Beyond Zero talks to Dr Thomas Mancini CSP Program Manager Sandia Laboratories

Beyond Zero's Matthew Wright and Scott Biliby talk to Dr Thomas Mancini, CSP Program Manager, Sandia National Laboratories.  Tom has a long history in the solar programs having worked at Sandia  since the 1980s Tom talks about Solar Thermal Power Towers, Molten Salt Storage, the US DOE Solar programs and the hopeful serious commercialisation of Solar Thermal power in the USA this year.

(Summary of interview below, with full transcript and podcast further down)

Relationship between Sandia Laboratories, government and private sector

 Sandia Laboratories (SL) and its sister concern, the National Resource Energy Laboratory, each work for the United States Department of Energy (DoE). They are the laboratory arms of DoE, helping with technology development activities as prime contractors in photovoltaics, solar energy, solar thermal energy, wind and geothermal. SL is managed by Lockheed Martin.

This arrangement is part of a special relationship between the private sector and the United States’ government. There are 13 national laboratories in the United States that perform contract work for the DoE while administrative responsibilities are undertaken by private sector managers.

Role of Sandia Laboratories

The role of SL is to help industry become more competitive and to do longer term research, development and analysis to support the development of CSP technology. SL has a test facility; they are working on thermal storage; stimulus funding has provided them with funding for a molten salt facility.

Molten salt research

 The salt used is fundamentally fertilizer, that is, sodium and potassium nitrate. Its characteristics include melting at approximately 220 degrees Celsius, low volatility (can be operated up to 600 degrees Celsius). Its first utilization was in the 1980s in response issues of thermal inertia regarding water steam power towers. Molten salt power towers provide opportunities for electricity generation, giving dispatchability with low volatility, without high pressure and attendant reliability and material issues.

 Currently, SL are trying to integrate these results into the more commercially viable technologies such as the parabolic trough system. (There are significant CSP developments in Spain. One plant, for example, has thermal storage, heating molten salt to assist the dispatch of electricity).

Mancini indicated that there is enough thermal intertia in most CSP systems to “coast through the small scale interruptions in solar energy” due to cloud cover etc. In the longer term, there is great value in the fact that large scale storage could provide dispatchable electricity to truly provide power whenever required.

 Towers or troughs?

 This is complicated.

 For example:

Tower plants use less salt due to higher temperatures.

If less salt is used, the expense of the salt itself and all the ancillaries are reduced. Thermacline storage was subject of experimentation ten years ago and experiments are being undertaken again now.

There are issues regarding the maintenance of stability with thermacline storage and work is being done to try to reduce the cost and increase efficiencies.

Spicing the salt can lower freezing temperatures and the real advantage of this is to potentially replace expensive oil with molten salt.

The dish collector is the most efficient solar dish as it always tracks the sun.

The parabolic trough tracks east to west.

Optical efficiency for a trough system is lower than for a power tower or a dish.

Molten salt will also increase the operating temperature of a trough field and thus their power block efficiency (SL is also working with parabolic troughs).

The Solar Two project

This experiment is funded by DoE. A consortium of utilities was involved. The project aimed to convert water steam power tower to a molten salt power tower. The experiment went from 1996-1999. It was very successful and demonstrated very efficient thermal storage capabilities. The plan was to then build a full scale prototype but due to the restructure of the electricity industry in the US, there was no firther funding for research and development.

Power utilities’ interest in tower technologies with molten salt storage

Utilities have changed their position on the deployment of renewable energy in the last ten years. There is potential for towers to reduce the need for fossil fuel dependant peaking plants, however, lack of investment capital frustrates this potential. 

 There have been 300GW worth of power purchase agreements signed in the USA, the bulk of them in California, Nevada and Arizona. The deal is to try to help the process along by the provision of loan guarantees and assisting people demonstrate the technology.

