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The Esky, the polystyrene cool box Australians use to keep their beer
chilled, is about to go solar. The University of Sydney has come up with two
prototypes with solar panels in their lids. In one design, solar electricity
powers a cooling element that depends on the Peltier effect: when electricity
passes between two different metals, heat is absorbed. In the second design, the
solar panel generates energy to compress a salt solution and drive it through an
evaporator. As water evaporates, the remaining liquid expands and draws heat out
of the Esky. The Peltier design adds 4 kilograms to an Esky鈥檚 weight, while the
salt version adds 2 kilograms.