The parabolic cylinder solar collector is another type of solar thermal collector. This type of solar panel used in solar thermal installations uses parabolic cylinders to concentrate all the solar radiation in a point. Instead of heliostats, this type of collector employs parabolic trough mirrors. For the focus of the parabola passes a pipe that receives the concentrated rays of the Sun, where the fluid is heated, usually a thermal oil. Currently the fluid reaches temperatures close to 400º C.
Until recently, the use of thermal solar CCP concentration systems was restricted to the field of research, industry or electricity generation, since this technology required complex tracking systems and large areas to locate them.
In the domestic field, it was not justifiable to install sensors with these requirements to reach high temperatures of over 200ºC. But currently we have, in the market, "compact parabolic cylinder" (CPC) concentration sensors that have a format and dimensions similar to those of flat collectors. The thermodynamic efficiency of these new sensors has improved significantly.
The collectors are formed by pipes with a selective coating that run longitudinally through the collector and act as an absorber. These pipes receive the solar radiation reflected by the curved walls that surround them, thus achieving a higher amount of energy per unit area of absorber (watt / m2).
Therefore, this type of collectors can be used both to produce sanitary hot water and to support heating or to supply cold equipment by adsorption or absorption.
Components of a parabolic cylinder solar collector
The main components of a parabolic cylinder solar collector 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 absorber tube. For this purpose, it is constructed with reflective materials. At present the most used support media are metal sheet, glass and plastic.
- The absorber tube: The absorber tube consists of two concentric tubes separated by a vacuum layer. The interior, through which circulates the fluid that is heated is metal and the outside of glass.
The working fluid that circulates through the inner tube is different according to the technology.
- The tracking system of the Sun: The most common tracking system consists of a device that turns the parabolic trough reflectors of the collector around an axis, in this way it is possible to maximize the capture of solar radiation and optimize the angle of incidence.
On the other hand, these solar thermal systems can be used to generate electricity.
Parabolic solar panels heat the thermal oil. This oil, with a high calorific energy, 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 just as it would be in a solar tower or solar furnace.
The operation of these solar power plants is similar to the operation of a thermal power plant, or of a nuclear power plant. All systems take advantage of heat to generate steam. With the steam, operate some turbines and obtain electricity. The differences between the two is the method of obtaining heat.
On the one hand, solar power plants use solar radiation as an energy source. On the other hand, thermal power plants use fossil fuels to take advantage of the heat from the combustion of coal or natural gas. Finally, nuclear power plants take advantage of the nuclear energy generated in the fission of nuclear fuel atoms.
Although the electricity generation system is similar among the three power plants, only the solar power plant is considered as a source of renewable energy. The others, the thermal power plant and the nuclear power plant are considered non-renewable energy sources.