Thermodynamic analysis of a heat-driven metal hydride cogeneration cycle

A heat-driven metal hydride cogeneration cycle has been analyzed using clas sical first and second law analysis as well as finite-time thermodynamics. Second law analysis introduces important limitations on operating condition s not previously mentioned in the literature. The system being investigated is based on a cycle developed at Brookhaven National Laboratory. Predicted performance is compared to data from two other hydride power systems, HYCS OS (developed at Argonne National Laboratory) and a system developed by Bom in Solar, GmbH. Power generated per kg of hydridable alloy was highest for the present cycle (0.11 kW.kg(-1)) while useful heat or cold rates were hig hest for the HYCSOS cycle (0.30 kW.kg(-1)) and the system developed by Bomi n Solar (0.30 kW.kg(-1)). Fuel-use efficiencies were highest for the presen t cycle (0.23), while second law efficiencies were highest for HYCSOS (0.60 ). Power and efficiency diagrams based on the finite temperature difference between the hydride bed and external heat transfer fluid are also presente d. (C) 2001 Editions scientifiques et medicales Elsevier SAS.