Posted in Technology - Heat Storage & Heat Transport
Latent-heat storage and Phase Changing Materials
Materials that can store thermal energy reversibel over a long time periode are often refered to as latent heat storage materials. The release of the stored energy is typically initiated by a seed crystal which starts the crystallizationm process of the supercooled medium, which releases the initially stored energy. A prominent example for latent heat storage are pocket warmers in which the crystallization of a saturated salt solution is initiated by bending a small metal plate. Latent heat process mainly focus on the release of thermal energy.
Similar to latent heat storage media are phase change media (PCMs) which store energy on the phase transition from solid to liquid and release the stored ernergy in the reversed transition from liquid to solid. Contrary to latent heat storage this process focuses on buffering heat or coldness. Today PCMs based on parafines are used for passive air conditioning of buildings. Important for this process is that the PCMs have phase transition temperatures in the so calles comfort zone. A major drawback of prafines, which are also used for the manufacturing of candles, in this technology is that they are inflammable.
The common definition of ionic liquids defines these materials as salts with melting points below 100°C. Even though many ionic liquids are liquid at room temperature, there are some that have phase transition temperatures in a temperature range that makes them suitable for PCMs of latent heat storage.
Most suitable are ionic liquids that
- Show a low tendency for supercooling
- Are non inflammable
Show a low hysteresis between melting and crystallization point and
have a high heat capacity.
IOLITEC has identified suitable materials in a BMWi funded project with its partners from Fraunhofer Institute ISE and UMSICHT.
If you are interested in more information on this technology, please contact us.
Text: Dr. Thomas J. S. Schubert, IOLITEC GmbH, 2011. (German Version; English Translation: Dr. Tom Beyersdorff, IOLITEC Inc.)