This shiny tangle of pipes and ducts at a facility of the power company Industrielle Werke Basel in Basel, Switzerland, is an air-conditioning system that is actually driven by heat. Likewise, heat actually helps to cool banks, hotels, and offices in the Adelgade district of Copenhagen, a T-Mobile data center in Munich and Fumincino Airport in Rome.

The company that engineered all of these systems, Thermax of Pune, India, markets them as one of its “sustainable solutions” for today’s environmental concerns, but the technology—absorption chilling—has been in commercial use since the 1920s. Like standard air conditioners, absorption chillers rely on a refrigerant with a low boiling point. When the refrigerant evaporates, it removes heat from the air. Standard air conditioners then change the refrigerant gas back to liquid using an electric compressor. But absorption chillers rely on thermal compression to restart the cycle; they need only heat—no moving parts—to drive the operation (more…)