Tuesday, April 29, 2008

Parabolic Trough Thermal Energy Storage Technology

National Renewable Energy Laboratory

TroughNet


One advantage of parabolic trough power plants is their potential for storing solar thermal energy to use during non-solar periods and to dispatch when it's needed most. As a result, thermal energy storage (TES) allows parabolic trough power plants to achieve higher annual capacity factors—from 25% without thermal storage up to 70% or more with it.

Parabolic trough thermal energy storage technology includes:

Thermal Energy Storage Systems

Two-Tank Direct

The first Luz trough plant, SEGS I, included a direct two-tank thermal energy storage system with 3 hours of full-load storage capacity. This system simply used the mineral oil (Caloria) heat transfer fluid (HTF) to store energy for later use. It operated between 1985 and 1999 and was used to dispatch solar power to meet the Southern California Edison winter evening peak demand period (weekdays between 5-10 p.m.).

Because power plants later moved to higher operating temperatures for improving power cycle efficiency, they also switched to a new higher temperature heat transfer fluid—a eutectic mixture of biphenyl-diphenyl oxide (Therminol VP-1 or Dowtherm A). Unfortunately, this fluid has a high vapor pressure. Therefore, it cannot be used in the same type of large unpressurized storage tank system similar to the one used for SEGS I.

Pressurized storage tanks are very expensive. They cannot be manufactured at the large sizes needed for parabolic trough plants.

Two-Tank Indirect

An image of two large storage tanks: a hot tank and a cold tank. Heat exchangers can be seen between the two tanks. The molten-salt pumps can be seen inserted into the top of the tanks.

Figure 1. Two-tank indirect thermal energy storage system for Andasol 1 and 2. Credit: Flagsol

In recent years, a new indirect thermal energy storage (TES) approach has been developed. This approach takes advantage of the experience with the storage system used in the Solar Two— a molten-salt power tower demonstration project—and integrates it into a parabolic trough plant with the conventional heat transfer fluid through a series of heat exchangers.

The thermal energy storage system is charged by taking hot, heat transfer fluid (HTF) from the solar field and running it through the heat exchangers. Cold molten-salt is taken from the cold storage tank and run counter currently through the heat exchangers. It's heated and stored in the hot storage tank for later use. Later, when the energy in storage is needed, the system simply operates in reverse to reheat the solar heat transfer fluid, which generates steam to run the power plant. It's referred to as an indirect system because it uses a fluid for the storage medium that's different from what's circulated in the solar field.

Several parabolic trough power plants under development in Spain plan to use this thermal energy storage concept. For future parabolic trough power plants, a number of alternative approaches are being considered for reducing the cost of the thermal energy systems.

A two-tank indirect thermal energy storage system is relatively expensive—its primary disadvantage. The expense is due to the heat exchangers and the relatively small temperature difference between the cold and hot fluid in the storage system.

For more information, see our publications on two-tank indirect thermal energy storage systems.

Single-Tank Thermocline

A single tank for storing both the hot and cold fluid provides one possibility for further reducing the cost of a direct two-tank storage system. This thermocline storage system features the hot fluid on top and the cold fluid on the bottom. The zone between the hot and cold fluids is called the thermocline.

A thermocline storage system has an additional advantage—most of the storage fluid can be replaced with a low-cost filler material. Sandia National Laboratories has demonstrated a 2.5-MWhr, backed-bed thermocline storage system with binary molten-salt fluid, and quartzite rock and sand for the filler material.

Depending on the cost of the storage fluid, the thermocline can result in a substantially lower cost storage system. However, the thermocline storage system must maintain the thermocline zone in the tank, so that it does not expand to occupy the entire tank.

An image of a thermocline storage system that utilizes a single tank containing both the hot and cold fluid. The zone between the hot and cold fluid is known as the thermocline. The Sandia test used a propane heater to heat molten-salt and an air cooler to cool salt. The test evaluated the performance of the thermocline storage through several charge and discharge cycles and during a long-term hold.

Figure 2. Thermocline test at Sandia National Laboratories. Credit: Sandia National Laboratories

For more information, see our publications on thermocline systems.

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Direct Molten-Salt Heat Transfer Fluid

Using molten-salt in both the solar field and thermal energy storage system eliminates the need for expensive heat exchangers. It allows the solar field to be operated at higher temperatures than current heat transfer fluids allow. This combination also allows for a substantial reduction in the cost of the thermal energy storage (TES) system.

Unfortunately, molten-salts freeze at relatively high temperatures 120 to 220°C (250-430°F). This means that special care must be taken to ensure that the salt does not freeze in the solar field piping during the night.

The Italian research laboratory, ENEA, has proven the technical feasibility of using molten-salt in a parabolic trough solar field with a salt mixture that freezes at 220°C (430°F). And Sandia National Laboratories are developing new salt mixtures with the potential for freeze points below 100°C (212°F). At 100°C the freeze problem is expected to be much more manageable.

For more information, see our publications about molten-salt heat transfer fluid.

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Thermal Energy Storage Media

Concrete

A photo of concrete slab walls, which enclose a long, rectangular thermal energy storage system. Horizontal piping is shown on the facing, short wall.   PIX#14939

The German Aerospace Center constructed a facility at the University of Stuttgart for testing a concrete, thermal energy storage system.

The German Aerospace Center (DLR) is examining the performance, durability and cost of using solid, thermal energy storage media (high-temperature concrete or castable ceramic materials) in parabolic trough power plants.

This system uses the standard heat transfer fluid (HTF) in the solar field. The heat transfer fluid passes through an array of pipes imbedded in the solid medium to transfer the thermal energy to and from the media during plant operation.

The primary advantage of this approach is the low cost of the solid media. Primary issues include maintaining good contact between the concrete and piping, and the heat transfer rates into and out of the solid medium.

At the Plataforma Solar de Almeria in Southern Spain, Ciemat and DLR performed initial testing that found both the castable ceramic and high-temperature concrete suitable for solid media, sensible heat storage systems. However, the high-temperature concrete is favored because of lower costs, higher material strength, and easier handling. There is no sign of degradation between the heat exchanger pipes and storage material.

DLR has also developed a design tool that helps optimize the storage layout, including the geometric dimensions and piping and module arrangement to minimize pressure losses and optimize manufacturing aspects and costs.

Because of the modular nature of concrete storage, DLR has identified approaches that allow the storage system to better integrate with the solar field and power cycle. This allows for improved overall utilization of the concrete storage system. DLR is also testing a new, more optimized concrete storage module at the University of Stuttgart.

Phase-Change Materials

Phase-change materials (PCMs) allow large amounts of energy to be stored in relatively small volumes, resulting in some of the lowest storage media costs of any storage concepts.

