A COMPARATIVE STUDY OF SENSIBLE AND LATENT THERMAL STORAGE TECHNOLOGIES COUPLED TO FLAT PLATE SOLAR COLLECTORS

Abstract

Storage systems are important technologies that aid renewable energy sources in increasing their penetration in the energy grid and making them sustainable choices. Solar thermal collectors need thermal storage devices in order to store heat for short or long periods. This paper investigates two of the most usual thermal storage systems coupled to a classical flat plate solar collector. More specifically, the sensible storage with a water tank and the latent storage tank with phase change materials (PCM) are studied in this paper. Energy and exergy investigations are performed for different operating temperature levels. The system is monitored daily with both storage technologies. The results show that the use of PCM is more efficient energetically for all studied scenarios. On the other hand, the use of sensible storage leads to higher exergy performance due to the temperature increase of the stored water, especially for the scenarios with lower initial temperature levels in the storage tank in the morning. It is useful to state that the daily energy efficiency with the latent storage ranged from 21.9% to 69.1%, and the sensible storage from 14.2% to 55.3%. Furthermore, the exergy efficiency ranged from 1.23% to 5.64% for the latent storage, and from 3.99% to 7.53% for the sensible storage. Also, it must be pointed that the optimum temperature for the phase change material is 75ºC, while the optimum initial temperature in the water storage tank is 40ºC. These results indicate that PCM can be a beneficial choice for applications of high temperatures, such as solar cooling systems with absorption or sorption machines.