Approximately eleven projects are currently “on the fast track” and Mancini is very hopeful that at least half of them will “break ground” this year and that one of them will be a molten salt power tower.

 Electricity grid reliability and energy storage systems (such as solar thermal)

 If the objective is to displace coal from the grid then what is needed is something to provide power at a high capacity factor and to integrate with other resources on the grid whether they are photovoltaics, wind or other renewable. Baseload capacity is sought and the molten salt tower has the capability to displace carbon.

 The problem today, however, is that the incentive for utilities is merely to meet requirements and fulfill renewable portfolio standards for renewable CSP-type power. The utilities do not value the incremental storage capacity in a solar plant as they currently have storage on the grid. Consequently investors are not overly concerned with storage! Yet, investors are always interested in something new. The reality is, it is the utilities themselves who need to come around to valuing dispatchable capability in a renewable resource.

Originally Aired 100305

Beyond Zero talks to Dr Thomas Mancini CSP Program Manager Sandia Laboratories

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Transcript

Scott Bilby:  Today we're excited to be talking with Dr. Thomas Mancini, Concentrated Solar Power Program Manager at Sandia Laboratories in the United States.  He joined Sandia in 1985 and before that he was a full professor at the Faculty of Mechanical Engineering at New Mexico State University.  Hello Tom and thanks for joining us from the U.S. today.

Thomas Mancini:  Hi Scott, Hi Matt, it's nice to talk to you guys.

Scott Bilby: And we're very happy to have you on the radio show with us.  Now, we'd like to start off very quickly asking you a little bit about your history and how you got interested when you were younger in renewable energy.

Thomas Mancini: When I was a graduate student I had an opportunity to work on a project that involved solar energy and that got me interested in the topic.  And later when I graduated and was looking for a full time job, New Mexico State, where I worked for ten years, was looking for someone that could do solar energy work and so the two matched very well.

Scott Bilby: Ok and now, Sandia are part of the Department of Energy Solar Energy Technology Program, so you have a close relationship with the Department of Energy.  Can you just tell us a little bit about how Sandia, how your solar program, fits in with the Department of Energy?

Thomas Mancini: Yes, of course.  The Sandia National Laboratories and our sister laboratory in Golden, Colorado, the National Renewable Energy Laboratory, both work for the Department of Energy as prime contractors in the areas of potable takes as well as solar energy, solar thermal energy, which is the area I work in, and also in other areas like wind and geothermal.  We're the laboratory arms of the Department of Energy and we do a lot of the R&D and work with a lot of the industry partners to help them with their technology development activities.

Matthew Wright: And your particular National Security Labs is run by Lockheed Martin.  Are there different companies that run these labs for different purposes for the U.S. Department of Energy or just Lockheed Martin?

Thomas Mancini: No, in fact, there are 13 National Laboratories in the U.S. that do work for the Department of Energy and they're typically managed by private companies for the Department of Energy.  It's a very special type of relationship between the private sector and the government.  The management of the Laboratories fundamentally is purely an administrative activity.  And the labs contract with the DoE then for the work that DoE wants us to do. 

Matthew Wright: And with the other solar program lab, the National Renewable Energy Laboratories, is that a bit different?  Is that run directly by the U.S. DoE?

Thomas Mancini: No, it's also contracted by a consortium involving Midwest Research and a couple of other private concerns.

Scott Bilby: And, Tom, you're the Concentrated Solar Power Program Manager at Sandia Laboratories.  Can you quickly give us an overview of that?

Thomas Mancini: Sure, we at Sandia, our role in the program is to help industry become more cost competitive so we work a lot with industry.  And we also do some longer term R&D and analysis to support the development of concentrating solar power technologies.  We have a test facility here in Albuquerque, that's about 117 acres.  It includes a 5MW thermal power tower for testing power tower equipment, heliostats, receivers.  We currently have 10 dish sterling systems installed here, which are under test and evaluation.  And we've done a lot of work with industry to help them develop those systems.  We also are working on thermal storage in the area of molten salt thermal storage.  And with stimulus funding, I don't know if we need to discuss what that is, but it's a special funding mechanism that is a response to the economic situation that has occurred around the world here about 1 1/2 years ago and it's one of the U.S.'s responses to that, provided us with some additional facilities funding for upgrading facilities so we're working on a molten salt facility and we also have trough test capability here.  So we do a lot of testing.  We're very much an experimental lab, but we're also working on advance technology development.

