SUMMARY

The goal of this exploratory thesis research is to quantify the heat transfer coefficient of sand in a proposed Thermal Energy Storage (TES) system which intends to compliment solar thermal power generation. Standard concentrator solar thermal power plants typically employ a heat transfer fluid (HTF) that is heated in the collector field then routed to the power generators or TES unit. A fairly clear option for a TES system would be to utilize the existing HTF as the working storage medium. However, these fluids are quite costly for the quantity needed for storage and for many fluids their associated high vapor pressures require expensive highly reinforced containment vessels. The proposed storage system seeks to use sand as the storage medium; greatly reducing the expenses involved for both medium and storage costs. Prior TES designs using solids employed them in a fixed bed for thermal exchange. The proposed TES system will instead move the sand to drive a counter flow thermal exchange allowing for a close temperature of approach. As cost and performance are the primary goals to tackle in the proposed system, experiments will be conducted to measure the effective heat transfer coefficient between the sand and representative heat transfer conduits. Additional experiments will look at are wear caused by the sand as a consideration for long term design viability as well as angle of repose of the sand and its effect on scoop design for improved materials handling. Key investigational aspects of these experiments involve the sand grain size as well as shape of the heat exchanger surfaces. The thesis will evaluate the resulting convective heat transfer coefficient of the sand as related to these features. The data will then be compared and verified with available literature of previously studied characteristic thermal properties of sand. The measured and confirmed data will then be used to further aid in a design model for the proposed TES system.