1 00:00:05,589 --> 00:00:10,580 Dear Solar Energy students, we have arrived at the end of the course. 2 00:00:10,580 --> 00:00:15,969 You have been introduced to a wide range of topics, which cover the various technologies, 3 00:00:15,969 --> 00:00:20,650 which try to harvest the energy in the light coming from the sun. 4 00:00:20,650 --> 00:00:25,830 Let's look at a short overview of the important things you have learned. 5 00:00:26,920 --> 00:00:32,180 In the first week, we have discussed that the current energy infrastructure heavily 6 00:00:32,180 --> 00:00:34,400 depends on fossil fuels. 7 00:00:34,560 --> 00:00:41,960 Fossil fuels are mainly used for energy conversion into heat, mechanical energy or electricity. 8 00:00:42,380 --> 00:00:48,160 Solar energy is an alternative sustainable route converting the energy in sunlight into 9 00:00:48,170 --> 00:00:50,890 heat, solar fuels or electricity. 10 00:00:51,920 --> 00:00:57,920 The photovoltaic approach, which converts solar energy directly into electricity using 11 00:00:57,920 --> 00:01:02,800 semiconductor based devices has been an important part of this course. 12 00:01:04,629 --> 00:01:09,979 I've discussed that the effective installed solar power is the fastest increasing power 13 00:01:09,979 --> 00:01:12,520 generation technology in the world. 14 00:01:12,520 --> 00:01:18,479 If we extrapolate the trend of the last 5 years, the contribution of solar energy to 15 00:01:18,479 --> 00:01:25,189 the electricity generation, could be on the same level as nuclear and hydro energy before 16 00:01:25,189 --> 00:01:26,629 the end of this decade. 17 00:01:27,729 --> 00:01:34,729 The forces behind this fast growth are the decentralized character of domestic PV systems 18 00:01:34,999 --> 00:01:39,259 combined with the grid parity achieved in many countries. 19 00:01:39,259 --> 00:01:46,639 Soon, PV installations around the world will break through the magic level of a 1% contribution 20 00:01:46,729 --> 00:01:49,089 to the worldwide electricity production. 21 00:01:50,540 --> 00:01:56,399 We started the theoretical part of this course by discussing the spectral shape and irradiance 22 00:01:56,399 --> 00:01:57,299 of sunlight. 23 00:01:58,270 --> 00:02:03,689 The spectrum of the sunlight incident on the Earth's surface is determined by the temperature 24 00:02:03,689 --> 00:02:10,689 of the sun and the absorption, scattering and reflection losses in the Earth's atmosphere. 25 00:02:10,840 --> 00:02:16,840 You now understand that this spectral shape basically determines the potentially achievable 26 00:02:16,840 --> 00:02:23,260 conversion efficiencies of the various semiconductor materials, when used in a single junction device. 27 00:02:24,500 --> 00:02:31,920 In weeks 2 and 3 we have discussed the physical fundamentals of photovoltaic technology. 28 00:02:31,989 --> 00:02:38,879 We have discussed various properties of semiconductor materials, such as the valence and conduction 29 00:02:38,879 --> 00:02:45,879 band, its band gap and the transport mechanism of the charge carriers like drift and diffusion. 30 00:02:46,409 --> 00:02:50,950 We have discussed the working principle of p-n junctions. 31 00:02:50,950 --> 00:02:57,640 These junctions separate the light-excited minority charge carriers. 32 00:02:57,640 --> 00:03:02,530 In week 3 we saw that the behavior of the solar cells can be explained in terms of the 33 00:03:02,530 --> 00:03:07,800 external parameters: open-circuit voltage, the short-circuit current density, the fill factor, 34 00:03:07,800 --> 00:03:12,840 the maximum power point and the conversion efficiency. 35 00:03:12,840 --> 00:03:18,489 In addition we have discussed the design rules of solar cells and categorized them in terms 36 00:03:18,489 --> 00:03:24,459 of spectral utilization, utilization of the band gap energy and light management. 37 00:03:24,459 --> 00:03:31,459 These are handy tools to understand the differences between the various PV technologies. 38 00:03:32,660 --> 00:03:38,020 In weeks 4 and 5, we have looked at the various PV technologies. 39 00:03:38,030 --> 00:03:44,540 As example we have discussed the three c-Si wafer based solar cells with the highest achieved 40 00:03:44,540 --> 00:03:50,489 conversion efficiencies up to date, like the PERL solar cell, the interdigitated back contacted 41 00:03:50,489 --> 00:03:53,569 solar cell and the heterojunction based solar cells. 42 00:03:53,569 --> 00:04:00,079 You have seen the various silicon processing methods to make electronic-grade silicon and 43 00:04:00,079 --> 00:04:02,619 multicrystalline and monocrystalline wafers. 