Waste heat recovery from a biomass heat engine for thermoelectric power generation using two-phase thermosyphons. (April 2020) - Goswami, Rohtash
Abstract: In this study, we propose a thermoelectric generator ( TEG ) based power generation system operated through waste heat of a biomass engine. Power generated by TEG s is utilized for recharging a 12 V uninterruptible power source ( UPS ) battery. Experiments are done to study the variation of power output, current and conversion efficiency with average flue gas temperature, output voltages, thermosyphon filling ratio ( TFR ) along with source and sink temperatures. Gasifier operation is optimized to identify the appropriate equivalence ratio ( ER ). The optimized ER for the present system is evaluated as 0.305 yielding a maximum flue gas temperature of 283 °C. Thereafter, experiments are conducted to study various performance parameters when 48 TEGs are provided on the two-phase octagonal-shaped thermosyphons. Experimental results indicate that the maximum open circuit voltage of the present system is 31.52 V (17.12 V at ΔT max., 1 = 39 °C and 14.40 V at ΔT max., 2 = 31 °C) at an optimum TFR of 0.496. A thermal resistance based model is finally developed from which the maximum temperature gradient across the TEG for two thermosyphons is found as 40.12 °C with a maximum relative error of 14.91% between model and experimental values. The total power generated from the system is found as 1.033 W, whereas, the maximum conversion efficiency is calculated as 2.218%. Highlights: A novel TEG based heat recovery system from biomass engine is proposed. Waste heat to electric power is realized through TEG s and two-phase thermosyphons. Optimum operating conditions for biomass engine and thermosyphons are proposed. Parametric studies along with battery charging time are carried out. A thermal resistance based model to predict temperature difference is developed.