Concentrated solar power
A solar thermal power plant or solar thermal power plant is a power plant that uses the heat of the sun across the absorber as a primary energy source. Therefore, next to the names of solar thermal power plant or thermal solar power plant are common, from English and CSP for Concentrated Solar Power.
Solar thermal power plants achieve depending on the design more efficient than photovoltaic systems, but have higher operating and maintenance costs and require a certain minimum size. They are economically feasible only in very sunny regions of the world.
Previously, SWK had lower specific investments (investment per installed kilowatt ) than photovoltaic systems. In 2011, the selling prices for solar panels fell but massively - by about 38.2 %. Therefore, in 2012, for example, were built in the southern United States several large-scale photovoltaic power plants where solar thermal power plants were originally planned. Projects such as DESERTEC have become more questionable. In solar thermal power plants can be compared to photovoltaic systems integrate a memory cheaper. Advantages for solar thermal power plants are therefore seen primarily in sunny locations with corresponding memory requirements.
There are different concepts for the use of solar heat for power generation, which can be divided into two categories: power plants, which concentrate the direct radiation of the sun with reflectors on a solar absorber, and those that operate without concentrating reflectors and the entire global radiation ( direct and make diffuse radiation ) available.
- 2.1 Thermal power plants
- 2.2 solar pond power plants
- 2.3: Wind power plants
Solar thermal power plants with pooling of direct radiation
These power plants use focusing reflector surfaces to concentrate the incident sunlight onto the absorber. The reflectors or absorbers follow the sun. Solar farm power plants collect the heat in many absorbers distributed over the surface, while in solar tower power plants and Paraboloidkraftwerken the sun's radiation is bundled with Punktkonzentratoren to a focal point. This type of energy is used in various studies, including the German Aerospace Center (DLR ) and the Trans-Mediterranean Renewable Energy Cooperation ( TREC ), great potential for economic energy in desert areas of North Africa and the Middle East and in arid southern Europe (Spain, Italy, etc. ) awarded. Here, these concepts are related to a low-loss power transmission to Europe or Central Europe.
Water steam generator end systems are suitable for support and thus saving fuel in conventional steam power plants. In the pure solar power plants, same heat storage from the fluctuating solar radiation, alternatively can support the generation of heat in periods of low insolation here other energy sources. This happens for example in Austria, where solar thermal systems are already widely used. It combines solar panel, Bioheizwerk and conventional replacement or peak energy power plants. Since the solar thermal energy in spring and autumn only little energy and in winter provides almost no energy, one other power plants switched additionally at this time to take advantage of the installation all year round can. The same purpose can meet alternatively seasonal heat storage, while over-dimensioning of the plant in the summer months.
Solar farm power plants
The collector field of a solar farm power plant consists of many parallel parabolic trough or Fresnel collectors, so-called Linienkonzentratoren. However, the interconnection of Paraboloidanlagen to a large collector field is possible, very expensive compared to Linienkonzentratoren. Parabolic trough plants are already operating commercially.
In the collector field, a heat transfer medium is heated, either thermal oil or superheated steam. Thermo Oil Units temperatures of up to 390 ° C are reached, which are used in a heat exchanger for steam generation. The direct steam generation ( DISS = Direct Solar Steam) does not require such a heat exchanger, as the superheated steam is generated directly in the absorber tubes. Therefore temperatures greater than 500 ° C are possible.
