Okay. Okay. Well, I hope somebody's on here. I can't really tell [LAUGH] if you guys are or not, today. So today is office hour number three. October 9th 2014. And I'm going to let Carlos introduce himself, and, and tell you what his background is. You should have already seen his videos. And we're going to talk about those and answer questions today. >> My name is Carlos I'm a professor in mechanical and aerospace engineering at UC San Diego, and most of my research is related to solar forecasting and solar integration. So this is integration of a variable renewable resource into the grid. So we do when I have a large group, you know, we work on several issues related to that. It involves at most physics it involves a lot of learning, machine learning. Putting all of these things together to try to understand, how much power is generated from both central and distributed solar plants. >> Okay. And we've got some questions that people have already sent in. So we're going to look through some of those and answer them. There was a really simple one here that showed up, just a second. And that was, I love this one because we're going to start with a really simple one. How can I use solar energy at home? I'm going to let Carlos answer that, and I'm, and then I'm going to tell you what I'm doing about it. >> Yeah, the the many different technologies that you can use and some of them, the, pay off almost immediately. Depending on where you live and the price of the energy, the price of of the gas that you use to heat up your house, or what mechanism do you use to heat up your house. One thing that one technology that pays off almost immediately, almost anywhere in the world, is solar thermal heating. So, using solar energy to heat up the water that you use at home like, for example, to take showers and so on. So that one is a, is a given I can remember from, the mid 80's when system absorbed thermal heater or the probably took four, five, six, seven years to pay, the initial investment that time has been reduced because of increasing in price in gas and other. From the beginning to just a few months in some places and and not more than two years in, in the vast majority of the, locations around the world. So that's one thing that you can do. >> So can, can I ask you a question about that one. >> Mm-hm. >> So is, is that different than having photovoltaic on your roof that it, that your using to heat the water this is a specific one where you're. You're pumping the water up and through the- >> Yes. That's, that's a heat-exchanger, basically. >> Yeah. >> So, the, the old design was just a tube and fin, like on, you have a black plate that absorbs the energy and pass that to the water. >> Mm-hm. >> So the water can be in most cases, like >> Really you're literary taking a shower with the water that circulated through that heat exchanger. >> Yeah. >> That's one way like there are evacuated tubes now that are much more efficient over over gas states and it's the same principle. The water passes through the evacuated tubes and I heat up that and you use the hot water. Typically, coming out of their collective uncertified Centigrade to, to 90 degrees centigrade. So that's, that's different than using a p panel and then using the electricity to heat up. For that would be a very inefficient way of doing it. >> Okay. All right. So I'm, so I'm going to say. So I'm putting pb panels on my house. Sometime in the next month or two. So I bought a, I bought an electric car about a month ago. And that pushed my electric bill up high enough that I'm going to put those on. So what you're saying is, I should get the PB. Because that'll take care of the electricity in my house, and charging my car. And then I have a separate system, that I put on that heats the hot water. >> Absolutely, yeah. >> Okay. >> Absolutely. And And in your case the PB would. Would also make perfect sense. One thing you have to take into, to watch out [INAUDIBLE] obviously are very strong for her. So her energy is, you don't to put on your roof and then cut the trees around it. To make sure that you are getting like the radiance. So, this is really dependent on where you are. >> Yeah. >> Like what, how it is, and how much are [INAUDIBLE] you know, a case of [INAUDIBLE] it pays off right away because of your electric current. >> Right, yeah and so actually, at least here in San Diego now so a guy came out, surveyed my roof, they looked at it from Google. And from that they can kind of measure the trees and then calculate where the shadows are going to be on the rope. And they found three or four places on my rope that worked quite well but then I think now what they do is they're going to come out maybe next week and they actually put little monitors on there. And just to see, just to make sure there's no shadows from the trees, or etcetera. So there's lots of different things you can use for solar energy at home. Some of them are kind of expensive, I will say that. That it's not cheap to put, so I'm going to get a six kilowatt system on my roof, and that's about 26,000 bucks here in the US we get about 30% off of our taxes if we put one of those one. So my 26000 bucks will cost me about 19000, I think out of pocket. And then that pays off by reducing my electricity bill. That will pay back in about seven years. Six and a half years, I think I get paid back. And then the other nice you have for getting an electric car. If you agree to charge it between midnight and 5 am which I do, and you set your car to only charge at those times, then you get cheaper electricity all day. 24/7. And, that apparently works out well for the utilities because they have. Very low utilization from midnight to 6 am, and it helps them if people are actually using power at that time. Okay. All right. Let's go. Here's another one, and it says can we use solar thermal energy combined with other energy sources? For example, warm up water with solar energy then evaporate it with natural gas if solar energy is not enough to reach required temperature. Okay. >> Yes. That, that's an excellent question. and, In fact, in our central plants. One of the most efficient designs that you can have is to have a, a, a dual cycle, where you use the stored energy to, bring the vapor to a particular, temperature, like [INAUDIBLE] low temperature cycle. And you use natural gas, like, to, in another turbine, to run a high temperature cycle. So the cycles are very different If you, if you do that you can connect the two the axle of the turbine, like this is one easy way to think about it. So that when the viability of the solar energy is high you are actually supplementing that. With natural gas and are producing from almost a flat line amount to the rig. And the, the short