(176c) High Operating Temperature Transfer and Storage (HOTTS) System for Concentrated Solar Power Generation and Metals Production

Authors: 
Bonino, C., RTI International
Cook, B., RTI International
Newman, J., University of California, Berkeley
Trainham, J., RTI International
Hlebak, J., RTI International
Gould, R., North Carolina State University
Coleman, L., RTI International

High Operating Temperature Transfer and Storage (HOTTS) is a solar energy-based process currently under development, designed to provide high-quality heat to industrial processes.  This system includes a dry, particle-based heat transfer fluid (pHTF) that can be heated to temperatures of 1,100°C, some 400°C higher than molten salt-based systems.  The pHTF can store thermal energy to enable continuous operation through day and night cycles.  The HOTTS system also contains Mo-Si-B composites and coatings as the material of construction (MOC), which resists oxidation and particle erosion at these elevated operating conditions. 

In this study, we report the heat-transfer performance of different materials as pHTFs in a low temperature (up to 200°C) bench-scale unit.  Heat-transfer coefficients are determined for mass fluxes up to 75 kg/m2-s.  We also correlate the flow rate of the particles to the outlet size of the bench-scale unit.  The flowability of the pHTFs after high-temperature thermal cycling is also reported.  In addition, we discuss the oxidative resistance of hot-pressed, Mo-Si-B composites at temperatures up to 1650°C in air.  One Mo-Si-B composition is examined after long-term (100 h) isothermal conditions, as well as thermal cycling to simulate solar-thermal operation.  Engineering approaches to implement the pHTF and Mo-Si-B MOC into a pilot-scale HOTTS process are also discussed.