Session: 30-10 Component Design and Testing

Paper Number: 153599

Inventory Management and Control Options for Transient Operation of sCO2 Brayton Cycles 

Supercritical Carbon Dioxide (sCO₂) based Brayton cycles coupled to renewable heat sources hold promise for an efficient and low carbon power generation. However, with increasing integration of variable renewable energy sources, there is a need for a suitable control system to ensure stable and efficient operation to manage large variations in loads. This paper aims to assess different inventory control schemes for achieving high ramp rates and thereby understand its implication on the dynamic response of the sCO₂ cycle.

In the first part of the paper, a linear control system tailored to regulate the inventory tank valves has been investigated. The step response characteristics of the system during both, inventory rejection and inventory injection is examined. Preliminary models indicate that inventory rejection provides a rapid response to changes in demand, while inventory injection reveals non-minimum phase behaviour. A transfer function is derived by linearizing the model of Brayton cycle. An equivalent spring-mass system is used to gain insights into developing a simple controller.

The second part of the paper presents the development of a Proportional-Integral-Derivative (PI(D)) controller designed using classical Bode plots. The robustness of the controllers against the variations in plant parameters is investigated. While PI controllers demonstrate satisfactory robustness, the study highlights that the performance worsens as the ramp rates increase and during ramp-up due to the plant’s non-minimum phase behaviour. Methods to mitigate these shortcomings are discussed. Subsequently, turbine bypass control is explored as an alternative control strategy. Initial results suggest that bypass control provides first-order dynamics, enabling faster ramp rates by avoiding limitations imposed on inventory control.

By comparing the various inventory control options with turbine bypass, it is demonstrated that simple and cost-effective PI controllers are sufficient for regulating sCO₂ cycles during varying loads, offering promising pathways towards reliable and flexible power generation solutions.

Presenting Author: Shrey Sahai Gupta Indian Institute of Science, Bangalore

Presenting Author Biography: Hi, I am Shrey Sahai Gupta, a Ph.D. candidate at the Indian Institute of Science, Bengaluru, working on Thermal Controls of Supercritical Carbon Dioxide Power Systems. I have a knack for Interdisciplinary research and am skilled in System Simulations and reduced-order modeling.

After completing my bachelor's in mechanical engineering from the Indian Institute of Technology, Ropar, India, in 2020, I briefly worked at Hindustan Petroleum Corporation Limited, India, for around a year. I joined my Doctoral Degree in August 2021. Currently, I am investigating the potential for sCO2 cycles for modern power needs and cost-competitive heat-to-power systems.

Authors:

Shrey Sahai Gupta Indian Institute of Science, Bangalore
Pramod Kumar Indian Institute of Science, Bangalore
Pramodchandra Gopi Triveni Turbines Limited