Recent developments of control strategies for organic Rankine cycle (ORC) systems

Organic Rankine cycle (ORC) is one of the most rapidly growing approaches to utilizing low grade thermal energy. This paper deals with the main control problems existed in ORC systems and overviews the main approaches presented in literature. The main ORC operating modes are introduced, the control strategies of ORC systems are then surveyed. Thus, this paper presents a comprehensive review of overall control strategies for ORC energy conversion systems and points out research trend on ORC control systems

Nonlinear Dynamic Model Identification and MPC control of an Organic Rankine Cycle (ORC) based Solar Thermal Power Plant

International audienceIn this paper a nonlinear dynamic model for a solar thermal Organic Rankine Cycle (ORC) power plant is identified and validated using experimental data gathered on a real 4kWelec ORC based solar thermal power plant prototype. The applied identification structure enables the dynamics of the key quantities (variables to be regulated and constrained variables) to be captured. This leads to a control-oriented model that is used to design a constrained optimal control strategy for the ORC power plant that has to track some reference electrical power while respecting the system constraints in terms of temperatures and pressures for some key thermodynamic variables. Prior to the control design step, an analysis of the admissible desired steady states is performed to derive feedforward terms that enhance the controller performances

Dynamic modeling and control strategies of organic Rankine cycle systems: Methods and challenges

Organic Rankine cycle systems are suitable technologies for utilization of low/medium-temperature heat sources, especially for small-scale systems. Waste heat from engines in the transportation sector, solar energy, and intermittent industrial waste heat are by nature transient heat sources, making it a challenging task to design and operate the organic Rankine cycle system safely and efficiently for these heat sources. Therefore, it is of crucial importance to investigate the dynamic behavior of the organic Rankine cycle system and develop suitable control strategies. This paper provides a comprehensive review of the previous studies in the area of dynamic modeling and control of the organic Rankine cycle system. The most common dynamic modeling approaches, typical issues during dynamic simulations, and different control strategies are discussed in detail. The most suitable dynamic modeling approaches of each component, solutions to common problems, and optimal control approaches are identified. Directions for future research are provided. The review indicates that the dynamics of the organic Rankine cycle system is mainly governed by the heat exchangers. Depending on the level of accuracy and computational effort, a moving boundary approach, a finite volume method or a two-volume simplification can be used for the modeling of the heat exchangers. From the control perspective, the model predictive controllers, especially improved model predictive controllers (e.g. the multiple model predictive control, switching model predictive control, and non-linear model predictive control approach), provide excellent control performance compared to conventional control strategies (e.g. proportional–integral controller, proportional–derivative controller, and proportional–integral–derivative controllers). We recommend that future research focuses on the integrated design and optimization, especially considering the design of the heat exchangers, the dynamic response of the system and its controllability