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Endesa - Electricity, Gas, People

  • How electricity is generated (Part 1)

How electricity is generated (Part 1)

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First part of a very short and simple course to help you understand the basic concepts of electricity, where it comes from and how it reaches your home, enabling us to live the modern lives we do.

Electricity is the energy that makes a lightbulb turn on, moves the most efficient cars and even makes Frankenstein come alive. It is marvellous, but it can’t get to your house all by itself. Pressing the switch is easy, but actually making something happen is not so easy.

Nobody can argue with the fact that the capacity to generate electricity would be a finalist or the winner in any debate on the most significant invention in the history of mankind. Modern society cannot be totally understood without electricity, and neither can our lives.

Have you ever asked yourself where the electricity that reaches your house comes from? This is the first part of a short course that will help you understand what lies behind many of electrical things you do on a daily basis.

What is electricity

We all use it, but, who can define what it is?

Electricity is the energy created by positive and negative electrons inside conductors.

Or, in other words, opposites attract and positive and negative electrical charges join, creating two types of electricity: static electricity (generated by friction) and dynamic electricity (created by current).

Where does electricity come from

Electricity goes on a long journey before reaching your home but it does so very quickly. It is not magic or divinely inspired science; it is a step-by-step process that explains many queries one may have regarding the electricity sector:

  • Generation: Electricity is produced in power plants capable of obtaining electricity from primary energies. These primary energies may be renewable energies (wind, solar radiation, tidal power…). Or non-renewable energies (coal, natural gas, petroleum…). The companies that (totally or partially) own the various power plants sell the energy they generate to reseller companies.
  • Transmission: Once the energy has been processed and converted into electricity, it is sent via overhead or underground lines (transmission towers) from the power stations to the substations. Here the power transformers ensure the correct supply voltage is guaranteed. Substations are normally open-air stations located near the power plants and/or on the outskirts of towns, although, if they are not too large, they may also be located within the town, inside a building.
  • Distribution: The electricity is sent from the substations to households in the nearest surrounding areas. As a consumer, you are not able to choose your distribution company, since it will depend on where your property is located. This company is responsible for ensuring the electricity reaches your household and it will also resolve any faults you may have. This company also owns your electricity meter, electricity meter and sends the readings thereof to your reseller company.
  • Sales: What you can always choose is your reseller company. This is the company that sends you your bills, since it is the company that purchases the power from the generation companies and sells it to you. Reseller companies offer various tariffs and offers, although in Spain there is a deregulated market (you pay according to your contract, as with your mobile tariff) and and a regulated market (the amount you pay is established by a system designed by the Government).

The company that ensures electricity reaches your household is not the one that sends you your bills

Types of power plants

As mentioned above, in order to generate electricity, we need the energy in the primary materials to be released. How do we do this? It depends entirely on the type of power plant in question:

  • Conventional-cycle thermal power stations (coal, fuel oil and natural gas): They burn coal, natural gas or fuel oil. As it burns, water is heated. This water turns into steam and spins a steam turbine. This movement will generate electricity via an alternator that converts mechanical energy into electric energy. Finally, the steam goes to a condenser to be converted into water again and the cycle is repeated.
  • Combined-cycle thermal power plant (coal, fuel oil and natural gas): They work in a similar way to conventional-cycle power plants. Like these, they have a turbine that moves with the steam from the heated water. But they also have another different turbine that moves with the air obtained from the atmosphere and heated with fossil fuels. The main advantages compared with conventional-cycle power plants is that they are more efficient, more flexible (they can work at full load or “at half throttle” depending on requirements) and they are more environmentally-friendly (fewer emissions into the atmosphere).
  • Nuclear power plants: The heat released by the nuclear fission in a reactor heats large amounts of water at a high pressure. The released steam produces electricity as it goes through a turbine connected to a generator. The fuel normally used is uranium.
  • Geothermal power stations: The system is like the preceding ones (water is heated to emit steam that moves a turbine) but in this case, se aprovecha the natural heat of the Earth’s interior is used via underground channels.
  • Biomass-fired power plants: In this case, the heat is generated by burning organic materials, which may be plant matter or any type of waste (animal, industrial, agricultural and urban).
  • Hydroelectric power plants: These do not require heat, since these types of power stations are the next generation of old water mill. They use significant amounts of falling water to move a hydraulic turbine. They are usually built on dams and reservoirs.
  • Wind farms: this is where wind moves a turbine to produce electricity
  • Solar power plants: There are two types of solar power plants: Solar thermal power plants use the heat of the sun to heat water and use the steam generated to move a turbine. Photovoltaic power plants directly transform solar energy into electricity, thanks to photovoltaic cells.
  • Tidal power stations: The movement of water produced by the rise and fall of tides drive a turbine, which produces electricity via a generator.
  • Wave power stations: Similar to the preceding ones, but they use waves instead of tides.

The main difference between renewable and non-renewable energies depends on the primary energy used to generate electricity. Does this “fuel” have to be replaced, or is it not necessary as nature offers it free of charge?

The most common power plants today are non-renewable, since they use primary energies that need to be extracted from the earth (coal, natural gas, uranium…). But the future is set to be much more renewable.

In the next part of this course, we will explain how each power plant works. Don’t’ skip class!

Electricity is renewable if the fuel used to generate it does not need to be replaced

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