Initially phase-change materials were considered for use in conjunction with parabolic trough plants that used Therminol VP-1 in the solar field. Luz, and later ZSW, proposed an approach that used a cascading set of phase-change materials to transfer heat from the heat transfer fluid (HTF). In this approach, thermal energy transfers to a series of heat exchangers containing phase-change material that melt at slightly different temperatures. To discharge the storage, the heat transfer fluid flow is reversed. This results in reheating of the heat transfer fluid.

Although testing proved the technical feasibility of this system, further development of the concept was hindered because of the:

  • Complexity of the system
  • Thermodynamic penalty of going from sensible heat to latent heat and back to sensible heat
  • Uncertainty over the lifetime of phase-change materials.

More recently DLR is evaluating phase-change thermal energy storage for application with direct steam generation in the parabolic trough solar field. This allows for a better thermodynamic match between the phase-change material and the phase-change of steam used in the solar field. In this approach a single phase-change material can be used to preheat, boil, and superheat steam. DLR has found that the cost of the system is driven not only by the cost of phase-change storage material, but also by the rate at which energy will be charged or discharged from the material.

Also, DLR has developed a graphite foil that it uses to sandwich the phase-change material for increasing heat transfer rates. Lab scale tests of this approach have demonstrated its feasibility. And future tests will be integrated into the DISS facility at the Plataforma Solar de Almeria.

For more information, see our publications about phase-change materials.

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Tuesday, April 22, 2008

eSolar Announces Breakthrough Pre-Fabricated Solar Power Plants

Raises $130 Million from Idealab, Oak, Google to Accelerate Deployment

PASADENA, Calif.--(BUSINESS WIRE)--Today, eSolar, a producer of scalable solar thermal power plants, announced that it has closed $130 million in funding from Idealab, Google.org, Oak Investment Partners, and other investors for the construction and deployment of pre-fabricated power plants. Designed to address the complex issues surrounding large or utility-scale power projects, eSolar's distributed solar thermal plants achieve economies of scale at 33 MW, and are modularly scaled to fit the needs of large and small utilities.

"The eSolar power plant is based on mass manufactured components, and designed for rapid construction, uniform modularity, and unlimited scalability," said Asif Ansari, CEO of eSolar. "Rather than over-engineering the solution, eSolar's smart scalable solar architecture targets what we see as the four key business obstacles facing the sector: price, scalability, rapid deployment, and grid impact."

In order to deliver on the promise of Big Solar, the typical utility-scale installation faces huge construction costs and requires large tracts of real estate, combined with expensive transmission line improvements to bring the power out of the deserts and into the cities. eSolar's modular approach stands in direct contrast to this 'bigger is better' strategy. eSolar has replaced expensive steel, concrete, and brute force with inexpensive computing power and elegant algorithms. This new method of installing a solar power plant minimizes costly civil construction and the use of heavy equipment, dramatically reducing project cost and deployment time.

Centering on eSolar's 33 MW pre-fab form-factor, the company's modular design translates to minimal land requirements. The company's solar power plant solutions are tailored to fit local resources and produce a low environmental footprint, favoring a straightforward siting and permitting process. Myriad locations combined with a multitude of interconnection options mean that eSolar can deliver more clean, carbon free power where it is needed: near the cities and towns where it is consumed.

"eSolar's primary business goal is nothing short of making solar electricity for less than the price of coal, without subsidies," said Bill Gross, eSolar Chairman and Founder of Idealab. "This is not only attainable, but will truly change the world."

Bandel Carano, Managing Partner of Oak Investment Partners, added, "eSolar is the only cost effective solution that can deliver gigawatts of solar energy generation at market prices today, because they have developed a truly disruptive scalable solution that can be deployed rapidly."

eSolar has secured land rights in the southwest United States to support the production and transmission of over 1 GW of power. eSolar will have a fully operational power plant later this year in southern California.

About eSolar

eSolar is an Idealab company founded by CEO Asif Ansari in 2007 to develop, construct and deploy modular, scalable solar thermal power plants. eSolar's approach marries a low-impact, pre-fabricated form factor with advanced optics and computer software engineering to meet the demands of utilities of any size for clean, renewable and cost-competitive solar energy. By focusing on the key business obstacles that have characterized large solar installations from its inception price, scalability, speed of deployment and grid impact eSolar has developed a proprietary solution to make a dramatic reduction in the cost of solar thermal technology. eSolar is based in Pasadena, California and has 70 employees. For more information please visit http://www.esolar.com/.

About Idealab

Idealab's mission is to create and operate pioneering technology companies. Founded in 1996 by entrepreneur Bill Gross, Idealab provides a broad range of operational support to its companies, allowing the operating company management teams to focus on getting to market quickly and cost effectively and to take advantage of the serial start-up experience of the Idealab team. Bill Gross and Idealab have founded companies such as eSolar, Inc., Energy Innovations, Overture Services, Inc., CitySearch, Picasa and Internet Brands. Current operating companies are providing innovative technology solutions in industries such as software, search, robotics, 3D printing and alternative energy fields. Additional information may be found at www.idealab.com.

About Google.org

Google.org aspires to use the power of information and technology to address the global challenges of our age: climate change, poverty and emerging disease. Google invested in eSolar to create utility-scale electricity from clean renewable energy sources that is cheaper than electricity produced from coal.

About Oak Investment Partners

Oak Investment Partners is a multi-stage venture capital firm with a total of $8.4 billion in committed capital. The primary investment focus is on high growth opportunities in communications, information technology, Internet new media, financial services, clean energy, healthcare services, and consumer retail. Over a 28-year history, Oak has achieved a strong track record as a stage-independent investor funding more than 435 companies at key points in their lifecycle.

Google-Backed Solar Startup Picks Up Steam, $130 Million

By Alexis Madrigal Email 04.21.08 | 6:45 PM

Rising oil prices lift all alt-energy boats.

For proof, look no further than the fat $130 million investment scooped up by eSolar, a company whose basic solar power strategy -- using sunlight-reflecting mirrors to generate steam -- was all but abandoned in the 1980s, and has recently recently caught investors' attention again.

The money, from Google's philanthropic arm, Google.org, and venture capital firms Idealab and Oak Investment Partners, will go towards the construction of eSolar's first functioning solar power plant.

"ESolar's long term is to become a viable replacement for all fossil fuel," said Robert Rogan, a Cal Tech Ph.D. and eSolar's executive vice president for corporate development. "The reason Google invested in us is that they saw the potential of this technology to beat the cost of using coal."

