Development of a Standalone, Liquid Fuelled Miniature Power Generation System

This paper aims at developing a mesoscale combustion based thermoelectric power generator as an alternate to the electrochemical batteries. Most of the micro and mesoscale combustors investigated till date are based on external fuel and air supply systems, which may not be beneficial for a practical system. The proposed design is a standalone system which makes use of the heat conducted through the combustor walls, as an energy source to evaporate the liquid fuel stored in a surrounding tank and supply the vaporized fuel to the combustor. The high momentum fuel (vapor) jet is designed to entrain the ambient air in appropriate proportion so as to form a combustible mixture. The partially mixed fuel/air mixture is fed to a mesoscale combustor and the flame is stabilized by facilitating hot gas recirculation regions. The heat conduction through the combustor walls is controlled by providing an air gap between two concentric, low thermal conductivity, ceramic tubes so as to transmit desirable amount of heat to the fuel tank. Note that the heat lost from the combustor, is recovered via increased enthalpy of the supplied fuel. The hot products then flow over the hot side of a thermoelectric module to generate electricity. The cold side of the module is maintained at relatively lower temperature and the rejected heat is used to boil the stored water. The prototype is designed to produce an electrical power output of 15 W with an overall efficiency of about 3% and endurance of 1 hour in a single fuel (and cold side water) refill. The paper presents detailed thermo-fluid and heat transfer analysis of the constituent components and evaluates the performance of the system.