Illustration eath and plants

What is a renewable energy?

How do we define renewable energy?Petrol, wind power, gas, nuclear power, solar power… which source is said to be "renewable" and why?

By the way, what is a renewable energy source?Why use it? How do wind or solar power answer environmental and business questions? Let's go back to basics to better understand the issues. 

What is a renewable energy source? definition

We put our questions to Hugo Haas, a research engineer at the French Renewable energies observatory (Observ’ER). He brings his expertise on the subject.

Let's start at the beginning! energy allows us to transform our environment. To exploit this, we need to have a source to convert into a form we can use. You can think of water, wind, solar radiation, then wood or coal burning. "Anything that produces heat when burning, for example, can be considered as a source of energy: a fuel", explains H. Haas.

These energy sources — heat, electricity, petrol — then allow us to meet our everyday needs: help us to operate our industries, heat and light up our houses and propel our cars.

What is renewable energy?

We refer to renewable energies (RE) as opposed to those energies said to be "non-renewable" (gas, petrol, coal), because their reserves are running out. A renewable energy source is, therefore, by its very nature, virtually inexhaustible.And, unlike fossil fuels, their use generally produces little or none of the greenhouse gases responsible for global warming. 

What are the renewable energies?

In concrete terms, renewable energies can be classified into 5 large categories. These different technologies use:
- wind: think of land-based or offshore wind turbines;
- sun: solar panels produce electricity or solar thermal energy, allowing us to heat;
- water: hydroelectric dams or tidal power stations ;
- biomass: used in raw form, transformation or converting organic materials (plants, agricultural waste, wood, etc.) into gas or liquid fuel.
- geothermal, air generation… : heat derived from the ground or the atmosphere is captured by heat pumps and made to circulate, for example, in a house or in an urban heating network. We can also include projects that aim to use heat said to be "recuperation" emanating from all kinds of waste or other industrial processes.

The potential use of RE depends on geographical or climate factors. They cannot all be utilised everywhere all the time. Their production, therefore, is variable.

Illustration renewable energy cities

What is a non-renewable energy?

"It's everything else. Petroleum derivatives such as petrol, diesel, kerosene, heating fuel, coal, gas or uranium" reminds us H.Haas. There are two 2 big energy sources considered non-renewable: fossil-based (petrol, gas or coal) or nuclear fuel. The distinctive characteristic of a non-renewable energy is that it is used faster than the rate at which nature produces it.

But fossil fuels are the hardest to replace. We are thinking, in particular, of coal, historically the first one used and which we can still find in most countries around the world.

Why is the term renewable energy incorrect?

The term "renewable energies" is simplyshort for "renewable energy sources".

According to H. Haas, "with all energies being renewable, the real question is: on what timescale?". For example, humans use up petroleum-based resources faster than the rate at which they are naturally renewed. It takes a few million years to produce it!Petrol is, on a human timescale, a non-renewable energy source. Unlike the sun that appears each day. You, therefore, need to ask yourself if the energy source that we are next going to utilise with the assistance of a machine (wind turbine, solar panels, etc.), is actually renewable.

Illustration of hydroelectric dam

Is nuclear power renewable?

If we go back to the definition of "renewable" — a source that will regenerate quicker than its used — nuclear power is a non-renewable energy. In fact, Uranium, used in inducing nuclear fission, is a finite resource.

Even though it is one of the least carbon-intensive electricity-producing industries,nuclear, like all other industries, produces other forms of pollution: especially certain wastes, emitting radioactive radiation, making it necessary to cool it down and store it buried.

Ilustration of solar energy

Why use a renewable energy?

There are several reasons why we would, as individuals, want to opt for renewable energies. It could even, for some, correspond to an actual philosophy of life. For example, in the case of solar panel installation at home, to be more self-sufficient from the power distribution network or simply be able to understand the process. It can also be a means of using sunshine's added value.

Your motivations can also be environmental, a way to lower your energy impact, reduce your reliance on public networks if the choice is made to be self-sufficient.Or even be economical, in the case where you sell your electricity to the national grid.
As for public authorities,they may find the development of renewable energy resources is a means to reducing their carbon footprint and meeting the different objectives that they agreed to as part of COP summits and on a European level. There could be an opportunity to re-establish a national industry "so long as the resulting industrial jobs are maintained in the territory" " specifies the research engineer.

The development of RE in this framework could subsequently be economical and help control energy prices.

Illustration of CO2

Do renewable energies emit co2?

In principle, renewable energy resources don't emit CO2, or very little, when used. For example, operating a solar farm will not generate CO2 when in use — apart from maintenance vehicles, for example — as opposed to coal power stations.
As for a solar panel's life cycle — from manufacturing to recycling — this remains a source of emissions. It will have more or less of an impact, depending on the country where the panels are manufactured."In any event, with panels' life cycle included, a solar farm's emissions rate is largely inferior to that of a coal power station for an equivalent amount of electricity produced",ensures H. Haas.

In the case of biomass, there are emissions as soon as there is combustion. "If we produce heat by wood-burning, we initially estimate that wood developed through photosynthesis and therefore absorbed CO2 already present in the atmosphere". So biomass is considered as RE so long as it is utilised as part of a reforestation and responsible farming cycle. In other words, the emissions are offset by natural reconstitution.

What is the future of renewable energy sources?

If we summarise, it is primarily the legal and regulatory frameworks that define what are renewable energy sources, according to certain criteria and technologies. According to H. Haas, "there are a lot more and very different ones, which for the most part are at the prototype stage. And finally still very few are used for industrial purposes. There is very active research on this subject". The difficulty in seeing them develop is not so much technical as economic.They, therefore, cannot be deployed without support from the public authorities. Given the intermittency of RE production, it is, for example, necessary to invest in adapting the electricity distribution network.

But of course, renewable energy resources appear to be way out of fossil fuels and their harmful effects on the environment. This is where associations like negaWatt or The Shift Project work to control, prioritise and reduce the energy demands with a more energy-efficient approach. Some scenarios include an energy curfew to achieve this. They then recommend shifting towards an energy mix favouring RE.
At the same time, the development of renewable energies is taking centre stage more and more often in debates. It cannot actually be done without taking into account a certain number of environmental issues.

For example, "as part of the renovation of a mill to produce hydroelectricity, it is imperative to assess, understand and control its impact on the wildlife and biodiversity as a whole", reminds . Haas.

And lastly, there remains the debate surrounding the so-called "green" technologies developed on an industrial scale to produce renewable energies. Doesn't the large scale production of solar panels contribute to the very system that the development of RE actually seeks to combat?

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