The company's core technology is an implementation of concentrating solar power, which uses mirrors to turn liquid into steam that drives standard electricity-generating turbines. CSP, also sometimes called solar thermal, is considered a promising replacement for fossil fuel power plants, particularly the coal plants that generate more than half of U.S. electricity. It's been around for decades, last seeing popularity in the early 1980s, when oil hit an inflation-adjusted price of $82 per barrel. Higher oil prices make fossil fuel plants more costly, making it easier for alternative technologies to compete. (Oil is currently trading for more than $115 a barrel, its highest level ever.)

Google's green-energy plan goes by the formula-like name RE<C, which sets out the goal of the company's operation -- to find renewable energy sources that reliably generate electricity more cheaply than burning coal. In modern times, that's been impossible, with fossil fuel plants able to generate power for a few cents a kilowatt-hour while solar energy from photovoltaics has cost upwards of $0.25 per kwh.

But times are changing as coal and natural gas plants have gotten more expensive to build. That's happening for a variety of reasons: Banks are including the risks of climate change legislation in their pricing for power plant loans, the raw construction materials used in power plants have become more expensive, and natural gas and coal prices have gone up alongside the skyrocketing price of oil. Within this changing marketplace, wind power has been growing phenomenally fast, but is too intermittent to power the whole grid. As a result, many clean-energy advocates are turning to solar thermal power plants as the solution du jour.

"There's hope and optimism but a little bit of skepticism as well," said Ryan Wiser, a renewable energy analyst at Lawrence Berkeley Labs. "No one knows whether the technologies are really cost competitive with other energy alternatives."

That hasn't stopped Abu Dhabi's clean-tech fund, Masdar, from funding a $1.2 billion solar thermal company called Torresol. Another competitor in the market, Ausra, has received more than $40 million from blue-chip venture capitalists. Yet another player, Abengoa, recently signed a $4 billion deal with Arizona Public Utilities, and Brightsource recently landed a 900-megawatt deal with the California utility PG&E. Stirling Energy Systems, a company that has adapted the Stirling Engine, a 200-year-old invention, for concentrated solar power, even pulled in a $100 million investment.

For its part, eSolar has a gigawatt of electricity production capacity planned.

In the near term, these deals are being driven by southwestern states' laws, which have built solar requirements into their renewable energy dictums. Nevada, Arizona, New Mexico and Colorado all require between 15 and 20 percent of their power to come from solar sources.

In the medium term, any sort of system that puts a price on emitting carbon dioxide -- either a carbon tax or a cap-and-trade framework -- would help these companies because it would penalize fossil fuels and aid cleaner technologies.

Long-term, though, the vision of truly cost-competitive solar energy is what drives all the competitors in the space.

"Once cost parity is reached, we'll see a flowering of solar power," said Rogan. "It's a question of time and place and technology. Right now, that perfect storm is developing."

But with more than a dozen competitors crowding into concentrated solar power, picking a winner looks extremely difficult.

"You have this diversity of designs ... but until we have more plants that are actually built, it's going to be hard to know which design will come out on top," said Wiser.

ESolar claims that its method for tracking the sun uses superior algorithms to focus its mirrors. Further, the company argues that its modular manufacturing processes, which allows it to build relatively small power plants ranging from 33 to over 500 megawatts, gives it time-to-market and cost-efficiency advantages over its competitors.

"If everyone else is building Cray supercomputers, we're building blade servers," Rogan said, coining an info-tech analogy. "If you took all the subsidies away, we believe that we're half the price of other solar technology."

Ausra's CEO Bob Fishman, however, who was formerly a natural gas executive with big utility Calpine, disputed eSolar's "smaller is better" assertion.

"I've looked at it, and I can tell you right now, there's a direct correlation between size and cost. If they want to build 30 megawatt plants, they can have at it," Fishman said. "Why do you think people build big coal-powered power plants and not small ones?"

Both eSolar and Ausra are planning to have demonstration plants up and running later this year. Several other plants from competitors are planning to come online within the next five years. Soon, some of these companies' claims will be subject to rigorous scrutiny by analysts like Wiser. But for now, hard data is hard to come by.

"We've been tracking the CSP market to some extent," Wiser said. "But we haven't done any analytic studies like we have for photovoltaics."

That means that pesky problems, like transmitting the power from the world's deserts to cities where it's needed and finding ways to store the energy for nighttime usage, remain subject to competing claims.

But while the different solar power plant companies have different approaches, they all agree that deploying any renewable technology is better than building more coal plants.

"The world needs all of these solutions," said Rogan. "One power plant is not going to solve the emissions problems of the world."

Monday, April 21, 2008

Solar Concentrating Systems -- CIEMAT Review Article

Present Situation

Solar Concentrating SystemsThe new legal framework defined in Spain by the Royal Decrees 436/2004 (BOE of 27/03/2004) and 2351/2004 (BOE of 24/12/2004) has given an important boost to the Spanish industrial activity related to solar thermal power plants.

The bonus of 0,18 €/kWh established for the electricity produced with concentrating solar power plants in any of their three options (parabolic-troughs, central receiver or Stirling dishes), together with the possibility of gas hybridization up to a maximum of 12% - 15%, has consolidated the interest of industries and investors in solar concentrating technologies. The result of this interest is the promotion of 5 solar thermal power plants with central receivers and parabolic-troughs in Spain.

Medium Concentration:

With regard to parabolic-trough collectors technology, the technical and commercial maturity reached by solar power plants (mainly due to the valuable experience gathered by the SEGS plants in California) contrast with the lack of development in other fields that are also interesting for this type of solar collectors, such as industrial heat processes and air conditioning.

The lack of solar collectors and industrial equipments with adequate characteristics for this type of applications make an intense R&D activity necessary to achieve the same level of development than in electricity generation. Spain, like many other Countries located in the so-called Earth Solar Belt, have climatic conditions that make very attractive these other applications of parabolic-trough collectors.

If we add to this fact the experience gained by CIEMAT at the Plataforma Solar de Almería (PSA), it seems evident that at present it is convenient to work in the development of components for air conditiong and industrial process heat applications. For this reason, we are participating in Task 33/4 ('Solar Heat for Industrial Processes', SHIP; www.iea-ship.org/) of the International Energy Agency, to exchange experience and know-how with other international institutions working on these fields.

At the same time, direct steam generation in the absorber tubes of the parabolic-trough collectors is being consolidated as a very important wayfor cost reduction and maintenance simplification of this type of solar collector plants. 

High Concentration:

Central receiver systems, after the scaling-up and demonstration phase, are now ready to start their commercial exploitation. Testing of more than 10 experimental small solar power plants of this type (0,5 - 10 MWt), mainly in the 80s of last century, served to demonstrate the technical feasibility of this concept and its capability to operate with large thermal storage systems. The biggest experience took place at the Plataforma Solar de Almería and in the Solar One and Solar Two plants in Barstow (California).

