Phase change materials
Phase change materials (PCM) are materials that have high heat of fusion and therefore are able to store and release thermal energy during melting and crystallization.
Some ionic liquids are good candidates for the use as PCM, due to following properties:
- clean transition from liquid to solid state can be achieved (no supercooling)
- high heat capacity and heat of fusion
- high thermal conductivity
- negligible vapor pressure, which results in
- no pressure rice during heating due to evaporation of material
- no loss of energy at higher temperatures due to evaporation of material.
Ionic liquids can be used as phase change materials, both neat and/or as a part of formulations. Such materials can be used for:
- cyclic storage and supply of thermal energy
- waste heat recovery
- off-peak power utilization
- latent heat storage devices
- heat buffers
- cold buffers
As can be seen from figure 1, some ionic liquids can release big amount of energy latently (virtually without raise of the temperature of the system) during crystallization. In this particular case, the IL may be used for example for the household heat management, storing up the energy at the temperatures above 32 ⁰C (e.g. hot day) and releasing it at 18 ⁰C (e.g. during colder night).
Figure 1. Energy profile of phase change of DecMIM PF6, measured with differential scanning calorimetry.
IoLiTec has been investigating this topic since 2005 within a joint project with the Fraunhofer Institute for Environmental, Safety and Energy Technology (FhG UMSICHT) and the Fraunhofer Institute for Solar Energy Systems (FhG ISE). At the moment, a number of promising systems exist at the prototype stage, whose properties could result in their use as latent heat storage devices and as heat and cold buffers.
If you are interested in developing latent heat storage technologies based on ionic liquids, have any questions regarding our activities, applications or products in this field please feel free to contact us.
For more information on PCM: https://iolitec.de/node/608