What is energy? From wind to solar and nuclear, we explain the basics of global power

Energy cannot be created or destroyed; it can only be converted from one form into another. This rule, one of the fundamental rules of physics, is the first law of thermodynamics, and it plays a part in all aspects of life.

What is energy? From wind to solar and nuclear, we explain the basics of global power

What is energy?

In physics, energy is defined as the ability to do ‘work’. This could be heating something up, thermal work, or moving something, known as mechanical work. There are many different kinds of energy including kinetic, gravitational potential, thermal, nuclear and magnetic. When it comes to providing energy for human use, the biggest form we receive energy is when it has been converted into electrical energy.

What is electrical energy?

Electricity is the movement of electric charge, usually known as the flow of electrons through a conducting material. Electricity generation is the process of making electrical energy from other forms of energy.


What is oil?

We all know how the story goes. Animals eat plants, storing the energy in their own cells as chemical energy. When animals and plants died millions of years ago, they eventually became buried by rock. These rock layers created high temperature and pressure environments and over time, these changed the remains into fossil fuels like oil, coal and gas.

Crude oil is one of the main forms fossil fuels are extracted from the ground in. It is unrefined, meaning it is a mixture of hydrocarbons, and has to be separated into its parts by fractional distillation. These include gasoline, which is used for petrol, naphtha, which is used in making plastics, and kerosene.

What is gas?

Natural gas, or methane, is another example of a fossil fuel created from the remains of sea creatures.

Chemical energy is energy stored in the bonds of atoms and molecules. Batteries, biomass, petroleum, natural gas and coal are all examples of sources of chemical energy. The energy is released through burning the fuel, which is an exothermic reaction – meaning heat is generated. This heat is used to turn water into steam, which drives a turbine, generating electrical energy.

What is coal?


Coal is the fossil fuel generated by remains of plants. Compared to gas, it produces around 50% more carbon dioxide per unit of energy, which is why countries are trying to move away from it as a source of energy. Coal is cheaper than gas, but many countries, including the UK, have placed a tax on producing carbon dioxide that means it has become more profitable to burn gas for power. Britain’s last coal plant is scheduled to close in 2025.

What is nuclear energy?

The physics behind nuclear energy involves interactions between some of the tiniest particles imaginable. At the centre of every atom in the universe lies a tiny collection of protons and neutrons called a nucleus – and nuclear physics involves the making or breaking of a nucleus.

What is wind energy?

There are two types of wind generation – onshore and offshore wind. Both work using the same principle, the difference is just whether they are in the ocean or on land. The wind turns propellor blades around a rotor, which is connected to a shaft. This spins a generator as it turns, which generates electricity.

What is solar energy?

Solar power is another popular method of renewable electricity generation.

Solar cells make use of the photovoltaic effect, when a photon, or a particle of light hitting the cell and causes an electron to flow. Photovoltaics have the demonstrated capacity, the reliability, and the available resources to the world, according to experts.


“The one missing ingredient at present is large-scale, robust, and cheap electrical energy storage,” Robert Jaffe, MIT physicist, told Alphr. He added there are no obvious candidates at present.

However, not everyone agrees. “In general, I would say that large scale commercial energy storage on the global stage has already been realised,” Marek Kubik, market director for AES’s Advancion energy storage systems, told Alphr. He mentioned large-scale lithium ion battery systems in the US as examples.

Image: Jeff Kubina, used under Creative Commons

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