Dynamic Modeling of Organic Rankine Cycle Power Systems

Abstract

New promising applications of organic Rankine cycle (ORC) technology, e.g., concentrated solar power, automotive heat recovery and off-grid distributed electricity generation, demand for more dynamic operation of ORC systems. Accurate physically-based dynamic modeling plays an important role in the development of such systems, both during the preliminary design as an aid for configuration and equipment selection, and for control design and optimization purposes. A software library of modular reusable dynamic models of ORC components has been developed in the MODELICA language and is documented in the paper. The model of an exemplary ORC system, namely the 150 kW e Tri-O-Gen ORC turbogenerator is validated using few carefully conceived experiments. The simulations are able to reproduce steady-state and dynamic measurements of key variables, both in nominal and in off-design operating conditions. The validation of the library opens doors to control-related studies, and to the development of more challenging dynamic applications of ORC power plants

Part-Load Performance of aWet Indirectly Fired Gas Turbine Integrated with an Organic Rankine Cycle Turbogenerator

“…Given the lack of publicly available data and considering the particular system layout and control strategy proposed here, an in-depth validation is currently beyond the possibilities of the present work. Nonetheless, the model of the ORC system is based on the methods used to model a 150 kW ORC system using toluene as the working fluid, and successfully validated for steady-state (and transient) operation against experimental data as discussed in Casella et al [41]. The model of the bottoming cycle unit is, therefore, deemed reliable, considering the similarity of the application at hand with the one presented in the cited reference.…”

Dynamic Simulation of an Organic Rankine Cycle—Detailed Model of a Kettle Boiler

“…The presence of hot spots in heat exchangers during transients can be limited, avoiding thermal degradation of the working fluid [46]; • The increasing complexity in the dynamics of the electricity grid, associated with the increasing penetration of variable-source renewables (i.e., wind and photovoltaics), requires a higher contribution from controllable power plants (biomass, geothermal) for security margin, load reserve and grid stability; • Renewables-based ORCs could be used as stand-alone systems in remote areas and operated under strong dynamic conditions [47]; • The design of systems operated most of the time in off-design conditions (e.g., waste heat recovery) could be improved; stresses and plant lifetime can be increased [48,49]; • Start-ups, shutdowns and emergency situations (turbine trips, safety valve lifting) can also take help from dynamic simulations [50].…”

Increasing the efficiency of Organic Rankine Cycle Technology by means of Multivariable Predictive Control

“…Dynamic modeling of power plant has been studied in the last years, for energy conversion units (Colonna and Van Putten. [2007]), as well as for ORC systems (Casella et al [2013]). …”