Parabolic trough collectors are another type of solar thermal collector. This type of solar panel is used in solar thermal energy installations. They use parabolic cylinders to concentrate all the solar radiation at one point.
Instead of heliostats, parabolic solar collectors use rows of parabolic cylinder-shaped mirrors. A pipe passes through the parabola’s focus that receives the concentrated rays of the Sun, where the fluid is heated thanks to thermodynamic processes, usually a thermal oil. Currently, the liquid reaches high temperatures close to 400 degrees Celsius.
Until recently, concentrating solar thermal systems was only used in research, industry, or electricity generation. The reason was that this power source’s technology required complex tracking systems and large surfaces to locate them.
The collectors are made up of conduits with a selective coating that runs longitudinally through the collector and acts as an absorber.
Because of his shape, people call it using several names:
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Parabolic solar collector
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Concentrated solar power parabolic trough.
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Cylindrical parabolic concentrator.
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Cylindrical parabolic collector.
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Cylindrical solar collector.
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Cylindrical parabolic collector components
The main components of a parabolic trough solar systems are:
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The metallic structure gives rigidity to the whole.
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The parabolic trough reflector: The parabolic trough receiver’s function is to concentrate the solar radiation on the absorbing tube. For this, it is built with reflective materials.
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The absorber tube: The absorber tube consists of two concentric tubes separated by a vacuum layer. The interior, through which the heated fluid circulates, is metallic, and the exterior is glass.
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The working fluid that circulates through the inner tube is different depending on the technology.
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The Sun Tracking System. The most common system to track the sun’s energy consists of a device that rotates the collector’s parabolic trough reflectors around an axis.
How do cylindrical parabolic collectors produce electricity?
We can harness concentrated solar power projects to generate electrical energy and supply it directly to the grid.
Parabolic solar panels heat transfer fluid. This transfer fluid oil is pumped through a series of heat exchangers to produce superheated steam. The heat present in this steam is converted into electrical energy in a conventional steam turbine. The basic system is the same as in a solar tower or solar oven.
These solar power plants’ operation is similar to thermal power plants operation - including a nuclear power plant. All systems take advantage of heat to generate steam that drives turbines and obtains electricity. The difference between one and the other is the method of getting heat.
How does a concentrated solar power plant work?
It consists of the use of thermal energy from solar radiation to transfer and store it in a heat-carrying medium, generally water. The most commonly used technology to store this energy is thermal storage molten salts. The composition of these salts is variable, the most widely used mixture of potassium nitrate, sodium nitrate, and lately has been incorporated calcium nitrate.
It is necessary to concentrate solar radiation so that high temperatures can be reached, from 300 °C to 1000°C. At these temperatures, we can obtain an acceptable performance in the thermodynamic cycle.
The capture and concentration of the solar rays in CSP plants are done using mirrors with automatic orientation to track the sun. These mirrors point to a central tower where the fluid is heated or with smaller parabolic geometry mechanisms. The reflected surface and its orientation device is called a heliostat or parabolic trough concentrators solar.
What is concentrated solar power CSP?
Concentrated solar power is to generate solar power by using mirrors or lenses to concentrate the sun's rays onto a small area. Electricity is generated when solar light is concentrated and converted into heat (solar thermal energy). This energy drives a heat engine (usually a steam turbine ) connected to an electric power generator.
In most cases, the current CSP technology can not compete in price with solar photovoltaic panels, which have experienced substantial growth in recent years due to a decrease in prices, and operating costs are much lower. CSP generally requires large amounts of direct solar radiation to produce energy at a large scale. Its energy generation drops dramatically with cloud cover. It differs from photovoltaics, which can generate electricity as well from diffusion rays.
However, the advantage of CSP over photovoltaic conversion is that as a thermal technology, CSP plants can incorporate thermal energy storage. These plants can store energy either in sensible heat or as latent heat. It allows these plants to continue to generate electricity whenever needed, day or night.
It makes CSP projects a source of solar power that can be delivered when needed. It is precious for places that have experienced high PV penetration, such as California. It happens because the peak energy demand at night increases, while the PV output weakens at sunset (a phenomenon known as the duck curve).
List of the ten most important trough plants
This list is subject to change and may not be complete or up to date.
This is a list of the largest electricity generation CSP projects plants using concentrated solar power parabolic trough:
| Electric power MW | Central name | Nation | Location |
|---|---|---|---|
| 359 | Solar Energy Generating Systems (SEGS) | United States | Mojave Desert, California |
| 280 | Mojave Solar Project | United States | Barstow, California |
| 280 | Solana Generating Station | United States | Gila Bend, Arizona |
| 250 | Genesis Solar Energy Project | United States | Blythe, California |
| 200 | Solaben Solar Power Station | Spain | Logrosán |
| 160 | Noor I | Morocco | Ghassate, Ouarzazate Province |
| 150 | Solnova Solar Power Station | Spain | Sanlúcar la Mayor |
| 150 | Andasol solar power station | Spain | Guadix |
| 150 | Extresol Solar Power Station | Spain | Tower of Miguel Sesmero |
| 100 | KaXu Solar One | south Africa | Pofadder, Northern Cape |