1 00:00:06,150 --> 00:00:11,960 I would like to welcome back all of you to the last two weeks of the Solar Energy course. 2 00:00:11,960 --> 00:00:18,960 So far, you have seen the basic principles of semiconductor based solar cells, the operation 3 00:00:19,330 --> 00:00:26,330 and design of solar cells, the various PV technologies, solar thermal concepts and even 4 00:00:26,920 --> 00:00:31,500 novel, state-of-the-art concepts like solar fuels. 5 00:00:31,500 --> 00:00:36,810 In this video I will briefly explain what to expect from the last two weeks of this course. 6 00:00:37,800 --> 00:00:43,840 In these last two weeks, we shall focus on the more commonly known field in photovoltaics, 7 00:00:43,840 --> 00:00:47,020 PV systems. 8 00:00:47,020 --> 00:00:51,570 First let us look at a typical PV system. 9 00:00:51,570 --> 00:00:55,640 Here I show a grid-connected PV system. 10 00:00:55,640 --> 00:01:02,300 The grid-connected topology is especially very common in countries that have supporting 11 00:01:02,300 --> 00:01:10,300 solar policies, where excess power generated by the consumer can be fed back to the electric grid. 12 00:01:10,310 --> 00:01:17,310 In this case, a set of PV panels are responsible for power generation. 13 00:01:17,620 --> 00:01:23,170 The PV generated power is not only able to meet the load requirements, but is also able 14 00:01:23,170 --> 00:01:29,710 to feed the excess power generated to the electric grid when the supply exceeds the 15 00:01:29,710 --> 00:01:31,659 load demand. 16 00:01:31,659 --> 00:01:38,210 Let's look at such a system in action in the following 3D illustration. 17 00:01:38,210 --> 00:01:45,210 On a normal day with the sun out, the PV modules on top of this rooftop are busy converting 18 00:01:45,450 --> 00:01:49,960 the incoming irradiance into photogenerated power. 19 00:01:49,960 --> 00:01:55,530 The grid-connected solar inverters used in the system are also constantly converting 20 00:01:55,530 --> 00:02:01,520 the DC output of the solar modules into usable AC power. 21 00:02:01,520 --> 00:02:07,390 The PV system is able to meet the load demand of the household. 22 00:02:07,390 --> 00:02:14,010 On a different day, if it's a very sunny day, the PV system is providing much higher power 23 00:02:14,010 --> 00:02:15,709 than what the load needs. 24 00:02:15,709 --> 00:02:21,620 Under such a condition, the excess power is fed to the grid. 25 00:02:21,620 --> 00:02:27,340 In most countries, the consumer can offset his electric bills in this manner. 26 00:02:27,340 --> 00:02:31,650 This facility is called net metering. 27 00:02:31,650 --> 00:02:36,489 Even after a solar cell has been designed perfectly using the concepts you learned in 28 00:02:36,489 --> 00:02:42,129 the first 6 weeks, there are still many other factors that contribute to the working of 29 00:02:42,129 --> 00:02:44,010 a good PV system. 30 00:02:44,010 --> 00:02:50,209 In week 7, we shall look at the various system components and their properties. 31 00:02:50,209 --> 00:02:57,800 In week 8, we shall look at how these components come together and function as systems that 32 00:02:57,829 --> 00:03:01,819 are widely in use today. 33 00:03:01,819 --> 00:03:05,329 What do we mean by PV system components? 34 00:03:05,329 --> 00:03:08,569 Let's look at this figure for instance. 35 00:03:08,569 --> 00:03:15,189 Here, a typical off-grid or stand-alone PV system is shown. 36 00:03:15,189 --> 00:03:20,189 Different components that constitute this PV system can be seen. 37 00:03:20,189 --> 00:03:27,189 The PV system uses a PV module or a bunch of modules interconnected to form an array. 38 00:03:27,370 --> 00:03:34,189 PV modules, although just an interconnection of solar cells, have a different set of design 39 00:03:34,189 --> 00:03:40,290 and operational constraints when being used in a PV system. 40 00:03:40,290 --> 00:03:45,579 Is it just enough that we place the PV modules randomly on the rooftop? 41 00:03:45,579 --> 00:03:50,969 Do harsh summer and winter conditions have any impact on the PV output? 42 00:03:50,969 --> 00:03:57,389 We shall learn more about all these in the next block. 43 00:03:57,389 --> 00:04:03,510 You can also see a battery that is responsible for storing the excess energy. 44 00:04:03,510 --> 00:04:10,900 The stored energy can be used when the PV generated power is not enough to meet the load demand. 45 00:04:12,099 --> 00:04:17,570 In order to ensure the electrical specifications of the battery are being respected by the 46 00:04:17,570 --> 00:04:22,770 rest of the circuit, a charge controller is used. 47 00:04:22,770 --> 00:04:29,770 An inverter is used to convert the DC power into usable AC power for the required application. 48 00:04:31,330 --> 00:04:36,680 All these PV system components, and important concepts like maximum power point tracking, 49 00:04:36,680 --> 00:04:39,300 will be discussed this week. 50 00:04:39,300 --> 00:04:45,020 By putting together these components we can get different topologies for PV systems. 51 00:04:45,020 --> 00:04:50,400 The main features of designing such systems shall be discussed in week 8, 52 00:04:50,400 --> 00:04:53,650 the last week of this course. 53 00:04:53,650 --> 00:04:59,009 What makes a stand-alone PV system different from a grid-connected one? 54 00:04:59,009 --> 00:05:04,220 Which system topology is a better choice for a particular application? 55 00:05:04,220 --> 00:05:10,020 And how do we go about designing a PV system for a specific application? 56 00:05:10,020 --> 00:05:16,710 These are some of the main questions that I will answer in the last week of the course. 57 00:05:16,710 --> 00:05:23,159 I would also cover in the final week the economics and the environmental aspects of the PV system. 58 00:05:23,159 --> 00:05:31,200 A lot of people complain that 'going solar' is not cheap enough, or that rooftop PV doesn't 59 00:05:31,200 --> 00:05:35,900 pay back in its lifetime the money invested in the system. 60 00:05:35,900 --> 00:05:42,900 We shall examine these claims on the economics of PV systems with an unbiased, objective approach. 61 00:05:42,960 --> 00:05:51,400 I shall introduce you to basic terms like the payback period and the levelized cost of electricity. 62 00:05:51,810 --> 00:05:57,669 At the end of the final week you would hopefully be in a position to perform basic calculations 63 00:05:57,669 --> 00:06:04,500 and see for yourselves as to which factors would make the economics of a PV system more favorable. 64 00:06:04,500 --> 00:06:13,500 Lastly, I would also include in brief an interesting topic in week 8 - that of the energy payback time. 65 00:06:13,900 --> 00:06:20,250 A lot of people believe in the myth that solar panels consume more power in their manufacture 66 00:06:20,250 --> 00:06:24,919 process than they would ever produce in their lifetime. 67 00:06:24,919 --> 00:06:25,870 Is this really true? 68 00:06:25,870 --> 00:06:30,610 If it were, I would not be standing here advocating solar power. 69 00:06:30,610 --> 00:06:34,099 But how do the numbers actually compare? 70 00:06:34,099 --> 00:06:37,909 That is something we will see in the final week of this course. 71 00:06:37,909 --> 00:06:44,069 So, are you ready for the last and the most interesting 2 weeks of this course? 72 00:06:44,180 --> 00:06:46,840 Then, see you back in the next block!