Solar, wind, geothermal, biomass… Renewable energies promise to produce electricity without emitting CO2 , unlike fossil fuels such as oil and coal, and thus limit global warming . Are these renewable energies really the right solution for a “cleaner” planet?
Renewable energies and energy transition
Solar, wind, hydraulic, geothermal and biomass (burning waste) energy are so-called renewable energies or ENRi, because they are inexhaustible on a human scale. All these energies, as well as nuclear energy, are said to be decarbonized, that is to say that they generate very little CO2 for a cleaner planet .
The energy transition is the shift from polluting and CO2 -emitting energies to less polluting energies. This transition attempts to electrify technologies as much as possible (today, we use oil and gas much more than electricity), to produce this electricity without carbon to reduce CO2 emissions, and above all to improve technologies so that machines consume less energy. The energy transition is therefore the transformation of our energy consumption towards less polluting sources in order to limit global warming which threatens the planet.
CO2 , enemy number 1?
When we talk about energy transition, we always talk about transition to renewable electricity. Indeed, in the face of global warming, the number one enemy of pollution is carbon, one of the main greenhouse gases ( CO2 , methane).
If we compare the rate of CO2 emitted for the same quantity of electricity produced at a power station for each energy source:
- coal emits 1000g of CO2 to provide 1 KWh (kilowatt hour)
- natural gas, 400g of CO2
- hydroelectric dams, from 6 to 140g of CO2
- solar 55g of CO2
- geothermal energy 45g of CO2
- wind 14g of CO2
- and finally the anti- CO2 champion, nuclear power which only emits 6g of CO2 to provide the equivalent of 1 KWh.
If renewable energies seem to be the solution to reduce CO2 emissions, this implies above all reducing our dependence on oil and coal, in favor of nuclear power which does not contribute to global warming.
The key role of nuclear power
The energy transition aims to get rid of fossil fuels as much as possible, first coal, then oil and gas. A very ambitious goal because these energies, which are very important in daily life, also play a crucial role in the financial balance of the planet. This is the whole difficulty of this energy transition. It must massively develop renewable energies (in priority in countries that have a lot of wind and sun) while sparing nuclear power which allows the switch to be made smoothly. This transition must also avoid constraints and restrictions that risk weighing on populations. It is the combination of nuclear + renewable energies that will allow an efficient and comfortable transition.
Are renewable energies polluting?
Solar and wind farms must be built massively, which generates many polluting effects. Indeed, to transform the renewable resource (sun and wind), it is necessary to build installations (solar panels and wind turbines) which require thousands of tons of materials (concrete, cement, steel, glass, rare metals, etc.). In the end, this program will require 10 to 15 times more materials than for nuclear power at the same power produced. However, these materials are non-renewable resources since they have consumed energy and polluted the environment to be extracted, then transformed. Not to mention their manufacturing process which uses fossil fuels and therefore emits CO2 upstream.
What about the footprint? In other words, what is the average land area that will be occupied, so how much natural land will be destroyed for the same amount of energy produced: hydraulic 180km2, solar 170km2, coal 80km2, geothermal 50km2, and below 5km2: wind, gas, and finally nuclear which is always in the best position. The development of renewable resources is not without consequences.
Limits to renewable energy
First, most renewable energies, whether solar, wind or hydro, produce only electricity. But electricity is not the only energy used.
In France, electricity only represents 25% of the energy consumed, we need a lot of oil (for transport, industry, agriculture and housing), but also gas and even coal. Clean electricity is good (we already have some in France with nuclear and hydroelectricity), but it does not solve the whole problem. Be aware that there is still 68% of fossil energy directly consumed that will have to be replaced as much as possible by electricity, provided that it is decarbonized, therefore nuclear or renewable.
Why are renewable energies insufficient?
Because of their "intermittent" operation and their low efficiency. Whether solar or wind, these energy sources are insufficient to cover the demand for electricity on their own. Indeed, they depend on the sun for one, only available during the day, and depending on the weather, and on the wind for the other, which also blows randomly. Their production is therefore variable and relatively unpredictable.
It is impossible to see France's main electricity production system, which is also intermittent, with frequent power cuts. This is why ENRi still needs on-demand energy production systems, such as thermal (gas/coal), nuclear and hydraulic power stations, which can produce electricity quickly if needs increase massively.
Conclusion, ENRi are not the unique and perfect solution to replace all other energy production systems.
A major problem, storage
In this "all renewable" and "all electric" scenario, the problem is the storage of electricity to solve the problem of the intermittency of these sources. At present, this minimal storage is done via batteries (generally "Lithium-ion") which are unfortunately very polluting during manufacture and at the end of their life.
So how can we store large quantities without causing an ecological disaster in the future? Pumped storage plants or "STEP" (specific hydroelectric dams). This is the only large-scale, non-energy-intensive storage solution today that could well become a sector of the future, even though it has existed for a long time. These special plants are technically capable of storing surpluses and filling the deficits of tomorrow's intermittent renewable energies.
A major problem remains: the massive increase in the number of these dams will lead to the displacement of populations.
Should we stop nuclear power?
In France, it would be an aberration to deprive ourselves of nuclear power plants that produce about 70% of our electricity without CO2 , and this, to fight against CO2 emissions and replace fossil fuels! Indeed, we would then be forced to replace these plants with other controllable, non-intermittent systems, in other words gas (coal being almost banned).
Germany had this experience about ten years ago. This country wanted to phase out nuclear power in favor of renewable energy. Result? Germany is now the European champion of CO2 emissions, because it had no choice but to rely on coal and gas to compensate for the intermittency of its wind turbines, and meet the growing demand for electricity from its population.
How to optimize renewable energies?
The solution? Consume different energy sources depending on where they are used to find the best "energy mix" for each country. In France, electricity only represents 23 to 25% of our energy consumption and the majority of the energy used (especially for cars and heating) comes from oil and fossil fuels.
And as we have seen, these are the ones that pollute the most. More than the transformation of energy sources, it is the reduction of the consumption of these fossil fuels that is the real challenge of the energy transition.
Energy sobriety above all
Getting rid of oil, gas and fuel oil is proving extremely complicated. Converting the car fleet to electric requires infrastructure to recharge the cars, a lot of resources for the batteries. And what's more, if all French people drove an electric car , we would have to produce a lot more electricity. And producing a lot of electricity with renewable energies is a problem.
This explains why experts believe that the most important objective in the energy transition is first of all the reduction of energy needs (especially car travel and heating).
What are the risks of all-electric?
The energy strategy pursued by the European Union at present promotes intermittent renewable energies to replace coal first, then gas, and also nuclear in parallel (depending on the country).
This programme is likely to cause major energy and resource supply problems in the coming decades. This is already the case in some Nordic countries that have switched to electric cars en masse and have had to face shortages.
The question can be asked for France, which is continuing its policy of closing certain nuclear power plants in order to replace them with ENRi. Indeed, the massive electrification imposed by widespread decarbonization, particularly in transport, is leading to an ever-increasing demand for electricity.
If renewable energies are essential for the energy and especially ecological transition, none are perfect. Hence the interest in diversifying these energies and maintaining nuclear power for its low CO2 emissions, versus high efficiency. But above all, the transition to renewables must be accompanied by a significant reduction in energy needs, which requires awareness and a change in lifestyle on the part of everyone.
