Clean energy

What is clean energy?

Energy efficiency Energy transition

Clean energy is energy in full development to fulfill our current desire to conserve the environment and deal with the non-renewable fuel crisis. With no pollution or waste, there are differences between clean and renewable energy sources, as we will explain later on.

Clean energy is necessary for the sustainable development of human activities.
Clean energy is necessary for the sustainable development of human activities.

In light of the climate emergency and the energy crisis threatening the planet, we have a duty to find solutions and implement policies and measures to deal with these problems. One highly effective, efficient way to do this is by investing in clean energy, as we will explain in detail later on.

Definition of clean energy

Clean energy comes from generation systems that do not produce any kind of pollution, notably greenhouse gases like Co2, which cause climate change. Therefore, clean energy - in full development - drives advances to conserve the environment and palliate the crisis with non-renewable fuels, such as gas and oil. 

Differences between clean and renewable energy sources

Clean energy and renewable energy are two concepts that are bundled together, but they are not the same thing and it is important to understand the difference. The first difference is the pollution they cause. You may not realize that renewable energies can cause pollution.

For example, biogas and biodiesel are renewable sources of energy because, among other things, they come from natural, inexhaustible sources. However, unlike most renewable energies, they pollute the atmosphere on combustion, emitting greenhouse gases.

Clean energies do not pollute and, therefore, it is fair to say that most renewable sources of energy are also clean and vice versa.

The most common types of clean energy and how they work

Most clean energy is also renewable and therefore, in addition to nuclear energy - which we will address later on - the following are currently the most common:

Wind energy

It is a clean, renewable, local, inexhaustible source of energy obtained by transforming the kinetic energy from the wind into electricity. There are two types, according to where the wind turbines are installed:

 Learn about the Flagship project: R&D+i for floating offshore wind power

 Wind energy

Photovoltaic solar energy is clean, renewable, local and inexhaustible source of power that converts sunlight into electricity using the photovoltaic effect.


We are leaders in solar energy.

 Hydroelectric energy

Hydroelectric energy is a clean, renewable, emissions-free, local source of power that uses the force of water falling from a height or running down a slope to produce electricity. This type of power generation can be divided into hydroelectric pumping stations, the most efficient, large-scale energy storage method in existence.


Energy storage, in addition to integrating renewables, brings efficiency savings to the electrical grid.

 Energy from green hydrogen

Green hydrogen is based on generating hydrogen, a universal, light and highly reactive fuel, using a chemical process known as electrolysis. This method uses an electric current to separate the hydrogen from the oxygen in water, so if this electricity is obtained from renewable sources, we will produce energy without emitting carbon dioxide into the atmosphere.

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Green hydrogen is efficient and 100 % sustainable, with some experts predicting that it will be the fuel of the future.

 Energy from biomass

It is a source of clean, renewable energy that produces electricity by burning natural organic material or organic waste produced by human activity.

 Geothermal energy

It is a type of clean, renewable and inexhaustible energy that harnesses the heat that radiates from the center of the Earth using power plants located on deposits. These may be hot water deposits, in which case the heat comes from layers of hot water flowing beneath the surface, or dry, which uses heat from rocks.

 Tidal energy

It is a source of clean, renewable, local and inexhaustible generation that converts the power of waves into electricity.

Other types of renewable energy include solar thermal energy, which uses the heat of the sun, wave energy, which converts the energy from waves, and ocean thermal energy conversion, which uses the ocean thermal gradient between cooler deep and warmer shallow or surface seawater. As well as these, more and more hybrid energy projects are emerging that combine different renewable generation sources to ensure a more stable, efficient supply.


Learn how hybrid plants work.

 Nuclear energy

Despite what many people think, nuclear energy is clean throughout its generation, as well as being almost inexhaustible using current uranium reserves, which will be able to continue producing the same quantity of energy for thousands of years.

In fact, most nuclear reactors only emit water vapour into the atmosphere. Neither CO2, nor methane, nor any other type of polluting gas that aggravates climate change is part of the equation. What's more, we must not forget the enormous amount of energy a single power station can generate because of the massive power stored in nuclear energy.

This energy is obtained in two ways: nuclear fusion and fission. In the first of these, energy is released when the nuclei of atoms combine or fuse together to create a larger nucleus. In the second, the nuclei separate to form smaller ones and, in turn, release energy.

