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A solar cold weather
To cool off with the sun ? It is not the science-fiction but a reliable and clean technique. Used since one year in offices, she/it could arrive soon at home.
By Matthieu ECOIFFIER
Saturday May 22, 2004 (Liberation - 06:00)
Sophia-Antipolis, special messenger,
During the heatwave of last summer, they cooled their offices. But not with a traditional air-conditioning, this refrigerator polluter. "On average, one had 5 °C of less than outside. Only problem, that worked less well to the passage of the clouds and the gray days of storm", tell Pierre Richard, engineer to the scientific and technical Center of the building (CSTB) of Sophia-Antipolis. Not astonishing when one has a "solar air conditioning." To first view, nothing distinguishes these buildings of the beginning of the years 80, with their sunshade waved in concrete. Were not, calm on one the terraces overhanging the pines and the garrigue of the hills of the hinterland antibois, two impressive rows of solar panels. A magnificent succession of glass tubes. In every tube, placed vacuum for an optimal insulation, a copper plate under which short a small hose filled of water absorbs the heat of the UV. "I have a software to orient the panels in 60 ° of the radiance", explain Pierre Richard.
Natural and free
To make the cold weather thanks to the sun ? The "solar cooling" is not the science-fiction, nor an ecologist-utopian oxymoron, but a reliable technique, already put in work. In France, the offices of the CSTB were the first to equip itself, one year ago. Whereas with the beautiful days comes back the fear of a new murderous heat wave and that the individuals rush without discernment on the mobile air conditioners, the solar cooling is a spare solution that seems promised to a beautiful future. "90% of the market of the solar thermal remains the sanitary hot water production, recall Dominique Caccavelli, director of the laboratory of the renewable energies in the CSTB. But two other applications have a strong potential : the heating of the swimming pools and especially the solar air-conditioning. It is the most logical : one has need to cool off when it is hot and it is the moment where there is the more of sun." Better, the summer, the episodes of heatwave come with strong atmospheric pollutions, coupled to decreases of the electricity production capacity. As many problems solved by the solar that uses a clean natural energy locally. And free. The solar thermal must not be confounded with the photovoltaic, whose cells convert the radiance in electricity, that can nourish a classic air conditioner then. This other process, less virtuous as regards to the environment, is not again to the point. "One had customers of Bahrain who wanted to install photovoltaic cells on their tents in the middle of the desert ! One first advised them to improve the insulation of their habitat", tell Caccavelli. With the thermal, it is about unlike to use the luminous radiance to heat water. Then to manufacture the cold weather with this heat. How ? Deposit a drop of ether on your palm : when she evaporates, she procures a sensation of freshness instantaneously. The "machine to absorption thermochimique" uses an analog principle. "The energy of the solar sensors permits to make evaporate the water, that is mixed with a salt (bromide of lithium), as it is the case of the alcohol in a still. Then, this saline solution acts like a sponge : she attracts the water that in the meantime has been condensed again and absorb it while making it iron as steam of water. It is at that moment that the cold weather is produced, explain André Joffre, CEO of Tecsol, the research department that achieved the installation. In a refrigerator, the refrigerating gas, compressed by a motor, produced of the cold weather when he relaxes. In this case, it is the hot water that relaxes. The advantage, it is that water is neutral on the environmental plan. Whereas in a plain air-conditioning, the fluid frigorigène contributes heavily to the greenhouse effect at the time of the flights." Only energizing tear of the process : a small cooling tower is necessary to make turn it. She consumes a very small quantity of electricity... That works and it is reliable
About comfort, the solar air-conditioning permits to avoid the permanent buzz of the classic compressor. "Except some jangles, the machine is silent. Otherwise, when it makes 30 °C outside, people tend to adjust their air-conditioning in 22 °C. With the solar, one avoids this slap of the hot cold. The transition is very cool, underline Rodolphe Merlot, engineer in the CSTB. And not to be at the mercy of the cloudy passages, one can imagine to have an electric balance." "The solar air conditioning, that works and it is reliable", summarize André Joffre. The proof ? A similar installation functions since twelve years in the cellar of Banyuls, close to Perpignan, : 130 solar sensor square meters permit to maintain 2 millions of bottles of wine of Collioure there to the constant temperature of 17 °C. The building of the direction of the environment (Diren) some Guadeloupe has, him also, the solar air conditioning. In the CSTB of Sophia-Antipolis, 63 square meters of sensors cool 1 000 square meters and the 70 salaried employees. A few farther on the same hill, a subsidiary of The Oréal is passing to the solar cooling : more than 500 solar tube square meters are integrated to pergolas made of wood and are going to produce more 500 kW of cold weather soon. But it is abroad that the solar air-conditioning develops itself the most quickly. "In Germany, about thirty buildings are already equipped some and many programs are in progress", indicate André Joffre. All are tertiary buildings of large size. For the hour, the available devices are again too big and too dear for the market of the individual house. 1 square meter of sensors is necessary to cool 5 square meters. If you don’t have a roof-terrace of 300 square meters, you are stuck", explain Pierre Richard. Other Achilles’ heel, the cost of the process. "The solar air-conditioning is three times more expensive than the classic : 2 500 euros the kW of cold weather, against 800 euros. The return on investment is of eight years", one recognizes at Tecsol. There are certainly the public helps (Ademe, regional advice) that makes to lower, a few, the cost. Without forgetting an invoice of electricity amputated of half. To term, the industrialization will have the costs lowered. The pilot installation of the CSTB (96 000 euros) cost 40% less dear than the one of Banyuls. Idem for the material. The Chinese already produce vacuum with strength some tubes. The Germans converted their heating specialists in industrial of the wind and solar climatic genius. In France, two manufacturers, Giordanos and Clipsols, survived to the risks of the market of the solar, that had been subsidized after the second oil shock, before being abandoned when the price of oil lowered. "With the solar, one is not anymore in the baba cool handicraft. But so much that electricity will remain so little expensive, this system won’t have any interest on the economic plan", recognizes Dominique Caccavelli. The house of the future The gain in terms of picture is not yet negligible. The solar air conditioning remains a good vector to promote... the solar heating. Three numbers summarize the French delay : in 2003, China installed 4 millions of square meters of sensors, the Germany 1,5 million, France, 40 000 square meters hardly. The promoters of the energies spare remain yet stubborn. "The Ademe (Agency of the environment and the mastery of the energy) is opposed to the solar air-conditioning. For them, a very conceived, oriented building and ventilated, doesn’t have need" of it, one explains to the CSTB (to read next page). "We have nevertheless a part of these demonstration facilities financed, forbids itself Jean-Louis Bal, the director of the renewable energies to the Ademe. One doesn’t want to make the promotion of the solar air-conditioning so much that it will be expensive and that there won’t be any machinery for the individual houses." what won’t linger maybe to change. Prototypes of small machinery are in the cardboards of manufacturers in Japan, in Spain and across the Rhine. "The house of the future will be bioclimatique, few consumer of energy and equipped of at least 15 square meters of thermal solar sensors", predicted André Joffre. Hot water all year and a little expenses in summer...