PERFORMANCE INVESTIGATION OF A PACKED BED SOLAR ENERGY STORAGE SYSTEM HAVING SPHERES WITH PORES AS PACKING ELEMENTS

Abstract

The solar energy is one of the most adopted renewable energy resource due to its abundant availability and eco-friendly behavior. However, there is a need to manage few technical obstacles like low efficiency, instability in energy supply and monetary impediment for its sustainable development. In order to eliminate instability in energy supply, the solar energy systems require an effective energy storage technology to store the energy during its availability and deliver it on its requirement. For solar thermal energy systems, many thermal energy storage (TES) techniques exist and packed bed storage system (PBSS) is the one which can be integrated with applications of all temperature range. The PBSS can store thermal energy in the form of sensible heat, latent heat and thermo-chemical energy. For low temperature applications, TES in the form of sensible heat is recommended due to its lesser storage cost. There are various modes of energy transfer involved in PBSS, however, the thermal performance is majorly dependent on the convective heat transfer between heat transfer fluid and packing elements in low temperature applications. The convective heat transfer rate between heat transfer fluid and packing elements is a function of the physical properties of heat transfer fluid and packing elements, local temperature at surface of packing element, various characteristics of packed bed such as void fraction, packing arrangement, sphericity and mass flow rate of heat transfer fluid.