"The energy transition is not going fast enough"

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Secretary of Energy Barack Obama between 2009 and 2013, Steven Chu received the Nobel Prize in physics in 1997, with Claude Cohen-Tannoudji and William Phillips. He is now a professor at Stanford University (California) and returns, for The world, on the development of renewable energies.

Four years after the Paris agreement on the climate, fossil fuels still represent more than 80% of the energy mix, and the world consumes more than 100 million barrels of oil per day. Is the energy transition on track?

We have every reason to be worried. The energy transition is not going fast enough. In Europe or the United States, CO₂ are stable or decrease slightly. But that's not enough. The latest scientific studies on the climate show us that the risks are more and more important. The environment in which we live is more sensitive than we thought.

However, we are witnessing a very strong development of renewable energies, such as solar or wind power. Can they replace fossil fuels?

In part only. We can discuss the proportion of renewable energy in the future electricity mix, but we know that their place will be dominating. However, it must also be recognized that integrating renewable energies into an electricity grid is not possible without significant technical difficulties. I do not think it's possible to reach 100% renewable energy in the near future. We do not have enough electricity storage.

The cost of batteries has however been divided by five in the last ten years …

Currently, batteries can not store enough electricity to ensure that there are no power cuts. Their cost has fallen sharply, with the emergence of electric vehicles, but they remain very expensive to store large amounts of electricity. The electricity grid will continue to need manageable means that can be mobilized on demand.

What types of energy could then take over renewables without increasing emissions?

You have the choice between producing electricity with nuclear energy or fossil fuels, but with a system, carbon sequestration, which can limit CO₂, and which does not exist today on an industrial scale. The subject is important: the people will not agree to give up the light, close the factories and stop the economy.