Solid Oxide Fuel Cell-gas Turbine Hybrid System Research Articles

Techno-Economic Analysis of Solid Oxide Fuel Cell-Gas Turbine Hybrid Systems for Stationary Power Applications Using Renewable Hydrogen

Solid oxide fuel cell (SOFC)–gas turbine (GT) hybrid systems can produce power at high electrical efficiencies while emitting virtually zero criteria pollutants (e.g., ozone, carbon monoxide, oxides of nitrogen and sulfur, and particulate matters). This study presents new insights into renewable hydrogen (RH2)-powered SOFC–GT hybrid systems with respect to their system configuration and techno-economic analysis motivated by the need for clean on-demand power. First, three system configurations are thermodynamically assessed: (I) a reference case with no SOFC off-gas recirculation, (II) a case with cathode off-gas recirculation, and (III) a case with anode off-gas recirculation. While these configurations have been studied in isolation, here we provide a detailed performance comparison. Moreover, a techno-economic analysis is conducted to study the economic competitiveness of RH2-fueled hybrid systems and the economies of scale by offering a comparison to natural gas (NG)-fueled systems. Results show that the case with anode off-gas recirculation, with 68.50%-lower heating value (LHV) at a 10 MW scale, has the highest efficiency among the studied scenarios. When moving from 10 MW to 50 MW, the efficiency increases to 70.22%-LHV. These high efficiency values make SOFC–GT hybrid systems highly attractive in the context of a circular economy as they outcompete most other power generation technologies. The cost-of-electricity (COE) is reduced by about 10% when moving from 10 MW to 50 MW, from USD 1976/kW to USD 1668/kW, respectively. Renewable H2 is expected to be economically competitive with NG by 2030, when the U.S. Department of Energy’s target of USD 1/kg RH2 is reached.

Techno-Economic Optimization of SOC Design and Operating Conditions in a Solid Oxide Fuel Cell-Gas Turbine Hybrid System

Solid oxide fuel cell-gas turbine (SOFC-GT) hybrid systems can reach exceptionally high fuel-to-electricity conversion efficiencies while emitting virtually zero criteria pollutants. Due to these characteristics and their fuel-flexibility, SOFC-GT hybrid systems are seen as a key technology in sustainable power generation. In this work we explore SOFC cell design parameters that can synergistically reduce thermal stress and cost, as well as system-level design strategies to maximize economic performance. Results show that NG-fueled hybrid systems can reach efficiencies of 75%-LHV at a cost-of-electricity of 77.73 $/MWh. A similar biogas system with integrated anaerobic digester and biogas upgrading resulted in an efficiency of 53%-LHV and a cost-of-electricity of 137.19 $/MWh.

Comparative study of fuel types on solid oxide fuel cell – gas turbine hybrid system for electric propulsion aircraft

As a novel aviation power generation system, the solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system has high electrical efficiency. Because aviation applications are sensitive to weight, the research of this system should not only consider thermodynamic performance but also focus on mass. Fuel is the energy source of the aircraft powered by SOFC-GT hybrid system, and the types not only affect the power generation performance and mass of the system but also determine the storage capacity. Therefore, the impact of fuel types on the SOFC-GT aircraft can be fully evaluated through the comprehensive analysis of the performance and mass. In this paper, the aircraft powered by SOFC-GT hybrid system fueled by hydrogen, ethanol and alkanes (n-decane, n-octane and liquid methane) are investigated. By establishing the thermodynamic model and mass model, the influence of fuel types on the performance of autothermal reforming, SOFC-GT hybrid system, and aircraft cruise is studied in sequence. The results show that in the reforming process, methane has the best hydrogen production performance and makes SOFC efficiency the highest. However, the performance of the SOFC-GT system is influenced by many factors. For non-hydrogen fuels, n-decane can achieve higher electrical efficiency, while methane has lower fuel consumption. The thermodynamic performance of the hydrogen-fueled system has absolute advantages, but it depends on the larger heat exchanger. Furthermore, for the electric regional aircraft powered by the SOFC-GT hybrid system, the range of aircraft fueled by hydrogen and ethanol is poor, and liquid hydrogen can only take advantage of its high energy density at lower payload due to the mass penalty of the cryogenic tanks, while n-decane and n-octane are superior. Meanwhile, CO2 emissions can still be significantly reduced by matching n-decane with the efficient SOFC-GT hybrid system.