Advantages of clean energy

As you can see, there are numerous types of renewable energy, but what do they all have in common?

  • They are environmentally friendly: no clean energies generate greenhouse gases or other polluting emissions into the atmosphere.

  • They are unlimited: we obtain them from inexhaustible or rapidly regenerating natural resources, so they can be used indefinitely and without limit.

  • They are safe: they do not entail additional hazards like nuclear power, and they are simple to dismantle, so there are no waste management issues at the end of the facility’s useful life

  • They promote energy independence: because they use natural resources found all over the planet, so that countries and regions are able to develop their own technologies rather than depending on electricity produced abroad.

  • They create jobs and boost the local economy: most renewable facilities are labour-intensive to build, maintain and operate, which creates jobs and stimulates the national economy.

The future of energy is green

The United Nations predicts that the world population could reach 8.5 billion by 2030 and 9.7 billion by 2050, and exceed 9.7 by 2050, which is 20 billion more people than are alive now. Two-thirds of them live in cities and living standards are improving as emerging countries join the global middle class.

All this means a higher worldwide demand for energy, which could increase according to the most recent report issued by the U.S. Energy Information Administration   (EIA). Fossil fuels cannot satisfy this demand. Firstly, because it is estimated that oil reserves will be exhausted within 40 to 50 years and natural gas, within 60 to 80 years. Secondly, because fossil fuel combustion releases greenhouse gas emissions into the atmosphere, causing global warming and climate change, the main menaces to humanity in the 21st century.

In such a scenario, it is crucial to opt for safer, more plentiful and less environmentally damaging sources of energy

The importance of renewable energy and its zero environmental impact

2021 was a strong year for the energy transition: almost 257 GW of renewables were installed worldwide, increasing the energy stock by 9.1%. 

Solar PV alone accounted for more than half of new renewable energy installations with a record 133 GW, followed by 93 GW of wind power overall, 21 of which are offshore wind installations.


At the Iberdrola group, we are a world leader in renewable energies, in addition to being leaders in installed renewable capacity. These energies are the fundamental pillar on which our clean, reliable and intelligent business model is built.

Thanks to our 2025 investment plan - extended to 2030 - we aim to double this renewable capacity to 60 GW in 2025, while reaching 95 GW in 2030. 

One of the main keys to the group's future growth is offshore wind, which is the second most important technology thanks to the strong growth experienced in the last year. Our goal is to consolidate our position as a global benchmark in offshore wind, and thanks to the expansion of our offshore wind portfolio, we are in an unbeatable position to participate in auctions and tenders that arise, both for existing projects and for new opportunities.

Which are the most widely used clean and renewable energies in the world?

Hydropower is the clean, renewable source with the largest installed capacity worldwide. By the end of 2021, according to the IRENA report, global renewable generation capacity amounted to 3,064 GW. Hydropower accounts for the largest share of the global total, with a capacity of 1,360 GW (44.39% of the total). Solar and wind account for 849 GW (27.7%) and 825 GW (26.9%), respectively, while other renewables include 143 GW of bioenergy and 16 GW of geothermal, as well as 524 MW of marine energy.

How does clean, renewable energy help to stop global warming?

In 2020, IRENA published the first report on renewable energy sources, Global Renewables Outlook: Energy Transformation to 2050 Enlace externo, se abre en ventana nueva.. The report argued that to overcome the health, humanitarian, social and economic crisis triggered by the COVID-19 (coronavirus) pandemic, it is imperative that economic stimulus policies are aligned with the need to ensure sustainability and strengthen resilience, as well as improve people's health and well-being.

To achieve this goal, it is essential to commit to Green Recovery and to effectively carry out the energy transition. This is the only way we can aspire to meet global climate targets and decarbonise the economy.

The Iberdrola group plans to invest 150 billion euros by 2030 to remain at the forefront of the global energy revolution, thereby consolidating its business model, based on more renewables, more grids, more storage and more smart solutions for customers.

The fight against climate change is the great challenge for humanity in the 21st century, and the necessary shift towards a decarbonised economy based on renewable energy is everyone's task. The minimum target of 32% renewable energy by 2030, set by the European Parliament and the Council on the Renewables Directive, is achievable. To achieve it, we must without fail assume a scenario of high decarbonisation and electrification of the economy, using decarbonised fuels in niches and sectors that are difficult to electrify.