Matthew Wright: And that molten salt really interests us is because the thing that we've found with solar thermal storage is that what can give you firming power to enable modern electricity grids to be potentially run entirely or almost entirely on renewable energy.  Can you tell us about the molten salt research trajectory, where we're at today and what sort of direction you're heading?

Thomas Mancini: Sure, I'd be happy to do that.  The advantage of the molten salt, just to give you a little brief picture of why or how we got involved in it.  First of all, this isn't sodium chloride, it's a mixture of sodium and potassium nitrate, it's fundamentally fertilizer.  And it has some interesting characteristics.  First of all, if you heat it up, it melts at about 220 degrees C.  And maybe that's a little higher than where you'd like it to melt but that's what it does.  And it has a very low volatility and can be operated up to as high as perhaps 600 degrees C or maybe even higher temperatures than that. 

The first utilization of this in any form of thermal storage was in response to some water steamed power towers that we ran in the California desert back in the 1980s.  And we had a lot of trouble with high temperature and pressure in the receivers and we had a lot of trouble with tripping the turbine block because we didn't have enough thermal inertia in the system. And so we started to look at what some of the solutions to the problems we had running that system were, and a molten salt power tower looked like an opportunity.  And the idea was that once you melt the molten salt, it's always in a liquid phase here - we're not dealing with phase change here, and you pumped it up to the top of the tower and you heat it with the heliostat field up to say 560 C, which is where our conventional steam generating power block wants to operate and you return that hot salt to hot storage tank and then when you want to generate electricity, you remove the hot salt, generate steam at the temperature and the pressure you want and you have both dispatchability but with the low volatility, you have the high temperature in the receiver but you don't have the high pressure and the reliability issues and material issues around that.  So it provided great advantages to us there. 

Now the current direction that this is moving is to try to integrate that into the more commercially viable technologies that have been out in the market place for a while and that's the parabolic trough system.  And this brings us to another topic, which is the great explosion of CSP technologies in Spain, there's currently over 800 MW being developed in Spain and a large part of those are parabolic trough plants.  Now parabolic trough plants use a synthetic oil that they heat in a long tube that flows through the focus of the parabolic trough. And they heat that from 290 C to about 390 C.  And that oil then is used to generate steam and generate electricity.  In Spain, at one particular plant they implemented thermal storage with the hot oil and what they do is the heat the molten salt and keep it above 220 C in the cold tank and they heat it up to about 390 C in the hot tank and then they use that to dispatch electricity.  So molten salt offers tremendous opportunities for firming of the electricity and firming that you mentioned earlier is exactly right.  There's enough thermal inertial in most CSP systems to coast through the small scale interruptions you might have in solar energy due to clouds, small clouds and that sort of thing but when you get to larger scale storage is where the value lies in the longer term for providing dispatchable electricity to truly provide power when the utility needs it.

Matthew Wright: Now in my understanding is in talking to some of our experts at Australian national universities that the current trough plants are using about 75 tonnes of molten salt per MW/h electrical and that if you switch to towers, suddenly because of the higher temperatures, you're only using 25 tonnes per MW/h electrical.  And then apparently if you could possibly add a thermocline system that could reduce again.  Can you tell us about how the cost of the salt is significant and the potential is there to use a lot less salt in the future?

