Académie des technologies

Evolutionary trajectories of the electricity mix 2020-2060

Comments on an ADEME study on the future energy mix published on 10 December 2018

In December 2018, the French Environment and Energy Management Agency (ADEME) widely publicised its assessment of the evolution of the electricity mix until 2060. In essence, it recommends shutting down existing power plants (including the nuclear power plants) before their end of life, replacing them massively with solar and wind power installations (multiplication by more than ten of the current installed capacities), and developing a hydrogen economy with surplus electricity during periods of favourable wind and sunshine.

The National Academy of Technologies of France, as it has already stated, is fully in line with the policy of developing renewable energies. It considers that the success of this policy requires realistic assumptions. It therefore considers that the conclusions of the ADEME study should be taken with great caution. They should under no circumstances be used as a basis for public policy decisions and their media coverage is premature. The Academy’s opinion, justified in the attached note, is based in particular on the following elements.

1. ADEME has only published a “summary” of its study, which it has not submitted to a scientific evaluation. It does not enable experts to exercise their legitimate role in evaluation and control role. Presented as a “response to its opponents”, the ADEME study is affected by numerous methodological errors and contradictions.

2. ADEME’s approach focuses on the electricity sector. However, the assumptions it makes have an impact on other energy sectors, particularly Gas. There are interactions between these sectors; for example, ADEME proposes the development of large quantities of biogas, particularly from hydrogen produced by electrolysis. However, it is doubtful that this strategy is compatible with the constraints specific to the storage and transport of hydrogen in the Gas sector.

3. ADEME assumes a near stagnation of electricity demand until 2060, despite new uses. This hypothesis is lower than that adopted by the National Low Carbon Strategy (NLCS) of the Ministry of the Environment. Over such a long period, taking into account a growth, if only 1% per year, would radically change the results
Despite these low demand assumptions, ADEME’s trajectories do not ensure carbon neutrality in 2050 – which is nevertheless a government objective – or even in 2060. On this horizon, ADEME’s trajectories require significant electricity imports to compensate the vagaries of the sun and wind. But neighbouring countries will be subject to similar weather conditions, and they will not be able to guarantee French electricity needs.

4. The costs incurred in the Gas sector by the proposed electricity mix are not presented. ADEME wrongly bases its conclusions solely on the electricity economy, without taking into account the necessary investments and operations of the gas sector.

5. Many of the economic hypotheses adopted by ADEME (a) seem very questionable:
– The load factor for onshore wind production adopted by ADEME is significantly higher than the current load factor; however, ADEME admits that future sites will be worse than current sites (b), which is inevitable.
– Hydrogen production facilities will have low load factors; in addition, the expected efficiencies of the conversion processes (electrolysis using of excess electricity, hydrogen transport and storage, production of electricity from hydrogen) are subject to physical limitations; they are, in the end, very low. Have these penalties been properly taken into account?

6. Some prospects for a downward trend in renewable energy investment costs are overestimated by ADEME; for example, still very significant decreases in the cost of onshore wind energy – a mature technology – are unlikely.

7. ADEME does not seem to realistically take into account two difficulties of an electrical system based on a high proportion of intermittent energies: guaranteeing synchronism (c) – the key to network stability – and adjusting to rapid and frequent load variations. ADEME agrees that “additional analyses would be necessary”.

8. The costs of ADEME’s trajectories are very similar (less than 3%); in view of such small gaps at such a distant horizon, and such large uncertainties, ADEME’s conclusions are premature. In the absence of significant differences between trajectories, it would be more appropriate to recognise the need to diversify the energy mix, without giving exclusivity to the development of intermittent renewable energies.
The energy transition will mobilise hundreds of billions of euros; it will bring major changes for future generations. It would be a mistake to base this transition on erroneous technical and economic assumptions both about the production sectors (renewable, nuclear) and about the global energy system, neglecting the achievements of France, where electricity is already essentially decarbonised in favour of hypothetical and random solutions. The guidelines proposed by ADEME are risky.

(a) Or: that appear to have been retained – we have only a summary of the study, with a very partial knowledge of its hypotheses.
(b) The agency’s study identifies a load factor that is significantly higher than that proposed in its hypothesis portfolio.
(c) That is, the instantaneous adjustment between production and electricity demand


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