Fuel Cell Hybrid System Research Articles

Multi-Stack Lifetime Improvement through Adapted Power Electronic Architecture in a Fuel Cell Hybrid System

To deal with the intermittency of renewable energy resources, hydrogen as an energy carrier is a good solution. The Polymer Electrolyte Membrane Fuel Cell (PEMFC) as a device that can directly convert hydrogen energy to electricity is an important part of this solution. However, durability and cost are two hurdles that must be overcome to enable the mass deployment of the technology. In this paper, a management system is proposed for the fuel cells that can cope with the durability issue by a suitable distribution of electrical power between cell groups. The proposed power electronics architecture is studied in this paper. A dynamical average model is developed for the proposed system. The validation of the model is verified by simulation and experimental results. Then, this model is used to prove the stability and robustness of the control method. Finally, the energy management system is assessed experimentally in three different conditions. The experimental results validate the effectiveness of the proposed topology for developing a management system with which the instability of cells can be confronted. The experimental results verify that the system can supply the load profile even during the degradation mode of one stack and while trying to cure it.

High-efficiency conversion of natural gas fuel to power by an integrated system of SOFC, HCCI engine, and waste heat recovery: Thermodynamic and thermo-economic analyses

A novel natural gas utilization system for power generation including solid oxide fuel cell (SOFC) and homogeneous charge compression ignition (HCCI) engine is proposed and modeled to evaluate the thermodynamic and thermo-economic performance in this paper. The results show that the SOFC-HCCI engine hybrid system has a net electrical efficiency of approximately 59% and the exergy efficiency of 53.5%, both of which are more than single fuel cell system and comparable to other hybrid fuel cell systems. It is also found that the SOFC contributes to the total power of 80% and has a relatively low exergy destruction. Through the parametric analysis, the power distribution between SOFC and engine can be adjusted by controlling SOFC fuel utilization to optimize the system overall performance. Besides, the specific electric energy cost of the proposed hybrid system is calculated to be 6.91 ¢/kW h, which is comparable to the specific cost of electric power (6.92 ¢/kW h) generating from a biogas-fueled fuel cell hybrid system. The payback period and annual return on investment can reach 1.53 year and about 6.41%. These results reveal that the proposed conversion technology of natural gas fuel to power is efficient and economical, which could be a promising natural gas fuel utilization.

Impact of Different Volume Sizes on Dynamic Stability of a Gas Turbine-Fuel Cell Hybrid System

Abstract A dynamic model is developed for a microgas turbine (MGT), characterized by an intrinsic free-spool configuration, coupled to large volumes. This is inspired by an experimental facility at the National Energy Technology Laboratory (NETL) called hybrid performance (Hyper), which emulates a hybrid MGT and Fuel Cell system. The experiment and model can simulate stable and unstable operating conditions. The model is used to investigate the effects of different volumes on surge events, and to test possible strategies to safely avoid or recover from unstable compressor working conditions. The modeling approach is started from the Greitzer lumped parameter approach, and it has been improved with integration of empirical methods and simulated components to better match the real Hyper plant layout and performance. Pressure, flowrate, and frequency plots are shown for the surge behavior comparing two different volume sizes, for cases where gas turbine shaft speed is uncontrolled (open loop) and controlled (closed-loop). The ability to recover from a surge event is also demonstrated.

Techno-economic evaluation and technology roadmap of the MWe-scale SOFC-PEMFC hybrid fuel cell system for clean power generation

This paper proposes a novel hybrid fuel cell power generation system with high efficiency. The thermo-economic modeling of the MWe-scale systems using different fuels is conducted to evaluate the economic feasibility under the subsidy policy of Eastern China. This work aims to develop the technology roadmap for this kind of clean power system. It is found that the energy efficiency of the natural gas and biogas fed systems could reach up to 64% and 63.5% respectively, thus they are efficient and cost-optimal for the hybrid system while liquefied petroleum gas and water gas yield low efficiency and high electricity cost. Moreover, under the subsidy policy, the biogas-fed hybrid system is more suitable for a small-scale power system, while the natural gas-fed system is preferable for the large-scale case. The specific electricity cost of small-scale biogas hybrid fuel cell power plant is 0.365 CNY/kWh, lower than the present feed-in-tariff price 0.475–0.704 CNY/kWh of other biogas plants in China. Also, the cost of 0.345–0.347 CNY/kWh of large-scale natural gas-fed hybrid system is much lower than the on-grid electricity price 0.7655 CNY/kWh in Shanghai. These results reveal that the proposed hybrid fuel cell power system is efficient and economically feasible. The payback period and annual return on investment are 0.8–1.2 year and 11–12%, respectively.

