METAL HYDRIDE ENERGY-SYSTEMS PERFORMANCE EVALUATION .B. PERFORMANCE ANALYSIS MODEL OF DUAL METAL HYDRIDE ENERGY-SYSTEMS

A model for performance evaluation of dual metal hydride energy systems is presented. The complete model has been implemented by assembling the dynamic model of heat and mass transfer between two coupled hydrides, previously developed by the author, with the model developed here to describe all feasible cyclic operations occurring in metal hydride energy systems, such as heat pumps, temperature upgrading devices, refrigeration plants, etc. It seems that a reasonable compromise between accuracy and simplicity, suitable for practical use, has been attained: the peculiarity of lumped-parameters models allows a rather fast resolution, so that several parametric analyses may be developed, while the accuracy is ensured by taking into account all major determinants of the dynamic behaviour of the heat and mass transfer process. In this regard, a validation of the heat and mass transfer model has been carried out previously, and this has pointed to a good agreement between calculated and experimental results. Thus, the present model provides a realistic estimation of the overall system performance: cycle time, amount of cyclic transferred hydrogen, input and output thermal power, effective attainable temperature levels, efficiency, etc. Moreover the model may be usefully employed to analyse the influence of the operational parameters, heat transfer and heat exchanger characteristics on the overall system performance in order to improve the design of the present metal hydride energy systems.