Joe Cordaro is a principle member of the technical staff at Sandia National Laboratories in Livermore. He is a research chemist who received his PhD in chemistry from UC Berkeley. He talks with us about his work in concentrated solar power systems.
Transcript
Speaker 1: Spectrum's next
Speaker 2: [inaudible].
Speaker 1: Welcome to spectrum the science and technology show on k a l [00:00:30] x Berkeley, a biweekly 30 minute program bringing you interviews featuring bay area scientists and technologists as well as a calendar of local events and news [inaudible].
Speaker 3: Good afternoon. My name is Brad Swift. I'm joined today by spectrum contributors. Rick Karnofsky and Lisa [inaudible]. Rick and I interviewed Joe Carderock, a principal member of the technical staff at Sandia national laboratories in Livermore. He is a research chemist. [00:01:00] Joe received his phd in chemistry from UC Berkeley. He talks with us about his work in concentrated solar power systems. Joe, welcome to spectrum. Thank you. Rick. Can you explain to us a little bit about concerted solar power? Sure. I'd be happy to. People have looked at using mirrors to focus light to do exactly what we are now doing in the 21st century since the mid 17 and 18 hundreds. There's a few reports that people using mirrors to focus [00:01:30] sunlight to heat up water in a boiler to generate steam for creating a pump for irrigation. And there's also been a report of a printing press that was powered off of steam that was generated using mirrors to focus light to once again heat up a boiler.
Speaker 3: Um, that all happened in the 19th early 20th century. But from about the early 1920s until the 1970s not a lot of work went into looking at concentrated solar power to make electricity. Primarily that was because at the same [00:02:00] time that research to make solar electricity from sunlight was taking off, oil was discovered and that became much cheaper and economical than it was to invest in technology to look at concentrated solar power. So concentrated solar power is a method by using in mirrors to focus the sun's rays onto a type of central receiver in order to boil water, to turn a turbine to generate electricity. So it's really a complicated way to boil water just to make electricity, but it works [00:02:30] and it only uses the sun. Is this sort of input for energy? Yeah, it's actually pretty amazing that we, that we don't use this more often because there is no emission from it.
Speaker 3: There's no greenhouse gases, there's no radioactive material and it's mostly made using commodity parts that can almost 70% be made in the United States. So there's three main architectures for concentrated solar power. There's the sterling engine, there's parabolic trough systems and then a central receiver tower [00:03:00] vista. Then engines are maybe the most efficient type of concentrated solar power, but they also have the most moving parts and a reliability is somewhat low right now. Their module, so you can add one and then another and another and another and increase your field side to base on demand. You can also just stick one in your backyard if you had the money to buy it and uh, didn't mind the thumping noise at the sterling pump makes so they're a little loud. The most employed type of concentrated solar [00:03:30] power facility right now is a parabolic trough system. And in a parabolic trough system you have a field of mirrors that are focused on a central tube that runs through the parabolic trough.
Speaker 3: And this tube is about three inches in diameter. And inside the tube is a working fluid and it's usually a silicon based oil. And the silicon based oil is used because the uh, operating temperature for that is around zero degrees Celsius up to 450. If you're in the desert, you typically have cold winter nights, [00:04:00] so you need to have a flu that doesn't solidify at nighttime in the wintertime. And so zeros are pretty good, that lower limit, but the a heat transfer fluid and based on silicon is slightly expensive. And how does that upper limit established? How hot can these things really go? So the upper limit would be the thermal stability of working fluid and the upper stability is just dependent on the chemical nature of the fluid. So the bond strengths of the actual carbon oxygen and silicon bonds within the heat transfer fluid.
