Combination of a Biomass Fired Updraft Gasifier and a Stirling Engine for Power Production

Biomass is the largest renewable energy source used in the world and its importance grows larger in the future energy market. Since most biomass sources are low in energy density and are widespread in space, a small scale biomass conversion system is therefore more competitive than a large stand-alone conversion plant. The current study proposes a small scale solid biomass powering system to explore the viability of direct coupling of an updraft fixed bed gasifier with a Stirling engine. The modified updraft fixed bed gasifier employs an embedded combustor inside the gasifier to fully combust the syngas generated by the gasifier. The flue gas produced by the syngas combustion inside the combustion tube is piped directly to the heater head of the Stirling engine. The engine will then extract and convert the heat contained in the flue gas into electricity automatically. Output depends on heat input and the heat input is proportional to the flow rate and temperature of the flue gas. The preliminary study of the proposed direct coupling of an updraft gasifier with a $25kW$ Stirling engine demonstrates that full power output could be produced by the current system. It could be found from the current investigation that very little attention and no assisting fuel are required to operate the current system. The proposed system could be considered as a feasible solid biomass powering technology.