Operation strategy and suitability analysis of CHP system with heat recovery

In order to coordinate and balance the demand of combined heat and power (CHP) system, a solution of optimal operation strategy of CHP system with heat recovery in a distributed energy system has been presented. This paper will discuss more deeply the suitability of the CHP system under different operation strategies. The selections of electricity determined by heat load (EDHL) and heat load determined by electricity (HLDE) are actualised by Aspen Plus and formula computing. In addition, the performance difference of the CHP system operating in EDHL and HLDE is analysed by comparing thermoelectric output and fuel consumption. The result shows that the optimal heat to power ratio (HPR) is 1.75 and is derived when the electric output is approximately equal to the electric demand and the heat output is approximately equal to the heat demand. EDHL is the optimal selection when the HPR is greater than or equal to 1 and less than 1.75, and HLDE is adopted suitably when the HPR is greater than 1.75 and less than or equal to 2.5. Additionally, the total thermal efficiency does not vary with increasing or decreasing regenerative temperature or variable HPR on CHP system, maintaining 87-88% thermal efficiency, meanwhile, the total exergy efficiency is about 24.7%-28.8% when the CHP systems operate in EDHL, and 23.1%-31.4% when the CHP systems operate in HLDE. The final research results show that, it has great significance in operation strategy and suitability analysis of the CHP system.