The next time you are in the city of Tours take a trip along the rue Bernard Palissy and stop outside of number 4. There you will see an old stone plaque on the facade of a house: “A. Mouchot construisit dans cette maison de 1864 à 1866 le premier appareil pour l’utilisation de la chaleur solaire “ or “A. Mouchot built in this house from 1864 to 1866 the first device to use solar heat.”
So, who was Augustin Mouchot? Augustin became a Bachelor of Science in 1850 and gained his degree in mathematics-science two years later. On September 15, 1853, he was appointed assistant professor of pure and applied mathematics at the Imperial School of Alençon in Normandy and it was during his time at Alencon that he became interested in solar energy. Building upon the work of Claude Pouillet (1790-1868) Mouchot made a “solar furnace” that allowed him “to use the sun to make an excellent stew, consisting of a kilogram of beef and mixed vegetables.” On March 4, 1861, he filed a patent on the use of solar energy by the process called “héliopompe” (1) for heating the water from the sun. The principle is based on the concentration of solar radiation through a tapered funnel.
As he wished to live close to his elderly father he transfered from Rennes to Tours and, in October 1864, he was appointed professor of mathematics at Imperial High School (renamed ‘Lycée Descartes’ in 1888). It was during his time at Tours he lived at 4 rue Saint-Étienne (now called 4, rue Bernard Palissy) and is here that he invented the first solar motor with a parabolic reflector and a cylindrical glass boiler feeding a steam engine. He managed to run a pump and two steam engines in 1866: “From the year 1866, I already had two small steam engines running […]. In June 1866, the success has exceeded my expectations, since the same solar receiver was enough to maintain the movement of a second much larger machine than the first.”
Mouchot received financial support from the French Association for the Advancement of Science. At the end 1869 Mouchot published his major work, Solar heat and industrial applications. The foreword says: “This book covers a new branch of applications that can have the greatest influence on the future of certain countries. Finding a convenient way to collect and use sunlight directly for agriculture and industry in the warmer regions of the globe….There will necessarily come a day when, for lack of fuel, industry will be forced to return to the good work of other natural agents. Deposits of coal and oil will provide for a long time enormous calorific power, we do not doubt. But these deposits will be depleted without a doubt…. One can only conclude that it is prudent and wise not to fall asleep in this regard in false security. ”
Mouchot was hoping to permanently leave his teaching obligations and secure financial support from the French imperial government. But the war of 1870 disrupted his plans and when the city of Tours, bombed December 21, 1870, was occupied by the Prussians in January 1871 the educational premises where he was based was use to house military ambulances. After the fall of the Empire, Mouchot did not abandon its work on solar energy, he conducted himself in the yard of the high school and, searching for alternative funding, turned to the General Council of Indre-et-Loire. After much discussion, a grant of 1,500 francs was granted and Mouchot built a solar oven and a generator of 2.60 meters in diameter which was installed in Tours and used for experiments in the garden of the Prefecture.
On October 4, 1875 Mouchot exhibited his work to the Academy of Sciences in Paris. The following year, during the ceremony of the Descartes prize in Tours, Pellet, professor of special mathematics, honored Mouchot: “You will not be surprised that a science teacher talking about this invention that this year has shown our school. It is the work of a man of studies, but it has a firm eminently useful purpose “.
By 1876, Mouchot’s was at the hight of his fame. He registered patents, publisheed a book on mathematics, and presented the findings of his work for the encouragement of French industry. Newspapers and journals recounted his essays relateing to the use of solar heat. Thus, in 1876, the Revue des Deux Mondes published a laudatory article “Industrial use of solar heat.” In 1877, the National and Central Agricultural Society of France published a report entitled “Solar and Mouchot“.
In 1876, Mouchot was granted leave from his teaching post to devote himself entirely to his research. With the support of Baron de Watteville, the Director of Science and Letters at the Ministry of Education, Mouchot was provided with a grant of 10,000 francs from the government for a mission in Algeria where he launched into public demonstrations, testing numerous versions of its devices. The Algiers General Council granted him an additional 5,000 francs to build new machines and on March 12, 1878, Mouchot gave a lecture to the military circle of Algiers on the use of solar energy for military purposes.
As a result of his Algerian research Mouchot designed, with the help of Pifre Abel (1852-1928), a young engineer from the Ecole Centrale who became his partner, a “large unit of 20 square meters”. This is the largest ever made solar receiver. The steam produced operated under a constant pressure of about 3 atmospheres, a pump capable of lifting 1,500-2,000 liters of water per hour to a height of two meters. In September 1878, the unit was demonstrated during the Paris Universal Exhibition of 1878. The press reports enthusiastically about this machine while audiences were “impressed and amazed“.
The jury of the Universal Exhibition awarded Mouchot a gold medal. The Ministry of Agriculture and Trade appointed Mouchot, “inventor of the use of solar heat system as a driving force.” He received the Knight of the Legion of Honor on October 20, 1878.
Although Mouchot devices continued to fascinate scientists and general public Mouchot, himself, received diminished government support of just 5,000 francs. Mouchot’s approach was to provide an alternative energy source or a complement to then insufficient coal production for the needs of French industry. But the discovery of new coal deposits in eastern France and the improvement of the rail network that enabled the supply of coal across the country led the government to believe that solar energy is not profitable and stopped financing Mouchot’s research. Similarly, after the Universal Exhibition of 1878, combustion engines and the massive applications of oil radically changed the industrial landscape.
Without grants to support his work Mouchot returned to the field of education. For the tercentenary celebrations of René Descartes in Tours in December 1896 Mouchot was appointed member of the Honorary Committee. On 23 December, the President of the Archaeological Society of Touraine paid him tribute “as modest and as passionate about science cultivated for itself, Mr. Mouchot works in solitude reminiscent of the hermitage of Descartes. His mathematical work is the continuation of the work of that which we celebrate. So I am pleased to join in this day, in the same thought, the master of the seventeenth and the nineteenth-century disciple. “
Augustin Mouchot life ended in poverty, he was physically tired and from 1907 received a pension from the Academy of Sciences. Separated from his wife and almost blind, he died poor and anonymous in Paris on October 4, 1912. His funeral was held on October 7 in Saint-Lambert de Vaugirard church and he was buried in the cemetery of Bagneux in southern Paris.
Oil and the combustion engine have destroyed the works of Mouchot that have almost fallen into the dustbin of history. However, Augustin Mouchot had a subtle and daring foresight about the future of energy that faces humanity today.