 So therefore, so far there are technologies that have been developed into artistly solar energy. I divided it into two categories, solar-electric. You can also call it for the Voltaic, or the short form is PD, or solar-thermal. So in the solar-electric version we directly convert solar power into electricity, whereas for solar-thermal case, we convert solar energy into heat, and somehow use that heat to do either space heating, water heating, or convert that heat into electricity. So from the first category we have flat panel TVs. That's basically the most well-known technology that everybody kind of says TV for the Voltaic or solar power. That is what, to your mind, I'll talk about it more. There is another category of solar-electric technology which is called concentrated TV. Concentrated TV is very similar to TV, but for the solar power before reaching the TV that converts solar energy into electricity, there is an optical stage. So you have an optical stage that concentrates the solar energy and then delivers it to the solar cell to convert it to electricity. For the concentrated TV there are low concentration, high concentration TV, and for high concentration that optical stage can be based on reflection or based on refraction. Also there is ancient technology that's very similar to TV, but the molecular structure of the material is slightly different. So they provide more electrical power density per mass. I put it in parenthesis because I'm not going to talk about it. First, if you're interested to read or understand more about this field, you can go and do some Google search, we'll learn a lot. But on the solar thermal part, we have, as I said, we want to generate heat from solar energy. We can use it by parabolic drops or power technology, dish sterling, or just use it for hot water generation. So what is going to happen from this point on, I'm going to briefly explain each one of these technologies, so you get an idea of how things work. Please feel free to stop me if you have any questions. I'm not going to dive deep into the technical details, but if there is something bothering you and you want to understand more, don't be shy because the way you're handling it is more than happy to explore it. So that's what the bulk tank or the short form is key. It's basically based on semiconductor technology. We have a P-type semiconductor and an N-type semiconductor. They are attached next to each other. When this happens, something called junction forms and this junction has a very interesting property that if an external energy comes to that junction, it has the potential to release electrons in holes and once you collect the electrons and load the electrons to an electric circuit, you can actually extract the power that is stored in the system. So basically what happens? In short, you have the semiconductor junction P-type, N-type, the sunlight hits and then your electrons and holes are released. You connect this whole thing to an electric circuit, the electrons from the circuit, they convert that external power, which here is in form of sunlight into electricity. So the portable tank is used for residential purposes. We have the TV panels that are basically that semiconductor technology, that diode that are fixed on the roofs. In this technology, the panels are fixed. Keep in mind why I'm emphasizing on fixing because during the day, sun is moving in the sky and throughout the year also sun angle versus earth changes. So if you want to get the maximum power out of the system, the best thing is to always point to the sun. So basically move with the sun during the day and also move during the year from, let's say, winter to summer. But all the tree comes down to economic measures. So if you want to build this, if you want to work to build all those gears, all the mechanical and moving parts to just move these things, or even on the roof of the house, we have the physical capability of doing it. So once you sit down and do all the calculation, you see, you know what, I'm better off to put the solar panel on the roof, not move it. Yes, it won't be the best case, it won't be optimal, but even the self-optimal case is good enough to generate enough energy, enough electricity that a household can use for generating electricity. From residential, we go to commercial. Commercial solar panels are slightly larger installations. For residential, for example, you need anywhere between 3 to 5 kilowatts installation. Each panel is about 200 watts. So, you know, you need 10 to 15 or 15 to about, what, 20 panels, and that's enough. For commercial purposes, the amount of power that you want to generate is slightly larger. It's maybe like tens of kilowatts to maybe hundreds of kilowatts, depending on the amount of area you have. And usually they call these buildings as big boxes because they look like big boxes, like your grocery store, the Yerevan city. It is an example of a big box because it has a flat roof, nothing happening in that roof, and it's a perfect location to install solar panels. Now, what is the business approach for that is different. Some people come and lease the roof of that big box from the owner and say, you know, I'll pay you this much rent, I'll install the solar panel on that, and then I'll offset your electricity bill by this much, and all the excess power that I'm generating from this system, I'll push it back to the next one. Okay? Or some people, if they would like to do that, they just buy the solar system and install on top of their big