1,720,973 research outputs found
A battery-to-electrolyzer pathway for energy management in a hybrid battery/hydrogen microgrid
Full text linkA RES-based microgrid with two simultaneous storage options - battery and hydrogen - is considered. While the battery pack serves as a short-term storage solution, the hydrogen-cycle (consisting of an electrolyzer, a hydrogen pressurized tank and a fuel cell stack) provides for a long-term (seasonal) storage in order to improve the system resilience and to allow off-grid operation for longer time. With respect to the most classical energy management approach, where energy is transferred either from PV to battery (as the priority transfer) or from PV to electrolyzer, the novel strategy adopted in this paper also adds the possibility of a battery-to-electrolyzer energy conversion route. This route is enabled whenever the energy stored in the battery is expected to overcome the estimated short-term energy needs. The novel strategy reveals significant potential to increase the hydrogen production during the summer months, by redirecting to the electrolyzer part of the excess energy that would be otherwise curtailed or transferred to an external grid. Application of the strategy during autumn and winter time reveals on the contrary a clear worsening of the microgrid performance and should be avoided
An adaptive controller-observer scheme for temperature control of non-chain reactions in batch reactors
No full textIn this paper an adaptive controller–observer temperature control scheme is developed for a class of irreversible non-chain reactions taking place in batch reactors. The scheme is based on a nonlinear observer for the estimation of the heat released by the reaction, where the heat transfer coefficient is adaptively estimated. Tracking of the desired reactor temperature is achieved via a two-loop control scheme, where an independent adaptive estimate of the heat transfer coefficient is used as well. Remarkably, the observer and the controller can be designed and tuned separately. The convergence of both the nonlinear observer and of the overall controller–observer scheme is analyzed by resorting to a Lyapunov-like argument. A comparative simulation case study is developed to test the performance of the proposed scheme and compare it with other approaches already known in the literature
Effect of non-ideal mixing on control of cooled batch reactors
No full textIn this paper, the effect on a temperature control law of unmodelled non-perfect mixing in a cooled batch reactor, in which a strongly exothermic reaction takes place, has been tested. Reactor non-ideality has been described by means of a compartment model, obtained by subdividing the reactor into perfectly mixed interacting zones, while the temperature control scheme has been based on the assumption of ideal reactor behaviour. The proposed model allows to quantify the quality of mixing in terms of a dimensional internal circulation flow rate Xc. Detailed analysis has been carried out by comparing temperature tracking error in different reactor compartments and for different mixing degrees. In addition, the effect of temperature sensor location has been assessed. Main results highlight how the decrease of Xc is responsible for an increase of temperature gradients inside the reactor volume, with consequent worsening of temperature controllability; in correspondence of very poor mixing, run-away conditions can be reached. It can be also observed that, when temperature measures are carried out in peripheral reactor regions, temperature errors are generally larger and the values of Xc at which run-away onsets increase, i.e. a better mixing is required to avoid safety problems. Noteworthy, the effect of Xc on reactant conversion depends on the sensor location as well. In fact, average conversion degree is higher when temperature is measured in peripheral regions, since the temperature controller yields higher average temperatures in the reactor
An Integrated Approach to Fault Diagnosis for a Class of Chemical Batch Processes
No full textThis paper deals with the problem of fault diagnosis for a class of chemical reactions taking place in a jacketed batch reactor. An integrated diagnosis scheme, using redundant temperature measurements and a bank of state observers, is adopted to detect, isolate and identify faults. A unified framework is developed to take into account faults affecting sensors, actuators and process. Redundant sensor measurements, together with the estimates provided by two isolation observers, are processed by a Decision Making System, providing information about the faulty sensor as well as healthy measurements. Then, healthy measurements are processed by a bank of adaptive observers, aimed at detecting, isolating and identifying actuator and process faults. In order to test the effectiveness of the approach, a detailed simulation case study is developed
A controller-observer scheme for adaptive control of chemical batch reactors