44 00:04:04,420 --> 00:04:10,379 We have quickly touched upon the various other PV technologies, like III-V semiconductor 45 00:04:10,379 --> 00:04:17,379 multi-junctions, the CdTe PV technology, the CIGS PV technology, the thin-film silicon 46 00:04:17,380 --> 00:04:21,020 technology, and the organic based PV technologies. 47 00:04:21,380 --> 00:04:27,780 Every PV technology has its own advantages, such as the high conversion efficiencies, 48 00:04:27,940 --> 00:04:34,620 abundantly available source materials, low cost price per watt-peak, the possibility 49 00:04:34,630 --> 00:04:38,670 to process it on flexible substrates, etc. 50 00:04:39,700 --> 00:04:47,020 In week 6 we have looked to alternative energy conversion approaches using solar energy. 51 00:04:47,280 --> 00:04:53,060 We have looked to the welcome technology of using solar energy to heat water and concentrated 52 00:04:53,060 --> 00:04:57,000 power approaches using heat engines to make again electricity. 53 00:04:57,940 --> 00:05:02,800 We addressed the challenge, for any sustainable energy technology in the future, which is 54 00:05:03,000 --> 00:05:07,360 the ability to store the generated energy. 55 00:05:07,370 --> 00:05:13,620 In that light, we shortly talked about the combination of photoelectrochemical and photovoltaic 56 00:05:13,620 --> 00:05:20,620 approaches, to convert solar energy in fuels like hydrogen and methane. 57 00:05:21,270 --> 00:05:27,979 In week 7 we looked at the crucial components, besides the PV module, that make a PV system, 58 00:05:27,979 --> 00:05:34,410 like inverters, charge controllers, maximum power point trackers and batteries. 59 00:05:34,410 --> 00:05:42,500 In week 8 we have discussed the design rules of both a stand-alone PV system and a grid-connected PV system. 60 00:05:42,500 --> 00:05:48,259 The economic and environmental aspects have been looked into in more detail. 61 00:05:49,960 --> 00:05:56,199 Arriving at this final point in the course, you can be proud of yourself. 62 00:05:56,199 --> 00:06:03,199 You have learned and mastered a broad range of topics related to solar energy technology. 63 00:06:03,640 --> 00:06:08,180 Be aware that this course has the function of being an introduction. 64 00:06:08,820 --> 00:06:16,080 If you are interested, fascinated and inspired by the various topics addressed, you can find 65 00:06:16,199 --> 00:06:21,819 many books and scientific literature that tackle the various topics in more depth. 66 00:06:22,420 --> 00:06:28,600 Several universities around the world offer education focused on solar energy technologies. 67 00:06:28,610 --> 00:06:34,740 For example, at Delft University of Technology, we have a PV profile in our Master's program, 68 00:06:34,740 --> 00:06:41,740 including courses like PV Basics, PV Technology, PV Systems and the PV Lab Course. 69 00:06:42,539 --> 00:06:46,800 After this final lecture, you will find the final exam. 70 00:06:46,800 --> 00:06:53,800 After you have finished your exam, I would like to ask you a last favor. 71 00:06:54,080 --> 00:07:01,460 Could you make a short video, not longer than 2 minutes, in which you talk about 72 00:07:01,460 --> 00:07:03,780 your solar energy system. 73 00:07:04,400 --> 00:07:10,940 If you don't have a system, make a short movie where you interview your neighbor, your friend 74 00:07:10,949 --> 00:07:14,349 or your relative, who has a PV system. 75 00:07:14,349 --> 00:07:20,220 Upload your movie on YouTube and share the link with us in the dedicated discussion blog 76 00:07:20,220 --> 00:07:23,819 on the Solar Energy edX platform. 77 00:07:23,819 --> 00:07:29,509 We can learn from other people's experiences and inspire each other. 78 00:07:29,509 --> 00:07:36,509 As examples, I will upload some homemade movies myself, of people talking about their PV or 79 00:07:36,659 --> 00:07:39,789 solar thermal system. 80 00:07:39,789 --> 00:07:44,610 Finally, we arrive at the end of my lecture. 81 00:07:44,610 --> 00:07:50,669 I personally would like to thank everybody from the edX and DelftX team who helped us 82 00:07:50,669 --> 00:07:54,569 making this Massive Open Online Course. 83 00:07:54,720 --> 00:08:00,460 This time I can't finish with saying "see you in the next block". 84 00:08:00,740 --> 00:08:05,280 Therefore I would like to close with the words, 85 00:08:05,280 --> 00:08:12,280 "I hope to see you and your learned skills back in helping solar energy to become an 86 00:08:12,520 --> 00:08:17,900 important and sustainable contributor to human kind's energy need."