A novel comparison of energy-exergy, and sustainability analysis for biomass-fueled solid oxide fuel cell integrated gas turbine hybrid configuration

Conventional gas turbines (GT) are working with limited fuels and exhibit thermal efficiency between 30 and 40%. This restriction with the fuels and its efficiency range can be improved by adding an electrochemical fuel cell, i.e; a Solid Oxide Fuel Cell (SOFC). This paper proposes three different types of biomasses, including pine sawdust, poplar sawdust, and almond shell, which may all be used to power the novel biomass-fueled solid oxide fuel cell gas turbine (SOFC-GT) presented herein. MATLAB based simulation is used to validate the results of this fuel cell based hybrid cycle performance. Three performance parameters are considered namely, current density (id), turbine input temperature (TIT), and pressure ratio (rp) to evaluate the performance of the proposed system. For this, energy-exergy approaches based on the first and second law of thermodynamics are used to assess each cycle component as well as the entire system. The sustainability index and environmental impact factor of each component are evaluated using dimensionless modified exergy indicators. With all three of the suggested biomass fuels, the SOFC-GT hybrid system runs most effectively at pressure-ratio of 6 and TIT 1250 K. Pine sawdust (Case-1) exhibits the largest levels of exergy destruction (2653.14 kW), environmental effect (0.91), and the lowest sustainability index (2.09) but it also has the highest levels of thermal efficiency (63.12%).

Study on an adaptive multi-model predictive controller for the thermal management of a SOFC-GT hybrid system

A SOFC temperature control system based on adaptive multimodel predictive control (MMPC) method is designed for a solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system with anode and cathode ejectors. Two multi-input and multi-output MPCs (under 100% and 90% load) are designed to control the anode and cathode inlet temperatures. The accuracy of the identified linear models are both more than 95%. The control performance of the designed MMPC is compared with a single MPC and traditional PI. The comparison results demonstrate that the proposed MMPC is most effective and competitive in SOFC thermal management. During the load following, the controller overshoot is less than 1.19K. The settling time is about 2000s, and the integral of time-weighted absolute error is less than 472.

A novel control strategy with an anode variable geometry ejector for a SOFC-GT hybrid system

A novel control strategy was developed with an anode variable geometry ejector for a solid oxide fuel cell-gas turbine (SOFC-GT) system. The anode inlet temperature was controlled by combining two modes to achieve a greater controllable range: anode variable geometry ejector adjusting and after-burner fuel valve adjusting. Two tests were carried out under small-scale and large-scale load steps. The results indicate that all controlled variables can be effectively kept around set-point. Moreover, the critical parameters are kept within safe ranges, including steam-to-carbon ratio higher than 2.0, peak temperature gradient below 10 K/cm, peak time-dependent temperature gradient below 3 K/min, and surge margin higher than 15%. The developed novel control strategy can maintain almost constant SOFC spatial temperature. The spatial temperature variation is within 2.50 K under 5% load step, and within 14.30 K under 30% load step. Besides, the novel control strategy can keep the system efficiency at a high level (more than 63.21%) during the load tracking. Compared with the conventional control strategy with a fixed geometry ejector, the results demonstrated that the novel control strategy can significantly improve the system performance, especially the transient behaviors of after-burner fuel rate, turbine inlet temperature, and system efficiency.

Comparison of different fuel cell temperature control systems in an anode and cathode ejector-based SOFC-GT hybrid system

Solid oxide fuel cell-gas turbine (SOFC-GT) hybrid systems are facing challenges in terms of fuel cell temperature control due to its significant effect on safe and efficient operation. In this study, five different temperature control systems are designed according to different SOFC control strategies and control points in anode and cathode ejector-based SOFC-GT hybrid systems. Firstly, three SOFC temperature control strategies including only anode-side control, only cathode-side control, and two-side control are compared. The comparison results indicate that the cathode-side temperature control strategy can effectively maintain the system efficiency. In addition, the two-side control strategy is better than one-side control strategies considering the safe operation of the anode and cathode differential temperature. Then, three SOFC temperature control points including input temperature, output temperature, and average temperature are chosen in order to investigate the effect of control variables. The comparison results indicate that maintaining the average temperature is better than the other temperature control points. Therefore, the two-side average temperature control system of SOFC is more appropriate to guarantee efficient and safe operation. The temperature distribution in SOFC is more feasible, and the efficiency of SOFC and the whole hybrid system is most efficient at a part load condition.