Thomas Mancini: Well that's exactly right. They're right on the mark and actually I work in the International Energy Agency Solar Pasis*10:18* Group, I chair that group and Australia is a member of that group and we work with our friends at ANU and other locations around Australia all the time so I know many of these people.  They're exactly right and the reason for that is that the thermal storage is a direct heat capacity effect.  And because in a trough plant you're raising the temperature only 100 degrees C and in a tower plant you're raising the temperature almost 300 degrees C, from 265 up to almost 600 degrees C, that in fact that's directly proportional that difference, or that ratio, is directly proportional to the amount of salt you need.  And it's not just a question of the salt, because the salt, to be quite honest with you, is a lot cheaper than the oil.  But it's also because the insulary equipment you have to have - the size of the tanks gets smaller for the same amount of storage, the energy density is higher.  It just works for you in all kinds of directions.  So their take on it is exactly correct. 

Matthew Wright: So is their research going on at Sandia about combining thermocline systems at higher temperatures?  I understand I think Sandia or NREL had done research in the past into thermocline with quartz filler, which is very cheap, for trough sort of temperatures of 400 degrees or maybe 500, but not the higher temperatures?

Thomas Mancini: Yes, in fact, we did those experiments almost 10 years ago.  We haven't continued with it and there are a number of explanations for that, they're not technical.  But recently we got started again looking at thermocline storage. 

There are a lot of issues around thermocline storage.  The issues have to do with not only the cost, the ability to add less expensive filler materials that can also store heat is an advantage.  But if you think about a thermalcline, you're trying to maintain a temperature gradient across this vertical tank while you're adding hot fluid to the top and removing hot fluid from the top and adding a cold fluid in the bottom and removing cold fluid from the bottom so there's a hydrodynamic stability issue in a porous medium that plays out here and there's a lot of issues around that in maintaining the stability and there are questions that have to be answered.  There are a number of, DoE currently has a number of contracts with people who are looking at all kinds of different storage including phase change, thermoclines, solid storage, trying to look to the future in terms of how we can reduce the costs and improve the efficiency and reliability of energy storage.

Matthew Wright: And also there's this notion of spicing the salt to lower the freezing temperature.  Is that purely just to get salt around trough fields or is that also to be able to extend the amount of heat that can be stored in the same mass or volume of salt?

Thomas Mancini: Well the correct answer to your question is both.  And by going to a lower temperature you could potentially make use of a larger delta T in your power conversion cycle.  So that's an advantage, but the real advantage is that you could potentially replace the expensive oil in the field with the molten salt and there are a lot of issues around that.  This is not a slam dunk by any means but it's certainly something that the DoE laboratories and that the industry are all looking at right now.

Matthew Wright: Now something that interests us very much is the Solar 2 program.  I'm wondering if you had any involvement in that and if you could tell us about, I think it was Bechtel and a few other partners who put that together, the success of that program.

Thomas Mancini: Yes, Solar 2 was a program that was actually funded by DoE and with Sandia led that project.  It was a consortium of a number of utilities in the southwest U.S. and also some people like Bechtel, the Electric Power Research Institute, Southern Cal Edison, Arizona Public Service, I'm going to forget a whole bunch of them, but it was like 15 different companies were involved in this project.  The project was to convert a power tower that was Solar 1, a water steamed power tower, to a molten salt power tower.  And so we installed tanks, we used the same heliostat field, we put up a new receiver and we operated a 10 MW electric power block using molten salt.  This experiment went on for about 3 years between 1996 til about 1999.  And it was very successful.  It demonstrated a very efficient thermal storage in excess of 95% roundtrip efficiency on the thermal storage.  Thermal Storage works very well in this type of a situation.  We were able to go through cloud transients very effectively. We actually reduced the output of the turbine down to low levels to demonstrate we could dispatch power for longer periods of time even though we didn't have a great deal of thermal storage in that system.  So it was an extremely successful campaign. 

