 demand of space technology. 59 00:05:37,900 --> 00:05:42,930 Various satellites in the series Vanguard, Explorer and Sputnik were launched 60 00:05:42,930 --> 00:05:46,140 with PV powered systems on board. 61 00:05:46,340 --> 00:05:54,040 In 1962 Bell Telephone Laboratories launched the first solar powered telecommunications satellite, 62 00:05:54,040 --> 00:05:59,560 whereas in 1966 NASA launched the first Orbiting 63 00:05:59,560 --> 00:06:06,560 Astronomical Observatory powered by a 1 kW photovoltaic solar array. 64 00:06:07,150 --> 00:06:13,650 In 1968, Professor Giovanni Francia built the first concentrated solar power plant 65 00:06:13,650 --> 00:06:16,129 near Genoa in Italy. 66 00:06:16,129 --> 00:06:23,829 The plant was able to produce 1 MW with superheated steam at 100 bar and 500 degrees Celsius. 67 00:06:24,430 --> 00:06:29,080 Note that these pictures do not reflect the plant in Italy. 68 00:06:29,580 --> 00:06:37,880 In 1970 in the USSR Zhores Alferov develops the high-efficiency solar cell based on 69 00:06:37,880 --> 00:06:41,460 gallium arsenide heterojunction solar cells. 70 00:06:41,669 --> 00:06:47,189 This is the first demonstrator of a solar cell based on III-V semiconductor materials. 71 00:06:47,189 --> 00:06:51,579 We will discuss this technology in week 5. 72 00:06:52,979 --> 00:06:59,979 At RCA Laboratories, Dave Carlson and Chris Wronski develop in 1976 the first thin-film 73 00:06:59,979 --> 00:07:03,789 photovoltaic devices based on amorphous silicon (a-Si). 74 00:07:03,789 --> 00:07:10,789 In 1978 in Japan, SHARP and Tokyo Electronic Applications Laboratory bring the first solar 75 00:07:11,009 --> 00:07:15,400 powered calculators on the market. 76 00:07:15,400 --> 00:07:20,200 In the seventies, due to the oil crisis, and the increasing oil prices, 77 00:07:20,200 --> 00:07:25,949 the public interest in photovoltaic technology for terrestrial application is increasing. 78 00:07:25,949 --> 00:07:31,550 PV technology is not only a niche technology for space applications anymore. 79 00:07:31,550 --> 00:07:40,089 In the late 70s and 80s many companies start to develop PV modules and systems for terrestrial applications. 80 00:07:40,430 --> 00:07:47,020 In 1980 the first thin-film solar cells based on copper sulfide or cadmium sulfide with conversion 81 00:07:47,020 --> 00:07:53,289 efficiencies above 10% were demonstrated at the University of Delaware. 82 00:07:53,289 --> 00:07:59,020 In 1985, at the University of New South Wales in Australia, crystalline silicon (c-Si) solar cells 83 00:07:59,020 --> 00:08:02,860 with efficiencies above 20% were demonstrated. 84 00:08:02,860 --> 00:08:10,019 In week 4, the background and current status of high-efficient c-Si PV devices will be discussed. 85 00:08:10,889 --> 00:08:17,989 In 1984 up to 1991 the largest solar thermal energy generating facility 86 00:08:17,999 --> 00:08:19,919 in the world was built. 87 00:08:20,019 --> 00:08:29,000 These 9 solar plants built in the Mojave Desert in California, have a combined capacity of 354 MW. 88 00:08:29,329 --> 00:08:36,929 In 1991 the first high-efficiency dye-sensitized solar cell was published by the École Polytechnique 89 00:08:36,980 --> 00:08:41,880 Fédérale de Lausanne (EPFL) in Switzerland by Michael Grëtzel and co-workers. 90 00:08:41,880 --> 00:08:46,440 The dye-sensitized solar cell is a kind of photoelectrochemical system, 91 00:08:46,440 --> 00:08:51,530 in which a semiconductor material based on molecular sensitizers, is placed between a 92 00:08:51,530 --> 00:08:54,160 photoanode and an electrolyte. 93 00:08:54,160 --> 00:08:58,510 We will discuss this technology in week 6. 94 00:08:58,510 --> 00:09:03,910 In 1994, National Renewable Energy Laboratory (NREL) in the US developed the concentrator solar cells, 95 00:09:03,910 --> 00:09:06,890 based on III-V semiconductor material. 96 00:09:07,090 --> 00:09:13,880 The cell based on a GaInP/GaAs based two terminal concentrator solar cell 97 00:09:13,880 --> 00:09:17,650 exceeded the 30% conversion limit. 98 00:09:17,650 --> 00:09:24,650 The concentrator PV technology will be discussed in weeks 5 and 6. 99 00:09:25,130 --> 00:09:31,250 And at the end of the nineties, the total worldwide installed photovoltaic power reached 100 00:09:31,250 --> 00:09:34,410 1 GW in 1999. 101 00:09:34,410 --> 00:09:41,810 From 2000, solar energy entered the era in which environmental issues and economic issues 102 00:09:41,870 --> 00:09:45,520 renewed the public interest in solar energy. 103 00:09:45,720 --> 00:09:52,140 It is the era in which the solar market has transformed from a local market to a global market. 104 00:09:52,180 --> 00:09:58,920 In the new millennium Germany took the lead with their progressive feed-in tariffs policy, 105 00:09:58,920 --> 00:10:03,080 leading to a large national solar market and industry. 106 00:10:03,080 --> 00:10:10,060 In 2010, 43% of the worldwide installed PV systems were installed in Germany. 107 00:10:10,060 --> 00:10:15,950 From 2008, the Chinese government has heavily invested in the local solar industry 108 00:10:15,950 --> 00:10:20,690 and has become, in a few years, the dominant PV module manufacturer. 109 00:10:20,890 --> 00:10:30,390 In 2012 the worldwide solar energy capacity surpassed the magic barrier of 100 GW installed power. 110 00:10:30,570 --> 00:10:36,820 This is 100 times more than the installed capacity 13 years earlier in 1999. 111 00:10:36,820 --> 00:10:43,720 This means the solar market has been annually growing with on average 40% for the last 13 years. 112 00:10:43,770 --> 00:10:49,990 Since 2008, installed PV power has shown an unprecedented growth, and shows the potential 113 00:10:50,090 --> 00:10:56,660 of solar energy to soon become the largest energy source that is not based on fossil fuels. 114 00:10:57,020 --> 00:11:02,400 In the coming weeks it will be my pleasure to introduce you to the energy technology 115 00:11:02,400 --> 00:11:06,000 of the future: solar energy. 116 00:11:06,000 --> 00:11:11,020 In this block I have given you a quick journey through the history of solar energy technology. 117 00:11:11,020 --> 00:11:13,640 In the next block we will look at its future.