Efficient Cooling

Using Heat to Cool Buildings - Kevin Bullis

All refrigerators and air conditioners cool by evaporating a refrigerant, a process that absorbs heat. They differ in how that refrigerant is condensed so that it can be reused for cooling. Unlike the technology inside most air conditioners, which employs electrically driven compressors to mechanically compress the vaporized refrigerant, adsorption chillers use heat to condense the refrigerant. Adsorption chillers are typically far less efficient than chillers that use electrical compressors, and are bulky and expensive. But they have the advantage of being cheap to operate, since they require very little electricity. "If you have waste heat, you can run it for free," McGrail says.

So far these chillers have been limited to applications where there is a lot of waste heat—such as industrial facilities and power plants—or where electricity isn't always available. Cutting their size and cost could make them attractive in more applications, including in homes, where they could be run using hot water from solar heaters, McGrail says.