The R+D projects carried since then, have allowed components and procedures enhancement, so that a global efficiency of 23% (conversion from solar to electricity) is predicted for design point and a value of 20% for annual global efficiency. Nevertheless, the greatest challenge for central receiver systems at present is the start up of the first generation of commercial plants connected to the grid under market conditions and with routine operation. The three central receiver technologies that are preparing their first commercial plants are based on the use of molten salts, saturated steam and air-cooled volumetric receiver.

The high investment cost is still a handicap for the complete commercial exploitation of central receiver systems. The first commercial applications, which are ready to come out, still show a specific cost of) 3.000 Euro per kW of installed power, and an electricity production cost between 0,18 to 0,20 Euro/kWh. Cost reduction in the technology is, therefore, essential for the commercial expansion of these solar systems. Since we are well aware of this problem, PSA permanently keeps a R+D program related to central receiver technology, aiming at cost reduction and efficiency improvement.

Solar Fuels and Solarization of Industrial Processes:

As far as solar furnaces are concerned, the number of applications for these high concentration solar systems is increasing and new reactors are being developed to supply heat to industrial processes requiring thermal energy and to eliminate contaminants by using concentrated solar radiation. The main objective is to demonstrate the technical feasibility of solar furnaces to supply thermal energy to industrial processes that work at high temperature and are different from electricity production or metallurgical treatments.

At the same time, the control systems are being improved to keep the temperature and solar flux more stable at the focus.

Due to the valuable experience gathered during the past years and the experimental facilities available, PSA is at a leading position also in this solar field at present. Test facilities wil be soon improved with the start up of a new solar furnace with vertical axis and provided with a 3,5 m diameter high-quality concentrator, which is placed at the top of a 18 m tower. It is expected that a concentration of 8000X will be achieved with this new solar furnace because it does not need a mirror to rotate 90º the focus from the original vertical focal plane to the horizontal plane.

The concentration and nominal power of this furnace is thus increased. Since hydrogen is a clean source of energy, its production is considered of high priority in Spain and Europe at present. Nowadays, 95% of the hydrogen consumed is produced from natural gas and a great effort is needed to develop new non-pollutant production processes.

This is the goal of the new R+D projects in this field. The way how a economy based on hydrogen can be implemented is currently under discussion and there is not a global agreement about the feasibility of R+D projects to develop new technologies for massive hydrogen production.

The significant technical development of renewable energies in Spain, together with the searching of ways to increase the value of the national coal, are key factors when selecting hydrogen production processes suitable with our national interests, just as Iceland has approved an ambitious program to use geothermal energy for hydrogen production. Under the same premises, France has launched the Pan-H Program aimed at hydrogen production using nuclear energy.

As far as Spain is concerned, there are several R+D projects currently underway: there are several projects at the Plataforma Solar de Almería aimed at using solar energy for hydrogen production, the company EHN is investigating the use of wind energy for hydrogen and CEDER (Centro Español de Energías Renovables) is participating in the integrated European project CHRISGAS which is investigating the use of biomass for hydrogen production. There are also demonstration projects promoted by REPSOL with in-situ methane reforming in fuel stations; the Spanish pilot plant ELCOGAS (coal gasification) is also worthwhile to be mentioned here.

It must also be mentioned that CIEMAT, in collaboration with the French CEA and the Italian ENEA, is preparing the set up of the Experimental Platform SUSHYPRO, and a work plan to test hydrogen massive and clean production systems using thermal processes at high temperature and without CO2 emissions.

Following the strategic guidelines defined in SUSHYPRO, the Plataforma Solar de Almería has started several R+D projects in the last two years to develop new technologies for hydrogen production using thermo-chemical processes based on concentrated solar radiation (Projects PDVSA, INNOHYP y SOLTER-H). These activities are performed within the Group of Solar Fuels, which is included in the Unit of Solar Concentrating Systems.

Inauguration of new Fresnel collector at Plataforma Solar de Almería in Spain


9 July 2007

 Fresnel reflector at the Plataforma Solar de Almeriá
zum Bild Fresnel reflector at the Plataforma Solar de Almeriá

Solar thermal power plants offer great potential for a future sustainable energy supply, particularly in the Earth's "Sun Belt". An important condition for broader market penetration is lowering the cost of solar power production using new technologies. A new prototype called the "Fresnel collector" has been installed at the Plataforma Solar de Almeria (PSA, owned and operated by the Spanish research center, CIEMAT) in Spain to evaluate the potential of this new technology for contributing to cost reduction in solar thermal power generation.

The new Fresnel collector was  built with funding from the Federal Ministry for Environment and Nature Protection (BMU) under the direction of MAN-Ferrostaal. Among other institutions, the DLR's Institute of Technical Thermodynamics Department of Solar Research has been indispensable in planning this initiative.

New technology for the concentration of solar radiation

Fresnel collectors consist of numerous slightly curved mirrors which focus solar radiation onto a central absorber pipe. In this pipe, water can be evaporated and superheated up to 100 bar pressure and over 400 degrees Celsius. The thermal energy is then converted into electricity by a steam turbine. Measuring 20 metres by 100 metres, the 1-megawatt prototype is connected for testing to the already existing PSA DISS (DIrect Solar Steam) facility, which is based on parabolic-trough technology.

The Fresnel collector as an economical alternative to parabolic troughs?

 Fresnel reflectors and Parabolrinnen collectors in comparison
zum Bild Fresnel reflectors and Parabolrinnen collectors in comparison

Test operation of the new plant will verify whether Fresnel collectors represent an economic alternative to the current parabolic trough collectors. Advantageous costs are expected because of the simpler technology and the more economical flat mirrors. On the other hand, because it is less efficient, a Fresnel reflectors collector field will have to be larger than a field of similar capacity using parabolic-trough collectors. One of the main results of the Fresnel project is expected to be the economic balance of these opposite tendencies for investment and electricity production cost.

DLR's role

DLR researchers have been involved throughout the project, from its planning to its execution. DLR has been particularly influential in optical and thermal measurement of the Fresnel reflectors, the optimisation of the evaporation process, and the dynamic simulation and regulation of the steam cycle. Coordination of test operation of the pilot plant and cooperation during interpretation of test results are also major DLR tasks.