answer to your question is yes. And there are some designs like this, got some or a fence that works like this. I wish more departments were actually designed this way because these are very efficient ways of using of steel, concentrated solar power, but also to use the natural gas that is available. So you are using the natural gas to enable a higher solar penetration, is the best use of natural gas that you can have. All right. Great. So do you know about the concentrating solar panels that are on the way between here in San Diego and Las Vegas? Have you ever seen those? >> Me? >> Yeah. >> Yes, I work very closely with that power plant. That's So these are not. These are, heliostats, like they are mirrors that they focus the power into, three different powers. Like there are boilers on top of the towers. That far our plant itself can only use a very little amount of our natural gas, by contract. They, they can only use less than 3% of the power that they produce. >> Those guys? >> Yeah, yeah. So, we are, we are, we work very closely with them. >> Okay, so when those guys, when I drove by, so I drove out to Las Vegas, last two weeks ago. And when I drove by Friday afternoon, they were down. It was late in the evening. It's, maybe 4 or 5 o' clock. And the towers appeared to be jet black. And then when I drove by Sunday afternoon at one on the way back, they were glowing bright white. Now it, is that because the. You know, is that just reflection coming off those, or is that actually the temperature of the thermal excitation, and you're seeing light come back out? You know? >> Yeah, so, it's, it's really like a combination of the boilers like there. The boilers are black like, you know, after room temperature, but when you reflect all the light. Yeah. >> Just by reflection like you would have a very bright spot. So when they are flexing like when that's true. But the temperature there is not high enough to actually emit the, the white colorated soil. Okay. >> But he's a very bright spot. Like all three of them like will open their [INAUDIBLE] right spots, yes. >> Yeah. And then that is my understanding is those are heating up molten salt or something. >> No. That's ammonia vapor. So, that one has no storage. It like a, it's a, it's a power plant that runs vapor and has a very small thermal inertia because there's no in that particular >> Okay, but in other ones like that I understand you could. >> Yes, exactly. You could. That's one of the great advantages of, CSP over [INAUDIBLE] the storage component is cheaper, and, it's even though it's working with salts and modern salts which are not easy materials to work with, in general you'll, you'll get, a much. Better return for the investment you're putting on it. >> Okay, and then where's the power from those going? That just goes onto the grid, or is that specifically used for something? Are those experimental, or are they fully functional? >> No, they are fully functional, they are hooked up to the grid, almost from day one. >> Okay. >> They have two powers to one utility company in California. All the power comes to. So you say the company is in California. So two towers are from what, to one utility, the other tower is to another. >> Okay. And, and somebody told me a rumor that Google owned one of those. Do you know anything about that? Who owns those? >> Google is a partner like the, the Hobart plant is is owned by Solar Partners. >> Okay. >> Which is Google, NRG and Right Source. >> Okay. >> And they enter with different components of [INAUDIBLE] One was financing, the other one. Is the technology and the other one actually manages the plants. >> Okay. All right. Great. They look totally cool, by the way. Everybody. >> [CROSSTALK]. >> I'll see if I took some pictures with my iPhone as I was driving by. I'll see if I can. I'll get Travis to see if we can load them up so you guys can see them. Okay. Here's one from someone down in Brazil and they say I live in Brazil, close to the equator where it is basically summer all year long. I was there in November. I can vouch for that it's summer all year long. In your opinion. What would be the potential of the application of photothertaic or photothermal energy production here compared to what you have in San Diego for instance? That's a good question. >> Okay that's great. I'm from Brazil too so I know the, the resource in Brazil very well. Brazil is is blessed with a with a fantastic solar resource Not in terms of the oil intensity, but by how uniform it is, around the territory, and along the year. So the potential in Brazil for, for for the is fantastic particularly. Because of all things are not that strongly influenced by clouds as, as a, a concentrated origins. So, of course, if we look at the whole territory in Brazil. There are places that are excellent for. Concentrated in technologies. And there are places that are excellent for fab kernels. I assume that you live in the north or the northeast, which is much closer to the equator. I know Brazil is only 16 degrees south of the equator. So the, the resource is excellent in, in the vast majority of the, of the country. Ironically, I think where. So energy is very well developing in Brazil where there is amongst installations which is by the coast of St. Catharina in the South. But i understand that they are new changes in the way that the grids manage the, and the new laws coming up. That would allow for much larger penetration than what exists today. >> Yeah and, and many of you will also know that Brazil is now the number two producer of ethanol in the world. The produce theirs from sugar cane ethanol and that's actually very profitable. In Brazil. And then they also a fantastic hydroelectric potential there. So Brazil kind of wins on many fronts, when it comes to renewable energy. >> That's one thing that you measure is very important, like, Brazil, because of their very high penetration of hydropower. Into their electric grid. In fact the ethanol contributes, or used to contribute a few years ago, more to the, energy matrix than the, hydro power. Because of all the, the cars, everybody use ethanol. But the hydro power gives this fantastic inertia to the grid. It's almost like you have, you know. >> 85% of a nuclear in your, in your, generations. So these allow you to have quite a lot of ability of solar without creating any problem [INAUDIBLE]. So we, from this perspective, the fact that they use hydro power in Brazil [INAUDIBLE]. Asset in terms of, increasing the, the, or complimenting the hydro power with the solar, because these are two very complimentary, source of energy. >> Yeah. >> OK, here's one, and this will allow us to get into a, a couple other, questions as well, which are also on our list for today. So, what