Experimental Investigations of Thermochemical Heat Storage System Using Hydrated Salt Based Composite Sorbents for Building Space Heating Applications

Energy is one of leading problem all around the world. Increasing urbanization and industrialization, improving life conditions and standards and increasing world population have been creating a dramatic rise of energy demand. As a consequence of population growth, this resulted in high rate fossil fuel consumption. Besides, use of fossil fuels creating irrecoverable environmental damages such as global warming. Renewable energy and its storage systems are most promising solutions to overcome this problem. North Cyprus is an island good and suitable candidate for renewable energy utilization and its storage applications. Particularly, solar energy is abundant throughout year in North Cyprus and it represents a high potential to be used for building space heating. The main barrier is the imbalance between the heating demand and solar energy availability. Due to the cyclic nature of it, there is no solar radiation available at nighttime once the heat losses increasing. This condition indicates the need of utilizing thermal energy storage coupled with solar collector systems to store the solar energy once it is available to be used later when it is needed. Despite latent and sensible heat storage systems have been researched widely for this purpose, they have some major drawbacks such as low energy storage density and high heat losses limiting the storage potential and duration. A new thermal energy storage method; thermochemical heat storage, based on reversible sorption-desorption cycles is purposed in this study. Such thermal energy storage system could provide higher heat storage density and long-term heat storage potential making it attractive for solar thermal applications. From this point of view, aim of the presented study is; to develop a prototype thermochemical heat storage system and to test it under laboratory conditions. A novel composite sorption material; CaCl2–Vermiculite was synthesized and used as the heat storage material. Three different cycles (discharging-charging) with the same flow rate were carried out. Throughout the testing, some optimal results were obtained. For charging temperature between 80-90 °C, discharging average temperature lift of air between 15-20 °C was obtained. Besides, cumulative energy output in the range of 1.6-1.8 kWh was attained, corresponding to an energy storage density between 200-230 kWh. Observed results in this experimental study demonstrated that, for both long and short term heat storage, thermochemical process using V-CaCl2 sorbent is satisfactorily promising and a good candidate to be utilized in solar thermal applications in buildings for sustainable space heating.