sources of primary energy

Reading time: 11 min

Energy is the capacity that an object or system has to produce changes in itself or in others. Fundamental for the development of humanity, the UN classifies it as something “indispensable for almost all of the major challenges and opportunities facing the world today.” However, the concept of energy is very extensive, and here the focus will be on primary energy. Then we will show you what primary energy is, its main energy sources, and some examples of them.

What is primary energy?

By primary energy we mean all natural energy sources in their original and unaltered form. In other words, all those which are available in nature before that energy is converted or transformed

The energy sector distinguishes between different stages that range from the production of primary energy to its storage and transportation in the form of secondary energy, and then to its generation and consumption as final energy. Among the sources of primary energy, the main ones are:

  • Wind
  • Sun
  • Water
  • Heat (coming from the center of the Earth)
  • Biomass
  • Fossil fuels 
  • Radioactive minerals
Biomass energy plant

Understanding the sources of primary energy

Firstly, wind produces what's known as wind energy; from the movement of wind turbine blades electrical energy is produced.

With regards to solar radiation, its energy can be harnessed in two ways: as solar thermal energy (i.e., heat) or as photovoltaic solar energy, which allows the energy from the sun to be transformed directly into electricity.

With regards to energy from the water, it can be used in different ways. On the one hand, in waterfalls and reservoirs it's possible to obtain hydropower, while the sea produces tidal power or wave power (depending on whether tidal or wave force is harnessed, respectively).

For its part, geothermal energy makes use of the heat at the center of the Earth to generate electricity, while biomass is energy that comes from biological resources (e.g., wood, olive stones, or animal excrement).

On the other hand, coal, oil, and natural gas fall within what are known as fossil fuels. 

Finally, radioactive minerals (uranium or plutonium) release the energy inside their atoms when the nucleus is broken apart through the process of nuclear fission to release heat, which can then be harnessed to generate electricity.

Renewable primary energy sources

wind turbines in the sea

Renewable energy sources are those that can be regenerated naturally, so they are virtually endless. For example, the sun, the Earth's heat, wind, and water are the main ones. Some of these sources are still in the experimental phase such as tidal power and wave power. Energy obtained from biomass (bioenergy) is also considered renewable.

Today, the main limitation of these renewable primary energy sources is that the availability isn't constant. For example, the wind doesn’t always blow with the same force nor the sun shine with the same intensity, which has an impact on the amount of energy that can be produced from them. Therefore, it's currently necessary to have back-up generation systems, which is usually a thermal component, in order to guarantee the electrical supply.

In Spain, we have some very favorable weather conditions for the generation of PV solar , hydro, and wind energy. In fact, in the last few years, renewable energies have reached record highs in contribution to the country's electricity mix (i.e., the combination of different primary energy sources). The aim for 2030 is for the share of renewable energies to reach 74% in electricity generation and 42% in the final use of energy (transportation, heating/cooling, and electricity).

Non-renewable primary energy sources

Among the sources of non-renewable primary energy are fossil fuels (gas, oil, and coal) together with radioactive minerals. In the case of fossil fuels, their combustion allows energy to be obtained, which may be mechanical (for example, to start up vehicles), thermal (to heat), or electrical. Currently, energy obtained from oil is the most used in Spain, and other derivatives are also extracted from it like certain types of plastics. For its part, gas consumption in homes, businesses, and industries is the second most used energy in Spain.

The extraction of nuclear energy occurs through a process called nuclear fission, which causes the disintegration of atoms from radioactive minerals to generate heat.

These primary energy sources are present in nature in limited amounts, hence they are considered non-renewable resources. 

renewable electricity generation and electric car charger

How is primary energy transformed into secondary energy?

Secondary energy sources come from the transformation of primary energy sources. In other words, they're generated directly from primary energy sources and aren’t present in nature by themselves. Some secondary sources include electricity and oil derivatives (gasoil, fuel oil, kerosene, coke, etc.). When secondary energy is placed at the disposal of the final user, it's called useful or final energy. 

In order to transform primary energy into secondary energy, different processes are carried out according to the energy resource. To that end, there are different types of electrical substations. 

For example, in refineries oil refining is carried out, which separates this raw material into different components. These, in turn, are used in homes, industry, or transportation as a final energy.

In thermal power plants (which may use natural gas, oil derivatives, coal, or biomass), the combustion of any of these materials is used to generate water vapor, which moves some turbines in order to produce mechanical energy, which is transformed into electrical energy. Within thermal power plants, combined cycle ones allow the thermal energy from natural gas to be transformed into electricity thanks to the joint action of a gas turbine and a steam turbine. 

On the other hand, nuclear power plants generate a large amount of energy from the nuclear fission process; this energy also serves to heat water and generate water vapor, which will move some turbines to produce electricity.

With regards to power stations based on solar, hydro, and wind energy, the efficiency is lower or simply variable in the sense that the generation of energy reduces according to the availability of the resource and this can't be stored.

With regards to renewable energies, energy from the sun is transformed in photovoltaic power stations and solar thermal power plants, respectively. In the first case, solar panels capture solar radiation and convert it into electricity. In the second example, the heat from the sun allows a fluid to be heated, which then will heat the water to generate steam. Like with thermal power plants that use non-renewable energies, the steam will move a turbine to produce mechanical energy that afterwards is transformed into electrical energy.

Lastly, hydropower plants harness waterfalls (natural or artificial) to move some turbines that generate electricity.

Not all electrical substations have the same capacity to produce energy. For example, with regards to refineries, nuclear power plants, and gas-fired thermal power plants, the energy resource that feeds them can be stored, which facilitates its availability and, therefore, the supply.

Repsol is committed to new energy sources

solar panels in the countryside with a city in the background

We are a global multi-energy provider and we work to drive the evolution towards a low-emissions energy model. We have a firm commitment to advance in the energy transition and reduce the emissions of our operations and products in line with the climate goals of the Paris Agreement and in which renewable energies play a key role