Speaker 3: But as far as the amount [00:04:30] of heat energy that can be sort of harvested, that's going to be dependent on the thermal heat capacity of the fluid times the actual density times the uh, flow rate. So the more heat you can store per volume per time will give you a more energy out at the end of the day. But all of that is gonna be dependent on factors like your thermal conductivity between the two betters holding the heat transfer fluid, and then also the heat exchangers that are down the line when you convert from a silicon [00:05:00] oil heat to steam heat. So there's a lot of limiting factors that control your efficiency of these things and a lot of losses. Also third type of concentrated solar power facility called the central receiver tower. And in those systems you have one tower that could maybe be 50 to a a hundred meters above the ground and that tower surrounded by field of mirrors and those mirrors are flat.
Speaker 3: I also call them heliostats and those mirrors track the sun and then reflect the sun's rays onto the central receiver tower. And [00:05:30] the essential receiver tower has a molten salt inside of it and the temperature that usually goes up to about 550 degrees Celsius. And the reason why we're using molten salt is because you can get a higher operating temperature. Then you count the silicon fluid and this molten salt heats up to its operating temperature, which has been pumped only a short distance to a heat exchanger, which then boils water to turn a turbine to make electricity.
Speaker 2: This is spectrum on k a l x [00:06:00] Berkeley. We are talking with Joe Cordaro of Sandia national laboratories about concentrated solar power.
Speaker 3: And Are we limited at all about where we would deploy a concentrated solar power plants or are these all going to end up in the deserts of Arizona or so one of the main limitations for concentrated solar powers that you need to have good sunlight, you need to do need to have many, many days of sunlight [00:06:30] per year with a high intensity. So putting a concentrated solar power field up in northern Europe or the northeast of the United States doesn't always make sense economically. It's a much better to put it in the desert in California or Arizona or New Mexico or Utah or in Africa. So the key being cloud free, cloud free with a lower latitudes. And how prevalent are concentrated solar power plants right now? Well, [00:07:00] they're building them pretty rapidly, but I think the total percentage of the electricity we get in the United States, it's probably less than 1%, but they're building these plants in California and Arizona, especially essential receiver towers.
Speaker 3: There's a big plant being built in Ivanpah, which is outside of Barstow. There's a couple of being built outside Las Vegas and Phoenix. They're building them in Morocco. They're building them in Italy. There's quite a few in Spain and there's some in France. Israel is building them. The amount of electricity [00:07:30] coming from these plants is uh, increasing, but it's still nothing compared to coal or natural gas. So essentially receiver towers are being explored a lot more because they have the potential for higher efficiency because you can go to higher temperature. So the carnow efficiency basically says that the higher difference in temperature between your hot and cold for doing work gives you the higher efficiency. So if you can increase your high operating temperature to five, six, seven, 800 degrees Celsius, but keep [00:08:00] your low operating temperature is still above the boiling point of water, you'll have a much more efficient cycle.
Speaker 3: So if you're limited by our heat transfer fluid, thermal stability of 450 degrees, then you're uh, overall fishing in the plant will be limited. So a lot of the work that the Department of energy is doing to try to improve the efficiencies of these systems is to look at higher operating temperatures. But with higher operating temperatures comes also a materials compatibility issues. And then also higher losses. So as you go to higher temperature, you not only get better [00:08:30] efficiency for your carnow efficiency, but you also get higher radiative losses. So you actually start to lose more heat throughout your whole system. And your materials become more difficult to match. And Costco, Costco really high. And why is that? Well, materials are becoming a big issue. There's not a lot of industries that currently use high temperature materials that except the nuclear industry. So if you want to do large scale industrial power plants, you really [00:09:00] want to stick with commodity items that can be purchased cheaply.
Speaker 3: Otherwise the costs are too expensive. So there's a lot of analysis that goes into try to decide if I increase my temperature by just 200 degrees or even a hundred degrees, is the efficiency gain worth the cost? So one of the big issues with these costs and material selection are the corrosion issues with your heat transfer fluid. So if you have a fluid that's operating at 700 or 800 degrees Celsius, you start to have incompatible [00:09:30] materials between your heat transfer fluid and the actual material of the pipe is made out of, I don't know, most of these salt baths, very simple sort of two ion component systems like this. Well the only actual molten salt used in the fields now are based off of sodium, potassium nitrate and nitrite mixture. So there are four components, two to four components, and they're pretty simple. But they do have reactive properties with a lot of alloys.
