Cooled By Sun And Salt

By Adam Smith

If ever there was an innovation unlikely to come out of Sweden, it's this one.

Aiming to squeeze the amount--and cost--of energy used to cool homes and businesses in warm-weather areas, ClimateWell, based in balmy Haegersten, south of Stockholm, is marketing a novel solution: solar-powered air conditioning.

Unlike conventional cooling or heating systems fueled by such nonrenewable energy sources as oil and gas, ClimateWell's CW10 system--which can also warm your home in winter--slashes energy use by effectively running off water heated by the sun. And don't worry if it isn't always sunny: the clever system stores energy for conversion later into cooling or heating.

So how does it work? Air conditioning relies on some form of heat exchange. In this case, it's a thermochemical one between water and salt that takes place in a vacuum. Water evaporating from a tank inside ClimateWell's refrigerator-size unit is absorbed by salt housed in a connected tank the water molecules can't resist sticking to the salt, turning it into a slurry. As water evaporates, it gives up energy, which is then released inside the salt tank. The result of the energy transfer: the water becomes colder as the salt heats up. Pipe water through the slurry into radiators, and the system can heat the home; circulating the cold water will cool it.

Solar panels provide the energy needed to ensure continual cooling. The idea has been agonized over since the mid-'90s by Ray Olsson, ClimateWell's head of innovation, and as engineered by chief technology officer Goran Boelin, heat from water connected to the solar panels dries and crystallizes the salt, evaporating the water absorbed in it and storing energy inside the salt for as long as it is needed. As soon as water is remixed with the salt, that energy is released, again cooling the water tank.

The technology isn't cheap: installing the ClimateWell system costs roughly $25,000 in Spain, $10,000 more than standard combined heating and cooling systems. But going solar would slice $130 off the monthly energy bill of a standard home, says Per Olofsson, CEO of ClimateWell. And with electricity and gas prices rocketing, users would be "much less vulnerable to fluctuations in the future." Moreover, without leaning heavily on traditional sources of fuel (the pumps forcing the salt and water around the machine are electric but use only 100 watts), the average home could reduce carbon dioxide output by 13 tons a year.

But will home and building owners make the trade-off? The firm has launched its product in Spain, targeting the developers of some 200,000 single-family homes it says are being built in the country each year. Olofsson expects the first ClimateWell systems to be running in 2008-09, and says homes and businesses in warmer climates from Indonesia to South America offer great potential for the company. "Our core value is to find solutions that enable people to live lives they live today, but in a sustainable way," he says. "Changing behavior is more difficult than changing technology."