Performance characteristics of a solid oxide fuel cell hybrid jet engine under different operating modes

Solid oxide fuel cell (SOFC) technology is promising. Jet engines can be integrated with SOFCs (SOFC hybrid jet engine) for aircraft. The specific thrust of the engine is greatly improved by replacing turbines with SOFC systems. Four operating modes are designed for the engine to achieve about 50% ∼ 100% thrust variation. Mode 1: Regulating the fuel flow in the reformer under the constant air flow for the SOFC system. Mode 2: Regulating the fuel flow in the afterburner with zero fresh air for afterburners. Mode 3: Regulating the fuel and air flow for the SOFC. Mode 4: Regulating the fuel flow in the afterburner with constant air flow for afterburners. The performance and thermodynamic parameters of the engine under different operating modes are examined and compared according to the built mathematical models. The simulation results show that the effects of operating modes on the engine are remarkably different from that on the traditional SOFC gas turbine hybrid systems for electricity generation. All of the parameters of components change sharply in modes 1 and 3, and the thermal efficiency of the engine increases respectively from 0.577 to 0.687 and 0.491 to 0.687 with the increase of load. The component parameters of the engine are slightly changed in modes 2 and 4 except the parameters related to the afterburner. In mode 2, the thermal efficiency decreases from 0.577 to 0.454. It decreases from 0.491 to 0.434 in mode 4. In a nutshell, the performance of the engine can be varied in a wide range under the operating model 4 with increasing the afterburner temperature from 832 K to 2261 K. The operating mode 4 is the best.

Performance Evaluation of an SOFC-GT Hybrid System With Ejectors for the Anode and Cathode Recirculations

The ejectors used for the fuel cell recirculation are more reliable and low cost in maintenance than high-temperature blowers. In this paper, an anode and cathode recirculation scheme, equipped with ejectors, was designed in a solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system. The ejector model, SOFC model, and other component models and the validation were conducted to investigate the performance of the hybrid system with anode and cathode ejectors. The geometric parameters of the ejectors were designed to perform the anode and cathode recirculation loops according to the design conditions of the hybrid system with a blower-based recirculation loop. The cathode ejector geometries are much larger than the anode ejector. In addition, the sensitivity analysis of the primary fluid for the standalone anode and cathode ejectors is investigated. The results show that the ejector can recirculate more secondary fluid by reducing the ejector outlet pressure. Then, the anode and cathode ejectors were integrated into the SOFC-GT hybrid system. A blower gets involved downstream, and the compressor is necessary to avoid high expensive cost of redesigning compressor. The off-design and dynamic performance were characterized after integrating the anode and cathode ejectors into the hybrid system. The dynamic and off-design performances show that the designed ejectors are effectively integrated into the anode and cathode recirculation loops to replace the blower-based recirculation loops. The safety range of relative fuel flow rate is 0.62–1.22 in the fixed rotational speed strategy, and it is 0.53–1.1 in the variable rotational speed strategy. The variable rotational speed strategy can ensure higher system efficiency, which is more than 61% at a part-load condition.

Study on Fuel Utilization Dynamic model of a SOFC-GT Hybrid System Based on Deep Learning Technique

In order to perform operation management tasks, including state monitoring and control strategy optimization, of a solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system, a data-driven dynamic model based on deep learning technique of long short term memory (LSTM) network is developed to predict the behaviours of fuel utilization. In addition, a LSTM model with unsupervised deep auto-encoder (DAE) method was developed to extract the feature from input data. The comparison performance between the common LSTM model and DAE-LSTM model was investigated. The results show that the DAE-LSTM model can enhance the prediction performance. Moreover, the effect of data size was investigated. The results demonstrate that the unsupervised DAE-LSTM model trained by large data size can further improve the prediction performance. The maximum error is only 0.00529, and average error decreases to 0.00025. In conclusions, the unsupervised DAE-LSTM model is an effective approach to predict dynamic behaviours.