No full textIn this paper a novel adaptive controller-observer temperature control scheme for ideal chemical batch reactors is analyzed. The scheme is based on an adaptive observer for the estimation of the heat released by the reaction; tracking of the desired reactor temperature profile is achieved via a direct adaptive control scheme. Remarkably, the observer and the controller can be designed and tuned separately. The convergence of the overall scheme is analyzed by resorting to a Lyapunov-like argument, while the effectiveness of the approach is proven via computer simulations
Treatment of biomass gasification wastewater by adsorption on biomass gasification char
No full textIn this work, a novel approach to the treatment of biomass gasification wastewater, i.e. liquids deriving from wet gas cleaning operations, is explored. The proposed technology is based on adsorption on biomass gasification char, which is continuously produced by the plant itself. Samples of char were taken and characterized and then their adsorption isotherms were experimentally determined. Batch tests were conducted in a solid¬liquid contactor and a deterministic dynamic mathematical model was used for data interpretation. Results showed that the proposed process is able to achieve an extremely high reduction in the pollutants content, by using an adsorbent material which is practically costless
A Model-Based Control Scheme for Chemical Batch Reactors
No full textIn this paper a novel model-based temperature control scheme for batch chemical reactors is proposed. Namely, a controller-observer scheme is designed, where a nonlinear observer is designed to estimate the heat released by the reaction. The controller is based on the closure of two feedback loops, thus ensuring robustness of the overall scheme, while preserving the simplicity of the control laws. Remarkably, the observer and the controller can be designed and tuned separately. In the case of a poorly known heattransfer coefficient, both the observer and the controller incorporate a direct adaptive estimation strategy of the coefficient. The performance, in terms of accuracy and robustness, are investigated via computer simulations
A Nernst-Based Approach for Modeling of Lithium-Ion Batteries with Non-Flat Voltage Characteristics
Full text linkThis paper presents an easy-to-implement model to predict the voltage in a class of Li-ion batteries characterized by non-flat, gradually decreasing voltage versus capacity. The main application is for the accurate estimation of the battery state of the charge, as in the energy management systems of battery packs used in stationary and mobility applications. The model includes a limited number of parameters and is based on a simple equivalent circuit representation where an open circuit voltage source is connected in series with an equivalent resistance. The non-linear open circuit voltage is described using a Nernst-like term, and the model parameters are estimated based on the manufacturer discharge curves. The results show a good level of model accuracy in the case of three different commercial batteries considered by the study: Panasonic CGR18650AF, Panasonic NCR18650B and Tesla 4680. In particular, accurate description of the voltage curves versus the state of charge at different constant currents and during charging/discharging cycles is achieved. A possible model reduction is also addressed, and the effect of the equivalent internal resistance in improving the model predictions near fully depleted conditions is highlighted
Kinetic model reduction for control of phenol-formaldehyde reactive systems
No full text.This study aims at improving the performance of a model-based control scheme for chemical processes characterized by very complex kinetics. The highly exothermic phenol-formaldehyde reactive process for the production of phenolic resins is accurately modeled by taking into account a large number of reactions and compounds. Then, two simplified reaction networks, involving only a limited number of reactions and species, are proposed. The accuracy of the simplified models in terms of concentrations and heat release estimates, is assessed by comparing their behavior in a simulation environment. The analysis of the results suggests that the best match, both in terms of concentration estimation and heat estimation accuracy, is obtained with second-order kinetics and involves 4 reactions. The best performing reduced-order model devised in Section 3 has been adopted for the design of a control scheme for a jacketed batch reactor in which the phenol-formaldehyde reaction takes place. A reliable and accurate simulation model of the reactor has been built in a Matlab-Simulink environment, involving the mass balances of the 13 species of the high-order complete model and the energy balances written for the reactor and the cooling jacket, under the assumption of perfect mixing. The tracking error remains very low (below 0.05 [K]) over the entire reaction time and this confirms that the reduced-order model can be successfully used for control purposes
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