Renewable, carbon-free and intermittent energies

I often hear confusion about the different types of energy. The different categories under which we classify today “new” energies are based on intentions and stakes. Here is a clarification of clusters and related stakes.

An energy source is said renewable if it is once more available after production as much or even more than before; therefore the following energy sources are renewable ones: solar, wind, hydro, biomass, marine, geothermal energy but not nuclear energy. These energies are sought to ensure continuity of energy supply of the planet without depending any more from resources contained in its soil (uranium, coal, oil), necessarily finite. Ambiguity is often maintained about nuclear energy, given the importance of available stocks in major consuming countries (between 200 and 300 years of consumption in France).

A carbon-free energy is deemed not emit CO2 in production. But no energy is quite carbon-free if we include the manufacturing cycle of the production equipment. The development of these energy sources meets the need to drastically reduce CO2 emissions on our planet.

Intermittent energy is energy produced during particular periods; their production level is not controllable: are intermittent solar, wind and sea. Are not biomass, geothermal and energy from hydropower.

The call for these energies makes it difficult to balance load and capacity on an electrical network: it is difficult to adjust production levels to adapt to changes in consumption and it is sometimes necessary to resort to the consumption of flexibility or energy storage to compensate for variations in production.

The reduction of CO2 emissions, the very long-term sustainability of our energy supply, ensuring a balance of power grids on a not too expensive manner, are objectives that can not be sacrificed. This seems a lot and these are not the only ones. This vocabulary clarification once again shows that the energy mix, ie the portfolio of energy sources chosen to meet at some point our energy needs, can only be a temporary and maturely reflected compromises.