“At the time, I said to myself: Either I’m a visionary or I’m an idiot, at the moment I’m leaning towards the visionary side”, jokes, four years later, Emeric Cadalen, CEO of Fruit Gourmet, a company with 43 employees in Allemans-sur-Dropt, in the north of this South-West department.

While prices are soaring, Mr. Cadalen estimates that he has reduced his annual gas bill by around 20% (50,000 euros previously) since he bought a solar thermal energy oven, which he calls himself a “demonstrator”.

Its savings would even amount to 30,000 euros with contracts “at current prices”, assures the leader who could not measure, on the other hand, the effects on his greenhouse gas emissions.

In the parking lot of his processing shed, nestled on the hillsides, the entrepreneur has installed 200 square meters of solar mirrors, arranged in long strips one meter wide.

Taking up the concept of the Fresnel lens, “as old as the world”, the latter reflect the light of the sun on a duct capturing the outside air.

Heated up to 250 degrees, it feeds two ovens drying or pasteurizing bananas, apples, prunes, strawberries and figs, which usually run on gas.

On weekends or at night, when the SME closes its doors, another pipe carries the heated air into an airtight container, filled with gravel from the Garonne which allows the heat to be stored for up to four days before being send back to the ovens.

– “Mid-tech” – 

Steel for the structure, aluminum for the mirrors and pipes, gravel for storage: its inventor, Didier Martin, boasts “a mid-tech system”.

This mining engineer, founder of the IdHelio company in Albi (Tarn), was partly inspired by the solar oven in Odeillo in the Pyrénées-Orientales, one of the largest in the world, created in 1969 for research scientists.

By targeting companies specializing in drying – food, wood, building materials, waste – “in the sunny Mediterranean basin”, the inventor hopes to sell “a dozen” of these systems per year in the country, for a market of 100 -150 million euros.

According to Richard Loyen, general delegate of the union of renewable energies (Enerplan), this innovation “unprecedented in France” occurs while the solar thermal sector “finds colors”.

Launched after the oil shock of 1973, mainly to heat homes, it was neglected at the time of “abundant electricity” and then remained in the shadow of its cousin, solar photovoltaic, since the 2000s, relates Alain Mestdagh, solar thermal referent for Ademe in New Aquitaine.

At the end of 2020, the sector represented only 0.2% of heat consumption in France, including overseas, according to the Socol organization which brings together the players in the sector.

But with a production cost of 40 to 60 euros per megawatt-hour (MWh), solar thermal has become very competitive against gas, which currently fluctuates between 100 and 125 euros, explains Mr. Loyen.

To develop, the sector can count on a subsidy fund offered by Ademe, endowed with 500 million euros. But it will be necessary to convince the business world, which buys its energy “day by day”, to adopt a longer-term vision, according to the inventor of the process.

Current industrial solutions for saving energy, such as LED bulbs, “have a return on investment in less than three years”, but “investing in renewables means buying 20 years of energy stock from a sudden”, underlines Didier Martin.

“We will not be able to do without 100% fossil fuels”, considers the boss of Fruit Gourmet, while in front of his ovens where pallets of prunes are drying, the pilot light of the gas burners is activated as soon as a cloud passes over the solar receiver.

His company took six months to develop this precise solar-gas alternation and “secure” its production process.