the parabolic trough power plants andasol 1 to 3

The parabolic trough power plants Andasol 1 to 3 The largest solar power plants in the world –Technology premiere in Europe

Andasol 1 to 3

3Andasol 1 to 3

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Table of contents

Solar energy and solar-thermal power plants

The first parabolic trough power plants in Europe – the world’s largest solar power plants: Andasol 1 to 3

Regulatory framework in Spain

Project partners

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Solar energy and solar-thermal power plantsEurope’s energy supply today is highly dependenton the availability of low-cost, conventional energysources such as natural gas, oil and coal. The generalpolitical consensus is that that the energy-produc-tion system now desperately needs to be over-hauled. The reasons for this are well known. Oiland natural gas supplies are limited. Other sourcesof fuel such as uranium or coal are also finite. Inaddition, conventional energy production causesglobal warming which is a result of greenhousegas emissions, primarily carbon dioxide.

Rising energy consumption worldwide is increas-ing the severity of this development; the Inter-national Energy Agency (IEA) estimates that by2030, consumption will increase by 50%. Further-more, a World Energy Council study estimates anincrease of 70% to 100%, by 2050. Energy savingmeasures such as increasing the efficiency ofelectronic devices and machines could ease thesituation. At the same time, energy around theglobe needs to be produced on a sustainable basis,which can only be achieved through the extensiveuse of renewable energy sources.

Each year, the sun sends over a billion terawatthours of energy to the Earth, which is equal to60,000 times the world's electricity needs. From amathematical perspective, less than three percentof the surface area of the Sahara would be sufficient

to meet to the world’s energy demand with solarpower plants. In this way, the solar radiation thatreaches the earth’s surface every day offers farmore potential than any other renewable energysource. Solar energy can be utilized by differentmeans. In Germany, photovoltaic arrays are usedprimarily for power generation and solar-thermalcollectors for producing hot water. The solar-thermal principle i.e. solar heat usage, offers manymore far-reaching possibilities. Solar-thermalpower plants transform heat from the sun intoelectricity. This is done in large-scale powerplants with a capacity of up to 250 megawatts perplant. The technology has an important advantageover some other forms of renewable energy suchas photovoltaic or wind energy in that thermalenergy can be stored far more cost-effectively andefficiently than electricity. By using thermalstorage, solar-thermal power plants can providepower on demand, both when the sky is overcastand at night. In this way, electricity productioncan be achieved almost round the clock in summer.In the long-term, fossil-fuel power plants arebeing replaced. Until the fossil fuel power plantbecomes obsolete, solar-thermal power plantscan be combined with conventional power plants(hybrid operations) to reduce climate-damaginggreenhouse gasses.

50,000

45,000

42,500

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37,500

35,000

32,500

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27,500

25,000

22,500

20,000

17,500

15,000

12,500

10,000

7,500

5,000

2,500

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Studies

Greenpeace/ESTIA 2005

Sarasin 2007

Greenpeace EREC 2007

US Department of Energy

IEA min.

IEA max.

2010 2020

= 400 Power plants

= 100 Power plants

= 900 Andasol-type power plants

F O R E C A S T

Additionally, solar-thermal power plants can beused for other applications, such as combiningthem with desalination plants to produce notonly solar power in sunny regions, but also help-ing to provide valuable drinking water, which isoften a scarce commodity in these regions. Further-more, the plants are also suitable for producingsteam, heat, or cooling for industrial applications.

Market forecast

Today, solar-thermal power plants require statesupport e.g. in the form of feed-in tariffs, to securetheir competitive viability. In a few years thetechnology will probably no longer require suchsupport and will thus be able to compete withfossil-fuel peak-load and medium-load powerplants. Larger market volumes and technical ad-vances will also lead to lower costs for components.

Studies by renowned institutions have indicatedthat strong growth is predicted for solar-thermalpower plants. The overall capacity of installedsolar-thermal power plants will increase to at least20,000 megawatts by 2020 (see graph below) .

The majority of the global energy demand can be covered in thelong run through the use of solar energy.

The German Advisory Council on Global Change (WBGU) hascreated a primary energy mix forecast for the year 2100 (source:WBGU 2003).

The “MED-CSP” study by the German AerospaceCenter (DLR) assumes that by 2025, most renew-able energy sources will be cheaper than thosesupplied by fossil fuels. By the middle of thiscentury, renewable energy will have largely re-placed fossil-fuel based sources of energy in theMediterranean region. Though the studyendorsed a general mix of renewable energy, itindicated that solar-thermal power plants willplay the most important role. According to theDLR study, their capacity in the Mediterraneanregion will be as large as the combined wind,photovoltaic, biomass, and geothermal powerstations. Solar-thermal power plants can produceup to double the amount of energy when equippedwith thermal storage.