Thermo-economic assessment of molten carbonate fuel cell hybrid system combined between individual sCO2 power cycle and district heating

A molten carbonate fuel cell (MCFC) is a high-performance electric power generation system, but much research is still required to develop technologies to enhance its power efficiency, because the exhaust gases of an MCFC contain sensible energy. The high level of heat energy in the exhaust gases leads to a poor performance, with an increased electricity rate and decreased efficiency. This study investigated the supercritical carbon dioxide cycle with three different configurations as a bottoming cycle using the exhaust gases of an MCFC stand-alone system and compared the supercritical carbon dioxide cycle with a combined heat and power system in terms of economical operational strategies. The thermodynamic characteristics of each cycle were determined by varying the turbine inlet pressure and isentropic efficiency of the turbomachinery. The results of an analysis found that optimal discharge pressure of compressor, are remarkable parameter for supercritical carbon dioxide cycle. Furthermore, the net power efficiency was increased (3.41%–4.6%) compared to that of the MCFC stand-alone system. In addition, the levelized cost of electricity values for the supercritical carbon dioxide cycle and combined heat and power system were calculated, and sensitivity analyses were conducted for factors such as the heating cost and major equipment cost. The results showed that using the supercritical carbon dioxide cycle as the MCFC bottoming cycle was more economical when the heating cost was less than $28/Gcal and the printed circuit heat exchanger cost was less than $100/kW.

Design optimization under uncertainty of hybrid fuel cell energy systems for power generation and cooling purposes

Reliance on point estimates when developing hybrid energy systems can over/underestimate system performance. Analyzing the sensitivity and uncertainty of large-scale hybrid systems can be a challenging task due to the large number of design parameters to be explored. In this work, a comprehensive and efficient sensitivity/uncertainty methodology is applied on two fuel cell hybrid systems to help analysts to investigate hybrid systems more efficiently. This methodology also includes a step-by-step approach to perform design optimization under uncertainty of energy systems. The two hybrid systems are: molten carbonate fuel cell with thermoelectric generator (MCFC-TEG) and phosphoric acid fuel cell with refrigerator (PAFC-REF). Various sensitivity and uncertainty methods are utilized to analyze the design parameters and their effect on the performance of these two systems. These methods perform local and regression-based sensitivity analysis, Monte Carlo uncertainty propagation, parameter screening, and variance decomposition. Detailed approach is adopted to identify and rank the influential design parameters for each system. Results demonstrate that the optimum power output of the MCFC-TEG has 10% uncertainty, driven mainly by the operating temperature, cahtode activation energy, TEG figure of merit, and TEG thermal conductivity. However, PAFC-REF is more reliable with larger power output and 1.4% uncertainty, driven by the charge transfer coefficient, heat transfer in the refrigeration cycle, cold reservoir temperature, and operating temperature. Based on this identification, design optimization under uncertainty is performed using these sensitive parameters to improve the system performance through increasing the power output and reducing its uncertainty.

Uncertainty Quantification Analysis of a Pressurized Fuel Cell Hybrid System

Abstract Pressurized solid oxide fuel cell (SOFC) systems are a sustainable opportunity for improvement over conventional systems, featuring high electric efficiency, potential for cogeneration applications, and low carbon emissions. Such systems are usually analyzed in deterministic conditions. However, it is widely demonstrated that such systems are affected significantly by uncertainties, both in component performance and operating parameters. This paper aims to study the propagation of uncertainties related both to the fuel cell (ohmic losses, anode ejector diameter, and fuel gas composition) and the gas turbine cycle characteristics (compressor and turbine efficiencies, recuperator pressure losses). The analysis is carried out on an innovative hybrid system layout, where a turbocharger is used to pressurize the fuel cell, promising better cost effectiveness then a microturbine-based hybrid system, at small scales. Due to plant complexity and high computational effort required by uncertainty quantification methodologies, a response surface (RS) is created. To evaluate the impact of the aforementioned uncertainties on the relevant system outputs, such as overall efficiency and net electrical power, the Monte Carlo method is applied to the RS. Particular attention is focused on the impact of uncertainties on the opening of the turbocharger wastegate valve, which is aimed at satisfying the fuel cell constraints at each operating condition.