Speaker 3: So there are still some [00:10:00] corrosion issues, especially when you get above 550 degrees. So there's the longterm stability of the molten salt bath or the molten salt storage tank, or the molten salt pipes that have to be considered because it's a 30 year plant that leave expected design. So most power plants are built with the idea that it's going to have a 30 year lifetime. So you have to figure out what's gonna happen over 30 years. And the rate of a simple chemical reaction usually doubles with every 10 degrees increase in temperature. So if you have a simple first order [00:10:30] reaction, like the decomposition of a Moan Salt, and you increase the temperature by 10 degrees, you can expect your rate to double. And so that starts to really matter. If you're looking at something that's going to be a 30 year lifetime,
Speaker 2: you were listening to spectrum on k a l x Berkeley. Brad swift and Rick Karnofsky are talking with Joe Cordura about concentrated solar power and [inaudible].
Speaker 3: [00:11:00] So how intense is the beam once all these mirrors reflected into the molten salts? The central receiver tower like I described, has a large receiving window that maybe 10 by 10 meters and it's a target area that's painted black in order to absorb as much sunlight as possible from maybe a hundred, maybe 200 or maybe a thousand mirrors in the field, and they're focusing the sun's energy onto the central target in order to [00:11:30] get a really, really high temperature so that you can heat up some working heat transfer fluid. There's a way that a lot of the engineer's describe the intensity is it by the number of sons that are being focused onto that area and you're focusing all of those mirrors on a central spot, but you can get up to 3000 suns mean focused onto a single spot. 3000 suns is quite a high amount of energy and also very high temperature and there have been reports of birds that have flown [00:12:00] in the path of the sun. It's hot enough that they've burst into a little ball of fire and then fallen down into a fiery death below. Fortunately, it's only a few birds every once in a while, but that's how hot it does get in front of those receivers. You get nowhere that high of intensity and a parabolic trough system because you only have one large curved, mere focusing the sunlight onto a tube rather than hundreds of mirrors all focusing onto a central receiver.
Speaker 3: [00:12:30] Can you explain more about how you store the, is it the heat you're storing? Are you, what are you storing actually, so one of the biggest advantage of concentrated solar power is the ability to store thermal heat. When you use the sun to generate electricity, you're depending on the sun's sunlight to be consistent on the race to be consistent. And if a cloud goes in front of the sun and you're generate electricity using photovoltaics, your power drops to zero until the cloud moves [00:13:00] out of the sky. At nighttime, you can't generate any electricity either cause you don't have any sun. If you look at the peak demand time for electricity in the United States, it tracks with the date, time sun, which is good. But then it also continues into the evening until six seven eight o'clock at night when everyone comes home at night and turns on their washer and dryer turns on their television and it turns on their dishwasher.
Speaker 3: If you don't have any electricity on the grid available, then you're going to have a big problem. Coal and nuclear power plants can just generate electricity 24 hours a day without any problem. So [00:13:30] concentrated solar power offers the ability to do that as well through what we call thermal storage. So if you have a huge field of parabolic troughs that are heating up a heat transfer fluid to a high temperature, you can then take this fluid and store it into a large tank. And this hot fluid is going to stay hot for eight 1220 hours to pay on how big you build that tank. So now if you have a hot tank that's storing all of this heat, you can draw heat from that tank rather than drawing it from the field. [00:14:00] So you can decouple the power generation cycle from the actual solar sunlight.