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Die Investition in Spanien

Primary energy use [EJ/a]

Sample global energy mix in the year 2100Source: German Advisory Council on Global Change, 2003

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Geothermal

Other renewable energies

Solar collectors

Solar thermal

power plants and

photovoltaic systems

Wind

Biomass (modern)

Biomass (traditional)

Hydroelectric power

Gas

Coal

Oil

F O R E C A S T

Andasol 1 to 3

Spain has played a pioneering role in solar-thermalpower plants in Europe over the last few yearsand is now the largest market. The unanimousopinion of market participants is that the nextlarge market will be the south west of the UnitedStates. There, the first commercial power plantsworldwide have been producing solar electricityreliably for over 20 years. Further plants are nowunder construction in North Africa and the MiddleEast. The first projects are also being developed inAsia. Solar Millennium in China has signed a frame-work agreement with companies in the region forthe construction of a total of 1,000 MW of solar-

thermal power plant capacity. The Solar MillenniumGroup is also involved in the construction of Egypt’sfirst parabolic trough power plant.

The amount of energy provided by the sun is im-mense and it can be used in a targeted way. Thefollowing effect is familiar to everybody. Focusingthe sun's rays with a magnifying lens allowstemperatures to be achieved that can set paperalight. Parabolic trough power plants create sameeffect and focus the sun’s rays using parabolicmirrors. This allows solar energy to be utilized ona large scale, so that oil, gas, coal and nuclear powercan be replaced long-term as sources of fuel.

An intercontinental electricity federation wouldbe able to connect the best renewable energysources in Europe with one another, e.g. solarenergy from North Africa would be connected withoff-shore wind parks and Scandinavian hydro-electric power plants. A low-loss high-voltage net-work using high-voltage direct-current trans-mission could provide efficient transport of electric-ity. The German Aerospace Center (DLR) concludedits study of electricity grids by stating that, “By2050, twenty lines in the MENA (Middle East andNorth Africa) could use solar power to supplyabout 15% of European electricity needs”.

Technology

Solar heating is the term used to describe theconversion of incidental solar radiation to heatenergy. In Germany, this principle is utilized toproduce hot water using roof collectors. In sunnycountries, the concentration of direct radiation inparabolic trough power plants leads to such hightemperatures, that the energy can be used insteam turbines to produce electricity. In solar-thermal power plants, steam is produced byconcentrated solar radiation instead of burningfossil fuels. In contrast to power generated by

wind or photovoltaic sources, power derived fromsolar-thermal power plants can be supplied in acost-efficient and plannable way, thanks to theuse of thermal storage tanks or co-firing. Thus,solar power plants can also generate electricityafter sunset.

Parabolic trough power plants are proven andreliable technology

The main element of a parabolic trough powerplant is the solar field, which provides steam forconventional steam turbines. It consists of nu-merous parallel rows of solar collectors, arrangedon a North-South axis. They then follow the pathof the sun from east to west. The reflectors consistof parabolic mirrors made from extremely transpa-rent, silver-coated glass. They concentrate theincident solar radiation 80-fold, focusing it ontoan absorber pipe in the focal line of the collector.The metal structure, mirror elements, andabsorber pipe together form a high-precisionoptic device. The absorption pipe contains a heattransfer medium, which is a temperature-stablesynthetic oil in a closed circuit that can be heatedto temperatures of up to 400 degrees Celsius.Once heated, the oil is pumped to a centrallylocated power block, where it flows through a

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Solar energy and solar-thermal power plants

The amount of energy provided by the sun is immense and it can be used in atargeted way. The following effect is familiar to everybody. Focusing the sun's rayswith a magnifying lens allows temperatures to be achieved that can set paperalight. Parabolic trough power plants create same effect and focus the sun’s raysusing parabolic mirrors. This allows solar energy to be utilized on a large scale, sothat oil, gas, coal and nuclear power can be replaced long-term as sources of fuel.

7Andasol 1 to 3


heat exchanger. The remainder of the process issimilar to the steam cycle used in conventionalpower plants. The steam produced by the heatexchanger is used to drive a turbine connected toa generator. The steam in the turbine condensesback into water and the water is then re-circulated.Up to now, parabolic trough technology has beenthe only large-scale solar power plant technologyto have proven reliable over a longer period oftime. The power plants are above-average in termsof annual efficiency with very low power produc-tion costs in relation to other solar technologies.The first commercial parabolic trough power plantswith a total capacity of 354 MW have alreadybeen in operation for over 20 years in California’sMojave Desert (USA). The Andasol Power Plants insouthern Spain are the first parabolic troughpower plants in Europe. In terms of collector area,they are the world’s largest solar power plant inthe world to date.

Low energy amortization periods

The energy amortization period is used to measurethe time a power plant needs to produce theenergy required to build the power plant itself.Solar thermal power plants have a relativelyshort amortization period of about five months,which is low compared to other forms of renew-able energy. The time required for wind power is4 to 7 months and 2 to 5 years are needed for photo-voltaic power plants. In addition, solar-thermalpower plants distinguish themselves in that theyrequire little specific surface area calculated interms of the amount of energy produced per squaremeter.

