(371q) Modeling and Advanced Process Control of Supercritical Carbon Dioxide (sCO2)-Based Energy System

The National Energy Technology Laboratory (NETL) has been investigating the design, off-design, and dynamic performance of a 10 MWe (net) supercritical CO₂ (sCO₂) Recompression Closed Brayton Cycle (RCBC) [1, 2, 3]. The demonstration of cycle performance, integration, operability, and controls is important for the future commercialization of the sCO₂-based power plants. As part of the systems engineering, off-design and part-load performance has been studied [1]. In addition, the dynamic behavior of the process has been modeled to test regulatory control strategies for improving power ramp rates [2]. However, the implementation of advanced control strategies such as Model Predictive Control (MPC) methods, Biologically-Inspired Optimal Control Strategy (BIO-CS as MPC) [4] and other biomimetic agent-based algorithms [5] have not yet been tested to improve cycle performance during transient, off-design conditions.

In this study, a rigorous steady-state off-design model in Aspen Plus is updated and exported to Aspen Plus Dynamics to study the dynamic performance under disturbances in the form of periodic step changes in inputs. For the control study, a multi-input-multi-output system from the sCO₂ RCBC is selected. The control objective is load setpoint tracking by manipulating inventory (system mass), turbine inlet temperature control by manipulating the primary heater input, and main compressor inlet temperature control by manipulating water flow to the main cooler. System identification techniques are used to derive simplified dynamic models for testing MPC, BIO-CS [4], and agent-based control strategies [5]. In addition, open-loop dynamic studies are performed to evaluate operability and further assist the application of controllers on the system. The results will demonstrate the potential of such control strategies to tackle multiple challenges, including the nonlinearities of the advanced energy system.

References:

1. Zitney, S. E., Liese, E. A., 2018, Dynamic modeling and simulation of a 10MWe supercritical CO₂ recompression closed brayton power cycle for off-design, part-load, and control analysis., The 6th International Symposium on Supercritical CO₂ Power Cycles, Pittsburgh, PA.
2. Mahapatra, P., Albright, J., Zitney, S. E., Liese, E. A., 2018, Advanced regulatory control of a 10 MWe supercritical CO₂ recompression brayton cycle towards improving power ramp rates., The 6th International Symposium on Supercritical CO₂ Power Cycles, Pittsburgh, PA.
3. Huang, M., Tang, C. J., McClung, A., 2018, Steady state and transient modeling for the 10 MWe sCO₂ test facility program., The 6th International Symposium on Supercritical CO₂ Power Cycles, Pittsburgh, PA.
4. Mirlekar, G., Gebreslassie, B. H., Diwekar, U. M., and Lima, F. V., 2018, Biomimetic-based advanced control strategy integrated with multi-agent optimization for nonlinear chemical processes. Chemical Engineering Research and Design, 140, p. 229-240.
5. Mirlekar G., 2018, Development of Biomimetic-based Controller Design Methods for Advanced Energy Systems, PhD Thesis, West Virginia University.