The water vapor is then fed in a steam power plant as a centrally arranged steam turbine coupled to a generator. The turbines used today are specially adapted to the special conditions of use in solar thermal power plants. The highest possible efficiency allows a smaller solar field with consistent performance of the power plant. This reduces the investment cost, making the power generated profitable. The Tag-/Nachtzyklus and changing weather conditions also require very short start-up of the steam turbine. For these reasons, most dual casing steam turbines used with reheat in solar thermal power plants. Here, the exhaust steam of the high pressure turbine is passed prior to entry into the downstream low pressure turbine at a constant pressure in a reheater in the boiler, where it is superheated again. The steam circuit operates in this manner with a higher average temperature than a non zwischenüberhitzter circuit. This increases the efficiency, for the turbine provides the same heat in the boiler a higher performance. Similarly, reducing the moisture content in the low-pressure turbine and the usual, caused by drops of water corrosion. The reheating of the steam thus increasing efficiency and service life of the turbine. A special case design protects the steam turbine from excessive cooling at night and pays the low weight of the rotor in a short travel time. In order for the steam turbine can operate as effectively as possible, the steam must be condensed at low temperature. The highest efficiency is achieved with the aid of water cooling, such as in the case of Andasol. In the event that - as in many desert areas - no cooling water is available in sufficient quantities, can be used at the expense of the efficiency of dry cooling systems.
The particular advantage of this type of power plant is the conventional, relatively easily available technology.
Due to rising energy costs, the interest in smaller systems that allow a decentralized supply grows. Through the coupling of electricity, process heat, refrigeration and storage technologies, such systems could work economically.
Parabolic trough power plants
Parabolic trough collectors consist of curved mirrors that concentrate sunlight on a running in the focal line of the absorber tube. The length of such collectors, depending on the building type between 20 and 150 meters. In the absorber tubes, the concentrated solar radiation is converted into heat and transferred to a circulating heat transfer medium. The parabolic troughs are usually only a single axis tracked for cost reasons the sun. They are therefore arranged in north-south direction and tracked down or tilted only by the height of the sun during the day.
Currently, scientists at MIT on a prototype that could significantly improve the efficiency of parabolic trough power plants. The hybrid system concept is to generate in addition to thermal and electrical energy in the absorber pipes. The absorber pipe made in this design consists of three nested in itself concentric tubes with different functionality. The innermost tube is for heat dissipation and is only partially filled with liquid, the remaining volume takes up steam. The steam condenses within the system to a connected surface and the capacitors formed in the phase change liquid includes the liquid circuit. This system theoretically requires no pumps and the heat energy generated can be fed to the condenser surface by coupling other process systems. The central tube serving as a surface for the solar energy absorber and is connected to the inner tube via a thermoelectric material in the form of " legs ". The large temperature gradient between the tubes passing through the Seebeck effect, a voltage differential, which allows the use of electrical energy. Between the middle and outer tube prevents a vacuum that the resulting at the absorber surface heat will make to the environment.
As early as 1912 parabolic trough were used to generate steam for a 45 kW steam engine pump in Meadi / Egypt by Shuman and Boys. The five rows of collectors having a length of 65 m, an aperture width of 4 m and a Gesamtaperturfläche 1,200 m². Guiding was done automatically by means of a thermostat. Also, a certain heat storage for night operation was already possible. The price at that time was 31,200 Mark. The plant supplied " at ten hours working time per day steam for 50 horse-power ."
1916 had granted 200,000 Reichsmarks for a parabolic trough demonstration in German South West Africa the German Reichstag. The First World War and the emerging oil era, it did not come to a realization.
Between 1977 and 1982 parabolic trough process heat demonstration plants have been installed in the United States.
1981, a demonstration plant with 500 kW of electric power at the Plataforma Solar de Almería was put into operation in Europe.
Commercial operation began in 1984 in the U.S.. The now nine SEGS power plants ( SEGS = Solar Electricity Generation System ) in southern California produce a total output of 354 MW. Another called Nevada Solar One power plant with a capacity of 64 MW was built in Boulder City / Nevada in June 2007 and went to the net. The absorber tubes has been supplying the German Schott AG, which had also been involved in the California power plants. The steam turbine, a person working with reheat SST -700 with an electrical output of 64 MW, was supplied by Siemens AG. The efficiency of this type of power plant is given as 14%. More power plants are built, among others, in Morocco, Algeria, Mexico and Egypt.
