Browse Publications Technical Papers 2011-32-0574
2011-11-08

Study of Methods to Enhance Energy Utilization Efficiency of Micro Combined Heat and Power Generation Unit-Equipped with an Extended Expansion Linkage Engine and Reduction of Waste Energy 2011-32-0574

To increase energy utilization efficiency of a micro combined heat and power generation unit, methods for simultaneously enhancing efficiencies of power generation and of heat recovery, which are normally in the trade-off relationship has been studied.
To increase power generation efficiency, an extended expansion linkage engine higher in thermal efficiency than conventional engines has been adopted. The power generation efficiency was enhanced by 3.8 points to 26.3% from 22.5% of a conventional model.
However, since introducing an extended expansion engine increases kinetic energy and lowers the temperature of exhaust gas from the engine, it is difficult to enhance the heat recovery. Focusing on the fact that most released heat energy is discharged through ventilation from the unit, ventilation cooling system was reexamined, and reduction of the released heat energy was considered.
First, positioning of heat-generative electronic parts on the inverter was changed, and the minimum airflow necessary for cooling was determined. In order to cool the entire unit with this airflow, an effective way to cool the alternator and the engine room was examined, and a method in which the ventilation which previously cooled the alternator is then delivered into the engine room was adopted.
Consequently, it became possible to reduce the airflow rate from 35 m₃/h in a conventional model to 13 m₃/h, and the heat recovery efficiency was enhanced by 2.7 points to 65.7%. The simultaneous enhancement in efficiencies of power generation and heat recovery was realized, and energy utilization efficiency reached 92%, a 6.5 point increase from 85.5% (the efficiency is based on the lower heating value).

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