is the bottle neck issue with storing electrical energy in rechargeable batteries. But I want to put that as a, as a larger question which is what is the challenge of storing energy. Right, that, that's really our challenge. Whether it's, it's solar because of the times it comes or the wind because it's intermittent, or electric cars with our batteries. So, if you could just in general comment on what some of the big challenges are. And sort of evening out the grid and you know, getting renewables to, to integrate. >> I am not a battery expert but I'll, I'll give you my perspective. At this point the, the storage, you know it's very difficult to store electrons basically. So, batteries are very expensive in many systems, like depending on the size of the system. The storage system, would be as expensive as the whole power plant. So this is prohibitive, obviously if you are trying to bring, solar an other source of energy, renewable source of energy to be the battery. If you have a, [SOUND] if you have to add on a storage that there would be, as expensive as the, the whole power plant. You are really increasing a lot, real life cost of energy for the problem. So the, the technical difficulties, I think there are many many people working on, on, on improving their, their, reliability. Their robustness, like the life time, performance of a batteries and so on. The problem for me at this point, in terms of electrical storage, or electrical chemical storage, is really, one of a cost only. We could do it now, with the technology that exists, but like it's prohibitive in terms of cost. >> Yeah, I know here at UCSD we've talked about this before. That we've got a bunch of the, used batteries from, I think BMW. And, you know that are, that no longer have the capacity, you know, for car use. Because their, their storage capacity goes down over time, it's all batteries, right? But those are, you know, stack them all together in a, in a, something. We have them in a shipping container here someplace on campus. And then use that for short-term, storage of, floatable tech has worked pretty well. Okay, you know, sort of upscaling, they call it. So here's one that's related, and, and, and I am sure Carlos can answer this question. Why is thermal energy, easier to be stored than solar power, generated from panels? I think I just answered that one. >> Yeah. There's a physical reason for that. One of that is that thermal energy is disorganized, solar that you can, it's easier to just keep something at a higher temperature. Like the temperature's not very high, for thermal storage. So it's easier to, for example, if you use molten salt like you know, just basically trying to store all the energy as, latent heat. and, and, you can do that, like, you know, because you only need to insulate that from the environment. If you bring the energy level to that, to that level. If you insulate your installation very well, you can, you can keep that, energy level very high for, for a long time. It's automatically efficient, like a thermal, thermal energy, but, in terms of a cost, it's, it's there's no doubt about it. It's much cheaper to do that than to try to, we store electrons directly. >> Yeah, and, and the thermal energy to my understanding is that, it, it, very ones that go to very high temperature. You can actually recover a very high percent of the energy in and out of those things. Right, meaning that, for a, for a battery for example. You know, once you've stored the electrons and pull them back out, you'll lose some of that just, dissipation by heat, et cetera. But on some of the thermal storage are much more efficient. >> That's, that's correct, if you returned it. Because what you, you know, these are heat exchanges basically, so, you, you, if you leave. You can have these in your house by the way, like, you just talked about solar collectors. >> Yeah. >> If you use like a lot of, paraffin or like something that, melts, a little below, boiling point of water. you, you, the problem is to find a substance, that has good thermal conductivity. So that it can be, used efficiently, as a thermal in the heat exchanger. But also holds like the energy as latent heat. and, and the so the cost of is not nearly as high as the cost of materials used in the energy storage. >> Okay, and here's sort of a follow on question to that. And that's, that, so once you store the energy in thermal energy, how do you recover that? So the question is, do you use that to generate steam and power a turbine, or is there some other way that you recover that? >> That's exactly how you use that. So basically, you would store these on large tanks. That, when you press, like, you know the steam went through them, like, you would increase their enthalpy or energy level with steam. A, a high amounts of fuel can actually run these to the turbine. So that's, exactly what you do. It's different technologies that are used different, working fluids. So you can store these in oil, you can pass oil, to like a trough, for example, then oil would be, exchange energy with a Molten salt. And then you circulate the oil and you exchange that with a vapor in a different, heat exchanger. The details are not particularly important. And I think that, the most important thing is that you have a source of high temperature that can be used to elevate the energy of the vapor. >> Yeah. And then most of that, though, is turned back into electricity, at least in this country right now. Although, as you were pointing out. A fair amount of that can be used to warm water, right? Like in an individual home for example. >> Yeah, and industrial processes like sometimes we need the high, temperature vapor that is not high enough to run a turbine. But you can actually use the vapor directly. So like, that's, that's one application, that is done, if you have a plant that has, excess vapor that needs to be cooled off. To cool the cycle, one of the difficulties of CSB and the best used to be. That to close the cycle, you need to cool off the vapor now back to water. >> Yep. >> And that would require a lot of water to evaporating tolerance. But now they spend a lot of dry technology, dry cooling technology. And in fact, I don't know, we just discussed before, at power plants it does not lose, cooling powers. It's a the nuclear power plants do. >> Right. >> So that, plant uses, a fence, like a bright fence. >> Check. >> And it does not have access consumption of a water for cooling. >> Okay. And so, that, that's just an improvement in the technology over time. Or was there something that, that allows, is there something specific about that compared to a nuclear power plant, that allows you to use that? >> yeah, one is, is the, the temperature of the vapor cycle