Adsorption Chillers

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.

The technology behind adsorption cooling can be traced back to the mid-19th century, when French scientist Ferdinand Carré invented a similar system, known as absorption refrigeration, that used water and ammonia. Other designs followed, including one first patented in 1928 by German-born American physicist Albert Einstein and his former student, Hungarian-born American physicist Leo Szilard. Public acceptance of the Einstein-Szilard chiller was hampered by the device’s high energy cost, the onset of the Great Depression in 1929, and the introduction of freon (a key component of compressor cooling units) in 1930.

Further Reading

• Sustainable Energy: Using Heat to Cool Buildings MIT Technology Review
• Adsorption and other thermal chillers making trigeneration systems work Decentralized Energy