Development of a model of μCHP for residential application based on SOFC planar technology

Cogeneration Heat and Power systems (CHP) are playing important role on world energy scenario, CHP permit a global increase of electrical efficiency and offer further improvements in terms of first and second thermodynamic law performances. Small scale systems, microCHP, are a big section of this technology field and offer a relevant market due to the fact that can be integrated in residential building and produce from city natural gas thermal heat as main output and electricity as a byproduct. A 3 kW system model was developed and global performances were evaluated both in nominal and off design conditions. The model developed in Cycle Tempo, a commercial software, integrates the Solid Oxide Fuel Cell Stack with the balance of plant (BoP) to assure hydrogen supply to the stack and heat recovery for the specific application. The stack considered is a planar geometry and the hydrogen is produced in an high efficiency external steam methane reformer (SMR). The heat is recovered from exhaust gas produced in the system after internal thermal balance is satisfied. A previous phase of the study investigates the optimal integration of all components in order to reach the most efficient layout for the system. This configuration permits up to 61% gross electrical efficiency and 98% cogeneration efficiency (LHV). A second phase evaluates system modulation, thanks to regulation parameters, in order of thermal to electrical ratio (TER) variation to meet heat residential request in a thermal logic control. The model demonstrates a feasible layout of residential system both for thermal and electrical efficiency and presents previous results of system dynamic modulation to reach instant thermal request without producing any effect on standard building heat balance