Phase Change Slurries as Cold Storage Fluid with High Energy Density for Solar Cooling
Abstract
This paper presents the application of a high energy density fluid as cold storage medium in a solar cooling system. One possible realization of solar cooling plants is the combination of solar thermal collectors and thermally driven absorption chillers. The system availability depends on insolation and these plants cannot be driven only related to the cold demand. Thermal storages are needed in the system to balance between the required demand of cold and available solar energy to generate cold. Due to the fact, that the temperature difference in cooling systems normally is very small, the energy density of water is quite poor. Phase change slurries (PCS), which are using paraffin as phase change material (PCM) can extend the energy density through the latent heat of the melting/crystallizing of paraffin. For example, in the common temperature range from 6 °C to 12 °C the usable heat capacity of the PCS with paraffin as PCM is about two times higher than that of water. A further extension of the energy density seems possible in the combination of the paraffin/water dispersion and CO2 gas hydrates.