In the Spanish Andalusia three plants were from June 2006 to the summer of 2009 with Andasol, built to 50 MW, which is currently the largest solar power plants in Europe. Andasol 1 went on line in December 2008 and was officially inaugurated on 1 July 2009. Andasol 2 in mid-2009 took the test operation, Andasol 3 2011., The insolvent German company Solar Millennium was much involved in these solar power plants with project planning, technical development and control. The steam turbines and generators supplied, as for almost all Spanish parabolic trough power plant projects, Siemens AG. This type of power plant was in addition to other types of proposed Plan and the DESERTEC project for the Grand Solar, a final decision on the technology but has not yet been taken.
In Abu Dhabi ( United Arab Emirates) the largest now solar thermal power plant in the world was put into operation with Shams -1 on 17 March 2013. It has an area of 2.5 km ² and is intended to supply 20,000 households with energy
Fresnel collector systems
A further development of parabolic trough are the so-called Fresnel mirror panels. Several single storey arranged parallel ungewölbte mirror strips ( according to the principle of a Fresnel lens ) reflect the incident direct radiation of sunlight on the absorber tube. The strips are a single axis. An additional secondary mirror behind the tube directs the radiation to the focal line. This concept is currently in practical testing phase.
This construction combines the operating principles of parabolic trough collectors and power towers together, being dispensed with both curved mirror as well as multi-axis solar trackers and modular structure is preserved. By using the simpler to produce uncurved mirror strips cost advantages are expected. The absorber tube, in contrast to most of parabolic construction does not move. So can be made very long panels, which, due to lack of pipe bends and flexible connections low flow resistance for the heat transfer medium. The stand shading losses against between the mirror strips.
Since 2004, such a system supports the generation of steam in an Australian coal-fired power plant. The technology is being tested by the University of New South Wales and Sydney. The plant is scheduled after its full completion for the Liddell power station in the Hunter Valley, about 250 km north- west of Sydney, producing around 15 MWth and thus contribute to fuel savings. It is a 60 m × 30 m large field of flat mirrors that concentrate sunlight to about 10 m high line on the collector box. About 285 ° C where hot steam is generated by direct steam generation.
Since July 2008 on behalf of Gas Natural in Seville, Spain, a 352 sq. ft. facility, the company PSE AG in Freiburg with a peak output of 176 kW in operation, which uses the generated process heat to drive an absorption chiller and thus a building of the University of Seville cools.
Since March 2009, the Fresnelsolarkraftwerk PE is 1 (Puerto Errado 1) of the Karlsruhe Novatec Solar in commercial continuous operation. The solar power plant has an electrical output of 1.4 MW and is based on linear Fresnelkollektortechnologie. PE 1 comprises in addition to a conventional power block, a solar steam generator with a mirror area of about 18,000 m².
For steam production directly irradiated sunlight with the help of 16 flat mirrors series is focused on a linear receiver in 7.40 m height. In this focal line of the mirror array, an absorber tube is installed, is vaporized in the bar by the concentrated radiation water directly to saturated steam at 270 ° C and 55. By developing a new receiver designs 1 superheater steam temperatures above 500 ° C is produced since September 2011 on Fresnelkraftwerk Puerto Errado. A more detailed description of the PE-1 system with multiple images is in the links.
Due to the good experience with the PE-1 plant another Fresnelsolarkraftwerk has been built with a capacity of 30 MW and commissioned on 5 October 2012. Puerto Errado 2 is equipped with a mirror surface area of 302,000 m² ( 0.302 km ²), the world 's largest Fresnelkraftwerk in operation.
Solar tower power plants
When solar tower power plant, also called central receiver power plants, there are mostly steam power plants with solar steam generation. The previously fired with oil, gas or coal combustor is replaced by a solar " combustion chamber " on a tower. When the sun is hundreds to thousands of automatically positioning mirrors (heliostats ) align so that sunlight is reflected to the central receiver (receiver). By high concentration of solar radiation produced at the top of the tower temperatures up to 1000 ° C. more The technically feasible to handle temperatures will be around 1,300 ° C. The temperature values and the corresponding achievable thermodynamic efficiency are thus significantly higher than for solar farm power plants. The heat transfer medium used is either liquid nitrate salt, water, steam or hot air.