Experimental study of homogeneous charge compression ignition engine operation fuelled by emulated solid oxide fuel cell anode off-gas

A solid oxide fuel cell (SOFC) hybrid system is a system that combines an SOFC with an additional power generation device to increase the efficiency of the system. The SOFC–gas turbine hybrid system has been primarily investigated for SOFC hybrid systems. However, the current power generation capacity of an SOFC is less than several MWs; for this generation capacity, an internal combustion engine is generally more efficient and economical than a gas turbine. Focusing on this point, recently, the concept of an SOFC–internal combustion engine hybrid system was proposed. However, the operation of this system has not been experimentally studied yet. In this paper, as the first step in an experimental investigation of the hybrid system, an experimental study on the operation of an internal combustion engine fuelled by SOFC anode off-gas was conducted. To successfully combust the SOFC anode off-gas, which includes a large amount of diluents (H2O and CO2), the homogeneous charge compression ignition (HCCI) method was selected instead of spark ignition as the combustion strategy of the internal combustion engine in the hybrid system. For the HCCI engine experiments, a single-cylinder HCCI engine and experimental equipment for emulating SOFC anode off-gas were constructed. Various HCCI engine experiments were performed while varying several system control parameters, e.g., the fuel utilization factor of an SOFC, which primarily affects the composition and flow rate of the engine intake gas. The experiments indicated that, in general system operating condition, HCCI engine operation yields a significant amount of power (w/25–30% gross indicated efficiency) and produces significantly low NOx emissions (<5 ppm @ O2 15%) under stable HCCI combustion (<5% COV IMEPg, which is the coefficient of variance of the gross indicated mean effective pressure). Considering that the experiment was performed using a small single-cylinder engine, these experimental results reveal that the use of an HCCI engine as the bottoming cycle in an SOFC hybrid system is promising. In addition, it has been found how each system control parameter affects HCCI engine operation. It was confirmed that HCCI engine operation was not always stable in all system operating conditions. System operating conditions that induce an exceedingly low engine load (<1.8 bar IMEPg, which is the gross indicated mean effective pressure) should be avoided as it decreases the stability of engine operation. Additionally, system operating conditions that make an engine intake gas with excessive dilution (fuel molar fraction < 0.125) should be avoided to decrease the amount of unburned CO emission and maintain a CO combustion efficiency higher than 90%.

Thermo-environmental and economic comparison of three different arrangements of solid oxide fuel cell-gas turbine (SOFC-GT) hybrid systems

A comparative analysis is performed for three different layouts of SOFC-GT hybrid systems with internal reformer from the viewpoints of energy, exergy, environmental and economic. The three considered designs are distinguished by number of SOFC stack, as single SOFC stack is employed in one system, while two SOFC stacks (cell numbers halved) are used for the other designs. For the second system, two stacks are fed by fuel and air in parallel way; however, in the third case, two stacks are fed by fuel in parallel and air serially. A mathematical model is developed in EES software to simulate the performance of the cycles through a parametric study. In addition, exergy destruction rate of components of the plants are achieved to recognize the main sources of ireversibilities. The analyses demonstrated that two-stack SOFC-GT series type is more efficient, leading energy and exergy efficiencies to reach 63.22% and 60.81% correspondingly, which are about 20.3% and 8.89% higher than conventional SOFC-GT and parallel type, respectively. The highest source of exergy destruction amongst all system components belongs to after burner. Furthermore, it is observed that the highest total cost, 24.95 $/h, is attributed to conventional SOFC-GT hybrid system while the least amount corresponds to SOFC-GT series type, 18.5 $/h. The CO2 gas emission obtained for two-stack SOFC-GT hybrid system series type, 313.3 kg/MWh, obtained to be the lowest.

Study on control strategy for a SOFC-GT hybrid system with anode and cathode recirculation loops

The solid oxide fuel cell-gas turbine (SOFC-GT) hybrid power generation system offers a possible technology of high efficiency combined with low emissions. Due to its highly coupled system and complex dynamic characteristics, several vital parameters such as fuel cell temperature, thermal stress, steam-to-carbon, turbine inlet temperature, and compressor surge margin must be controlled and restricted to a feasible zone to guarantee the safe operation of the hybrid system. A novel control strategy was carried out for the SOFC-GT hybrid system with anode and cathode recirculation loops. In the SOFC thermal management system, two control loops were introduced to keep anode temperature and cathode temperature. The behaviors of the control system were compared with the control system without an anode temperature control loop during load following. The results reveal that the anode channel temperature and cathode channel temperature should both be controlled to avoid huge temperature differences and temperature gradient in SOFC. The designed control system 1 in this study for the hybrid system is feasible and effective.

