Adsorption chillers use a different mechanism than traditional chillers and are powered by heat, rather than using electricity. The cooling mechanism is still evaporative — water transforming into a vapor — but the reliquification is different. Instead of being compressed, the water vapor is adsorbed onto the surface of another medium, such as silica gel. Once the silica gel is saturated with water, it is switched out and the first chamber is then heated to remove the adsorbed moisture, so the chamber can be reused.