Related Contacts
Harald Pandl
German Aerospace Center

Geschäftsführung Stuttgart
, 40001
Tel: +49 711 6862-480

Fax: +49 711 6862-636

E-Mail: Harald.Pandl@dlr.de
Dr. Markus Eck
German Aerospace Center

Institute of Technical Thermodynamics
, Solar Research
Tel: +49 711 6862-429

Fax: +49 711 6862-747

E-Mail: Markus.Eck@dlr.de
Dr.rer.nat. Christoph Richter
German Aerospace Center

Institute of Technical Thermodynamics
, Solar Research
Tel: +34 950 387948

Fax: +34 950 365313

E-Mail: Christoph.Richter@dlr.de
URL for this article
http://www.dlr.de/en/desktopdefault.aspx/tabid-13/135_read-9671/

Solar energy even at night: DLR breakthrough with new heat accumulator


7 November 2007

Parabolic trough concentrator on Solar de Almería platform
zum Bild Parabolic trough concentrator on Solar de Almería platform

DLR begins operation of solar-generated steam energy accumulators at temperatures of more than 200 degrees Celsius.

Power from solar energy will in future play a key role in providing a sustainable energy supply. Solar power stations with direct solar steam generation are regarded as having the greatest potential in this field. But the solar energy produced in this way is not always available without interruption.

So-called heat accumulators are needed so that power generation can be extended to the night hours or times when there is heavy cloud cover. Thanks to scientists at the German Aerospace Center (DLR), it has now been possible for the first time for just such an accumulator to go into operation successfully.

Security of supply is also an important feature in the case of renewable energies. This means making energy generation independent of the variations in solar radiation. The heat accumulator developed at DLR can store the generated steam for many hours, and release it to the power station as required - at night, for example. It operates at the largest European test centre for solar energy, the Solar de Almería platform in Spain. The accumulator provides 100 kilowatts at temperatures of more than 200 degrees Celsius.

Breakthrough with latent storage principle

 Latent heat accumulator in Almería
zum Bild Latent heat accumulator in Almería

The steam accumulator is the result of the EU DISTOR (Energy Storage for Direct Steam) project started in February 2004. Solar Power Stations under the overall control of the DLR Institute for Technical Thermodynamics, a total of 13 partners from industry and research from five countries are working on the development of innovative storage systems for solar-powered steam generators. These storage systems will be designed to take the 200-300 degree Celsius steam generated by solar power, store it and release it again as required with a minimum of loss. So-called latent storage materials are used for this application. They are characterised by the fact that energy can be transported at an almost constant temperature from a solid to a liquid state and vice versa - a principle that has long been used in the low-temperature area with pocket hand-warmers, for example.

Until now however, no economically-attractive system has been devised for the kinds of temperatures encountered in solar-heat power stations. The reason has been the requirement for the scientists to achieve a sufficiently high energy density in the accumulator. The experimental results are now pointing to a sandwich concept with alternating layers of graphite foil and storage material. The concept has been submitted for a patent in collaboration with industry partner SGL and will form the basis for further development work..

 Solar energy research in Almería (Southern Spain)
zum Bild Solar energy research in Almería (Southern Spain)

Also of interest for industrial applications

In an associated project, researchers will extend their storage concept to a 1 megawatt facility. Temperatures of more than 300 degrees Celsius should be achievable, making the use of solar energy more attractive for some power station applications.

The concept of a latent heat accumulator also forms the basis for the use of solar heat in manufacturing industry. This is because industry needs a constant supply of energy to meet specific requirements. For example, solar-generated steam is suitable for use with processes in the construction materials and food industries.


Related Contacts
Harald Pandl
German Aerospace Center

Geschäftsführung Stuttgart
, 40001
Tel: +49 711 6862-480

Fax: +49 711 6862-636

E-Mail: Harald.Pandl@dlr.de
Rainer Tamme
German Aerospace Center

Institute of Technical Thermodynamics
, Thermal Process Technology
Tel: +49 711 6862-440

Fax: +49 711 6862-632

E-Mail: Rainer.Tamme@dlr.de
URL for this article
http://www.dlr.de/en/desktopdefault.aspx/tabid-13/135_read-10750/

Solar thermal power

MAN Ferrostaal enables the power of the sun to be utilized in large solar thermal power plants. For electricity, cooling energy and process heat. To achieve this, we work hand-in-hand with leading technology partners.

references

MAN Ferrostaal enters solar cooling market

MAN Ferrostaal expands its solar business

MAN Ferrostaal expands its solar business

09.07.2007 -

Following the approval of a joint venture with Solar Millennium AG, MAN Ferrostaal has further expanded its solar business with a 25% stake in Solar Power Group GmbH (SPG). SPG specialises in the construction of solar thermal power stations based on Fresnel technology and is the engineering partner for a new demonstration plan in Almería, which was officially opened on 9 July 2007. Fresnel technology is the most cost-effective of the four solar thermal technologies currently available and is intended to be used commercially in large-scale plants from 2008.


SPG has already built and operated two Fresnel test plants and has taken the technology a giant leap forward over recent years. Dr. Wolfgang Knothe, member of the Executive Board of MAN Ferrostaal, and responsible for the industrial plants business, asseses the shareholding as the logical step to expand these activities: "We are assuming that the solar sector will experience a considerable growth spurt over the coming years. We are therefore entering into strategic alliances with leading technology companies in the field of solar energy to position ourselves as general contractor for the construction of solar thermal plants." MAN Ferrostaal is planning to offer power stations, such as these, in Southern Europe, Near and Middle East, Africa, Asia and America, based on its global organisational structure and existing technology partnerships.


Renewable energies and fuels play a key role in MAN Ferrostaal's corporate strategy. MAN Ferrostaal is one of the first globally-active plant contractors to systematically develop and build power stations to produce solar power plants and plants for the production of bio fuels. As is the case in other fields of plant construction, MAN Ferrostaal does not develop the required technologies itself, but works with leading technology partners to turn projects into reality together with them.

Solar power is becoming cheaper

  • A demonstration plant using new technology is opened
  • Cost-effective with low construction and operating costs

09.07.2007 -

A new solar thermal plant was officially opened in Almería (Andalusia) in Spain on 9 July. The 1500 square metre demonstration plant on the Plataforma Solar is based on new technology, which allows solar thermal power stations to be built much more cost-effectively than in he past. At the moment a kilowatt hour of power from solar thermal power stations costs up to three times that of power from coal or gas power stations. Photovoltaic power stations cost around ten times as much. Using this new technology, electricity generated by solar power should have dropped to the same level as electricity from fossil-fuel power stations by the year 2020.


The demonstration power station was built by MAN Ferrostaal, in collaboration with Solar Power Group, the German Centre for Air and Space Flight (DLR), the Fraunhofer Institute (ISE) and PSE GmbH. The new plant is operated using so-called Fresnel technology, by which moving mirrors focus the sunlight onto an absorber pipe, positioned eight metres above the mirrors. Water in this pipe is heated to 450 degrees Celsius and turns to steam which then generates power by means of a steam turbine. The plant has a capacity of one megawatt and is modular in design. In large-scale power stations, several of these modules will be connected up in series.