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Data about the Andasol-power plants (Data per power plant)

Location

Project names Andasol 1, Andasol 2, Andasol 3

Location 10 km east of Guadix in the municipal area of Aldeire and La Calahorra in the

Marquesado del Zenete region, Granada Province

Terrain approx. 195 hectares (1300m x 1500M), North-South Axis

High-voltage line access Connection to the 400kV line near Huéneja (about 7 km away)

Solar Field

Parabolic trough technology used Skal-ET

Size of the solar field 510,120 m2

Number of parabolic mirrors 209,664 mirrors

Number of receivers (absorption pipes) 22,464 pipes each measuring 4 m

Number of solar sensors 624 sensors

Annual direct standard radiation (DNI) 2,136 kWh/m2a

Solar field efficiency approx. 70% peak efficiency, approx. 50% annual average

Heat storage capacity 28,500 t salt for 7.5 peak load hours

Power plant capacity

Turbine capacity 49.9 MW

Annual operating hours ca. 3.500 Volllaststunden

Forecast gross electricity volume about 180 GWh

Efficiency of entire plant approx. 28% peak efficiency, approx. 15% annual average

Estimated lifespan at least 40 years

The first parabolic trough power plants in Europe – The largest solar power plants in the world – Andasol 1 to 3

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Aw

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The Andasol power plants are being built in thesouthern Spanish province of Andalusia. Andasol 1is the first parabolic trough power plant in Europeand the largest in the world to date, when viewedin terms of its collector area of over 510,000 squaremeters. Three similarly constructed power plants

are planned for this site. Each with a capacity of50MW, they will produce enough combinedenvironmentally friendly solar electricity for up to600,000 people. This will reduce carbon dioxideemissions by 450,000 tons a year.

9Andasol 1 to 3


Andasol power plants honored with the EnergyGlobe Award at the European parliament

For its initiating and development of the Andasolpower plant projects (the first parabolic troughpower plants in Europe), Solar Millennium wasawarded the Energy Globe Award in the “Fire”category in May, 2008. The worldwide renownedenvironment prize honored the projects' innovativecharacter and its major contribution to climateprotection. The Energy Globe Award in the “Fire”category is awarded to innovative projects forenvironmentally-friendly power production. Theawards ceremony took place in the Plenary Hall of the European Parliament in the form of an inter-nationally broadcast television gala in Brussels.The fact that all three European institutions wererepresented by their presidents gave the eventspecial importance: José Manuel Barroso (EUCommission), Hans-Gert Pöttering (EU Parliament)and the Slovenian Prime Minister, Janez Jansa (EUCouncil) were all present at the event. MichailGorbachov received an Energy Globe Award forhis life’s work. Former UN General Secretary, KofiAnnan and singer Dionne Warwick appeared asprominent speakers during the ceremony. Since1999, the Energy Globe Award has been given toprojects which protect natural resources or userenewable energy sources. Around 800 projectsand initiatives enter the competition each year inthe categories of Earth, Fire (electricity), Water,Air and Youth.

Dr. Henner Gladen and Thomas Mayer, Board Members of SolarMillennium AG, pleased about the Energy Globe Award

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Location

The Andasol power plants are located on the Guadixplateau in the Spanish province of Granada withinthe municipality of Aldeire. The site’s coordinatesare 37°13' N; 3°04' W. The site is located at anelevation of between 1,090 and 1,100 metersabove sea level. The area has been excavated andis free from any shading. The site is located direct-ly on the A92 motorway running from Guadix toAlmeria. No residential buildings are locatedadjacent to the site of the power plant. The closesttown is La Calahorra. According to a geo-techno-logical study carried out in 2003, the ground isvery solid.

Solar resources

The decisive factor for the economic viability of asolar investment is the annual electricity produc-tion, which depends to a great extent on the solarradiation resources locally available. The strengthof direct solar radiation, i.e. radiation which pene-trates the atmosphere unscattered, is relevant forparabolic trough power plants and thus importantfor focusing solar thermal technology. In order toevaluate the intensity of solar radiation at theAndasol power plant’s site, measurements weremade on site and the evaluation of long-termsatellite data was carried out. An RSP Sensor (Rotat-ing Shadowband Pyranometer) was used in theon-site measuring station. It is a special measur-ing device that determines global solar radiationas well as the direct solar radiation. In addition,meteorological stations were used to measureambient temperature, humidity, wind directionand wind speed. The German Aeronautics Center(DLR) regularly checked the sensors in use todetermine and ensure their accuracy. The sensorswere also calibrated with a precision measuringstation. The measuring stations were speciallydeveloped by Solar Millennium for determiningthe suitability of potential solar-thermal powerplant sites. They are characterized by a high

11Andasol 1 to 3


degree of accuracy in measurement, independentoperations, and low maintenance. The radiationdata was collected at one-minute intervalsproviding the project team with very precise datafor the project development. Renowned researchinstitutes around the world have put in requestsfor Solar Millennium's meteorological stationsand they are now being used at about 40 sitesaround the world. The meteorological measuringstation at the Andasol site has been in operationsince March 2000. The radiation values measuredare entered in the graph below. In addition to thelocal measurement data, satellite data wasincluded to determine a long-term mean valuefor solar radiation at the site. Satellite data fromthe DLR for the period from 1983 to 2001 was alsoevaluated and then the direct radiation wasextrapolated from it. Using the satellite data andthe locally measured data, a long-term mediumvalue of 2,144 kWh per square meter annuallywas extrapolated.

The measuring station at the Andasol site willcontinue to be in use after the commissioning ofthe power plant, providing information for plantoperation, like wind speed, for example.