The same principle applies in the solar furnace used. In this way, can be produced, for example, virtually any temperature process heat and used to promote the flow of chemical processes. The solar furnace at Odeillo Font-Romeu (see photo right) was built back in 1968 to 1970 and is equipped with 1 MW of thermal power, about 3,000 work hours per year and temperatures up to 3,800 ° C to now one of the largest in the world.
The most heat generated in the absorber is used, however, a steam turbine and gas turbine for power generation. For the heat carrier medium is heated up to 1000 ° C and then used for steam generation in the receiver. This drives a turbine. So that it can operate efficiently, such as the steam in a solar farm power station after discharge from the turbine must be cooled. For cooling water can be used when there is sufficient presence. Since this is in desert areas often is not the case, come with the loss in efficiency and dry refrigeration equipment. The generated electricity is fed into the public grid. In addition to the parabolic trough power plant, the solar tower power plant is now another, well-developed plant type - though still connected with public funding - can make solar power economically available.
The largest solar thermal plant in the world is the solar thermal power plant with 392 MW Ivanpah. She went on February 13, 2014 to the network and claims to generate electricity for about 140,000 households.
On the PSA - a Spanish research facility in Almeria / Spain - Two pilot plants CESA -1 ( 7 MWth) and SSPS - CRS ( 1.2 MWth). Here are the different receiver types, including German developments DLR tested.
In Germany, was launched in July 2006 with the construction of a solar thermal demonstration and experimental power plant in Jülich (NRW), which began trial operation in January 2009 and 1.5 megawatts to provide power. As a heat transfer medium is air. Since the operating temperature of 600-800 ° C is very high, it is more efficient than other solar thermal power plants. Fluctuations in the power supply of sunlight to be balanced in this system by means of a novel heat storage of ceramic bulk. This can be relatively independent of the sunlight and thus consumption -based electricity generation in power plant. The structure and the further developments of the system is managed by the Solar Institute Jülich and DLR. In the future, this power plant could be conventionally operated in the absence of sunlight in bridging phase with biomass. With the help of this tower technology can also be hydrogen by solar energy produce .. But water vapor is passed through capillaries located in the receiver, which is provided with a metalloxidbasierten redox coating. At temperatures above 800 ° C the water molecules are broken down, the oxygen oxidizes the metal, hydrogen is released (see hydrosol project). In a further step, the consumption of CO2 from methane are obtained ( cf. Sabatier process).
In Seville, a solar park is operated with a total of 302 MW and different technologies. End of March 2007 was the first one built by the Spanish group Abengoa solar power tower ( PS10 11 MW and an annual output of 23 GWh) to the grid. The investment cost of around 35 million euros were five million euros from the European Union, funded by the Fifth Framework Research Programme, funded. In the second stage of a tower plant with 20 MW ( PS20 ) was built in 2009. After another plant with 20 MW ( AZ20 ) five more parabolic trough power plants are to be built with 50 MW.
Since 2011 ( the beginning of operation Mai, official opening in October ), the " high-tech solar power plant " Gemasolar in Fuentes de Andalucia near Seville works / Spain. The plant has an area of 185 hectares. It has 2650 levels with a surface area of 120 m², which focus the sun onto an absorber, which is installed in a 140 m high tower. As heat transfer salt is used at a temperature of about 500 ° C; this also serves as a heat reservoir, so that when the sky is overcast or even electricity at night can be generated. Gemasolar operating at a capacity of 19.9 MW about 110 GWh per year produce - enough for 27,500 households. Operator is Torresol Energy, a joint subsidiary of the Spanish engineering company SENER and the responsible for the development of renewable energy company of the Emirate of Abu Dhabi, Masdar.
Parabolic dish
In Paraboloidkraftwerken, also called Dish Stirling or dish- farm systems, parabolic mirror rotatable about two axes are mounted on a frame. These reflect sunlight onto a receiver mounted at the focal point of heat. This design is very compact - the mirrors are designed with diameters ranging from three to 25 meters, which powers up to 50 kW per module can be reached.