like makes a difference. But it is really, a recognition that, water is a commodity. And, you typically, you want to deploy these water plants in deserts where water is not available. >> Right. >> And so you don't want the water to be the bottle neck. >> Right. >> So that there was a push to develop, if you look at the power plants. They are always, sited in, in locations where you have access to cold water. >> Yeah, yeah, always, yeah. And now, you know, in the United States at least, we're no longer allowed to build power plants that have what's called once through cooling. Which means that you're taking water from a river or from a lake, you'll run it through the coolant and then pump it back out again. Here in San Onofre at the nuclear power plant, they used to do that with the ocean water, and, that greatly impacts it? >> Yeah, because a, a, a few degrees, that should increase the temperature of the water, has, a, a very large impact on the, on the, environment around it. >> Yep. Okay, so here's one. And we'll see if Carlos can handle this one. Could someone explain, oh it's not Carlos, I don't know who. How energy storage reduces utility transformer and line, and line load, loading during peak hours, especially in a not so smart grid. So maybe a more generic way to put that is, can you explain how intermittent energy, you know, gets onto the grid? And, and how that impacts line load, et cetera. >> And so in my group we, we have a, we are doing, some work with San Diego gas and electric. And, it's interesting to see that because, they have some transformer. Like in some feeders within the San Diego Gas and Electric territory, that have a very high penetration of solar energy. So if you look at the load on those transformers. And, traditionally when, you have the fixed generation of fossil fuel or nuclear generation. Most of the variability that needed to be balanced was on the demand side. So, this change is, of course like when you have wind or solar generation. Being a substantial a component of your, your portfolio. So, here in San Diego like there are some, feeders that have very high solar penetration. And now when you look at what they are cooling from the grid, you can totally see the signature of a solar generation there. Like if they are clouds, the load is going up and down, to extremes. Like, to, to, almost like, you know, sometimes four or five times what the normal load is. Of course if you go to other areas where the solar variation is very small. Like then it loads it would be, very only due to the, the man via, viability. >> Mm-hm. >> Which is what this web, is turning on and off the lights and, and, and all the equipment as well. So, I think your question was, how en, energy storage could do that. Of course like, you know, if you would store, energy. If you have like a, inertial, component, that you can actuate, and you can, demand from. When your solar grid falls down, you are actually changing the way that you are, tapping on the grid. So you need some smart storage. You need something that will tell okay, tap now from, from the battery instead of. >> Mm-hm. >> You know, providing from the solar panel, because and then that's, where, like forecasting and >> [COUGH]. >> And, storage control, come into play. and, and that's really the definition of this part. With, having something that can react in real time, and, equalize, the load, with, the generation. And so right now, do you know how that's done? So suppose, you know in, in California now we generate a fair amount of our electricity as renewable, either from wind or solar. >> Mm-hm. >> And, certainly you know they're on lots of different rooftops everywhere. So what happens now when we're not producing enough, from solar? Maybe clouds come by or maybe just demand is so high. How's that balance right now? That's what these peaker plants do, or what is this? >> Yeah, so, there, there are several times scales that come into play here. You know, the utilities they have scheduling, on a day half basis. They, and this goes all the way down to regulation, and, specs finding, you know, intervals. And you have to have some idea of what's going to happen. >> That's a projection of demand use, and sort of >> Of demand, and actually forecasting of a lull, >> Okay. >> The forecasting of a >> Okay. >> Of a variable generation. >> Okay. >> And with that, and, and due to a lot of the spatial liability, because we now have a spatial averaging. Which will have rooftops distributed over a very large, area. It's unlikely that, clouds will come and instantly, cover all of the panels. >> Got it. >> so, there's a combination of all of these things, and these are dynamic process. And it's becoming substantially more dynamic, and that's what [CROSSTALK] a smart grid is all about. >> Yeah. And, and right now that's managed in the United States by a grid operator right, that, that's sort of. >> Several, grid operators yes. >> Okay and then they, they they integrate with each other. >> Yes they didn't use to integrate like now, and I think there is interconnection. And the, the direction to go is actually to, to be able to, to buy and sell energy from any part of the country. My understanding is this is not a coastal happening at this point. Bu,t there are very large chunks of, of territories that are under dependent system operators or RTOs. Like hat can do that job, as if that section of the country is a small country. >> Okay, and then right now if demand is too high I notice that we will occasionally get emails on a hot day. You know when they predict it's going to be hot in the afternoon. And tell us, turn down things in your lab if you're not using these things, turn them off. What happens if people don't do that and you exceed and demand exceeds, you know, production? >> So the first thing that happens of course, like I don't know, if you have a situation that you actually cross that, that error bar. That the margin of error that exists that you cannot actually activate that ticker. Plans to come align, then like, you know, you cannot generate for everybody. You're going to have to, to turn off like a grid somewhere. And, and, and that's undesirable because you want to have a high reliability of the grid. >> Right. >> What, what happens in general is that people actually respond,. >> what's better then, then expected. So when we get those warnings, you know, our cellular phones like you know. >> Mm-hm. >> The vast majority of people actually, respond very well to that and they like try to turn off. >> Mm-hm. >> And they respond like for a very good reason. Like, you know, if they don't like all the, the cost of, each like, you know, kilowatt hour that they, they are spending is going to go up very fast. >> Yeah. >> So