All components are cost-effective standard components, which are available across the globe and thus create a high local added value chain. "Fresnel technology is comparatively simple to construct, cost-effective to procure and reliable to operate," commented Michael Pohl, Head of the Business Unit Solar Power at MAN Ferrostaal. "It has the potential to become the Model T of solar thermal technology."


The pilot plant is intended to demonstrate the commercial potential of the technology. The test period will run until 2008 and during this time all essential tests will be carried out as well as improvements to the plant. Thereafter the technology will be put into commercial operation. The success of the technology in practice and a positive evaluation of the tests are both prerequisites for large-scale Fresnel power stations becoming a reality. Only projects will be financed, where the technology is seen as being reliable and profitable.


Solar thermal power stations with a total output of more than 1,000 megawatts are already being planned in Spain and indeed some have already been built. The medium- to long-term prospects for this technology are very good. The price of electricity has on average doubled throughout Europe between 2003 and 2007 and a reversal of this trend is not anticipated at the moment. In light of rising oil and gas prices and the necessity to reduce CO2 emissions, the potential of solar thermal power stations is gaining significance in politics, economics and research.


"Solar power is well on its way to becoming the preferred energy source of the 21st century," Mr. Pohl went on to say. Sunlight costs nothing as a fuel and the only expenditure results from installation, staffing and maintenance. Security of supply plays a crucial role in the development process. The countries around the Mediterranean Sea in particular could benefit from a "solar boom" because it is here that sunlight is at it most intense and energy-hungry Europe lies close by. "From a purely mathematical point of view, solar thermal power stations would only have to be built on one percent of the Earth's desert regions to meet the total global electricity demand," states Mr. Pohl. "Key institutes are now assuming that by 2050 up to 25% of Europe's electricity demand could come from North Africa ? providing the political will exists."


This project is being run by reputable partners: MAN Ferrostaal is responsible for project management, operational management and maintenance of the project. The company will bring its experience in power plant construction to the table and will thus reduce the risk of mistakes being made. Solar Power Group, in which MAN Ferrostaal holds a stake, has already built two pilot plants and has brought the technology forward over several years, in terms of construction and build. For this reason, the Solar Power Group is assuming responsibility for the engineering of the plant. DLR, a leading institute in the field of solar energy, is responsible for measurement-taking and will also have a technical supervisory and support role in testing. The Fraunhofer Institute for Solar Energy Systems, Europe's foremost research institute in the field of solar energy, has made a significant contribution to the development of the coating for the absorber and will play a support role in the analysis and evaluation of the test results. The € 2.6 million demonstration plant is financially-aided by the German Federal Ministry for the Environment. The majority of the investment costs are borne by MAN Ferrostaal.

Fresnel technology: on the way to mass production

Friday, April 18, 2008

David Mills talks about the global political environment and his baseload solar thermal technology

Interviewing Dr David Mills former Sydney University academic now solar entrepreneur with US venture capital he has founded Ausra, a California based company that develops zero carbon utilities scale solar thermal power plants.

Listen to podcast Interview with Dr David Mills former Sydney University academic now solar entrepreneur with US venture capital he has founded Ausra, a California-based company that develops zero carbon utilities scale solar thermal power plants.

Dr. David Mills is known worldwide for pioneering compact linear Fresnel reflector technology and for his work in non-imaging optics, solar thermal energy and Photvoltaic systems. His laboratory at the University of Sydney developed and licensed the evacuated tube solar water heater technology and he also originated and ran the research program that in 1991 with colleague Dr QC Xiang, developed an absorbent coating now using evacuated tube receivers by China's largest solar company. He also developed and co-developed other commercial systems including the system that we know in Australia as Solarhart

Scott Bilby: As you know there was a change of federal government in Australia over the weekend. You previously said that you have no plans to build anymore stuff in Australian until our energy policy changes. Are you optimistic that it will change under a Labor government and do you have plans for Australia if it does?

Dr David Mills: While I think the Labor government has said it was going to change and I do find that encouraging. I think they are talking about a 20% electricity requirement for renewables by 2020 which is a good start. We are already starting to get some interest and early phone calls from Australia, from people who are recognising that there is a change possible project developers. So I think the election has started to trigger that process.

Matthew Wright: In terms of your technology which we are hoping will come down to a price competitive with what coal is generated out of or something just a little bit above that, what is it that you need to get to that point were you are mass producing concentrated solar thermal reflective fresnel panels and you are able to generate electricity at a price that can have that electricity dispatched into the market and used by consumers all over Australia and they don't see any difference? What do you need?

Dr David Mills:Basically time and to some incentive, but not necessarily a lot. What's happening here is really that kind of process in the United States where we have temporary incentives in place that are 30% tax credit, for example on large installations which help us through. And there may be some smaller incentives along the way in other areas, usually state-based.

Together these allow us to propose plants which are at a price point which the most aggressive utilities like Pacific Gas and Electric are able to contemplate using right away. That's typically around the 10-11 cent per kilowatt hour level here for generation. Now that's higher than the coal price in Australia definitely, but it's a beginning and the thing that allows us to drop that cost further is one, continued R&D. We have a very good R&D program here now that's well funded but secondly, building very large plants. Large plants are more efficient. More efficient turbines cost less; the more the banks have confidence in us the more they allow us to build bigger and bigger plants.

Matthew Wright: So, one of the electricity companies that you have done a deal with Florida Power and Light (FPL), they have an interest in one of the existing plants which has been operating for 20 years so they're confident in the actual idea of solar thermal. What's the difference, what have you go to offer compared to these Mahari desert plants and why are Florida Power and Light are happy to back you.

Dr David Mills: We are still in negotiation with FPL. But there are a couple of things. Our cost is definitely lower than those old plants, but it's also lower than the new versions of those plants, which are called parabolic trough plants. Ours isn't a classic parabolic trough and its different in design for a number of technical reasons. It's quite a lot cheaper to put the field down compared to those old designs. Secondly, we also have a very robust design. Its very strong and for the particular Florida case you have the occasional high wind as you recall and when a hurricane goes through you don't want the entire array blown away. The older parabolic troughs were not built to that standard and FPL knows this. The modern ones aren't either. They wouldn't be able to withstand a hurricane but we think ours can.

Matthew Wright: So, just for listeners who might not be quite up to where we're at with compact linear fresnel systems and with concentrating solar thermal, can you explain simply how your plant works?

Dr David Mills: The whole filed of solar thermal electricity makes use of the fact that you can use the sun's energy concentrated with a lot of mirrors on to a smaller spot and use that to boil water. That's what we do in the fields. Our solar field is a gigantic boiler basically for water. It converts water into steam and that steam is the same water that goes straight through to the turbine and runs the turbine. We are also developing storage systems which hold the heat overnight so that we can run those kinds of turbines on a night and day basis.