One of Solar Millennium AG's meteorological measuring stations

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Water availability

The power plant’s site is unique in Spain for itscomparatively above-average water availability.The Sierra Nevada mountain range which sur-rounds the site is the primary source. The Andasolpower plant’s annual water needs are aboutequal to the water which would be needed for thecultivation of crops such as wheat on the powerplant’s site. The plant requires about 870,000 m2

of water per year, which is mainly used for cool-ing the steam circuit, i.e. from the vaporization ofwater in the cooling towers. The water needs areprimarily met with ground water extracted fromwells on the site.

Technical description

In parabolic trough power plants, trough-shapedmirrors in the solar field concentrate the sunsrays by a factor of 80 onto an absorption pipe inthe focal line of the collector. In the pipes, a heattransfer fluid circulates in a closed circuit which isheated to 400 degrees Celsius by the concentratedsolar radiation. The heated fluid is then pumpedinto a centrally located power block and flowsthrough a heat exchanger. In this way, steam isgenerated which (similar to conventional powerplants) powers the turbine using an electricgenerator. The integration of a heat storage allowsthe power plant to function at full capacity bothon overcast days and at night. The Andasol powerplants each consist of a solar field, a thermalstorage tank, and a conventional power plantsection.

Solar field transforms solar radiation into heat energy

An Andasol power plant has a solar field thatcovers 510,120 square meters. The parabolictroughs are set up in 312 collector rows which areconnected by pipes. The rows are set up on anorth-south axis and follow the course of the sunfrom east to west. One row is made up of twocollector units. Every collector unit has its ownsolar sensors and hydraulic drives, which allowthe mirrors to track the position of the sun. Thecollector units each have 12 collectors, which are12 m long and 6 m wide. Every collector has 28mirrors and 3 absorption pipes. An Andasol powerplant requires 7,488 collectors. Specialists assembleand check these collectors photogrammetricallyto determine their precision in specially-con-structed factory buildings before the collectorsare brought to the field and anchored.

1. Solar field, 2. Storage, 3. Heat exchanger, 4. Steam turbine and generator, 5. Condenser

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Efficiency

Solar field

Peak efficiency ca. 70%

Annual average ca. 50%

Turbine circuit



Entire plant



13Andasol 1 to 3


Thermal storage tanks allow for plannedelectricity production

A portion of the heat produced in the solar field atthe Andasol power plant is not transferred to thesteam circuit but stored as liquid salt. A mixtureof about 28,500 tons of potassium, sodium, andnitrate salts are heated during the day when thesun is shining and can then provide the necessaryheat to operate the power plants at night or duringovercast periods. In addition, the molten saltmixture has an outlet temperature of about 290degrees Celsius and can be heated up to 390degrees Celsius. Each power plant has two tanks,which function like a thermos flask and are ableto assure that the salt maintains its temperatureover several weeks. A full thermal salt reservoir

can be used to operate a power plant turbine forabout 7.5 hours. This allows for almost round theclock operations in the summer months. In orderto fill the thermal storage tanks while simultan-elously operating the turbines, the power plant’ssolar field is significantly larger than that of apower plant without a storage tank. The annualoperating hours of the solar power plant at peakload operation can be almost doubled in this way.

Solar field Storage system Power block

»Hot«salt tank

»Cold«salt tank

Steamturbine

Generator

Cooling tower

6h 9h 12h 15h 18h 21h 24h 3h 6h

Solar field Storage system Power block

»Hot«salt tank

»Cold«salt tank

Steamturbine

Generator

Cooling tower

6h 9h 12h 15h 18h 21h 24h 3h 6h

The thermal storage system is loaded during the day.

During the night, the power plant can be operated with the stored energy.

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More than two decades of experience withtechnology in California

In California, nine parabolic trough power plants(SEGS I-IX) were built between 1984 and 1990;creating a total capacity of 354 MW. Up to now,these nine power plants have produced morethan 12,000 GWh of electricity, and netted over $2billion from feeding electricity into the Californiapower grid. This solar electricity volume representsa significant portion of the solar power volumecurrently being produced throughout the world.The remainder is produced by hundreds of thou-sands of photovoltaic plants. The power plants inCalifornia's Mojave Desert have a proven long-term availability of about 99%. They also illustratethe long-term durability of the components andthe low operating and maintenance costs generat-ed by them. They are still operating successfullyto this day. The condition of the power plantsafter twenty years of operation is immaculate,with power plant operators predicting that theywill remain in operation for a very long period oftime (see image above). Solar Millennium useddata from operations and experience gainedwhen conceptualizing the Andasol power plants.This data was supplemented by the results of along-term study carried out by a consortium underthe aegis of Solar Millennium. In the Californian

plants, two rows of collectors were erected withfurther developed collectors which have been incommercial operation since 2003.

Size

The Andasol power plants each cover an area of195 hectares (about two square kilometers). Eachpower plant’s solar field has 312 collector rowseach with a collector area of 510,120 squaremeters (aperture surface). This is roughly equal tothe area of 70 soccer fields. Approx. 90 kilometersof absorption pipes and curved mirrors with atotal area of 580,500 square meters are also used.The difference between the collectors’ aperturesurface and the larger mirror surface area is dueto the curve of the mirrors. The construction ofthe Andasol power plants is practially identical.

Collectors

Mirrors and absorption pipes are precisely mount-ed on steel support structures which, takentogether, form the collectors. The metal supportstructure is anchored in the ground using a steelpylon. The hydraulic drives can adjust the 150meter long collector chains with a precision of upto a tenth of millimeter allowing them to followthe sun on its daily course from east to west alonga single axis. Computers in the control room areused to direct the power plant's collectors.