The plan to follow onto that particular campaign was for the consortium of utilities then to move onto the next step, again with some DoE support and support from the labs, to build a full-scale prototype and test it and learn from that full-scale prototype, perhaps 50 or 100 MW.  The reason we didn't do that had to do with restructuring in the electric utility industry and we found that many of the companies that we had been working with were no longer in the business of doing R&D.  So it wasn't an option under the deregulation or restructuring, whatever word you want to use to describe the change in the utility industry in the United States.

Matthew Wright: Now I understand part of that concentration on towers has to do with projection affect as to why they can be better to troughs.  Can you explain to listeners just how at latitudes further away from the equator the tower's more optimal in terms of gaining winter energy?

Thomas Mancini: Well it's purely a question, if you think about where the sun is in the sky, if you're right at the equator it's always right over head and as you move further north it drops in the sky.  As it drops in the sky, a power tower or a dish won't lose efficiency as much.  In fact, most efficient solar collector of the three technologies, and we haven't really talked about dishes very much, is the dish collector.  It always tracks right on the sun so it's always giving you the maximum amount of energy that you can get from the sun.  A parabolic trough on the other hand, if oriented north-south, with it's axis going in north-south direction, will track the sun from east to west as it comes up in the morning and goes down in the afternoon.  As the sun drops lower in the sky, the projected area that it actually hits of the trough field is directly proportional then to the amount of energy that you're able to collect and focus onto the tube.  So the optical efficiency is sort of an annual integrated optical efficiency for a trough system is lower than it would be for a power tower or for a dish.

Matthew Wright: Sorry for a given amount of resources or a given surface area of mirror you can collect less heat with a trough than a tower system?

Thomas Mancini: You can, you can.  It's not as large a discrepancy as you might think. There's really more to it than that and the idea of going to higher temperatures in a power tower is a big advantage because that takes you to higher power block efficiency so you're really getting more bang for the buck, so to speak, out of that as well.  So it's kind of a combination of both of those issues. 

Certainly we're looking and we're working with parabolic troughs to try and increase the operating temperature range and increase the power block efficiency for them as well.  If we can use a molten salt in the field that will help us increase the operating temperature of a trough field as well.  So it's not quite just an either/or situation.  And certainly the experience in both Spain and in the United States, we've been operating trough fields over 350 MW in the Mohave Desert since 1985.  And so there's a lot of experience in trough plants and trough plants are a lot easier to finance because of that.  So we're struggling now as to how to get some of these other technologies to be deployed.

Scott Bilby: We're speaking with Dr. Thomas Mancini, Concentrated Solar Power Program Manager at Sandia National Laboratories in the U.S.A.  Tom, I just wanted to touch on that about getting some of these things built in the United States ASAP.  How favorably are the power utilities looking on technologies such as the tower technology with the molten salt storage given that obviously if you can get these things online they're going to reduce the need for peaking plants and stuff like that - fossil fuel peaking plants.

Thomas Mancini: That's a very interesting question and it would probably take longer than we have to really answer directly.  I guess I'd say that over the last 10 years, the utilities have changed their position on deploying renewable energy quite a bit and that includes concentrating solar as well as other types of renewable energy.  In terms of power towers and the potential to deploy power towers, over the last two months there have been two announcements of two power purchase agreements to deploy a molten salt power tower - one in Nevada and one in California.  And so there is a potential to move forward.  I think we're facing the same problem that much of the rest of the world is facing.  These projects are large capital-intensive projects and getting the investment capital necessary to take the next step and start building the plants is a very difficult proposition at the current time.

Scott Bilby: Now I recall we spoke to Nathan Siegel, he's a research assistant from the Solar Technologies department and one of the key things that stuck out in my mind about the interview was he had a lot of good things to say but at the end he stressed that he was so keen to see that first thermal tower plant or even a trough plant built in the United States.  He just wanted to see it ASAP and I assume that would be your point of view as well?