box. There are various business plans for this, and each person has a different approach. But again, since these big boxes aren't structurally very sturdy, they can't tolerate heavy stuff on their roof, right? So basically, again, this whole thing can't be too heavy. Therefore, they usually choose to have installations that aren't moving. They're just fixed, and it stays there, and mostly they are even flat. You know that, like, the optimal angle, because of how the earth is tilted with respect to its sun is, depending on where you are on earth, it's kind of about, like, 30 degrees, right? So basically, if you wanted the optimal, these panels should be tilted up by 30 degrees from the roof. But again, because of those mechanical and practical reasons, they choose to put the panels flat on the roof and operate at suboptimal operating points. The third version is utility scale, and as you see, there is huge area that is dedicated to solar panels, and you have all this, maybe hundreds of thousands or millions of solar panels sitting next to each other, and this is actually a solar power plant that is generating electricity in the range of gigawatts, or at least megawatts, depending on how big that is. But for utility scale, because everything sits on the ground, you have the freedom of choosing to track the sun in both directions, like azimuth and elevation, or put your solar panels in north and south directions that only track the sun during the day from east to west, or if you want to avoid all those moving parts and reliability issues that they cause, because they break. If they break, it won't work, right? So you say, okay, I don't want to do that, everything's fixed. These are all different options that you would see happening in the real world. And how much is the area of the solar panel? The area, how much? It depends on how much power you want to generate. So let me tell you back off the envelope calculation. On the average, the maximum solar irradiance we receive on the earth is 1,000 watts per meter square, okay? For every square meter we receive 1 kilowatt of solar power, and each silicon technology at the system level is anywhere between 15% to 20% efficient. So 15% of that power is converted into electricity. So now if you want to generate, let's say, 1 megawatt of power, you go back in efficiency, you calculate how much solar power you need, and then you know that every square meter you receive has it, and you calculate how much area you need to cover to get the energy. Okay, so that was the flat panel technology, which is very well known. It's developed technology, and that's what most people are actually now using and doing business on. From this point on, the technology that I'm going to talk about, they all are at the prototype stage. Although people have been working on them for decades, still they're at the prototype stage, because they have to learn a lot of things. You know, we build it in the lab, when it goes on in the sun in the field, lots of crazy things are happening that you weren't expecting. So still you have to go to the next religions, better and better, and as you do this, interesting ideas come to your mind, and you start working on those. So these are the things that really have a lot of room for contribution. And as I go through these things on like, maybe on like 10 or 20% of your brain, you start kind of playing, developing, so how I could do things better or in a different way. Okay? So the low concentration PD, which is also known as LCPV, is a similar thing. You have the same flat silicon cells sitting next to each other, let me go here, sorry. So each one of these cells is one quarter of a normal silicon cell, and they are all connected in series. So you come here, this is connected in series, series, they all go. So all these cells are connected in series, and there is this optical stage before the sunlight hits the cell that doesn't concentrate. So always in concentrating the solar power you have that optical stage, and depending on how much you want to concentrate, you design that optical mode. So in this case, which is, this is a technology by Sun Power that the headquarters is in Silicon Valley and they built everything in India and they just unveiled the first prototype power plant a few weeks ago based on this technology. This technology they call it C7, and they call it C7 because the optical layer concentrates at a time. Okay, so the optical layer concentrates the solar like seven times and then sends it to normal silicon cells. And I just put this picture here so you get an idea of how big the systems are. You know, they are way taller than a normal person. So these aren't like small things. They are big, big systems. They are usually aligned north to south direction and they have all these big gears to turn these systems from east to west during the day. Okay? And just imagine, to design that you need the electric monitor, you need the precision, you need your sensor, you need all the software that sits behind the system to handle that control and the motion and stuff. It's not only the mechanical part. It's not only the electric part. It's the combination of all the different knowledge that one person can have. Again, in the solar electric, we have now high concentration. I'm sorry, Arty, can I ask a question? Yes. So seven times a higher concentration of the solar radiation, right? Is that correct? Yes. Does that mean the 15% efficiency is now sevenfold more, what's the... Yes, power is very famous for itself