Speaker 3: So the tank is kept at a high temperature and constantly being recharged by the sun. But if the sun disappears, you have a reserve of fluid that's still hot that you can use to generate electricity by boiling water. And the size of that tank is dependent on how many hours of storage you want. So people will make these tanks based off of an eight hour storage cycle or a 10 hour or 12 hour [00:14:30] storage time. So typically they're made up of an eight hour storage time because no one needs a lot of electricity at four, five in the morning, and then the sun comes back up again and you can start your whole plant back up. And that makes it much easier to tie into the grid and much easier to distribute electricity to the population. So what we call a dispatchable electricity generation. That's a big advantage for concentrated solar power compared to wind or photovoltaics and what [00:15:00] happens to the system if the outage is longer so you don't just have to worry about nights they have to worry about clouds or dust storms or, so there's a lot of potential backups that can be engineered into a system.
Speaker 3: One of them being gas powered burners just put in line to boil water to power the system in reverse basically. So if there was a really big problem where you had no sunlight for a week, could potentially use natural [00:15:30] gas burners to boil water but cycle it in reverse and so then the water goes and operates as a heat transfer fluid actually warm up the salt again. Fortunately historical data I think shows that that just is not a big risk. I mean you wouldn't build a plant in the northeast where you actually could have a week of cloud cover and cold rainy weather. You'd build a plant in the desert and a week of no sun doesn't happen. There's been plants that have been in operation for 30 years [00:16:00] in the desert in California, and there's historical data that is available to kind of map out where in the world you would build these plants.
Speaker 3: That goes back many, many, many years and the Department of Energy has collected this data, specifically the national renewable energy lab. Our enrol in Colorado has a lot of this data and industry and the national labs work strongly together to try to figure out where the best places to build these plants that have not only the highest solar [00:16:30] radiation, but also the lowest environmental impact when you build a plant because despite it being a zero emitter of greenhouse gases, there are environmental issues related to water usage and also endangered species and the Atlantan usage. Pretty big. Yeah, they can be quite large. So there are some land issues that are associated with building a system in the middle of the desert. There's also issues about how do you get the electricity to where consumers actually [00:17:00] live. If you build a power plant in the middle of the desert but everyone lives a couple hundred miles away or thousands of miles away, how do you actually get the electricity to more populated areas? And this is an issue Europe is dealing with because they want to build power plant in North Africa and then have electricity ship to continental Europe somehow. So it's another topic, but they're looking at ways to make high voltage DC transmission lines from northern Europe down into Africa. So you can actually distribute the electricity from where it's generated.
Speaker 2: [inaudible]
Speaker 3: [00:17:30] Joe Cornaro is our guest. The show is spectrum. The station is k a l x Berkeley. The topic is concentrated solar power.
Speaker 3: And what are some of the other open research questions that are out there besides the materials compatibility issues that you, some of the other areas are looking at. How do you actually set up a field of mirrors that maybe [00:18:00] 50 acres big and then get everyone in those mirrors to actually align properly without making it an incredibly expensive task. So all of these mirrors have to track the sun at the same angle and you have to figure out how can you put all these mirrors on some type of mechanical platform that moves to track the sun and then direct the sunlight efficiently. Cause just a small error in one of the mirrors can really change your beam and decrease your efficiency quite significantly. [00:18:30] You also have to think about what happens when a big wind storm comes around in the desert and you have 70 mile an hour winds.
Speaker 3: Now all the mirrors have to be stowed, turned pretty much horizontal so that they don't get blown away. Then you have to worry about the sand that comes by and and polishes. The mirrors are unpolished as them heres so there's a lot of technology goes into the coatings figuring out new pumps, valves and fittings when you're running at 800 degrees. So you can pump a fluid at 500 degrees. We have commercial equipment to do [00:19:00] that, but using that equipment at 700 or 800 degrees hasn't been tested. So manufacturers will make things that they say possibly will work at 800 but it's not actually been tested at 800 and then we don't even have sensors to measure things that 800 on a large scale like this to measure what kinds of things? A viscosity is a big one. So we want to know how fast a fluid is flowing through a pipe so we can calculate how much heat is coming out.
