Installation of thermal solar energy

Solar power plant

Concentrated Solar Power Parabolic Trough

Concentrated solar power parabolic trough

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, this type of parabolic solar collector uses rows of parabolic cylinder-shaped mirrors. Through the focus of the parabola passes a pipe that receives the concentrated rays of the Sun, where the fluid is heated thanks to thermodynamic processes, normally a thermal oil. Currently, the fluid reaches high temperatures close to 400 degrees Celsius

Until recently, the use of concentrating solar thermal systems was restricted to the field of research, industry, or the generation of electricity. The reason was that the technology for this power source 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.

Components of a parabolic trough solar collector

The main components of a parabolic trough concentration systems are:

  • The metallic structure to give rigidity to the whole.

  • The parabolic trough reflector: The function of the parabolic trough receiver is to concentrate the solar radiation on the absorbing tube. For this, it is built with reflective materials.

  • 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.

  • The working fluid that circulates through the inner tube is different depending on the technology.

  • The Sun Tracking System. The most common system to track the sun's energy consists of a device that rotates the parabolic trough reflectors of the collector around an axis.

Generation of electricity by means of parabolic cylindrical collectors

Concentrated solar power projects can be harnessed to generate electrical energy that can be connected to the grid.

Parabolic solar panelsheat 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.

The operation of these solar power plants is similar to the operation of a thermal power plant, or a nuclear power plant. All systems take advantage of heat to generate steam. With steam it drives turbines and obtain electricity. The difference between one and the other is the method of obtaining heat.

How does a concentrated solar power plant work? 

It consists of the thermal use of solar energy 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 commonly used mixture of potassium nitrate, sodium nitrate, and lately has been incorporated calcium nitrate.

Instructively, it is necessary to concentrate solar radiation so that high temperatures can be reached, from 300 °C to 1000°C, and thus obtain an acceptable performance in the thermodynamic cycle, which could not be obtained with lower temperatures.

The capture and concentration of the solar rays in CSP plants are done by means of mirrors with automatic orientation in order to track the sun. These mirrors point to a central tower where the fluid is heated, or with smaller mechanisms of parabolic geometry. The set of 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 panels of solar photovoltaic, which has 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. This 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 the form of sensible heat or as latent heat (for example using molten salt). It allows these plants to continue to generate electricity whenever needed, day or night.

This makes CSP projects a source of solar power that can be delivered when needed. This is especially valuable for places that have experienced high PV penetration, such as California. This is because the peak energy demand at night increases, while the PV output weakens at sunset (a phenomenon known as the duck curve ).

What is thermal energy storage?

Most solar heating systems and some solar cooling systems rely on storing heat from solar energy in a material for a certain period. This is accomplished by heating a material that can store heat inside until it needs to be returned to the environment.

For refrigeration, on the contrary, the opposite process is done. Heat is removed from a material, that is, it cools it so that it can absorb more heat.

The passive heating or cooling of a space is fundamentally based on the same concept, which consists of creating a temperature difference between the material and its surroundings. For this reason, it is very important, when designing a building, to provide areas or sectors located properly so that they can store a sufficient amount of heat during the day and keep it at a comfortable temperature at night.

In the summer it should work the other way around, delivering enough heat to the outside at night to keep the interior cool during the day.

List of the 10 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
359Solar Energy Generating Systems (SEGS)United StatesMojave Desert, California
280Mojave Solar ProjectUnited StatesBarstow, California
280Solana Generating StationUnited StatesGila Bend, Arizona
250Genesis Solar Energy ProjectUnited StatesBlythe, California
200Solaben Solar Power Station SpainLogrosán
160Noor IMoroccoGhassate, Ouarzazate Province
150Solnova Solar Power StationSpainSanlúcar la Mayor
150Andasol solar power stationSpainGuadix
150Extresol Solar Power StationSpainTower of Miguel Sesmero
100KaXu Solar Onesouth AfricaPofadder, Northern Cape

Published: May 30, 2018
Last review: August 25, 2020