because they developed this IP, this technology that, as you remember, I mentioned the PD is like the IO, the N-type and P-type sitting on top of each other. So one of the electrodes has to be on this side, the other electrode has to be on that side, right? Because we have these two layers on top of each other. But the sound power kind of created this technology that they actually brought both electrodes on the back side. And the important of that is, so when you want to have an electrode here, you have to have these very tiny wires that are sitting on the top layer to collect the electrodes, right? And then once you have this tiny line, they prevent the sunlight to reach the cell. So it basically is suboptimal. But now, sound power brought everything on the back side, so there are no busbars or lines on top. So they basically utilize sunlight in a better manner compared to regular technology. And they use the same cell to build this because they already have the technology to design the optical stage before that. Okay. So for the high concentration PDs, as I mentioned before, we have to have, again, that optical stage before it reaches the cell or cell, that optical stage can be based on reflection. Like here, we have two mirrors, a primary mirror, so sunlight is the primary mirror, is reflected to a secondary mirror, and then it is reflected, again, inside a prism that then directs the sunlight at the bottom, which is a multi-junction solar cell. So what is a multi-junction solar cell? Multi-junction solar cell is basically a solar cell that is comprised of several junctions sitting on top of each other. In this particular case, like the most well-known multi-junction solar cell is a three-junction solar cell, that one junction in Seattle is arsenide, the second one is germanium, the third one is gallium, indium, phosphide. Okay? And what is the importance of these things? So the junction that is created with each one of these semiconductor technologies has a different band gap. Basically, it means that it responds to a different light spectrum of sunlight. Okay? Which means, like for a regular cell, and it only has one band gap and only can capture a certain spectrum band of solar energy based on the photons of that light spectrum that is coming to or is reaching the that the silicon. And the rest are gone, because they do not. They actually, they only become heat. And I think that, as I said, the efficiency is, let's say, 15% or 20%. The rest, sort of like 80 or 75% of the energy is converted into heat, because it doesn't have anything for the semiconductor. But here, you have three junctions, they sit on top of each other, as the sun goes through the stack of junction, each junction responds to a certain spectrum and converts the energy that is coming in that spectrum into electricity. So, we expect the multi-junction solar cells to be more efficient, right? Because they convert more of the solar energy into electricity, which are, they are close to 40% efficient, compared to 20%, but at the same time, because of this complicated technology, they are very, very expensive. They are not as cheap as the silicon technology that everybody can do it. Because initially, this technology was developed by Boeing and NASA for space applications, for powering satellites, for powering, like, solar panels on the International Space Station, and for those applications, money is not a problem. They just want to do this space project. If it's like 100 billion dollars, there is always money for that. But when it comes to, like, business and solar power technology on Earth, then money is an important thing. So, they can't use the same amount of triple-junction cells to collect energy from the sun. So therefore, they only can't afford to use a very small area, one centimeter by one centimeter, to collect that energy. But to compensate for that area, they use, like, relatively cheap optical layer or optical state to concentrate the solar energy into that small area. Does this make sense? What about, really great. So, you can see this technology being anywhere from 500 to 700 concentrations. And this other technology is refractive. They use random lens. They use random lens to do the same thing to concentrate the sunlight on the solar cell that is of the same multi-junction power. Yes, please. Do you mean that the number of junctions is the energy and the efficiency? For example, if you had a six-junction solar cell it would have 80% efficiency or not? Not necessarily. So, very quickly, by... So, the solar... If this is your spectrum... Which is not right. That's okay. Just imagine what happens, right? This is the energy that begins on the sun. Energy with respect to the spectrum. Okay? Thank you, sir. Just imagine something like this. It's not exactly that. It's off and down, okay? So, each one of these junctions captures one part of that. Let's say one captures this spectrum, the other one that's the spectrum, the other one is the spectrum. So, like if you have a triple junction it can capture the energy that comes in this area. Pardon me? Absolutely. Now, it's not exactly linearly proportional because it depends on what is the weight of this. Maybe you have a junction and only capture that. So, the energy in this area is less than that. Okay. So, it's normally fewer than that. They are the best way to capture one junction. They are the best way to capture as much as the energy and possibly only one junction. Absolutely. So, in this case, we have that technology plus