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Air conditioning goes green

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Air conditioning goes green

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At the Lac du Bourget near Lyon in France, researchers are testing new air conditioning technology aiming to cut the amount of energy needed to keep buildings cool in the summertime.

Here in the Port Authority offices, they have installed an air conditioning unit which cools the air using cold water from the bottom of the lake, which maintains a temperature of 6 degrees centigrade all year round. The system works via a pipeline forming a closed circuit, neither taking nor putting water back into the lake. Using a simple pump, the water just circulates around 150 metres of pipeline, going down to 37 metres beneath the surface of the water to be cooled. Says researcher Alain Henaut, “When you use cold water in air conditioning, it is like dropping ice cubes into a drink. You’re using the fact that it is cold and that it cools the environment naturally, physically, without using additional energy.” At the end of the pipelines, at the bottom of the lake, coil-shaped thermal exchangers like these – either plastic or copper – mean that the water circulates for up to two minutes at the bottom of the lake. Long enough for it to be cooled down. Divers fixed the coils on the lake-bed using weights to stop them floating to the surface. There are now 8 thermal exchangers in total at the bottom of the lake. Says engineer Bruno Garnier, “The main advantage is that it uses up to 80% less energy: another advantage is that classic air conditioning uses gasses which are poisonous for the atmosphere, whereas we don’t use those gasses at all. This technology means we can supply air conditioning at a minimum cost for people living beside a lake or beside the sea.” The only energy used by this technology in fact, is to work the pump which keeps the water circulating. The functioning of the system is supervised by a controller who measures the temperature and the water levels. As part of the struggle against the greenhouse effect, the new technology being tested at the Lac du Bourget, reduces the environmental damage caused by air conditioning.