Cycle analysis of solid oxide fuel cell-gas turbine hybrid systems integrated ethanol steam reformer: Energy management

A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system that uses such liquid fuels as ethanol is attractive for distributed power generation for applications in remote rural areas or as an auxiliary power unit. The SOFC system includes units that require and generate heat; thus, its energy management is important to improve its efficiency. In this study, a SOFC-GT integrated system with the external steam reforming of ethanol to produce hydrogen for the SOFC is proposed. Two SOFC-GT hybrid systems using a high-temperature heat exchanger and cathode exhaust gas recirculation are considered under isothermal conditions. The effects of key operating parameters, such as pressure, fuel use and turbomachinery efficiency, on the SOFC-GT hybrid system performance are discussed. The simulation results indicate that recycling the cathode exhaust gas from the SOFC-GT system requires less fresh air from the compressor, to maintain the SOFC stack temperature, and the heat recovered from the SOFC system is sufficient to supply both the fuel processor and air pre-heater. In contrast, an external heat is needed for the SOFC-GT system coupled to a recuperative heat exchanger.

Open Loop and Closed Loop Performance of Solid Oxide Fuel Cell Turbine Hybrid Systems During Fuel Composition Changes

The dynamic behavior of a solid oxide fuel cell gas turbine hybrid system (SOFC/GT) from both open and closed loop transients in response to sudden changes in fuel composition was experimentally investigated. A pilot-scale (200–700 kW) hybrid facility available at the U.S. Department of Energy, National Energy Technology Laboratory was used to perform the experiments using a combination of numerical models and actual equipment. In the open loop configuration, the turbine speed was driven by the thermal effluent fed into the gas turbine system, where the thermal effluent was determined by the feedforward fuel cell control system. However, in the closed loop configuration, a load-based speed control system was used to maintain the turbine speed constant at 40,500 rpm by adjusting the load on the turbine, in addition to the implementation of the fuel cell system control. The open loop transient response showed that the impacts of fuel composition changes on key process variables, such as fuel cell thermal effluent, turbine speed, and cathode feed stream conditions, in the SOFC/GT systems were propagated over the course of the test, except for the cathode inlet temperature. The trajectories of the aforementioned variables are discussed in this paper to better understand the resulting mitigation/propagation behaviors. This will help lead to the development of novel control strategies to mitigate the negative impacts experienced during fuel composition transients of SOFC/GT systems.

Effect of anode–cathode exhaust gas recirculation on energy recuperation in a solid oxide fuel cell-gas turbine hybrid power system

A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system supplying liquid fuel as ethanol exhibits promise as an auxiliary power unit. In this study, the recirculation of anode and cathode exhaust gas in the SOFC-GT system is proposed to improve the efficiency of heat management in the SOFC-GT hybrid system. The key operating parameters, such as fuel utilization factor and the cell and GT temperatures, are analyzed in terms of the performance of the SOFC-GT hybrid systems. The simulation results show that the recirculation of anode and cathode exhaust gas has a direct impact on the turbine performance. To maintain the inlet temperature of the small turbine in the range of 873–1223 K, the amount of fuel and air added to the combustor to control the turbine inlet temperature on the system performance is also investigated. A SOFC-GT hybrid system with both anode and cathode exhaust gas recirculation achieves the highest system and thermal efficiency.

Effects of SOFC Exhaust Gas Recirculation on Performance of Solid Oxide Fuel Cell-Gas Turbine Hybrid System Utilizing Renewable Fuels