some other junction. Exactly. So, if you remember, I said like TVs are about 20%. This is about 40%. But we've got to 40% efficiency by adding two more junctions. Right? So, it all depends what the, what is it called? It's called, it's called band yap. And what kind of efficiency do you call it? Yeah, something like that. I'll remember that. So, each one of these things has a different efficiency curve for this period. Okay. So, one is efficient like that. The other one is efficient like this. So, each one treats that spectrum in a different manner. Again, if you want to do this detailed calculation you can easily download the solar energy as a quantum spectrum and then this what is it called? Quantum. Quantum efficiency. So, each one of these junctions has a quantum efficiency. So, these are the quantum efficiencies of the spectrum and then you just do energy kind of efficiencies and tell you how much power you're going to have. Okay. Okay. So, these are the high-concentration version of the the volcanic and I'll give you some practical actually products that I have here. This is the reflective version. It is located in San Jose in the city of Bali. These are the two stages of wearer, primary state, secondary wearer and then it goes inside its prism and the cell is located at the bottom. This is one of the companies I've directed work with actually three years ago when we started I tell you about the power electronics stuff that I started the company was the first partner that we actually developed product for and they put each one of these cells next to each other they create a panel and the panels become a big tracker like this. You have 540 of these cells on this tracker. Each tracker has a huge electric motor that tracks the sun in two axes both elevation and why? Because once you do a 500 to 700 times concentration you have to be precisely following the sun. If you're off by let's say half a degree then your optical state is not going to work. It's not going to do the concentration right and the sunlight is not going to go inside the prism. You'll see the sunlight concentrated there. So for higher concentration ratios the tracking is essential and basically what happens in your optical layer has to see the sun. If cloud comes and passes by the sun during the time that the sun is behind the cloud the system is down it's generating nothing. So therefore this kind of technology is very good for areas that have very high solar regions like deserts. So all the places that have deserts they have like long days no cloud and high solar regions this kind of technology is the best because it works all the time and it has like double the efficiency of regular flat panels but it has the problems of tracking and electric motors so the other version for the reflective version is a company called Amonix actually the city of this company is Armenian his name is the Valangar Pushyan and they're located in the Los Angeles area it's very similar to so-focused technology what they do they have this huge mega modules each mega module is comprised of these departments basically empty boxes made of aluminum on one side you have these hard heads of frontal lens they're all you know molded or somehow built out of plastic on one side and on the other side you have this row of solar cells so basically they they also have heat sink because they're 40% efficient which means 60% of the solar power can remain special especially when you're concentrating on these little spikes so you have to have a nice heat sink to get rid of the heat why? because over semiconductor technology it kind of degrades its efficiency drops its capability of generating current drops and the temperature goes up so like semiconductor technology doesn't like heat so you have to always push the heat away as much as you can so this is the refractive technology version by Amonix and now we go into solar thermometers where we use solar energy to to heat the first technology is parabolic drop this huge field of parabolic drop they're all mirrors and you can compare the size of the human at the stand next to it and at the focal point of this parabolic drop you have an evacuated tube okay evacuated tube is like tube that has like a layer of glass around it and the area between the tube and the glass is evacuated to prevent heat loss here the monoclonal inside the system so what happens that they again are aligned north to south and you have all this control here and electric motors that track the system from east to west every day and they concentrate the solar energy on this tube and because it's concentrated maybe 30 to 60 times concentration it generates about 400 degrees C temperature at the receiver which is this tube and then they transfer this heat using boiler of a normal steam power plant and generate electric you know in steam power plants all you need to do is to generate steam that is super heated and then push it through a turbine and then it turns the generator and you have electricity now like a coal power plant generates steam by burning coal petroleum power plant currents petroleum to generate steam and here they concentrate solar energy to create that okay basically it replaces coal and this picture also I thought it was interesting it shows how they do the maintenance because after a while you have a layer of dust on this gears and it kind of degrades the system performance so everyone is saying why we haven't watched it and this is how they do the maintenance but this is something that basically was