Use of de phase change materials (pcm) in combisystem for its energetic optimisation

Resumen

The increasing energy demand in developed countries, usually based on exhaustive fossil fuels and its variable price due to the limited reserves, affects their economy countries. Moreover, a rational energy use and better energy management is necessary to face the worldwide energetic problem. In this complicated energy scenario, energy storage can play an important role. This thesis studies the benefits of thermal energy storage using phase change materials (PCM) in water storage systems. Thermal energy storage appears as a powerful option and as one possibility to help to mitigate the energy problem, specially combined with renewable energies. Furthermore, the Spanish Código Técnico de la Edificación (CTE) has to become one of the main pushing actors in Spain for the deployment of renewable energies such as solar energy and to increase energy efficiency concern. This thesis validates experimentally in a solar/electrical pilot plant set-up in the University of Lleida that the use of phase change materials in domestic hot water (DHW) tanks reports advantages to the system. Stratification is also analysed carefully in DHW storage tanks with water and with different PCM-water configurations. To characterise stratification, dimensionless Mix and Richardson numbers are used. The major impact on the stratification phenomenon is due to the flow rate used and not because of the introduction of PCM modules at the top part of the store Simulations of a combisystem are carried out in order to test the suitability of using PCM in a scenario with a continental climate and a system that provides DHW demand as well as space heating. These simulations were performed in the framework of the Task 32 of the Solar Heating and Cooling Program (SHC) of the International Energy Agency where the system and the boundary conditions were previously defined. Results were not as good as expected since no significant improvements due to the use of PCM are achieved.