there are peaker plans that are ready to go on line. The problem with these plans is that they are in general. The vast majority of them are highly pollutant, and they are, plants that are, are very costly to operate. >> Right. >> So they, they make their money like out of those situations. >> Yeah. >> Or those extreme situations. So, they don't run the whole year. >> Got it. Which is part of the reason why the cost of energy is so much higher when you click those things on. Okay, here, here's a very specific one, and I'm pretty certain Carlos is going to answer this one. it says can you explain what factors are not, considered in your clear sky radiance model, and how it differs from global horizontal radiants graph in your lectures? Alright, I guess I can't remember what [LAUGH]. >> That's the problem now, you have to remember what was in there. >> So the, clear sky radiance model takes into consideration you know, the, the all the important factors but,. Clause. So clear sky like notation constriction aerosol content like the aerosol optical depth. >> Mm-hm. >> And is something that has a time scale longer, much longer, like, on, on the range of between 30 minutes to several hours. Typically, several hours, like even a few days. Which is very different than the clouds. So we have like a clear sky model where you, you know like if there no clouds in the way of the, of the sun, you will have like an adaptive radius. So that's something you can adjust on a in cloud day basis. And it works very well. Because there again the aerosols have longer a scale. So the short answer to your question is like a clear sky model has everything but the clouds. It happens to be that clouds are the most important factor. >> [LAUGH] Yeah. >> So I would be very happy if my problem was only to forecast with a clear sky model, because we are very good at forecasting clear, clear sky. When the clouds come in, like that's what it is. The clear sky model has, is an, not related to global horizontal radiance model. The global radiance is what comes from the sky and the sun. So, it's, when you have a, guilt factor. Like when you can see the whole hemisphere here, that's all the radiance it's coming from. Global radiance can go higher than the radiance, the extraterrestrial radiance that hits the outside of the atmosphere because you can have what's called sometimes cloud edge effect. Or you can have like a code enhancement which is, you know, there's a bouncing of the energy and the, the clouds actually irradiate more than the solar constant, which is like 1.3 kilowatts per a square meter. so, all of this has to be accounted for, and this happens actually on a very, regular basis, you know, many locations and [INAUDIBLE] almost no place for is exempt from having cloud edge effects and peak somewhere the radiance that can go from 1.6 kilowatts per meter square. It depends It depends on the of your instrument and so on. >> So are the utilities using these predictive models now toward the production from solar? Because it's getting big enough in California now that it certainly is impacting the grid enormously every day. >> Yeah. So, I estimate that all, you can see that the MDIS also have some form of of solar forecasting. And the solar forecasting is being used by solar generators like those important automated plants in and in general this handshake between the utility that has a model a generator that has a model and they want to, to, be on the same page. >> Mm-hm. >> Okay, this is what we are predicting that we are going to generate, and so on. So if a generator that's producing very differently than what they are saying, to the utility, like this cause a problem to the utility. So, there is interest from from all the sides in this. These arrangements to, to have forecasting. >> Okay. Alright a little different, you know still storage question but is there a role for pump storage for electricity storage example, pumpening, pumping of water to higher elevation reservoir. When there's excess power and then hydroelectric generation when it is needed. >> Mm-hm. Yeah, that's a very good question, and the problem with this idea like this is one of the cheapest ways of storing energy. The problem is that you need the right geography to do that. So if you don't have a reservoir that is has high amounts for, you know, additional deportation, to, to, to store energy you, you don't know how to do it and that's that's the barometric part of it. But they don't know of far that, that you know, you have to be a little bit creative about storage like that the lowest cost stories that we have today are again, depending on their geography, or geology, or the place where you live, you could store a compressed in caves, like it's a very low cost of way of doing it. You could pump up, like, you know, water up by a water reservoir, and so on. If you don't have the reservoir, if you don't have the geography, the problem changes substantially, in terms of engineering. Because, if you have to create the reservoir then, like you know, the low cost, like it goes away. It's the same thing with with compressed air storage. You have to have the tank and you have to build that metal tank where we store compressed air. Then it's not that cheap anymore or less so that the problem is finished. But this is used in many different places, and I guess going back to that question about Brazil, is one of the advantages of a, of a having a very high hydro power plant just, like Canada has two. Is that you can, you know, if you have a lot of sun, you are, you are not using the hydropower that much. If you, if the sun is not there, like, if you have a, a overcast environment, you can go back and drive out of the reservoir, and so on. >> Mm-hm. And, and I know here in San Diego, we have built one of these. And within an existing reservoir. And they've now hooked up a short term storage plant to it. >> Mm-hm. >> Okay so, so here's a related one that I wanted to get to about hydrogen and fuel cells because this also has to do with energy storage again. Is there a perspective in storing energy in hydrogen than using it in a fuel cell electric vehicle? Or, I suppose, in any fuel cell. Is this approach more or less economically beneficial than battery >> All right. So the problem of hydrogen as, a fuel like, and I think you are much more of an expert on this than I am still but [INAUDIBLE] is, is really the, the, mass density of energy. Hydrogen is very light. So, like, for your to store in here I'm into hydrogen or to have any amount of hydrogen you need store this at a very high pressure. And then the tank ends up weighing way more than, than the fuel that you are using. Lets not forget about it, hydrogen is a great fuel because it is