developed as a prototype in like late 20th century okay and the new age version of this is a product that was developed by a company called Ostra this was in Silicon Valley too and basically it was acquired by Arriva which is a huge big computing plant that they do a lot of nuclear power plants so they started like a sector on renewable energies and solar power and as part of that development they purchased the technology from Ostra what Ostra is doing, it says you know what making all this parabolic trough is technically difficult it becomes very expensive to kind of curve the glass and put like the reflective layers behind it what I do, I use like flat mirrors but pieces of flat mirrors and you control the angle of each one of these rows separately to achieve the same purpose the whole purpose is to reflect the sunlight from these surfaces to the receiver and generate heat and this is the idea of the Ostra and so in order to for you to kind of not get too bored I'll show you a movie to see how this works I didn't have the movie I didn't have the software so you have to go through this yeah the 10, 20 second one basically the short movie shows how the sunlight hits the mirror reflects to the receiver comes heat and the heat goes through the boiler turbine and generates the electricity so this is that technology these are basically pipes and those are the receivers so it all reflects the sun generates heat and heat is transferred to the pipes to this basically boiler or the heat transfer area and then super heat the steam comes through the turbine it turns the turbine becomes mechanical power and the mechanical power returns the generator and generates the electricity ok so it's basically the same thing the steam power plant but the heat comes from the sun this was so efficiency from solar in thermal is about 24-35% and usually steam power plants are about 30% efficient so it's like the one cleared up 24 which is 8% so from sun to electricity you'll have 8% it is well it isn't about efficiency so will it be powerful? all of the PV yes that's correct if I may intervene I think that one of the last lectures I mentioned it's more important to look at the cost of the peak power that you provide efficiency can be even low but the cost if it is lower then you have the value that's the point thank you very much and again when it comes to efficiency don't be too distracted because as I mentioned solar energy comes from stream you don't pay for peak but we are paying for the development we are paying for it if you have a system that is 1% efficient but it's cheaper than a system that is like 20% efficient people are going to buy the cheaper people won't go, oh you know I'm going to pay 100 times more but it's like 10 times more right? so you always have to put yourself because you want to expand this technology and each moment they go something they first look at the price if it's cheaper okay, of course, attractive they go to the next one but it's already too expensive they go, oh no by the way this is more like efficient especially if it comes to this kind of maybe if a person wants to buy their cell phone or this kind of thing they might pay for it but who does how normal technology is solar power the way this works basically you have these flat mirrors they are continuous stats each one of these flat mirrors is kind of trapped in the sun in two directions and what they do they concentrate the solar energy on top of this tower again they generate heat and the heat goes in a normal steam power plant in a normal person and here you get higher concentrations at the level of 10,000 and about 600 degrees C at temperature that was again to an late 20th century prototype what is happening now in Pasadena there is this company called the Solar that they are building a different version so they have this smaller period of stats so they are more manageable and they have basically the main distribution of this company developing the software behind controlling each one of these fields of stats so the way the software works it controls each one of the mirrors so that the temperature at the top of this tower is constant so if the cloud comes and goes away and these kind of things like the software automatically kind of diverts all these mirrors off focus to actually always keep that temperature constant so the system knows that so it's a simple thing right you have racks, you have a flap here some electric motors but you have to develop that software that takes care of this the others get on this dish sterling it's a similar idea here mirrors are kind of like a satellite dish they concentrate the solar power at a focal point where you have a sterling engine sterling engine is a heat engine it's a closed cycle heat engine like the engine in your car or the car in your engine you have a full cycle on one end is your hot side the other end is your cold side and it basically converts heat into mechanical power motion and then you have a magnetic circuit and get power from it again this is from a sterling energy system company that two years ago in Bangkok because they basically couldn't design a system that was financially viable but anyways what they designed was a system with 37 feet diameter and each one of these dishes generated 25 kilowatts of AC power and here I want to show you how these huge monstrous dishes are trapped in this so every morning I'll play it again they have this software that wakes up the system they track the solar and at night they come back to the morning