15Andasol 1 to 3

Information from each individual collector unit istransmitted during this process. The orientationduring sunrise and sunset is carried out automat-ically. 624 sensors in the solar field combine toguarantee the precise control of each collectorunit, allowing them to follow the course of thesun. Flagsol GmbH, Solar Millennium’s technologycompany from Cologne, developed and suppliedthe sensors. The company also designed and super-vised the solar field construction site. The collectorswere constructed to withstand the most extremeweather conditions. The entire solar field cancontinue operating normally in winds of up to13.6 m/s (about 49 km/h). Should wind speeds behigher, some of the collectors will be put in awind-protected “sleep” position. During gales, i.e.wind speeds exceeding 20m/s (about 72 km/h)power plant operations will be halted entirely. Atthe Andasol location, winds exceeding 14.5 m/s(around 52 km/h) in the period from 2000 to 2007were measured in less than 0.3% of the total day-light hours.

Advanced collectors

The Andasol power plants’ technology was testedin the SEGS power plants in Kramer Junction,California. About 4,000 square meters of advancedSkal-ET collectors are used in Andasol and werealso installed the SEGS V power plant was operat-ing. A long-term study proved that the Skal-ETcollectors are about 10% more efficient than theprevious generation of collectors.

Precise mounting of collectors

Precise mounting of collectos is decisive for theefficiency of the solar field. In an assembly line,the parabolic mirrors and the mountings for theabsorber pipes are attached to the steel supportstructure. The optical precision of the collectorswill be controlled by a photogrammetric device atthe end of the assembly line.

1. Reflector

2. Absorber tube

3. Metal construction

4. Pipe installation


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Turbines

Turbines, generators and plant periphery areconventional power plant components, similar tothose used in fossil fuel power plants. The Andasolpower plant’s turbine has a capacity of 50 mega-watts and is specifically designed to ensure reliableoperations during the daily start-up and shutdown of the plant. Siemens in Sweden constructedthe turbines for Andasol 1 and 2. MAN Turbo willsupply the turbines for Andasol 3.

Absorption pipes

The absorption pipes were conceived especiallyfor use in parabolic trough power plants. Theyabsorb the solar radiation reflected by the mirrors,transfer the solar energy into a heat transfermedium located in the pipe, which then transmitsthe heat into the steam circuit.

Schott Solar AG in Mainz, Germany and Solel SolarSystems Ltd. of Israel produced the absorptionpipes used in the Andasol power plants. Solel hasyears of experience producing absorption pipesand supplied the absorption pipes for the parabolictrough power plant built in California at the endof the 1980’s. Shott has also developed absorptionpipes for parabolic trough power plants in recentyears. Quality and capability have been shown

successfully since 2003 by a demonstrationcollector chain in California which was erectedunder the direction of Solar Millennium AG.Schott produces the absorption pipes for thepower plant in Mitterteich, Bavaria. Schottdeveloped a special glass for the direct transitionbetween glass and metal and the glass has thesame expansion characteristics as metal. Thisallows the absorption pipes to reliably withstandthe temperature differences between cold nightsand hot days.

This construction allows maximum absorption ofsolar radiation and simultaneously minimizes thereflex radiation of heat from the metal pipe. Anabsorption pipe is four meters long and composedof a multi-layered stainless-steel pipe, whichSchott Solar states has an absorption level of 95%and radiates 14% of its heat at temperatures ofaround 400 degrees Celsius. The steel pipe issurrounded by a vacuum-isolated concentricborosilicate glass cladding tube with anti-reflexcoating, which allows for over 96% penetration of solar radiation.

Approximately 22,500 absorption pipes are usedin each power plant. The challenge when it comesto the longevity of the tubes is the interfacebetween the steel and cladding tubes, which are

17Andasol 1 to 3


sealed to form an intermediate vacuum. The dif-ferent thermal expansion of the steel tube and theglass cladding is compensated by a metal bellows.

A heat transfer medium circulates in the pipes, theso-called heat transfer fluid (HTF). The capturedsolar radiation heats the fluid, which then flowsto the power block and through a heat exchanger,thus producing steam for the turbine. According tothe EU Dangerous Substances Directive 67/548/EEC,the fluid is classified as non-hazardous.

Parabolic mirrors

The parabolic mirrors are made of 4 millimeter-thick, silver-coated, curved white glass. The silvercoating has an additional protective coating. Themirrors follow the course of the sun and reflectsolar radiation onto the absorption pipe.

The Flabeg Group produced and supplied theparabolic mirrors for Andalsol power plants 1 and 2in its factory in Furth-im-Wald, Germany. Accord-ing to the manufacturer, they have a reflectivelevel of about 93%. Type RP-3 mirrors come in twodifferent sizes for the interior-mounted and theexterior-mounted mirrors with an area of 2.79and 2.55 square meters respectively. The powerplants each have a total of 209,664 mirrors in theircollectors. A laser scan checks each mirror’s curveat 1,000 measuring points per mirror.