clean. >> Mm-hm. >> But the problem for using the hydrogen as a fuel in a moving vehicle is how much energy you can pack by volume in the, in hydrogen. Of course, this is not the same problem if you have a stationary system, right? You are, you are using that. My understanding of the, hydrogen equanomy that actually never, you know, developed completely was, the problem is within the cost of, of generating hydrogen. All the other alternatives seem to be, a little bit more expensive than, than things that we can actually rule in different ecologies. And becomes, and when you add that to the fact that, you know, a gas, as a fuel, is typically not [INAUDIBLE] viable then, it, it takes it out of the, of the equation. >> Yeah, so in California, we just spent $50 million, to put in hydrogen fueling stations. o, obviously when you burn hydrogen, when you oxidize it, you get water out, right? You know, it's, it's H2O that comes out of that. So, in that sense, but very clean water, right? So, in that sense it's environmentally gray, right? because you're not making any CO2 at all, right? Even with an electric vehicle you're also not putting CO2 out the tail pipe, but you're generating electricity someplace else, and if you're generating that electricity from burning coal, you're actually worse off, okay? Then as Carlos pointed out, its not just an infrastructure problem. So, so the, so were going to spend $50 million putting hydrogen fueling stations with this idea that its sort of the chicken and the egg problem. You know, you can't have hydrogen cars if you don't have hydrogen fueling stations and people won't build hydrogen fueling stations that there aren't cars to come and buy the hydrogen from them, that economics doesn't wok out, so the states stepped up and put money we'll see how it goes. But that is only one of the infrastructure changes that, that have to be built. You know you have to have fueling stations. Today we make our hydrogen from steam reformatting of methane. So we take a fossil fuel and at high temperature we can strip the hydrogen off that, that we turn that carbon that's in there into CO2. So we're still creating CO2 to make hydrogen again just like an electric vehicle at a different site. But then the biggest disadvantage that, that, that shows up is the low density of this. It's as low, it's as equally as low as a lithium battery. So you can store about as much energy in compressed hydrogen as you can in a lithium battery, and there's infrastructure already in place for lithium batteries. So, so that's one of those tough things. It kind of works, the, the, the technology for fuel cells, those can very efficient, those can be very clean. So a good side on that, but infrastructure and the cost of building infrastructure is an enormous barrier to this. You know, put that in perspective, the hydrocarbon fuels in this country have a $14 trillion with a t, trillion infrastructure, so that is all of the refineries, all of the you know oil lines, all of the gas stations, all of the cars. That is $14 trillion. You said we are not going to replace that very quickly, so it is a challenge. We are trying some things in California, but it is very much in the experimental stage. we'll, we'll I, I think sort of stay tuned and we'll see how that goes over the next couple years. Okay? Here's one that we kind of already answered that, but we'll just pop it up here just to make sure we close out any final thoughts on it. What are the economic issues of storage in handling the variables associated with renewables? >> Is the cost. >> Yeah. >> I think that's the the issue is that we don't have a a clean way of a stored energy that is very cheap. Thermal energy storage in, in the or power plants is much cheaper than than electric storage. So the bottleneck there, but is still is expensive. So, the bottle neck is, is just economical. >> Yeah, I think, you know what? To be honest we got so lucky I mean I don't know if lucky is the word, but you know, liquid hydrocarbon fuels are just, there's a reason we drive all of our cars and boats and airplanes on these things. They're, they're an amazing, you know? For their volume and for their weight. They just store a huge amount of energy. >> And [INAUDIBLE] a convenience, too. Like, if you think about it. If you have a gas, you know? If you, if you are driving, like, something that is powered by gas. You cannot just, like [INAUDIBLE] put the gas in a, you know, bucket. >> Yeah. >> And, and walk to your car. >> Yeah. >> so, but the convenience of a liquid fuel, is is, is [INAUDIBLE] a, a thousand times, or many, many thousands of times like higher. But the convenience is difficult to >> Yeah. >> Everyone has to recognize that. >> Yeah, yeah. I mean it is like said. If, you can imagine you know, you if your cars runs out of gas you walk up to the gas station and get a little gallon of one container which is barely a cubic foot. Walked that back down and put it in your car. And if you have a good efficient you know, engine nowadays that one gallon can get you 40 or 50 miles pushing a 3,000 pound vehicle for that far. And that's pretty amazing when you think about it so that, that's simply really hard to duplicate. And, and it's actually one of the reasons that I, I think you know, liquid fuels from algae or from sugar cane or from any other source that we can think of is still a really desirable thing. We don't have to replace the infrastructure we've got. And, we had this fantastic really high dense and very stable by the way. Right? Even though gas is obviously flammable, I don't think anybody worries that much carrying a gallon of gas. You know, down the road. This thing is not going to spontaneously explode. Right? >> So when [INAUDIBLE] just before we move on on this. It's very interesting like, I've, I've witnessed like in Brazil there. The rise of, always is, fuel, which it started with a heavily subsidized program from the government. Then it became very profitable like when it came nobody wanted to have a gas car. I, I went through this period where 97.5% of all the family cars were powered by ethanol. >> Mm-hm. >> They had to add a little bit of a gasoline to the ethanol but like this is for different reasons. [CROSSTALK] drink the ethanol. >> [LAUGH] Yeah. >> But much cheaper than buying you know like vodka or something. >> Yeah, yeah. >> So so when we go through that, and, and one interesting technology that came out of this was the full flex engines. >> Mm-hm. >> Ethanol has cars like they'll have a higher compression rate than, than the gasoline, and this used to be the problem, the mix had to be, like, the right, for your car. But now in Brazil, like, I think you may have witnessed this, when you went there in November. Like, if