Comparative study for four technologies on flexibility improvement and renewable energy accommodation of combined heat and power system

Insufficient flexibility of the combined heat and power (CHP) system brought by its inherent heat-electricity coupling limitation reduces its renewable energy consumption capacity. Accordingly, this paper integrates four technologies, including the electric boiler, heating energy storage, electrical energy storage and bypass compensation technology, into the CHP system for more flexibility. The flexibility improvement indicator and the operational model for the integrated CHP systems are developed from the feasible operation region perspectives. Besides, an operational optimization considering the punishment for renewable energy curtailment and load shedding is proposed to evaluate performance improvement quantitatively. Combined with the energy efficiency distribution within the feasible operation region, the operating performance promotion contributed by the technology integration is analyzed using a 350 MW CHP system. The results show that integrating the bypass compensation technology can increase the maximum heat-electricity ratio by 160.3% and the electricity adjustment capacity under the heating load of 375 MW by 90.95%in the same flexibility improvement rate. Besides, the electric boiler and bypass compassion technology effectively reduce total coal consumption due to their effectiveness in improving renewable energy consumption and the high energy efficiency distribution within the newly added feasible operation region. However, they hardly handle the load shedding. Inversely, the electrical and heating energy storage systems can address the load shedding but improve weakly renewable energy accommodation under a high renewable penetration rate.