Matthew Wright: In terms of water requirements, we're having significant water stress in Australia right now. How does it compare to a coal power plants or nuclear power plants' water requirements?

Dr David Mills: Currently, it would be roughly the same in the same area. That is if wet cooling were allowed, that's the thing that gives you these giant cooling towers with steam coming out of the top, we could use that and the coal plants could use that.

Actually, when you look at where we situate our plants, our plants are mostly in very dry desert areas where there is not much cloud, and water availability in those areas is a big issue. So, our very first plant which was recently announced as a project by PG&E (Pacific Gas and Electric Company), its a 177 megawatts, has what's called dry cooling. That's a conventional technology which coal could use as well but its quite costly and it lowers our efficiency but it allows us to operate in those kinds of climates. We are developing advanced dry cooling which will be much cheaper and will also be much more efficient, but it's one of the side R&D projects we have.

Matthew Wright: We at Beyond Zero Emissions have heard from Keith Lovegrove at ANU (Australian National University) that an area 35km x 35km in length and width could actually power Australia's electricity requirements at the moment. In doing so, what sort of locations in Australia would you expect plants to make up that 35km x 35km to be located. Would it make up the north of the Great Diving Range in Victoria, west of New South Wales, what sort of areas?

Dr David Mills: Most of the people live in the east and that's the kind of location you would be looking at, so perhaps starting in Mt. Isa in Queensland, proceeding through Moree and Cobar and then down maybe to Mildura, that sort of region. That's prime solar site. The main issue is really grid access. If you have a large enough electricity grid line going to the place of interest, once you do, practically all that area is useful.

Matthew Wright: So, would you be a proponent of using the new high voltage DC technologies to bring the power more efficiently into consumers?

Dr David Mills: I would and certainly here in the United States without a doubt because here the solar energy is concentrated in the south west corner, that's the richest part, although you could generate all across the south of the country right to Florida. But there are large parts of the country in the north east where the sun isn't nearly strong enough for our purposes and it's much cheaper to generate in the sunny areas and have a long, high-voltage link to those areas. But, in Australia it's a somewhat different situation where you have the population on the coast, hugging the coast all the way around, and perhaps in each areas all you need is a straight line going inland until it gets sunny which might be much shorter than the equivalent United States link.

Matthew Wright: We've heard a lot of spin from our former federal government, and even some members of the new government, around hypothetical clean coal technologies and how Australia was going to shoot above its weight and be developing technologies that aren't yet here and exporting them to China. What's China like for these technologies and could we actually be using your expertise, the ANU's expertise, the expertise from Victoria, and exporting that to China?

Dr David Mills: We can. I've already been involved in an exercise with China through Sydney University and dealing with China with regard to IP and getting the royalties back is quite an issue. I think its still being worked out. Nevertheless, the resource situation in China clearly favours solar thermal far above any other resource. It's just like the United States. There's a large western desert and a concentration of the population in the east. The electricity grid is roughly the same size now, and so if you're going to build a very large installation, or series of installations in the United States, you could easily to so in China. Arguably, the need in China is more desperate and the local pollution is terrible and it is a big issue with the people there. So, we've had contact with people in China at a very high level and there is no doubt they want the technology but our issues are making sure it's fully developed before it goes there.

Matthew Wright: There's report being written by Professor Ross Garnaut in Australia. It's sort of like a mini-Stern Report and they're looking at the economics of climate change. Is it possible that a company like yours could contribute something to that report so that they can see that the costs are likely to be lower than hypothetical clean coal and that the Labor party can afford to actually go for the right kind of targets that are required to address catastrophic climate change that we are likely to be seeing?

Dr David Mills: We are in a market situation where there is not a lot of enthusiasm inside the company for actually giving figures to the public about potential costs, but we do state very clearly that it is our intention to compete with conventional coal and my guess is that it would happen in the United States in about the timeframe of 2011 roughly. We will probably get to the plant size where that's possible.

And conventional coal is cheaper by far than coal with sequestration. Coal with sequestration usually requires at least an advanced form of coal technology which happens to be actually more expensive than our solar plants and then on top of that there's the sequestration that's unproven.

So it's not just a costs argument. It's actually a validation that has to take place. Solar thermal's been proved for many years but nobody has successfully proven a coal sequestration plant. There are a lot of people who state in fact it doesn't work or has great dangers associated with it from leakage.

And the final thing is that by the time they get one operating which will be in 2020 and we really have to have a lot of capacity down by that time, so that's an inappropriate time to begin.

Matthew Wright: With the Labor party's announcement of $500 million, pretty much for 'from research to deployment' sort of funding around solar technologies; is that the sort of money that you guys could tap into to start concurrently working in Australia, and not just focus in the United States?

Dr David Mills: Yes. As we said we are already starting to get enquiries from Australia. Our smallest offering now is 175 megawatts and its square mile in terms of the units that they use here, about 2.5 square kms. That would probably cost around about $700m for just one plant. So, the difference that it makes to us is, it might be welcome especially the first plant in Australia, but I think you can see that if you're really serious about putting in a large amounts of capacity, we need something more than a one-off gift, if you will. There has to be some change in the structure of how you value clean energy.

Matthew Wright: Exactly. We'd hopefully encourage our government to take that on. We actually, at Beyond Zero Emissions, believe in taking all our sectors of the economy to near zero emissions beyond 2020 and then using a means like terra preta, which is an agrichar method to sequester carbon in soils, to actually draw down atmospheric carbon so the net result is that we start lowering our atmospheric carbon levels.

If the Australian government, and there'd be an international consensus around this, decided that this is really serious, we need to treat it like the end of slavery or the advance of the Nazis towards Great Britain, how quickly could your company ramp itself, could you envisage that, if you had to build thousands of megawatts of capacity, if you had to build 35km x 35km of capacity?

Dr David Mills: We are looking in that time frame at fairly similar figures. That doesn't phase us at all. But usually in larger countries. Because, what we have is a situation where even though the Earth is more important than anything, countries will resist taking recently installed infrastructure and suddenly root it out and put something new in. The cost to society would be very large and there would be serious problems about the availably of turbines for example. Right now there is a three year back up on the delivery of turbines. So, if we wanted to do that we would be sitting on our thumbs waiting for three years before we even start.

So, there are actually structural problems in trying to proceed beyond a certain range. That being said, I'm very much aligned with you in the need to move quickly. I just think we have to be a little bit realistic and say that might not take 10 years, but we could probably certainly do it in 20-30 as a continuous program. Even then it would be an aggressive program.

