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Energy sources: renewable and non-renewable resources

Energy sources: renewable and non-renewable resources

In the world we live in, energy is a fundamental pillar that drives our daily lives. Energy allows us to light our homes, move vehicles, keep our electronic devices running, and much more. But where does this energy come from?

In this section, we will explore the concept of energy sources. Energy sources are the resources, both natural and artificial, from which we extract the energy necessary to satisfy our energy needs. These energy sources span a wide variety of forms, from solar, wind, and hydroelectric energy to fossil fuels , nuclear energy , and more.

Throughout this section, we will impartially examine the different categories of energy sources, considering their advantages, disadvantages, and their influence on the environment.

What is an energy source?

An energy source is a natural source or resource from which we obtain the energy we need to run our lives. This energy can be used to light our homes, move our cars, heat water or even charge our electronic devices.

There are different types of energy sources, such as solar energy, which comes from sunlight ; wind energy , which is generated from the wind; hydroelectric energy, which takes advantage of the flow of water in rivers and dams; and fossil energy, which is obtained from resources such as oil and natural gas .

There are also more modern energy sources, such as nuclear energy, which is generated from nuclear reactions, and geothermal energy , which comes from the heat of the Earth . Each energy source has its own advantages and disadvantages in terms of availability, environmental impact and costs.

Types and classification of the main energy sources

Energy sources can be classified mainly in two ways:

  • Primary or secondary sources.

  • Renewable and non-renewable sources.

Primary energy sources are present in nature. They include oil , coal , natural gas , firewood or biomass, nuclear fuels, hydroelectric, wind, geothermal and solar energy, in order of importance of current exploitation.

On the other hand, secondary energy sources are not directly present in nature and are resources derived from primary sources. Secondary sources include, for example, electricity.

Main source of energy on our planet

Most of the world's energy resources have the Sun as their primary source.

Energy sources: renewable and non-renewable resources

Solar energy is conserved indirectly in the form of fossil energy or as directly usable energy (e.g.  winds ).

Even hydroelectricity derives from solar energy that causes water evaporation and subsequent condensation when clouds meet the air of cold weather fronts or high mountains.

Non-renewable sources

Non-renewable energy sources are energy resources that do not have the capacity for regeneration or whose consumption speed is higher than their regeneration.

The availability of these sources is currently still quite high and, consequently, the cost relatively low.

The main non-renewable resources are the following:

Fossil fuels

As for the fossil fuel source, the combustion of coal or hydrocarbons such as methane or oil provides the maximum amount of energy, which is used partly for combustion heating systems, partly for the operation of engines , but especially for the production of electrical energy.

Nuclear energy

Nuclear energy can be seen as the mother of all energies, on earth and even in the universe. In fact, all energies, from solar to fossil energies , from wind to hydroelectric, are nothing more than a byproduct of the transformation of this type of energy.

There are two types of nuclear reactions: fission and fusion. Today, all nuclear reactors are fission reactors for technical reasons. 

Atomic fission energy is based on breaking a heavy atomic nucleus (usually Uranium-235) to obtain two smaller nuclei, which weigh less than the original nucleus. The small difference in mass is capable of producing a large amount of energy. 

Nuclear fission plants currently produce 16% of the world's electricity.

Renewable energy sources

Renewable energy sources are those types of energy that are inexhaustible. Its use does not imply a decrease in the resource.

The main renewable energy sources are the following:

Firewood and biomass

The combustion of biomass, wood or other easily available organic materials represents the oldest way of producing heat and therefore energy.

Lately, however, a renewed awareness in the fight against climate change, combined with a growing concern about finding energy resources, has brought this energy source back to the fore.

Solar energy

Solar energy is actually the engine of any activity on Earth : even oil is indirectly solar energy accumulated by the photosynthesis of ancient plants, whose organic matter is believed to have accumulated and transformed underground, during entire geological eras.

Solar energy can be harnessed through three methods:

Wind power

Wind energy is one of the oldest sources of energy: windmills have been used since the 7th century AD to convert wind energy into mechanical energy.

Energy sources: renewable and non-renewable resourcesIn modern times, wind turbines are used to produce electricity. A turbine consists of a large rotor with three blades, which is set into action by the wind.

The disadvantages are the geographical location, the large spaces required for centralized production and the environmental impact.


Hydroelectric energy is a clean energy that takes advantage of the potential energy of water located at high altitudes in mountain basins, which when falling acts on a turbine, producing electricity. The principle is the same as in a thermoelectric plant: the difference is that the medium that rotates the turbine is water, not steam.

Currently, 16% of the world's electricity is of hydroelectric origin: one of the disadvantages of hydroelectricity, however, is precisely the environmental and social impact of the construction of dams.

Geothermal energy

Geothermal energy is energy generated through geological sources of heat and can be considered a form of renewable energy. It is based on the thermodynamic use of the internal heat of the Earth  fed by the thermal energy released in the nuclear disintegration processes of radioactive elements such as uranium, plutonium or thorium.

As it penetrates deeper, the temperature gradually becomes higher, increasing by about 30 °C per km in the Earth's crust.

The exploitation of this source, in the case of high- enthalpy geothermal sources , consists of conducting the vapors from underground water sources to special turbines used to produce electrical energy. And in the reuse of hot water vapor for urban heating, greenhouse crops and thermalism.

Marine or ocean energy

Ocean energy refers to the set of energy contained in various forms in the seas and oceans. This immense amount of energy can be extracted from sea water with different technologies: based on the kinetic energy of fluids (currents, waves, tides) and on the gradient (thermal and saline). Today many energy extraction systems have been tested and some are already at a pre-commercial stage.

Nuclear fusion

Nuclear fusion  is a variant of nuclear energy . It is the process of joining the nuclei of two hydrogen atoms in which an enormous amount of energy is released.

This process gives rise to the energy of the Sun. It generates large amounts of heat that could be used to generate electricity. However, the temperatures and pressures required to maintain fusion make it a very difficult process to control.

One of the potential advantages of fusion is the theoretical possibility of delivering large amounts of energy safely and with relatively little pollution.

The fuel for nuclear fusion is hydrogen. Due to the enormous presence of hydrogen on the planet, nuclear fusion would be considered a renewable energy source.

Publication Date: February 21, 2022
Last Revision: October 25, 2023