you, if you drive a car, you stop by the gas station, which is not a gas station, it's a gas and output station, all of them and you choose, based on the price. You look like, and the gas is too expensive today. >> Yeah. >> You buy the alcohol. >> Yep. >> And the, if the alcohol is too expensive we'll buy the gas. >> Yeah. >> So this adds some robustness to the market too. >> Yep. >> Which I think is very important. >> Yeah, and you have a little chart to figure this out, right? Because sometimes it's not so easy because the energy density of ethanol is only 70% of gasoline, but. >> You went back within your mind, which is other interesting. You know, you actually make the, the mental population after, because it's just a, a proportion, that's all. >> Okay. Alright, excellent. Okay so here's one. And this says hi I'm a third year renewable energy student based in the UK, my question for this week's office hours is what potential do you see for the ren, marine renewable industry? And what are the likely problems, that the industry may face in the coming years? >> I think you were referring to cargo. [CROSSTALK]. >> And maybe a wave power. >> Yeah. >> I so, there's no doubt about it like we need some energy to be harvested there. I don't think it's very clear what the impact of harvesting wave energy is, like to the coastal areas and as far as I know, it can be a very small experimental more plans that they use either of those technologies. I, I think it is would be like you know, like a [INAUDIBLE] title is something that is much more predictable than, than wave energy like a, and I think it would be some place for using it future. I am not an expert in that area, so like I don't know what the growth and what the potential growth is for that. I, I see it at least in the next 10, 20 years like as a very small contribution to the overall but I may be wrong. >> Yeah, no well so, so with tidal energy that's very much geographic specific. So if you happen to be in one of the lucky places where there's a big tidal flow. And as we pointed out before on other things, you cannot afford to go build complex, brand new structures to capture this, you will have to have some either naturally occurring. You know, the most famous one is bay of Fundy up in Canada. Right? Enormous tidal flexes through there, very narrow bay, so there are places like that where specifically you have an opportunity to capture energy. The problem is that what people have calculated is, if you look at the entire ocean surface and the amount of energy and waves there, that's actually a pretty big number. The problem is, you don't have any infrastructure to capture that. Then there's also a general rule, which actually comes from NASA. And it says, if it cost you one, you know 1x to do something on land, and it cost you 10x to do that in the ocean, and it cost you a 100x to do that in space. And this was, this was, you know, born out by the last 40 years of, of sea explorations and all the rest of the stuff you have to do. But if you look at that calculation, then it becomes pretty clear that anything that we can do on land, is going to be much, much cheaper than what we can do in the ocean. If you have a windmill on land, and it breaks, you drive up to it in a pickup truck, and then you get your ladder or your harness, and you climb up and you fix it. If that same windmill breaks, out someplace in the ocean. Then you have to get in a boat. You have to go out there. That boat has to be anchored. There could be big waves at the time you're there. Those expenses just go up enormously. So even though there is a potential and you can look at the energy and people have calculated how much energy in these things, to actually build the systems that are going to capture those is really difficult to do and again, it, it simply gets down to economics. What's the cheapest place I can build? Right? And, and now, because solar and wind are, are getting so efficient. And, it's so easy to put them up, you know, there are dozens of companies now, here in San Diego, that will come put these on my roof. We don't have, we don't have wind here, but I was up in Reno earlier this year, and I see lots of houses that have little individual wind turbines on them. Reno, Reno, gets a little bit more wind, blowing thru there than San Diego does, we're, we're not a particularly windy place. But I think it, it just, again, it gets down to economics so its not just the size of the resource, this is true in fossil fuel by the way. Right? Everybody loves to tell you how great you know, Tarzan's, look how big that, that potential reserve is, shale, look how big that reserve is. You know, here in California we have this enormous shale reserve, potential reserve. Right? And, and a few years ago people came out and they said, 37 billion barrels of oil. And then a little more sober study was done this year and they said, well, the problem is it's fractured. It's not like the Bakken and the Eagle Ford shale. It turned out it's going to be very difficult to get these out of California, very expensive. Gee, that number really isn't, you know, 37 billion, that number is 5 or 600 million barrels. And so, so that's a big difference, what's that difference is, it's not that the new oil somehow disappeared some place. It's the cost of going and getting it, so exactly the same thing applies in all of these economics, trumps almost everything else. The best idea, you know, you know, the best theoretical idea on energy in the world. If its not backed up by really solid economics just, just doesn't work out. Okay? Lets see we have time for maybe only one or two more questions here, so lets scan down them and see what we've got. Well here's one and we'll see if maybe Carlos has some stats on this one. Right? Do you have any stats on solar electricity generated by country? I believe that those countries that are way ahead in solar in the developed world, are not those where the sun shines the most. So I'll, I'll let Carlos comment on that and maybe I'll throw in my two cents. >> That's correct I think not too long ago there was I don't, I don't have very good statistics, but like I think it's very easy for you to, to find these if you I think there's a Wikipedia page on solarization per country and so on. But if, again, and this changes very fast, by the way. I have to say like if you don't look for a couple of years, like I'm going to back there, like you know, just a couple of new power plants would change, like, those statistics substantially. Not long ago there was some news that Germany used in one particular day, I think it was a weekend virtually all of the energy generated in the country came from solar. We have a few days in California, where like, you know, we