For solar - Stirling systems the receiver, a Stirling engine is followed, which converts thermal energy directly into mechanical work. These plants achieve the highest efficiency in the conversion of sunlight into electrical energy. In an experiment in France with a parabolic mirror of 8.5 m diameter (area 56.7 sqm), a net power of 9.2 kW was achieved, which corresponds to an efficiency of 16%. The modules are suitable for decentralized energy supply in remote regions and allow any interconnect many of these modules into a large-scale solar power plant.
The Dish farm equipment rarely used at the focus an absorber in which heats a heat transfer medium and is used to generate steam. To this end, several parabolic mirror are connected together, where they can not compete economically with Linienkonzentratoren and tower power plants currently.
Dissemination of CSP plants
Currently, many plants are being planned or under construction. Especially in the United States caused several plants with more than 200 MW and dry cooling. The following list shows the solar thermal power plants with more than 10 MW which are already in operation or was first built. With one exception, real production figures are unknown, there are only predictions.
As the world's largest CSP plant (February 2014) the solar thermal power plant Ivanpah applies 60 km southwest of Las Vegas. It has a rated power of 392 MW.
In Spain alone are 2011/2012 power plant capacities of 1152.4 MW productive, 1103.5 MW under construction and 1662.08 MW in planning.
Solar thermal power plants without bundling
These power plants have not tracked reflectors, but use all of the incident solar radiation ( global radiation, ie the direct and diffuse radiation).
For solar pond power plants layers of different saline water form the collector and absorber, while those tasks in thermal power plants, a large collector roof (like a greenhouse ) belongs.
Thermal power plants
Thermal power plants, also called solar updraft tower to the chimney effect making advantage, in which warm air rises because of their lower density upwards. They consist of a large -area glass roof (collector), under which the air on the ground heats up like a greenhouse. The warm air rises and flows under the glass roof to a chimney in the middle of the plant. The resulting solar chimney, with the aid of one or more turbines, coupled to a generator is converted into electric power. The low technical requirements for such a system is offset by the very low efficiency even in the best case, only about 1%, which can be disproportionately large effort required and the size of such plants. In order to achieve a performance that is comparable to that of a conventional coal or nuclear power plant, the fireplace would have 1000 m or even higher, and the collector more than 100 km ² cover ( in this example, cheating the required diameter of the plant more than 12 km).
Solar pond power plants
In solar pond power plants, even Salinity Gradient Solar Ponds / Lakes called, form shallow salt lakes, a combination of solar collector and heat storage. The water at the bottom is much more saline and thus denser than at the surface. If solar radiation absorbed in the deeper layers, these heat up to 85 ° -90 ° C. Due to the existing by the different salinity density, the heated water can not rise, there is no convection takes and the heat is stored in the bottom water layer. The stored heat can be used to generate electricity in a turbine generator block and is an appropriate design 24 hours a day. Since the achievable temperatures are relatively low, must be used in power generation with working fluids which vaporize at low temperatures. The conversion of heat into electricity is therefore with the help of a so-called Organic Rankine Cycle power plant that uses, for example, ammonia vapor as the working fluid.
Since the available temperature differences reach only about 60 K, the efficiency of such power plants is small - it can, for thermodynamic reasons, the theoretical maximum reach only about 15%. Nevertheless, solar pond power plants are of particular interest to developing countries, as the present there sunny, barren and undeveloped areas can be used with relatively little investment. Economically attractive solar pond power plants are especially when the thermal energy can be used directly without going through power generation, eg as process heat for drying or cooling.
Case wind power plants
Case wind power plants currently exist only as a concept. They consist of a high ( > 1000 m) tower is at the tip of the ambient air removed by spraying with water energy. Due to the latent heat of evaporation and the weight of the water, the air drops down and drives on Kaminfuß wind turbines. They are suitable for hot and dry climates with large water resources ( marine environment).