Speaker 3: So we know how much steam we're going to generate and try [00:19:30] to measure viscosity at 800 degrees hasn't been done either. So we have active programs to look at making new sensors for viscosity. Some of the other issues, I'm trying to get more efficient steam cycles. Actually there are commercially available turbines to make steam for the uh, colon, natural gas industry that have been around for 50 75 years and they work really well up to a certain temperature. But if you can go higher with your heat transfer fluid, then you want to go higher with your turbine as well. And then [00:20:00] using steam no longer as efficient. And so people are looking at other types of cycles that don't use water anymore to make steam, but they're using super critical CO2 or helium or some other type of gas for what we call air brain cycles.
Speaker 3: And those could operate up to 1200 degrees and Japan has actually looked at those for quite awhile, but America has been pretty scared of looking at a 1200 degree high pressure systems. As far as the risk. Yeah, as far as the risk goes, it is a little bit more dangerous [00:20:30] when you have 1200 degrees and high high pressure systems, but the efficiency could be a lot higher. So all of this is still open for optimization. All of it requires inputs from systems engineers to finance people to determine the cost, whether it's worth it down to scientists, to the Terman stability and compatibility of parts to the last thing you want to do is build a big field and then have to replace a huge [00:21:00] portion of it in three years because you have something break that'll make the entire project economically a nonstarter. So the risks have to be reduced to save as much as possible.
Speaker 4: Joe, how was it? Did you became involved in concentrated solar power?
Speaker 3: After I got to Sandia national labs, I began working in the concentrated solar power research project because I was a chemist in looking at materials, compatibility issues and also stability issues of heat transfer fluids and while it doesn't sound like the most sexy [00:21:30] area of chemistry to be in formulating new salts and looking at high temperature materials, I really, really enjoy it because it is actually being built is actually real science being turned into engineering projects that is actually being deployed throughout the world to solve our problems and to make us energy independent. So unlike a lot of academic research that I did in school, concentrated solar power is real. It's been done and it's been put to use and that makes me incredibly [00:22:00] excited about being part of that project. Joe Codero, thanks for joining us. Thank you for having me.
Speaker 2: Regular feature of spectrum is to mention a few of the science and technology events happening in the bay area over the next few weeks. Rick and Lisa, join me for the calendar.
Speaker 5: UC Berkeley's Institute of East Asian Studies [00:22:30] will hold a symposium titled Towards Longterm Sustainability in response to the Fukushima nuclear disaster. It takes place today and tomorrow and it starts soon, one 30 to five 30 today, so you better hurry up and get over there, but if you can't make it today, tomorrow will feature three Speakers, all of whom have been actively involved in analyzing the Fukushima nuclear plant accident, its historical context, and the sociopolitical actions taken by the various stakeholders. The symposium [00:23:00] will situate the causes and the consequences of the disaster in the context of a longterm sustainable future. For more information, go to the website, I. E. A s@berkeley.edu
Speaker 4: cal day is tomorrow, Saturday, April 21st the Berkeley campus, the museums, the botanical garden are open to the public. There are a wide variety of presentations and facilities you can tour for details, go to the website, cal day.berkeley.edu
Speaker 5: [00:23:30] on June 5th, 2012 Venus will transit or pass directly in front of the sun. A transit like this is so rare. No human alive today. We'll witness it again. The next one will not be until 2117 get ready. This event by going to the transit of Venus Planetarium program at the Lawrence Hall of science this Saturday on cow day at 3:00 PM learn why transits are so rare, how studying transits taught us exactly how big our solar system is [00:24:00] and how they may be the key to discovering other earths and other star systems. Then come back on June 5th and observed the actual transit of Venus at the Lawrence Hall of Science. The hall will have several solar telescopes for viewing the eclipse safely on the main plaza. Most of us are aware of the obesity epidemic facing the United States, but is it simply a matter of calories in, calories out on Thursday, May 3rd from 1210 to 1:00 PM in the auditorium of the Berkeley Art Museum, [00:24:30] you CSF neuroendocrinologist Robert Lustig will present the lecture health, Darwin Diet disease and dollars. He will examine some of the more controversial dietary factors contributing to the obesity epidemic, the role that these obesogens potentially play in our evolution toward an unhealthy nation. And possible solutions for turning this trend around. You must register for this event. Go to u h S. Dot. berkeley.edu