Thomas Mancini: Absolutely, in fact we're really excited about the Hemisolar project in Spain, which is going to be the first molten salt power tower built in the world and it's under construction right now.  So we're real excited about seeing that one built.  We did have of course our first trough plant built in the United States since about 1992 was commissioned in 2007 south of Las Vegas and that's the Nevada Solar 1 plant so we were real excited about that.  And we were looking forward to more projects breaking ground - there are over 3 GW worth of power purchase agreements already signed in the southwest U.S., the bulk of them in California, Nevada and Arizona and we're real excited about getting some of those projects going and the DoE is trying to help that process along right now by providing loan guarantees for projects and also by trying to help the people demonstrate the technologies more so we're moving forward with all of these activities with the hopes of breaking ground soon on actually more trough plants as well as power towers and dish sterling as well.

Matthew Wright: And I understand that Bright Source Energy just got $1.8 billion in Federal loan guarantees and I think that projects must break ground by December 31.  How many projects do you think will break ground this year?

Thomas Mancini: Oh boy, that's really a tough one.  I'm told that there are 11 projects on the fast track to try and do that.  And you know it's going to be a tough sell but we're really hopeful and I'd like to take an optimistic position and say that at least half of them will break ground this year.

Matthew Wright: And are any of those likely to be molten salt power towers do you think?

Thomas Mancini: Ah, I sure hope so.  I'd like to believe that at least one of them would be.

Matthew Wright: That would be fantastic.

Thomas Mancini: I wish I could be more definite but you know my crystal ball is no clearer than yours right now.

Scott Bilby: I'd also like to ask you, Tom, about how energy thermal storage systems such as solar thermal with storage can help make electricity grids more reliable as increasing amounts of variable types of power generation come on stream.  Can you just run the audience through that a little bit?

Thomas Mancini: Well, it's the whole question of if you ultimately, if your objective is to displace coal from the grid, you have to have something that will provide power at a high capacity factor and integrate with other resources that are on the grid at the same time, whether they're large scale potable takes, whether they're wind systems, whatever.  And so the whole point behind storage in the long term is to try to look for something that would approach baseflow capacity.  And a malt salt tower or some other type of power system and there are options for that in the long term that we're exploring that also involve thermal storage and could give you a high capacity factor maybe at higher temperatures even in a molten salt system, would provide you the capability of displacing baseflow, fossil generation and displacing carbon.  The problem right now is that the incentive for utilities to buy renewable CSP type power is to fulfill renewable portfolio standards and meet those types of requirements.  They don't really care if they have storage or not because they have storage on their grid in the form of fossil plants or in some cases, nuclear plants or natural gas turbines.  So they don't really value if you will the incremental value of that capacity in a solar plant.  In the longer term I think that's going to have to change but right now that's the situation.

Scott Bilby: Ok so with the storage there's from the guys who actually have the cash, the bankers, the investors and stuff like that, they're not overly concerned about the storage issue at the moment but those of us, such as ourselves and yourselves, can just see the huge value in this stuff coming onto the future, we just want to see this stuff ramp up as soon as possible for the sake of energy efficiency, energy security and solving climate change.

Thomas Manici: Well I certainly agree with that statement, I'm not sure if I'd say the investors aren't concerned about molten salt storage.  They're always concerned about something that's new and has higher risk and they will charge a premium for that.  And that's why the loan guarantee program with the DoE may help move things along a little bit, to help reduce some of that incremental increase in cost.  It's the utilities themselves that have to come around to the thinking that having this dispatchable capability in a renewable resource is an important value to them.

Scott Bilby: Well Tom thank you very much for speaking with us to today.

Thomas Mancini: Well thank you Scott and Matt, thank you very much, I enjoyed it.

Matthew Wright: Thank you.

Scott Bilby: It was very informative.  We've just been speaking with Dr. Thomas Mancini, Concentrated Solar Power Program Manager at the USA's Sandia National Laboratories.  To find out more visit sandia.gov/csp.

Transcript by Nicole Caruso