High temperature composite thermal storage systems for industrial applications

An advanced, thermal energy storage (TES) subsystem is being developed by the Institute of Gas Technology (IGT which employs composite phase change material (PCM)/sensible heat media (CompPhase). This medium/subsystem is amenable to high temperature thermal storage applications such as industrial reject/process heat recovery and utilization, off-peak utility, and solar thermal and solar dynamic space power systems. The CompPhase concept allows for direct contact heat exchange between the latent/sensible storage media and compatible working fluids. A number of potentially significant TES system performmance and cost advantages are thereby offered over conventional tube intensive indirect contact molten-salt latent-heat-based storage subsystems. Materials processing, stability analysis, modeling and development efforts are progressing on composite systems from 390 to 1750/sup 0/F. Performance testing of a bench-scale packed-bed unit with approx.50 lbs of pellets has accumulated over 6000 hours and 200 thermal cycles, with excellent media stability (approx..3% weight loss in 1000 hours) and high heat transfer rates (approx.10,390 Btu/hr discharge heat removal rate). Preliminary economic assessments indicate that the projected cost for this advanced subsystem is below the maximum allowable cost for typical high temperature reject heat recovery applications, as well as being approx.30% lower in cost than current baseline sensible-heat based TES systems.