A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system run on renewable fuels, such as biogas and ethanol, is an interesting power generation technology due to its high efficiency. To avoid a carbon formation on the anode catalyst by the direct feed of hydrocarbon fuels to SOFC, a pre-reformer is needed to integrate with the SOFC system for hydrogen production. As the steam reformer and air preheater are units that require high external energy input, the efficient heat management of the SOFC system is necessary. Regarding the SOFC system, the anode and cathode recirculations are employed to recover high-quality waste heat for reformate gas and gas turbine cycle, affecting the electrical and thermal system efficiency. In this study, a steam reformer and SOFC-GT hybrid system with anode and cathode recirculations is investigated. The aim of this work is to analyze the effects of the anode and cathode recirculations on the performance of SOFC-GT systems. The mathematical model of SOFC, gas turbine, and auxiliary units based on mass and energy balances under steady-state operation is employed for this study. The parametric analysis of key operating parameters, such as fuel utilization, steam to carbon ratio and operating pressure, on the system performance is performed. The results indicate that the SOFC hybrid system with the anode recirculation can reduce the supplied heat for the external steam reformer; on the other hand, it degrades the gas turbine performance due to a decrease in the turbine inlet temperature. When considering the hybrid system with the cathode recirculation, it is found that the efficiency of the SOFC-GT system is higher. However, the turbine inlet temperature is extremely high, leading to the cooling problem of a micro turbine.

Effects of SOFC Exhaust Gas Recirculation on Performance of Solid Oxide Fuel Cell-Gas Turbine Hybrid System Utilizing Renewable Fuels

The use of biogas and ethanol as fuel for solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system needs of the external steam reformer. As the steam reformer and air preheater are units that require high external energy input, the efficient heat management of the SOFC system is necessary. Thus, the aim of this study is to analyze the recycling of the SOFC exhaust gas in the SOFC-GT hybrid system supplying fuels as ethanol and biogas. The effect of the recirculation ratio of the anode exhaust gas on the performance of SOFC-GT hybrid system, i.e., the SOFC efficiency, the turbine to SOFC power ratio, and the overall efficiency of hybrid system was firstly investigated. Additionally, the recirculation of both anode gas and cathode gas in the SOFC-GT hybrid system was studied.

Exergy Analysis of an Intermediate Temperature Solid Oxide Fuel Cell-Gas Turbine Hybrid System Fed with Ethanol

In the present work, an ethanol fed Solid Oxide Fuel Cell-Gas Turbine (SOFC-GT) system has been parametrically analyzed in terms of exergy and compared with a single SOFC system. The solid oxide fuel cell was fed with hydrogen produced from ethanol steam reforming. The hydrogen utilization factor values were kept between 0.7 and 1. The SOFC’s Current-Volt performance was considered in the range of 0.1–3 A/cm2 at 0.9–0.3 V, respectively, and at the intermediate operating temperatures of 550 and 600 °C, respectively. The curves used represent experimental results obtained from the available bibliography. Results indicated that for low current density values the single SOFC system prevails over the SOFC-GT hybrid system in terms of exergy efficiency, while at higher current density values the latter is more efficient. It was found that as the value of the utilization factor increases the SOFC system becomes more efficient than the SOFC-GT system over a wider range of current density values. It was also revealed that at high current density values the increase of SOFC operation temperature leads in both cases to higher system efficiency values.

Improved Controller Performance of Selected Hybrid SOFC-GT Plant Signals Based on Practical Control Schemes

This paper compares and demonstrates the efficacy of implementing two practical single input single output multiloop control schemes on the dynamic performance of selected signals of a solid oxide fuel cell gas turbine (SOFC-GT) hybrid simulation facility. The hybrid plant located at the U.S. Department of Energy National Energy Technology Laboratory in Morgantown, WV is capable of simulating the interaction between a 350 kW solid oxide fuel cell and a 120 kW gas turbine using a hardware in the loop configuration. Previous studies have shown that the thermal management of coal based SOFC-GT hybrid systems is accomplished by the careful control of the cathode air stream within the fuel cell (FC). Decoupled centralized and dynamic decentralized control schemes are tested for one critical airflow bypass loop to regulate cathode FC airflow and modulation of turbine electric load to maintain synchronous turbine speed during system transients. Improvements to the studied multivariate architectures include: feed-forward control for disturbance rejection, antiwindup compensation for actuator saturation, gain scheduling for adaptive operation, bumpless transfer for manual to auto switching, and adequate filter design for the inclusion of derivative action. Controller gain tuning is accomplished by Skogestad’s internal model control tuning rules derived from empirical first order plus delay time transfer function models of the hybrid facility. Avoidance of strong input-output coupling interactions is achieved via relative gain array, Niederlinski index, and decomposed relative interaction analysis, following recent methodologies in proportional integral derivative control theory for multivariable processes.