position to start the next morning but again this system doesn't exist anymore in the company in Bangkok but the new age version of this is designed by a company in Washington and they decided to build a very simple system like the mirrors like flat mirrors the system is not too big it's only 22 feet diameter and it only generates 3.5 kilowatts it's a small system it basically has enough power for like one residential home and the sterling engine that they have here as you see it's very tiny it's not too complicated it's not heavy, practically it's more viable this company still hasn't gone to mass production they are still developing customers and they are still trying to have prototypes install systems to validate that but they are still doing business and hopefully they will succeed to generate some hot water I am sorry to I have been always wondering this dish sterling system they have been promising for at least 20 or 30 years but they still remain promising what's the matter with this what is the key issue with this problem that are not really becoming a very complicated problem one of the major drawbacks of the sterling engine systems compared to PD is that the sterling system is a lot more important mechanically it might not be reliable because when a person designs a flat housing system and you want to sell it you give a warranty for 30 years you say hey I give this system to you after 30 years I'll come back measure the power I'm confident that the power is going to be more than 80% of day one 30 years and nothing is going to happen if it breaks I'll change the panel and all this kind of things but in this case the main problem is the reliability people still don't believe that a sterling engine can last for 30 years although this Invinia company designed a sterling engine for NASA for the deep space missions so because when they space vehicles go deep into space they don't see sunlight so they can't use multiple types to actually use the sunlight to generate the electricity means of the car so they use atomic reaction in the deep space vehicles to create heat and then they use Invinia's sterling engine to convert that heat into electricity as I said a sterling engine in a closed cycle engine so it doesn't have any exhaust or anything they have proven technology of long lasting systems because now a couple of their systems are in NASA's mission they are kind of going deep into space but since they only built one or two for NASA they are still considered prototype so once it comes to mass manufacturing the precision and all this kind of things becomes a big issue the piece to go inside the cylinder that has a fraction of a micron clearance you might be able to build once at like $100,000 and build one or two but when it comes to mass manufacturing you can't shoot for those precision at lower cost so they are just battling to balance these things manufacturing, reliability like in being designed all this kind of things it's very complicated very difficult but exciting you know good so quickly on the solar hot water this is flat plate collectors are the easiest way you put like a simple plate there you have passages for the water to flow through and you paint it dark there you go and the cold water enters hot water comes out you get temperatures in the render by 80 degrees one step more advanced version of this is just to cut all these sections and put them in an evacuated tube and an evacuated tube basically acts like an insulator around this plate so it prevents the heat to be wasted to the environment in this case you won't keep all the heat in any case you won't get the heat because it kind of deviates the cell and another version of so what happens here because everything is an evacuated tube you can't flow through the part so what you do you actually use like heat part technology it's a very interesting technology thermodynamics and what it does you put this tube in a manner and then it automatically increases cycle the heat comes up in this portion gives away the heat and turns it into liquid and comes down again that's a very interesting technology or another similar version is that you have the tube and then you put it on a bigger evacuated tube but you put a reflective layer so it reflects the sunlight and kind of does a little bit of concentration the practical version of this so you have the evacuated tube you have the heat part inside and then all the heads that are sticking out are in this manifold your main heat transfer fluid goes in the manifold gets the heat heats up and comes out and the third version you haven't seen any like mass manufactured version yet are called this town parabolic concentrated or CTC basically you have like two reflectors and your evacuated tube and these are the design of this optic is based on non-imaging optics it's a very interesting optical physics if you want to go and study it's called non-imaging optics it's different from like the convex or concave mirrors or lenses they are imaging optics this is intentionally non-imaging because the purpose of this optics is not to create an image but it's just to concentrate the into your output aperture which in this case is the good thing with this technology is that it responds well to this first sunlight when you have a cloud you have this first sunlight and also you don't need to track the sun you know it has a big second angle and no matter where the sun is it still works well and this is like a cut out of the prototype that we both have been playing with