Speaker 6: [00:25:00] on Saturday April 28th at 1:30 PM the Commonwealth Club and the Youth Science Initiative. Host the research group lead for Pixar and our guest on spectrum two weeks from today, Tony rose. Senator, the admission is $20 Commonwealth Club members get in for 12
Speaker 6: and is $7 for students 18 and under. The talk will be at the Los Altos High School Eagle Theater, two zero one almond avenue in Los Altos. Tony will discuss how math [00:25:30] is central to Pixar film production process and also the young makers program. That's the topic of our interview. In the next episode of spectrum, students are teamed up with adult mentors to design and build ambitious projects for the maker fair for tickets and more information, visit www.commonwealthclub.org another feature is spectrum guest Maggie Court. Baker will also be giving a lecture soon. Maggie is the science editor of Boeing, boeing.net and we'll be discussing her recent book before the lights go [00:26:00] out, conquering the energy crisis before it conquers us. She'll put the fun back in the infrastructure and described the surprising ways our electric system evolved, what we can and can't do about the energy crisis now and what the future might hold. This is the spring seminar for the Berkeley Science Review and will take place in the lead caching building room. Three four five on Wednesday May 2nd at 6:00 PM yeah, RSVP At B e r c. Dot. berkeley.edu [00:26:30] pseudo room, a newly forming East Bay hackerspace is having a free kickoff and fundraiser on Friday May 4th at 7:00 PM at Tech Liminal two six eight 14th street in downtown Oakland. Okay. Pseudo room is a collaborative community of tech developers, citizen scientists, activists and artists. Mitch Altman, cofounder of Noisebridge. We'll discuss hackerspaces for more information, visit s u d o room.org [00:27:00] now the news
Speaker 5: significant declines are expected in the number of emperor penguins over the next century due to earlier spring warming around Antarctica. A new study in the April 13th edition of Science Daily reports that an international team of scientists using satellite mapping technology reveals there are twice as many emperor penguins in Antarctica than previously thought. Using a technique known as pan sharpening to increase the resolution of the satellite imagery. They were able to differentiate between birds, [00:27:30] eye shadow and Penguin Guano. In the first comprehensive census of a species taken from space 595,000 birds were counted almost double the previous estimates.
Speaker 6: The origin of cosmic grays has long been and remains a mystery. The ice cube collaboration in which Berkeley lab is a crucial contributor published in an article in the April 18th issue of nature on their exhaustive search for a high energy neutrinos that would likely be produced if the violent extra galactic [00:28:00] explosions known as Gamma Ray bursts are a source of ultra high energy cosmic rays. They I know events they have correspondents to these bursts when they would predict to see at least 8.4 events that correspond to some of the 215 gamma ray bursts detected from two periods in 2008 and 2009 there are other popular models for the origin of cosmic rays including active galactic nuclei. The Ice Cube Neutrino telescope encompasses a cubic kilometer of ice under [00:28:30] the South Pole and has over 5,000 digital optical modules that track the direction and energy of speeding yuan's which are created when you Trina is collide with Adam's in the ice. On a later episode of spectrum, you'll hear from Spencer Klein and Thorsten Settle Berger about this experiment. Visit ice cube dot [inaudible] w I s c.edu for more information,
Speaker 2: thanks to Rick Kaneski [00:29:00] and Lisa cabbage for help producing show music heard during the show is by Lasagna David from his album, folk and acoustic made available through creative Commons attribution license 3.0 spectrum shows are now available online at iTunes university. Go to itunes.berkeley.edu thank you for listening to spectrum. If you have comments about the show, please send [inaudible] [00:29:30] email address is spectrum dot [inaudible] dot com join us in two weeks. Same time. [inaudible].
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