In many industrialized countries, city skylines are dominated by imposing glass faades and skyscrapers made of concrete and steel. There is a drawback to these magnificent structures, though they often get very hot in the summer, so they mostly need elaborate and costly air conditioning systems. And these already account for some 14 percent of Germany's annual energy consumption. Experts reckon that total cooling requirements in buildings will triple by 2020.
Cooling and heating using metal organic frameworks
Thermally driven cooling systems are one possible alternative to traditional air conditioning. These systems use the evaporation of fluids such as water at low pressure to remove heat from the environment an energy-efficient cooling method. Now researchers from the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg are working on innovative sorbents that can store a particularly large amount of water vapor. To develop this material, researchers have turned to metal organic frameworks (MOFs). "The material is highly porous and can adsorb more than 1.4 times its own weight in water," says Dr. Stefan Henniger from Fraunhofer ISE, describing one distinctive property of these sorbents.
MOFs can also be used in thermally driven heat pumps. Whereas electric heat pumps feature an electrical compressor, in these pumps an adsorbent performs the role of a "thermal compressor" while water serves as coolant. The gaseous coolant is adsorbed by the sorbent, thus leaving the gaseous phase. The heat that results from this adsorption into the material's hollow interior is transferred away by a heat exchanger and can be used for heating. For this to function, the sorbent must be applied to the surface of the heat exchanger in such a way that the coolant evaporates continuously until the sorbent is saturated. Once the maximum adsorption capacity is reached, driving heat is used to drive off the stored coolant and li
|Contact: Simone Ringelstein|