Energetic and exergetic analyses of a new energy system for heating and power production purposes

• The waste heat of a HCCI engine is used to run a STC and an AHT cycle.
• The cooling water of the engine is used for some heating purposes.
• The proposed system results in a major increase in the energy utilization factor.
• Exergetic efficiency equal to 48.56% is achieved with the proposed system.
• Exergy efficiency is increased by increasing pressure ratio of the STC.

Energetic and exergetic analyses are performed for a proposed cogeneration cycle of heat and power. The cycle includes a STC (steam turbine cycle) to produce power and saturated steam, an AHT (absorption heat transformer) cycle to produce hot water and a HCCI (homogeneous charge compression ignition) engine as prime mover. Furthermore, the cooling water of the engine is used for heating purposes. The effect of variation of the cycle variables on the performance of the STC and AHT cycles are evaluated in details. The results show that the integrated system improves the energy utilization factor from 44.65% for the HCCI engine to 86.01% for the proposed system. Also, the exergy efficiency of the system increases from 39.49% for the HCCI engine to 48.56% for the proposed system. The maximum exergy destruction for the HCCI engine happens in the combustion chamber and for the STC occurs in turbine and for the case of the AHT cycle takes place in the absorber. Results of parametric study show that the exergy efficiency increases by increasing pressure ratio of the STC. The COP (coefficient of performance) of the AHT cycle increases as the condenser and absorber temperatures increase, but slightly decreases by increasing the evaporator temperature.