we were getting to 30%, 40% of the energy is coming from solar, and it's rampant, to the wind at night and so on. If you integrate over the whole 24 hours, you can get in some particular days, like you can get very a high electricity from solar. it's true that Germany does not have a good weather for solar, like the climate is it would normally, [INAUDIBLE] is roughly equivalent to Chicago which is not known to be a strong solar place. there, there are very high potential for solar in the Southwest of US. It's one of the best place in the world to generate solar energy. There are many other places you know? In Northern Africa, like we just mentioned Brazil. The central plateau of Brazil is excellent there's a place in the South, Southwest of the state of Bahia in Brazil that has a almost perfect, insulation profile for insulation profile for, for installations. It is true like, you know, it's not only the resource and it is the resource rather the amount of energy that is there available, but the viability of the resource when the variability happens if for example during the summer, in a place where most of the load is coming from air conditioning. Then the variability can problematic for, for solar. But on the other hand for example, if you look at the central central valley in California, where you have a very large population. You have amazing amount of radiance during the summer it's very hot and some people love it. And because it's very hot, like people tend to use air-conditioning as if a necessity your load is very strongly correlated to the solar availability. >> Mm-hm. >> Then you have all the ingredients like are known for the economics to work. Because you are going to generate solar, at the highest peak load when people are actually using the air-conditioning. And this, this coincides when the solar energy is available. So if you can have those, different factors in the same equation. Then the system is ripe to develop. This is true, what you mention is true not only in terms of different countries but it's also true in terms of micro regions like, if you look at San Diego for example is, that US capital of solar utilization. We don't have the best solar profile not even in California but it's a combination of many different socioeconomic factors that make, San Diego right to have, still going to install in his house, you know, solar panels and so on. So it's incentives like what they did in Germany there was a very strong incentive over time phasing out nuclear like that was the option that was I have I've chosen that app. In fact, many decades ago, there was quite a lot of investment in solar in Germany, and it's paying off now by having these large distributor generation. Almost all solar in Germany is distributed as effectively different than what we can do in the, in the Southwest of US. >> Mm-hm. Yap, that's exactly right and the only thing I will add to that is one of the last lectures in this course will be on energy in Nepal. And in, in that case where there is no central electric grid. Right? There, there is no on and off switch in any house. Right, except maybe in Kathmandu in the main city but once you get outside of that. And in those cases you'd think oh, this is perfect for solar panels. Right? That there's, that if you could put a solar panel in and you could get a little bit of light into people's house, this would allow them to read at night. It would allow them to have light when they cook. It would just allow to do so many wonderful things for them. They simply don't have the resources, to purchase those and to, to, to even get them to those remote areas. They simply lack the funding to do it and that's something that would, that maybe we'll talk a little bit about in another office hour. We'll have Alex on in here, who's got an NGO there to talk about that. But, but, but social acceptance, and who has the resources to buy these things. Right? So obviously, in Germany, they do. Here in California, we do. And in San Diego, that's where we get them. It's a great idea, good for the environment, but you've still gotta be relatively rich to buy this stuff. Okay, we have time for just one last question and I'm going to throw this one out to Carlos, and it says, is there any new technology being developed that will decrease the price of solar panels, and, and, and I will give you the opportunity to say just, what is the coolest technology that you see sort of coming down the road on, on solar energy and how we're going to utilize it? >> Yeah so, the, the, the combination there is is interesting. You can't actually generate energy at the low efficiency very cheap with very cheap solar panels. the, the price of the solar panels went down so fast, I think nobody could predict how fast [INAUDIBLE]. If you go back ten years, like, you know, and then say that today you can actually buy a 100 watt panel under $100 nobody would believe you. So like the, the cost went down But these cost and efficiency, so you want to be able to bring down the cost of a 100 watt panel as to a low value, but keep like some efficiency. You can have like a much lower cost using thin films but the efficiencies are much lower. >> Yeah. >> The question here is, how can you, actually, go beyond the three, four, 5% efficiency with something that is so cheap that you could basically just ink and wear, and hook up some electrodes and take the [INAUDIBLE]. So these are the cool technologies that are coming out now, maybe a decade away, but, to, to make it into commercial products but are, I think they will become a reality very soon. >> Yeah, the really cool one that I just saw the other day, are these see through solar panels. So, what they're doing is they're absorbing the infrared light. So as you look at him through the window, you still see visible light coming through, but infrared which is most of the heat that comes in to the house now, you're capturing that so the house is cooler because it's effectively shaded, and then that energy is going to, to, you know, electricity. And I just thought oh, that's a great idea. >> Yeah, that's one thing that if, if you have your whole window [INAUDIBLE] with the solar panel opaque like, you know, you need to have no energy like you know, just to directly illuminate your inside. So you can play these there's no, no, the beautiful technology, it's on your they going to be thinking will become mainstream very soon. >> Okay? All right, that's all we have time for today we're going to thank Carlos for coming over here and, and talking with us, and again, if, if, you know, later on, you guys want to email him to me, I'll, I'll forward them on to our experts on solar stuff, thanks very much for participating today. >> Thank you, thanks a lot.
