The instability of production is one of the major problems of renewable energy (especially for solar)
Methanation, a solution for the future to overcome the variability in renewable energy production
Jean François Papot, associate director of the Les EnR design office, offers us an expert opinion on the usefulness of methanation for storing energy and alleviating the variability in the production of renewable energies.
"Yes, but what do you do when the sun and wind are gone?" This simple question too often ends the debate on the massive integration of renewable energies into our energy mix. Worse, it is often followed by a stereotypical spiel about the need to relight coal-fired power stations or the evocation of a return to the candle. The main criticism against renewable energies is indeed the intermittence of their production.
Renewable energy mix: the question is no longer "if" but "when"
Faced with the shortage of fossil fuels and the growing unacceptability of nuclear power, the massive use of renewable energies to produce our electricity is no longer seen as an ecological utopia but indeed as a necessary transition both from the point of view economic than environmental. From this need arises another: to provide an answer to the intermittency of renewable energies to store the surplus of the periods of production and respond to peaks of consumption.
Intermittence is expected: it's even a job!
First of all, it should be remembered that intermittence does not mean unpredictability. It is thus quite possible, on a regional scale for example, to predict the production of a wind farm or photovoltaic power plants several hours in advance. As any network operator already anticipates peaks in consumption, the most innovative (in Spain, Germany, etc.) have learned to integrate an energy mix with a strong renewable component (occasionally greater than 100%) and therefore to manage this famous intermittence. When production is greater than consumption, it is thus common to “store” electricity via, for example, pumped storage energy transfer stations (STEP) to “lift” water drawn from it. downstream to upstream of a hydraulic dam. This water can then be reconverted in a conventional manner into energy by the dam at the cost of a loss of yield of the order of 20 to 30%. This intermittent management (production by storage and consumption by demand response) is one of the challenges of future smart grids, which currently mobilize enormous financial, technical or industrial resources.
Methanation: building a bridge between gas and electricity
Despite this, the massive use (i.e. close to 100%) of renewable energies requires finding new storage methods. Some elegant tracks exist but come up against technical (regulation of charge / discharge cycles for electric batteries), quantitative (STEP, compressed air storage, etc.), environmental (exploitation of materials for batteries) or safety limits. (hydrogen storage) and therefore will not allow, even by combining them, to respond satisfactorily to the problem as a whole.
One of the great strengths of the negaWatt scenario is to have responded to this problem by highlighting the necessary complementarity between gas and electricity. It is classic to think of gas to produce electricity (cogeneration) but a known and French concept also makes it possible to reverse the paradigm to create an equivalence, with the loss of yield close, between these two energies: methanation.
Sabatier's formula: CO2 + 4 H2 = CH4 + 2 H2O
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