A Comprehensive review of sensible heat based packed bed solar thermal energy storage system

Solar thermal energy is an abundant and unique source of renewable energy and it will become an attractive and competitive option with the common equipment’s if these systems are incorporated with storage units. Packed bed storage system is one of the techniques to store the solar thermal energy which can be used for greenhouses heating, crop drying and space heating due to its simple mechanism and economic feasibility. In this study parameters affecting on PBSS performance and parameters which used for their performance evaluation has been explained. After that we focused on economic evaluation and some of PBSS applications. Between two types of stationary beds and fluidized beds; although the fluidized beds have higher rate of heat and mass transfer but they have more technical problems in design and construction. Between two types of radial flow and axial flow; the radial flow systems can achieve the same efficiency as axial flow system at higher cost. Among solid materials which can be used in stationary beds; cast iron has the highest level of energy density but gravel has recommended because of less refund return period than cast iron. Some of articles mentioned that sand performance is better than the others. Rectangular geometry for cross section of storage unit provides the lowest cost, but it makes high-pressure drop due to corner effects. In a study which use PBSS for greenhouse planting during the night; they see that if the system works for three months, refund return period will be five years.