1.-Hydroelectric power station
Hydroelectric power stations are facilities built at the foot of a dam in order to use the potential energy of the body of water located above.
Water is released at a high pressure (kinetic energy) through a pipe and moves a turbine. This rotating movement (mechanical energy) is transformed into electrical energy by means of an alternator, which then passes through a transformer and is transported to the places where it will be consumed.
You will have been able to verify, after analysing the figure and reading the explanation, that the most important element in this installation is the turbine. The turbine captures the energy from the water in order to be able to transfer it to the generator. Not all turbines used in hydraulic power stations are the same. In fact, according to the height of the water drop, different types will be used, with the aim of optimising the transfer of energy between the systems.
2.- Conventional thermal power station
A thermal power station is essentially a large steam generating system. The boiler is the component used to generate heat. The fuel used is taken from a deposit or is supplied directly through distribution pipes. The fuel is burnt and the heat produced goes towards a coil of pipes, through which cold water is introduced.
In the coil of the boiler, the cold water is heated until it becomes steam and is sent to a steam turbine. The turbine is a rotating machine that turns the force and pressure of the steam into mechanical energy in its shaft. This shaft is, in turn, connected to the alternator shaft to generate electricity.
The electrical energy produced in the alternator is put into service towards the electrical distribution lines through a transformer station located at the edge of the power station.
Then, once the energy from the steam is captured by the turbine, it no longer has a practical use, which is why it is sent to a heat exchanger to extract the residual heat. The exchanger is a machine made up of a casing, inside which cooling pipes run.
The steam from the turbine is housed inside the casing, while the cold water coming from the cooling tower circulates around inside the pipes. Between both fluids, the heat from the casing and the cold from the pipes, thermal energy is exchanged, which gives rise to the exit of hot fluid that was already cooled towards the boiler, thus closing the hydraulic circuit or steam cycle.
There are thermal power stations designed to use each type of fuel: petroleum, coal, natural gas, biomass, etc. Oil-based products are most commonly used. Needless to say that these types of power stations produce a lot of pollution.
Some power stations also use solar energy. However, these power stations are still not as developed as conventional thermal power stations and still don’t produce as much power.
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3.- The nuclear fission power station
Nuclear power stations are a specific type of thermal power station. The fuel they use is uranium, more specifically Uranian-238 isotope, a radioactive material that generates an enormous amount of heat when subjected to nuclear fission.
The heat, coming from the core of the reactor, turns water to steam, which is conducted through a secondary circuit not in contact with the reactor, towards steam turbines that move the shaft of an alternator. The residual water must be cooled at all times, in order to be warmed up again before closing the steam cycle. This cooling process is carried out in a cooling tower.
Once it has been used, uranium generates radioactive waste. This waste is stored in pools in the same power station until they can be taken to specially prepared deposits.
The most important element of nuclear power stations, which differentiates them from other types of power stations, is the reactor. It is located in its own building, the containment building, which is equipped with extensive safety measures, in order to confine the radioactivity from the nuclear fuel inside.
In order to control the heat that is extracted from the fuel rods, the reactor is partially submerged in water. This is how the energy that is transferred to the steam, and therefore the electric energy transferred to the power lines in a given moment, is regulated.
As an element for limiting the power, control rods made of boron carbide or silver, indium and cadmium alloys are placed between the fuel rods. These control rods absorb neutrons to regulate the nuclear chain reaction.
Nuclear power stations are used in countries that use this type of energy as their main supply. Once a nuclear power station has started to operate, it cannot be stopped unless a strict protocol is followed, which takes several days to be completed.
Documentary: Chernobyl 30 Years On: Nuclear Heritage
Documentary: Discovery Channel: Chernobyl
Documental: Discovery Channel:Disaster at Chernobyl
Chernobyl Disaster: An inside look at what happened in 3D
4.- Other renewable energy power stations
Most of the electrical energy we generate comes from conventional electrical power stations. In other words, it is mainly produced from non-renewable energy sources, in thermal power stations that use fossil fuels and in nuclear power stations.
A significant proportion of our electrical energy is also produced from renewable sources like hydroelectric power stations. Only a small portion is generated using renewable energy sources such as solar or wind. Experts say that, in order to prevent the global system from collapsing, the change towards cleaner energy sources must be gradual.
In other words, we must try to depend less on non-renewable resource gradually. In this way, we can go through a substitution process without the global economic system being thrown into crisis, and maintaining the demand.
In addition to wind energy, two good alternatives for change are the exploitation of solar sources by developing solar thermal power stations and photovoltaic stations. This type of energy depends fundamentally on the climate and their yields are greater in the equatorial and tropical zones, whereas their yield is obviously lower in more northern or more southern latitudes.
Solar thermal power station
A solar thermal power station is characterised by capturing solar radiation directly. The most important element is the solar updraft tower, on which the sun is reflected from a heliostat field. A heliostat is essentially a mirror mounted on a shaft that turns following the position of the sun through a control system.
All the solar reflections from the heliostats point towards a fixed point on the tower, where there is an opening. Inside this opening shaped like a window there are pipes with water. The impact of the solar radiation raises the temperature of the water up to hundreds of degrees, which makes it become steam and it moves through the pipes.
The thermal energy has been transformed into kinetic energy (steam in movement), which is transferred to the turbine which rotates together with the alternator. It is in this last element where kinetic energy is transformed into electrical energy.
Photovoltaic power station
The development of semiconductors has enabled photoelectric surfaces to be created. Photoelectric surfaces are panels that capture light radiated by the Sun and turn it directly into electrical energy.
A photovoltaic power station is therefore made up of rows of photoelectric generating panels (photovoltaic panels). Unlike the thermal solar power station, the panels are in a fixed position on frames. This leads to a smaller yield when capturing the solar radiation. Since the time of day in which it receives the most radiation is at noon, the panels are directed towards the south in the Northern Hemisphere or towards the north in the Southern Hemisphere.
