Energy and exergy assessment of scenarios utilizing a comprehensive combined heat and power and district heating systems

A new comparative study between different district heating scenarios fed by a combined power plant from an energy and exergy point of view has been presented in this research. The proposed scenarios provide the flexibility of the power plant cycle in different environmental and geographical conditions to produce balanced electricity and heat. The proposed scenarios have been divided into design and off-design conditions when the maximum electricity or heat is the purpose of system operation. Results show that by relying on off-design scenarios, affordable outcomes are achievable. The heat efficiency in an off-design scenario has increased more by than 30% compared with the base case by controlling the exact demands on the equipment in the maximum power generation scenario. The total energy efficiency varies between 56.6 to 87.6 in different scenarios. It has been similarly observed for the energy and exergy efficiencies by growing 2% in the maximum heat production scenario. In addition, preparing a balance between the highest power of heat production has been fulfilled by proposing a medium model that can be supplied in an acceptable range. Eventually, the highest value of exergy destruction has been observed in the combustion chamber of the gas cycle (about 68%) due to thermochemical irreversibility.