The mirror is anchored at four points to the steelstructure. The mirrors, mountings and adhesives allhave the same expansion coefficient, guarantee-ing durability even under extreme temperaturefluctuations. The mounting elements are madefrom special ceramics giving them a high level ofmechanical strength and are non-corrosive.Flabeg has already delivered parabolic mirrors tothe existing facilities in California’s Mojave Desert.Recent samples have proven that, even after twodecades of use, a loss in quality can hardly be de-tected. Rioglass Solar S.A. of Mieres/Asturia, Spain,produced the mirrors for Andasol 3.

Storage tank

The Andasol power plants have a thermal storagetank allowing the power plants to provide schedul-ed power, thus the plants can operate even onovercast days or after sunset. The heat requiredfor this is stored in a molten salt mixture, which is60% sodium nitrate (NaNO3) and 40% potassiumnitrate (KNO3). Both materials are used in foodproduction as preservatives and as fertilizer. Theliquid salt thermal storage functions under atmos-pheric pressure and consist of two tanks per powerplant, measuring 14m in height and 36m in diam-eter. During the pumping process from the “cold”to the “hot” tank, the molten salt mixture absorbsadditional heat at an outlet temperature of approx.290°C, where it is heated to a temperature of

390°C. A full storage tank can be used to operatethe turbine for about 7.5 hours. Molten salt hasbeen used in different industrial applications forabout 609 years to date, e.g. in galvanizing. Sincethen, over 3,000 plants working with molten saltare in operation to date. Solar Two in Barstow,California served as the reference project for thethermal storage tanks in the Andasol power plantsbecause it had the same salt mixture – eventhough the storage tank was smaller. When thetime comes to decommission the power plants atthe end of their lifetime, the salts can be crystal-lized and removed in their raw state to be usedthereafter in other applications e.g. in agriculture.

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»Cold« salt tank »Hot« salt tank

Pump Pump

19Andasol 1 to 3


Supply point

The thermal storage tank allows the Andasol powerplants to supply electricity regularly into Spain’shigh-voltage electricity grid. Other renewableenergies like wind are not able to supply electricityin a plannable way and require reserve powerplants in order to maintain stability in the grid.Access for these non-plannable forms of energyinto the Spanish high-voltage grid is thus limited.As an expression of its approval of the advantagesoffered by solar-thermal power plants, the operatorof Spain's national grid, Red Eléctrica de España(REE), classified the Andasol power plants as“predictable” sources of electricity. This not onlyeased the permit process for granting access tothe high-voltage grid, but also made it possible toincrease the percentage of renewable energy inthe state's energy mix because of the stabilizingeffects of solar-thermal power plants. A substationhas been built near the town of Huéneja aboutseven kilometers southeast of the power plant sitefor feeding the electricity into the grid.

Power supply contracts

The Spanish energy supplier Endesa purchaseselectricity from the Andasol power plants in accord-ance with Spanish energy law, which states thatthe power plants are permitted to feed in a maxi-mum of 50 MW into the grid. The power supplycontract includes general technical standards andconditions as well as the implementation of pro-gramming and the after-sales service for electricityproduction.

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Regulatory framework in SpainSpain is highly dependent on imported energy.Almost all petroleum and natural gas as well as70% of its coal have to be imported. However, ithas more than enough of one of the most environ-mentally friendly and cheapest sources of energyin the world – the sun. The Spanish government'ssupport plan “Plan de Fomento de Energías Ren-ovables (PER)” envisions the expansion of solar-thermal power plant capacity to 500 MW by 2010.Spain’s Ministry for Energy and Industry wants toincrease the annual volume of electricity producedin solar-thermal power plants to about 4,000GWh, which is the equivalent of the capacity ofabout 25 Andasol power plants.

Government-guaranteed feed-in tariffs for solarthermal electricity

Spain, like Germany, sponsors renewable energywith feed-in tariffs, especially solar energy pro-duction. These funding regulations are the resultof Spanish Law 54/1997 dated November 27, 1997,pertaining to the electricity industry. This law isfurther specified by regulatory statutes in the formof Royal Decrees, the final being Royal Decree661/2007. Solar-thermal power plants have theirown feed-in arrangements, which differ from thefunding guidelines for photovoltaic plants.

The funding for solar-thermal power plants catersexplicitly to nominal capacities of up to 50 MWper power plant. Spain is now one of the mostattractive markets for the construction and opera-tion of solar-thermal power plants because of thestate-guaranteed funding regulations.

Unlike in Germany, the operator of a plant canchoose between two feed-in arrangements everyyear in Spain. He can decide between deliveringenergy at a fixed price, i.e. at a tariff that remainsconstant throughout the year or to sell the energyproduced directly on the day market, the futuresmarket or through bilateral contracts. Should theoperator choose the second variant, he will receiveboth the trading price on the market as well as anadditional premium.

Option 1 (fixed tariff): Solar thermal electricity receives a feed-in tariff ofEUR 0.278399 per kWh*.

Option 2 (market option): Solar thermal electricity is reimbursed with themarket price, which was up to 0.15841 per kWhfrom 2001 to 2007 at the spot market in Spain,plus an additional premium amounting to EUR0.262509 per kWh*. The resulting total reimburse-ment is limited to a maximum of EUR 0.355499*kWh. At the same time a minimum total reimburse-ment of EUR 0.262548 is guaranteed. The marketoption presents an opportunity for significantlyhigher income through the production of well-remunerated peak load electricity. This option isinteresting as soon as the adequate experience ofrunning a power plant has been gained and aprognosis overview predicting the volume ofsolar radiation is available (see the graphs below).

