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How electricity is produced (Part 1)

This is the first part in a brief and simple series to explain what electricity is, where it comes from and how it reaches your home to power modern life as we know it.

Electricity is the energy which makes lightbulbs shine, drives the most eco-efficient cars and gives life to Frankenstein’s monster. It is a marvellous thing, but it cannot get into your home on its own. Pressing a switch is easy; making sure something happens when you flip that switch... not so easy.

It is indisputable that in any debate about the greatest invention in mankind’s history, the ability to generate electricity would win out. Modern society simply would not exist without electricity; our lives would be changed beyond recognition

Have you ever wondered where the electricity that powers your home comes from? This is the first instalment in a brief series which will show you the energy hardcore behind many of the things you do every day.


What is electricity?

Everybody uses it, almost without thinking, but how many of us can actually define what it is?

Electricity is the energy generated by the movements of electrons (negative charge) and positrons (positive charge) within conductive materials.

Amounting to the same thing: opposites attract, so the positive and negative charges come together, to create two types of electricity: static electricity (generated by friction) and dynamic (known as an electrical current).


Where does electricity come from?

Electricity’s journey to your plug is very long, but occurs at astonishing speed. It is not magic; it is not science fiction. It is a step-by-step process which explains many of the doubts that arise with regard to the electricity sector:

  • Generation: electricity is produced in plants capable of drawing electrical energy from primary energy sources. These primary energies may be renewable (wind, solar power, tidal power, etc.) or non-renewable (coal, natural gas, oil, etc.). The companies which (fully or partly) own the various power plants sell the energy generated to companies which supply it commercially.
  • Transmission: once the energy has been processed and turned into electricity, it is sent through overhead or underground wires from the plants to substations. There, transformers ensure sufficient electrical voltage. Substations tend to be above ground near to power plants, or on the outskirts of cities, though if they are not too large, they may also be within the actual city, inside a building.
  • Distribution: from the substations, electricity is distributed to the homes in the surrounding area. As a consumer, you cannot choose your electricity distributor; it is determined by where you live. That company is responsible for ensuring electricity reaches your home properly, and takes care of repairs when needed. It is also the company which owns your electricity meter, and sends readings from it to your commercial energy supplier.
  • Commercialisation: what you certainly can choose is your commercial energy supplier. It is the supplier who sends you the bill: the supplier buys the energy from the generation companies, and sells it to you. Commercial suppliers are the ones who offer various rates and offers, although in Spain, there is a free market (you pay under the terms of your contract, as happens with your mobile bill) and a regulated market (what you pay is set by a system designed by the Government).
“The company which delivers the electricity to your home is not the same as the one you get your bills from.”

Types of electricity plant

As we said earlier, in order to generate electricity, we need to release the energy contained in primary materials. How do we do this? It depends entirely on the type of electricity plant we are talking about:

  • Conventional cycle thermo-electric plants (coal, diesel oil and natural gas): energy is liberated by burning coal, natural gas or diesel oil. As they burn, they are used to heat a tank of water. That water transforms into steam, which is used to drive a turbine. It is this movement which generates electricity, by means of an alternator, which turns the mechanical energy into electrical energy. Finally, the steam passes through a condenser, turning back into liquid water, and starting the cycle anew.
  • Combined-cycle thermo-electric plants (coal, diesel oil and natural gas): these plants work in a very similar way to conventional-cycle ones. Like these, they have a turbine which is driven by steam from heated water. However, they also have another turbine, driven by air drawn in from outside and heated by the same fossil fuels. The major advantages of combined-cycle over conventional-cycle plants is that they are more efficient, more flexible (they can work at full capacity or at "half throttle" as required) and more ecologically friendly (producing less emissions into the atmosphere).
  • Nuclear power plants: the heat released by nuclear fission in a reactor is used to heat large quantities of high-pressure water. The resulting steam produces electricity as it passes through a turbine connected to a generator. The fuel used tends to be uranium.
  • Geothermal power plants: the system is similar to the previous ones (water is heated to create steam which drives a turbine), but in this case, we use the natural heat within the planet through pipelines in the subsoil.
  • Biomass plants: in this case, heat is generated by burning organic material, be it plant matter or any kind of waste (animal, industrial, agricultural and urban waste products).
  • Hydro-electric plants: these plants do not require heat, as these are the evolved version of the windmills of old. What they do use is a significant water drop to move a hydraulic turbine. They are typically built in barrages and reservoirs.
  • Wind farmsin this case, it is the wind which drives a turbine to obtain electricity.
  • Solar power farms: there are two types. Las Thermo-solar installations use the heat from the sun to heat water and use the steam to drive a turbine. Photovoltaic installations transform solar energy directly into electricity, using photovoltaic cells.
  • Tidal power plants: the movement of water caused by high and low tides drives a turbine, which produces electricity by means of a generator.
  • Wave power plants: similar to the previous technology, but using the force of waves instead of tides.

The major difference between renewable and non-renewable stems from the primary energy being used to generate electricity. Do we need to replace the so-called “fuel”, or is it no longer necessary, because nature provides it for free?

At present, the most commonplace power plants use non-renewable energies: that is, they use primary energy which must be extracted from the ground (coal, natural gas, uranium, etc.). However, the future looks much more renewable.

In the next instalment of this short course, we will go into detail about how each type of power plant works. Don’t miss it!

Click here to learn all about wind power.

Click here to learn all about photovoltaic (solar) power.

Click here to learn all about hydro-electrical power, tidal power and geothermal power.

“Electricity is considered renewable if we do not need to replace the fuel that is used to generate it.”
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