In the Promes laboratory, the solar saga with subscribers

In his very congested office of the University of Perpignan, Xavier Py is a bit like a survivor."Ten times, we almost closed the lab to us," recalls the teacher-researcher in the Promes laboratory (processes, materials and solar energy).

But, for ten years, the wind has turned.Climate change helping, we were once again interested in the work of this CNRS-University laboratory in Perpignan, pioneer in concentration solar.

Technology has, it is true, enough to dream: on a desert surface equivalent to that of Spain, it alone could produce all the electricity that the world needs.All without greenhouse gas emissions, hazardous waste and without risk of exhaustion of the energy source!

To put it simply, the solar thermodynamics with concentration is to have the sun's rays captured by mirrors which make them converge in a given point, where these rays are converted into very strong heat.

The steam created thanks to this heat turns an electric generator, as in any traditional thermal power plant supplied with gas, coal or fuel oil.

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A hibernation sector for twenty years

In the years 1970-1980, the Profes laboratory was running in the tie in the tamping of solar energy, thanks to two peak installations: the solar oven of Odeillo, the largest in the world, capable of raising the thermometerto 3,000 degrees in a few seconds;and the Thémis pilot electro-canal power plant, built in 1983 by the CNRS and EDF.Las, the oil counter-shock and the choice of nuclear power bring the sector into hibernation for twenty years.

In the early 2000s, the oven was reactivated, the mirrors of themis dusted and the 170 members of the laboratory took up the torch of their predecessors.Solar concentration has become fashionable again.Experts from the International Energy Agency even plan that it could ensure 10 % of global electricity production in 2050.

Centrals are starting to grow in the sunny areas on the planet… using the technology of melted nitrate salts that had been developed in Thémis.

"The concentration solar needs storage, otherwise the power plant would stop working when the sun sets," recalls Xavier Py.The use of melted salts, storing heat, which has been adopted by all the power plants installed today, is basically a French invention!»»

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Rather than resting on the laurels of Promes, Xavier Py then makes a quick calculation."A power plant with 50 MW needs 28,000 tonnes of salts to ensure its operation 24 hours a day," he said.To ensure 10 % of global electricity production, 400 power plants of this type per year should be built by 2050, which would require 10 to 20 million tonnes of salts per year.»»

Good use of waste

Problem: the world's main supplier of nitrates, Chile, only produces 800,000 tonnes, already largely pre -empted for the manufacture of agricultural fertilizers.

In his lab, which is both from the garage and the dispensary, Xavier PY is looking for a replacement solution.And find.Based on his asbestos retreating experience, he is working with his teams in the manufacture of industrial ceramics capable of storing heat.

Mais comment fabriquer des quantités astronomiques de ces matériaux sans faire exploser les coûts et les impacts environnementaux ? « D’une certaine façon, je me suis transformé en éboueur»», s’amuse Xavier Py.Asbestos, residue of steel manufacturing, flying ash captured in the chimneys of thermal power plants ... for Xavier Py, everything is good.Even egg shells.

"The food industry produces industrial quantities," notes the researcher.However, this waste is an interesting source of carbonate for our ceramics.»» Les petites tuiles gaufrées – qui jonchent son bureau – sont désormais au point : cent fois moins chères que les sels de nitrate, elles affichent même de meilleures performances.

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Exportable technologies, especially in Africa

"Technically, we are ready," he says.All that is missing is the industrialist willing to invest in series manufacturing.»» L’un de ses anciens doctorants a créé la start-up Eco-Ech-Ceram – qui vient de recevoir le prix du concours mondial de l’innovation – pour permettre ce transfert industriel.

At the same time, the concentration solar sector must lift another technological lock: finding the means of cooling the solar power plants - installed in the sunny areas of the planet, and therefore the driest - using as little water as possible. « C’est l’une des priorités de la communauté scientifique solaire mondiale»», assure Xavier Py.

In the absence of adequate spaces, solar concentration has little future in France.But the technologies developed to prommes are exportable.For example, a partnership was thus established with an engineering school in Burkina Faso.

« Entre l’artisanat local et les matériaux disponibles, l’Afrique de l’Ouest a les moyens de fabriquer de très bonnes céramiques»», se félicite Xavier Py.The researcher may have his head in the stars, his feet remain well anchored in the realities of his time.

"When I started, we were obsessed with performance, the yield," said the fifties.Now our challenge is to do things in a simple, socially acceptable and sustainable way.»»

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