Session: 30-09 Systems 1 and Components

Submission Number: 175509

Off-Design Performance Simulation, Control Strategies and Evaluation of Recuperated Supercritical CO2 Power Plant 

The supercritical carbon dioxide (sCO₂) Brayton cycle power generation systems have emerged as a promising alternative to conventional steam Rankine cycle plants due to their high efficiency, compactness, and potential for integration with low-grade heat sources. Power demand fluctuations may require the sCO₂ power plants to operate at part-loads for a substantial portion of their lifetime. Therefore, it is necessary to develop effective part-load control and operation schedules to operate sCO₂ power plants efficiently and safely at all part-load operating conditions. In this study, a new thermodynamic modelling approach is proposed for the part-load off-design performance simulations and analysis of sCO₂ power generation systems. In this approach, a set of system variables is identified to determine the status of the system, a set of matching errors is selected to assess the continuity of mass and energy within the system, and the Newton-Raphson iterative method is used to converge the performance simulation. The introduced performance simulation method provides the flexibility to analyse almost any sCO₂ cycle configuration. A 5-MW recuperated sCO₂ cycle power generation system is used as a case study to demonstrate the effectiveness of the introduced approach. Two power setting controls, which are compressor speed (N_c) control and turbine inlet temperature (TIT) control, are applied first. The simulation results show that the Nc control quickly shifts the compressor operating point towards the surge line, and power output can only be safely reduced to 46.5% of the design value. TIT control provides enough safety margin for the compressor until the power output drops to about 24.8% of the design value, but the system's thermal efficiency declines rapidly. A new hybrid Nc-TIT part-load control schedule is then introduced that can safely decrease the system power output to 20% of the design value while maintaining good thermal efficiency.

Presenting Author: Ahsan Alam Cranfield University

Presenting Author Biography: Ahsan Alam completed his Master of Mechanical Engineering (with a specialisation in Energy Systems) at NED University of Engineering and Technology, Pakistan. He worked for 10 years in Pakistan’s power generation sector before beginning his PhD at Cranfield University. Ahsan’s PhD research focuses on the off-design performance of supercritical CO₂ Brayton cycles for power generation. His work proposes a new thermodynamic performance simulation method for sCO₂ Brayton cycles, investigates part-load control schedules, and compares alternative shaft configurations and cycle layouts.

Authors:

Ahsan Alam Cranfield University
Yiguang Li Cranfield University