* The numbers stated correspond to the feed-in tariff for 2008 determined in the document“Orden ITC/3860/2007”, dated December 28, 2008. This annually updated documentcontains the tariff determined in the Real Decreto 661/2007 as well as the inflationaryadjustment also provided for in the Real Decreto.

Tariff version 1Fixed tariff

Tariff version 2Market option

27.8399 ct

26.2548 ctWith a marketprice below1.589 ct

35.5499 ctWith a market price over 9.299 ct

Feed-in tariff for one kWh*

35

34

33

32

31

30

29

28

27

26

25

Funding (price per kilowatt hour in the fixed tariffand the premium in the market option) is guaran-teed for 25 years. After 25 years, the feed-in tariffis reduced to 80% of the then applicable tariff.

The government-guaranteed feed-in tariff is an-nually adjusted to inflation, based on the Spanishconsumer price index IPC (Indice de Precios alConsumo). Until December 31, 2012, 0.25 percentagepoints of the relevant annual alteration in the IPCwill be deducted, and 0.50 percentage points willbe deducted thereafter.

Further conditions for feed-in tariffs

The directives governing Spanish funding policieswere set down in the funding policy plan “Plan deFomento de Energías Renovables (PER) 2005-2010”. Support is intended for the development of500 megawatt (MW) solar-thermal energy plantsuntil then. Since 2008, a new plan for renewableenergy is being prepared for the period thereafter(2011-2020). It will incorporate Spanish energydemand and will examine the reimbursementsystem for new projects. Royal Decree 661/2007as well as PER 2005-2010 are valid for the entirelifespan of all solar-thermal power plants alreadyoperating on the Spanish grid, like Andasol 1, forexample.

21Andasol 1 to 3


10.0

7

3.83

8

4.73

0

5.8

11

7.0

22

6.85

3

5.90

0

5.6

18

5.62

8

5.83

4

6.8

19

7.0

10

7.30

3

11.07

12.0

701.0

802.0

803.0

804.0

805.0

806.0

807.0

808.0

809.0

8

Euro cent per kWh

8

7

6

5

4

3

Average spot market price in Spain

The Spanish consumer price index (IPC) is the basis for the adjustment of the feed-in tariff.

2000

3,7 %

Average

2000 - 2007

3,5 %

2001

3,1 %

2002

3,7 %

2003

2,3 %

2004

4,1 %

2005

4,2 %

2006

2,4 %

2007

4,3 %

Source: Instituto National de Estadistica

** The hourly spot market price (here the average price over the last 12 months) is onlyrelevant for version 2 (market option). Source: Operador del Mercado Ibérico de Energia – Polo Español, S.A. (OMEL)

22

Project partners

Project developer: Solar Millennium AG

Solar Millennium AG initiated and developed theAndasol power plants. The global company isactive worldwide in the area of renewable energywith a focus on solar thermal power plants withcapacities ranging from 50 MW to 250 MW. Thecompany was founded in 1998 and has been listedon the OTC segments of the Munich and FrankfurtStock Exchanges since 2005 as well as on the ex-changes in Berlin and Stuttgart and in the Xetraelectronic trading system. Solar Millennium,along with its subsidiaries, specializes in parabolictrough power plants. The company covers allimportant business sectors of the value-chain forsolar-thermal power plants, from project develop-ment and financing to technology and the turn-key construction of power plants, to the operationand ownership of power plants. Flagsol, a techno-logy subsidiary of Solar Millennium is responsiblefor the engineering and technical construction,planning, and construction supervision on thesolar field.

Project development companies on site take careof all preparation work within the framework ofproject development, e.g. searching for sites andevaluating them, securing lands and rights, feed-in and funding as well as all other permit proce-dures and contractual negotiations.

Subsidiary Milenio Solar Desarrollo de ProyectosS.L. in Madrid is responsible for project manage-ment in Spain. To assure that local citizens feelinvolved in the project development, MilenioSolar has an office in the town of Aldeire, wherethe power plants are to be built and which isstaffed by local residents. Andasol 1 is Europe'sfirst parabolic trough power plant and wasdeveloped by Solar Millennium. In addition tosister projects Andasol 2 and Andasol 3, furtherprojects are being developed around the worldwith a total capacity of over 2,000 megawatts.Regional focus is currently on Spain, USA, Chinaand North Africa. In Egypt, the Solar MillenniumGroup is participating in the construction ofparabolic trough facilities for a hybrid powerplant there, which will use both natural gas andsolar energy to produce electricity.

23Andasol 1 to 3


The ACS/Cobra Group purchased shares in thepower plant company Andasol 1 Central Termo-solar Uno, S.A. from Solar Millennium AG in 2003;and in the power plant company Andasol 2Central Termosolar Dos, S.A in 2005. Afterwards,Milenio Solar Desarrollo de Proyectos, S.L tookover the project development for the power plantsat the request of the power plant companies.

