A novel peak shaving framework for coal-fired power plant in isolated microgrids: Combined flexible energy storage and waste heat recovery

Abstract

Coal-fired power plants (CFPPs) not only bear the burden of peak shaving, but the mission of energy saving. However, the increasing peak-valley difference leads to the difficulties of peak shaving and the energy waste caused by the ineffective utilization of waste heat, which undoubtedly becomes a new problem for CFPPs. So, a new integrated system combining flexible energy storage and waste heat recovery in the CFPP is presented. The scheme consists of a double-effect absorption heat pump (D-AHP) with an integrated thermal electricity storage system (IT-ESS). Waste heat from flue gas is recovered by D-AHP, while IT-ESS is responsible for peak shaving. Firstly, comprehensive satisfaction is used for demand-side management. Subsequently, D-AHP is utilized to recover waste heat to meet the users' heating demand. Finally, steam is extracted during off-peak time to store energy for IT-ESS, while energy is released for peak shaving during peak time. Throughout the process, the proportional-integral-differential is applied to control the airflow into the IT-ESS. Numerical results indicate that the maximum peak-valley difference is decreased by 55.3 MW after the optimization of comprehensive satisfaction, and the response time for the airflow to reach the target value is only about 10% of one period with the PID control strategy. Besides, the scheme successfully satisfies the electricity demand and heating demand in isolated microgrids, and the round-trip efficiency of IT-ESS is 23.11%. Lastly, the daily revenue of the system is 1.40 million dollars and the payback period is 3.16 years.