Renewable energies: find out what they are and what types exist

What are renewable energies?

Renewable energies are types of energy that come from natural resources and can be replenished before they are consumed, hence the renewable concept. In addition to this advantage, they usually emit a lower volume of pollutants into the atmosphere, unlike other types of energy. Another key advantage to bear in mind is their availability: given their natural origin, they can be obtained at different times and from different places on our planet. Their accessibility also affects their price: they are usually far cheaper than other types of energy.

Renewables are also called clean energies or green energies on account of the abovementioned qualities.

It needs to be borne in mind that renewable energies have limits. That is, they are a natural resource with maximum scope for exploitation, which means that they are inexhaustible.

Human beings have been benefiting from this type of energy since the dawn of time. The use of wind for mills and for sailing is an example of the exploitation of wind energy.

Renewable and non-renewable energies: the differences

To distinguish between renewable and non-renewable energies, please note the following:

• Renewable energies are derived from natural resources that can be replenished. Non-renewable energies come from finite resources, which are susceptible to depletion, a prime example being oil.
• Renewable energies do not come from fossil fuels, as these are limited.
• Renewable energies have a negligible impact on the environment: obtaining them generates hardly any waste or polluting gases.

What are non-renewable energies?

Non-renewable energies are types generated from sources that cannot be replenished. The resources used to generate them are limited and will inevitably end up being exhausted.

Types of renewable energies

There are many types of renewable energy. Here we provide a little information on the main types.

Solar energy

Solar energy   comes from the harnessing of the Sun's electromagnetic radiation. It is one of the oldest renewable energies: from the orientation of buildings to sundials, not forgetting warfare devices contraptions composed of mirrors or lenses, which magnified light and concentrated it in a point to attack enemy ships and cause fires.

Humanity has been developing and improving technologies for the exploitation of the Sun: there are active methods such as solar thermal or photovoltaic energy, or passive types such as bioclimatic architecture that makes full use of sunlight for natural illumination.

Currently, the use of photovoltaic energy is growing fast: the necessary infrastructure has improved its performance and reduced costs. According to Greenpeace, photovoltaic energy could meet a third of humanity's energy needs by 2030.

For example, China ended 2021 with installed capacity of 308.5 GW, heading the ranking of countries with the highest solar photovoltaic installed capacity. Spain is placed seventh, with 18.5 GW, according to the International Energy Agency. Worldwide, installed capacity is estimated to total 942 GW based on 2021 data. In addition, the technology is being improved so that the yield of panels improves and their waste is minimised.

Wind energy

Wind energy is the process of using the kinetic energy from wind to produce electricity. It is very cheap to generate and done by means of wind turbines. As with solar energy, technological advances have made wind generation cheaper and improved performance. In addition, no waste is generated (its elements can be reused).

In 2021 worldwide installed capacity totalled 837 GW. China is the country with the highest installed capacity, with 339 GW. Spain ranks fifth, with 27.5 GW of installed capacity, according to the Global Wind Energy Council (GWEC). It is another of the most popular types of renewable energy.

Hydraulic energy

Hydraulic energy takes advantage of the kinetic energy and potential of water in places such as rivers or waterfalls, always using fresh water. It has also been a resource used by mankind since ancient times, with water or tide mills.

To exploit this type of energy, sites are sought with a natural fall of water currents or dams are built where the water is accumulated and can be used as required. At the end of the fall is a turbine, which is powered by water.

Geothermal energy

Geothermal energy is a type of renewable energy taken from the heat of the Earth's core. This heat is transmitted through hot rock bodies, or by means of conduction and convection processes. In this way groundwater and rocks interact, resulting in geothermal systems.

It is another type of energy that has been used since ancient times, taking advantage of hot springs or geysers. There are currently different systems for taking advantage of heat, depending on water temperatures. Electricity is most commonly generated via the movement of a turbine driven by the force of water vapour.

Tidal energy

Tidal energy involves the exploitation of the surge of ocean waters during the rise and fall of tides. It is generated by means of an alternator that transforms the kinetic energy of water. In this section we must also mention wave power, which takes advantage of the force of waves. These renewable energies are the least developed and have the lowest installed capacity due to the complexity of their infrastructure. However, their characteristics mean there are significant plans for them.

Biomass energy

Biomass energy involves the use of organic material to obtain energy via chemical processes. The process ranges from burning wood to make a bonfire to using urban waste to generate electricity. Certain crops are also chemically treated to obtain biodiesel.

However, biomass causes some dilemmas when it comes to being considered a form of renewable energy. If the raw material comes from waste, it does not entail a depletion, so it ticks all of the necessary boxes to be considered a renewable and clean energy. But if it comes from crops, it does imply a limit and can take up resources inefficiently, so its biggest challenge is sustainability.

Nuclear energy: is it renewable?

Nuclear energy is obtained from atomic reactions. Based on research conducted in the nineteenth and twentieth centuries, it began to be used in the 1950s. Although it produces few emissions, it generates nuclear waste that is very dangerous for the environment. In addition, obtaining its fuel (usually uranium), both in the extraction process and its enrichment, generates polluting gases and waste and contaminates water.

Focusing on uranium, we must bear in mind that there are known and limited reserves of this mineral. There is calculated to be enough uranium to power nuclear plants worldwide for around another 70 years. In addition, these reserves are in the hands of certain countries and their accessibility is relative, so their price can increase according to the global backdrop and demand.

However, the European Union (EU) has opted include nuclear energy and gas within its “environmentally sustainable economic activities”, considering these to be green (but not renewable) energies.