General contractor:

A consortium made up of Cobra Instalaciones yServicios S.A. with 80% and Sener Ingeniería ySistemas, S.A. with 20% was responsible for theconstruction of Andasol 1 and 2. Solar Millenniumgave the contract to subsidiary Marquesado SolarS.L. for the construction of Andasol 3, which thenformed a project company responsible for theEarly Works, which in turn were carried out by aconsortium made up of MAN Solar MillenniumGmbH of Essen, Germany and the Spanish equip-ment manufacturer Duro Felguera S.A. Energía of Gijon (Spain). The consortium will completeconstruction of the solar power plant by thebeginning of 2011 under the leadership of MANSolar Millennium GmbH.

– Cobra Instalaciones y Servicios S.A. .

Cobra Instalaciones y Servicios S.A. belongs to theCobra Group, which is part of the Spanish construc-tion company ACS (Actividades de Construcción yServicios S.A.). The ACS group has its headquartersin Madrid and is one of the three largest construc-tion companies in Europe with 125,000 employeesand sales of over EUR 20 billion. The ACS Groupsupervises all areas of large-scale infrastructure pro-jects like motorways, railway construction, harborfacilities, airports, and power plants. The CobraGroup now owns 75% of the equity in Andasol 1and 2 and is responsible for the construction ofthese power plants.

– Sener Ingeniería y Sistemas, S.A.

Sener Ingeniería y Sistemas, S.A. which has itsheadquarters in Las Arenas, Spain is a companywhich specializes in providing engineeringservices and is also active in areas such as aero-nautics, shipping, energy and technology, andpower plant development.

– MAN Solar Millennium GmbH

MAN Solar Millennium GmbH is a joint venturecombining MAN Ferrostaal AG and SolarMillennium AG for project development, financingand for the turnkey construction of solar thermalpower plants with capacities ranging from 20 to250 megawatts. Each company owns 50 percentof the joint venture. MAN Solar Millenniumprofits from the expertise of its parent companies:MAN Ferrostaal supplies its experience as ageneral contractor and equipment manufactureras well as the financial strength necessary forinternational business. Solar Millennium is sup-plying the joint venture with proven, economicallyfeasible technology as well as long-term experi-ence in the development and implementation ofsolar power plants. Solar Millennium, togetherwith its 100% subsidiary Flagsol GmbH, providesthe technology for parabolic trough power plants –a proven, reliable technology in which the companyis a worldwide leader.

– Duro Felguera S.A. Energía

One of the Duro Felguera Group specializations isturnkey construction projects in the energy sector.It has almost 150 years of experience in variousindustrial areas, and the company is now develop-ing integrated projects for natural gas and steampower plants, industrial facilities, and fuel storagetanks. Duro Felguera is responsible for the com-plete execution of the project. The company isgeneral contractor and thereby assumes respon-sibility for the construction, start-up and operationof the facilities.

24

Project partners

Engineering

Sener Ingeniería y Sistemas, S.A is assumingresponsibility for the conventional sections of thepower plant like the turbines, generators, andplant periphery in Andasol 1 and 2. Flagsol GmbHof Cologne will provide the engineering for thesolar field. Flagsol is a 100% subsidiary of SolarMillennium AG. The work package includes thedesign and planning of the solar field as well assupervising on-site construction. In addition,Flagsol will provide the hardware and softwarefor the solar field controls. Some of the staff hasexperience dating back to the implementationand operation of the first parabolic trough powerplant in California in the 1980’s. The company isconstantly working on collectors for parabolictrough power plants. Flagsol will also beresponsible for the technological design of thesolar field in Andasol 3 (status: February 2009).

Power plant owner

Central Termosolar Uno, S.A. with headquartersAldeire, Spain is the owner of Andasol 1. Share-holders in this power plant company are CobraSistemas y Redes, S.A. with headquarters in Madrid,which owns 75% and is a company within theACS/Cobra Group and Solar Millennium Verwal-tungs GmbH, which own 25%. Central TermosolarUno, S.A. with headquarters Aldeire, Spain is theowner of Andasol 2. Shareholders in this powerplant company are Cobra Sistemas y Redes, S.A.with headquarters in Madrid, which owns 75%and Solar Millennium Verwaltungs GmbH, whichowns 25%. Solar Millennium Verwaltungs GmbHhas its headquarters in Erlangen, Germany andwas founded on September 23, 1998.

Marquesado Solar S.L., Spain is the owner of thepower plant Andasol 3 and is fully-owned by SolarMillennium AG.

Bibliography market studies:

Greenpeace, ESTIA, IEA SolarPACES 2005:

Solar Thermal Power Nowhttp://www.solarpaces.org/Library/CSP_Documents/051006%20Greenpeace-Concentrated-Solar-Thermal-Power-Now-2005.pdf

Sarasin 2007Solarenergie 2007 – Der Höhenflug der Solarindustrie hält an.

Greenpeace/EREC 2007:Globale Energie[r]evolutionwww.greenpeace.de/masterplan

International Energy Agency (IEA) 2006:World Energy Outlook 2006http://www.worldenergyoutlook.org/2006.asp

25Andasol 1 to 3

Solar Millennium AGNägelsbachstraße 40 D-91052 ErlangenGermany

Phone+49 9131 9409 - 0

Fax+49 9131 9409 - 111

[email protected]

Internetwww.SolarMillennium.de

© Solar Millennium AG 2008

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