부산대학교 도서관

An engine-generator system, with heat recovery and thermal energy storage, was designed to operate with filtered, scrubbed biogas as a fuel. The thermal and electrical generation provided the process energy for the digester system and for an ethanol production plant. The design criteria were: performance, economy, reliability, ease of operation and safety. The system consisted of a 4 cylinder SI engine, a 20 kW induction generator, an exhaust heat recovery silencer, open loop engine heat recovery from the engine and exhaust, and stratified hot water thermal energy storage. Detailed performance data of the system components as a function of the operating parameters was collected and presented. The fuel qualities of biogas were evaluated by measuring combustion pressures and by conducting parallel experiments with commercial propane. The engine maintenance intervals were monitored, the lubricating oil was sampled and analyzed regularly, and the engine was torn down after 1700 operating hours to determine wear and reliability. Maximum power output was 20 kW at an efficiency of 26%. Thermal output was 2200 kJ/min and the overall energy yield was 75% of the fuel input energy. The engine operated well on biogas within a limited range of air-fuel mixtures and ignition timings. Engine power output was lower than for propane, but brake thermal efficiency was equal. The induction generator was interconnected with the utility grid. Generator operation and control was simple. Stratification in the thermal energy storage was nearly ideal, and a storage temperature of 99/sup 0/C could be maintained. Overall, biogas proved to be well suited as an engine fuel, and the system performed above expectations.