There are examples of this happening in the past in terms of the rate of technology change. There was a huge amount of gas combined cycle plant that we did from 1995 to 2005, especially in the United States. And the rates there are such that it is quite possible to imagine solar doing the same thing over about 20 years and changing over the entire mix, but only if the funding is available and only if society really wants it.

Matthew Wright: There's a very, very small scale pilot plant at the Liddell Power Station in NSW. Are there many sites like that that could be suitable? Then you won't have to worry about that problem of being able to get steam generators. If you could supplant most of the coal use, you could you use their existing steam generators, or are they not really that suitable?

Dr David Mills:They are not really that suitable. Liddell itself is an old plant and it would be hard to see it, I'd imagine, working beyond say 2015. So its going to be replaced anyway by something so you're better off replacing it with a new solar plant.

So, I don't think that's a particularly good example. I understand what you're saying, but the actual change over of existing plants, while we can make some changes, they're limited for a number of technical reasons. In the case of coal plants they use a completely different turbine than we do and operate at a different temperature range. We would have to use another kind of solar thermal technology to provide those kinds of temperatures, which is possible, which can be done.

When you look at the expansion of the electricity industry and the rate at which its expanding around the world, the first step is to stop that expansion in coal-fired capacity. That's the first thing to go for as fast as you can. And then, and yes, if we can put a few auxiliary solar plants around on existing coal plants to reduce the amount of coal, that's also a good thing to do. We will probably be doing that as a sub-strategy in the United States over the next year.

Matthew Wright: In terms of the technology itself, once you've done all of your R&D side, in terms of retooling and getting factories up and running for plant capacity to build reflectors, like manufacturing capacity, is that the sort of thing you can do in an African factory or is it like solar photo voltaic, like the solar cells we have on our roofs where it's almost computer technology? What's the manufacturing process? Is it that complicated?

Dr David Mills: No, it's not that complicated and it is able to be distributed around the Earth. I don't think there would be many countries were this couldn't be put in. In other words, you would ship a commodity like steel or glass to that site and from then on the manufacturing would take place. I think that's all right. We have a couple of special components such as coated tubes that we use for the absorbers which would have to come from a central site, but those are relatively small in the amount of material compared to the rest of the plant. Also the turbines have to be shipped for Germany or Japan or the United States, wherever they're made.

Matthew Wright: Also, you're an expert in optics. Next week we are hoping to speak to Wieslaw Maslowski whose from the United States Post Graduate Naval School and he's going to tell us how he expects the Arctic ice summer extent to be completely gone by 2013. That's four and a half million square kilometres of light. I'm not quite sure how much that reflects back out to the atmosphere, out to space, but I think its a high proportion above 80%. What do you think that heating load is like, given that you can run Australia's power on 35km x 35km of your solar troughs?

Dr David Mills: Are you saying that we would produce heat?

Matthew Wright: No, I'm saying that in terms of the sun no longer reflecting off the Arctic ice cap, because that's what the United States Post Graduate Naval School guy is saying...that we're going to lose that reflectivity. We're pulling a lot of heat into the globe, are we?

Dr David Mills: That's right. It will have a big effect. I mean, I can't see how you can avoid that effect except by producing some sort of cloud over the top to stop the beams from reaching the ocean in the first place. And so you can probably do a calculation fairly quickly on how much extra power that is, and that would undoubtedly be colossal.

We believe that just our solar collectors can power the United States grid in a space which is about 145km on a side, and that's enough to power the entire United States. I think you're talking about ice quantities or areas which are much higher than that, so these sorts of natural measures in nature dwarf anything that we do in terms of our technology.

Matthew Wright: So, in that case, and obviously you're on a mitigation side, will we bankrupt ourselves with that adaptation when you start looking at those sort of positive feedbacks and those sort of points that we're crossing in terms of going down towards dangerous climate change. Is it mitigation or adaption, and can you just go down the adaptation root like the previous Liberal Government was advocating?

Dr David Mills: No, I think that certainly we have to change our ways and the faster we do that the better. But what I, and probably nobody else knows, is it fast enough? Let's say we have a Marshall Plan for solar energy around the world and we install these things in 15 to 20 years. Is that actually fast enough, or is there going to be positive feedback which causes the temperature excursion anyway because of the pollution that's already gone into the atmosphere? I don't think anybody can quite answer that question yet. But if it did happen, it would be serious and if there were a mitigation strategy that could assist, a replacement strategy for conventional plant, then I guess I would be in favour of that otherwise we still have a problem.

Matthew Wright: Okay, we will have to leave it there. We thank you very much for joining us today and really appreciate it.

Dr David Mills:Pleasure.

Matthew Wright: We hope it was good for you as well.

Dr David Mills: My pleasure.

Matthew Wright: I think our listeners will be pretty interested in that and really keen to know that there is a solar technology out there that we can use to replace a lot of farms that are going to the wall that happen to be near the electricity grid, those farmers can know farm solar power, so that's really great.

Dr David Mills: In fact, our first plant in California is exactly that. Its land being sold by farmers for income. So, it's interesting that you say that. It seems to be a pattern that's emerging.

Matthew Wright: That's just fantastic and I think that the farmers will be really proud that their land is now being used valuably for society going forward rather than just abandoning it.

Matthew Wright: That was Dr. David Mills. He now works with Ausra, which is a company he founded and it's been great speaking to him and over to Scott.

Scott Bilby: If you would like to find out more about Ausra, you can visit their website at www.ausra.com

To find out more about issues relating to climate change you can visit us at beyondzeroemmissions.org

Matthew Wright: We are just about ready to say goodbye. I would encourage listeners to check by our website.

This week there has been some pretty amazing stuff. Obviously the whole paradigm has changed now. Before we were tackling a government in denial and now we're moving forward with a government that accepts climate change and is making it a centre piece. But what listeners have to realise is that the effort really starts now, the fight starts now, because this government's likely to put economics ahead of environment and if we keep going down adaptation route we will end up bankrupting ourselves so mitigation is really important here. Mitigation means jobs, it means jobs in solar technology, more jobs than coal gives us, it means healthy cities, healthy lifestyles because there is less airborn pollution, local pollution from cars and coal power plants, so I'd like everyone to get active, get engaged because that's what Beyond Zero Emissions is about. Whether it's joining your local climate change action group or coming in and helping us, we'd really appreciate your support.

Listen to podcast

Links for further reading

Ausra homepage

Study: Solar Thermal Power Could Supply Over 90 percent of U.S. Grid Plus Auto Fleet

Download Peer Reviewed Study
Download Slide Presentation of Study

Youtube Interview with Dr Mills

Youtube Presentation - John O'Donnell of Ausra, Inc. at Power Play workshop

John O'Donnell at Going Green 2007

Youtube - ABC 7:30Report Ausra - David Mills and Vinod Khosla

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