Optimization and evaluation of a wind, solar and fuel cell hybrid system in supplying electricity to a remote district in national grid

PurposeThe important factors, which should be considered in the design of a hybrid system of photovoltaic and wind energy are discussed in this study. The current load demand for electricity, as well as the load profile of solar radiation and wind power of the specified region chosen in Iran, is the basis of design and optimization in this study. Hybrid optimization model for electric renewable (HOMER) software was used to simulate and optimize hybrid energy system technically and economically.Design/methodology/approachHOMER software was used to simulate and optimize hybrid energy system technically and economically.FindingsThe maximum radiation intensity for the study area is 7.95 kwh/m2/day for July and the maximum wind speed for the study area is 11.02 m/s for January.Originality/valueThis research is the result of the original studies.

Design of Stand-Alone Proton Exchange Membrane Fuel Cell Hybrid System under Amman Climate

Design of Stand-Alone Proton Exchange Membrane Fuel Cell Hybrid System under Amman Climate

Nonlinear control of air-feed system for proton exchange membrane fuel cell with auxiliary power battery

This paper proposes a novel nonlinear controller of the air-feed system for a polymer electrolyte membrane (PEM) fuel cell with an auxiliary power battery. To improve the fast response of the air-feed system, we designed a PEM fuel cell hybrid system, wherein the PEM fuel cell supplies the primary power for the load demand, and the buffered power battery satisfies the additional power requirement. A power coordination strategy is presented to distribute dynamically varying load power demand to the PEM fuel cell and battery. A reduced third-order nonlinear model is used to analyze the nonlinear characteristics of the air-feed system. Next, to improve the tracking performance of the oxygen excess ratio, a triple-step nonlinear controller is designed through the affinelike air-feed system model, and the stability of closed-loop system is guaranteed by the Lyapunov-based technique. Subsequently, the effectiveness of the power coordination strategy and controller is validated by some simulation comparisons. The simulation results indicate that the proposed approach performs better than the proportional-integral-derivative (PID) controller and the triple-step controller for a PEM fuel cell system without an auxiliary battery.

Performance assessment of a biogas fuelled molten carbonate fuel cell-thermophotovoltaic cell-thermally regenerative electrochemical cycle-absorption refrigerator-alkaline electrolyzer for multigenerational applications

In recent years, there has been increasing interest in fuel cell hybrid systems. In this paper, a novel multi-generation combined energy system is proposed. The system consists of a molten carbonate fuel cell (MCFC), a thermally regenerative electro-chemical cycle (TREC), a thermo photovoltaic cell (TPV), an alkaline electrolyzer (AE) and an absorption refrigerator (AR). It has four useful outputs, namely electricity, hydrogen, cooling and heating. The overall system is thermodynamically modeled in a detailed manner while its simulation and modeling are done through the TRNSYS software tool. Power output, cooling-heating and produced hydrogen rates are determined using energetic and exergetic analysis methods. Results are obtained numerically and plotted. The maximum power output from the system is 16.14 kW while maximum energy efficiency and exergy efficiency are 86.8% and 80.4%,. The largest exergy destruction is due to the MCFC.

Development of new energy management strategy for a household fuel cell/battery hybrid system

This work aims to construct an efficient and robust fuel cell/battery hybrid operating system for a household application. The ability to dispatch the power demands, sustain the state of charge (SOC) of battery, optimize the power consumption, and more importantly, ensure the durability as well as extend the lifetime of a fuel cell system is the basic requirements of the hybrid operating system. New power management strategy based on fuzzy logical combined state machine control is developed, and its effectiveness is compared with various strategies such as dynamic programming (DP), state machine control, and fuzzy logical control with simulation. Experimental results are also presented, except for DP because of difficulties in achieving real-time implementation and much faster response to load variation. The given current from the energy management system (EMS) as a reference of the fuel cell output current is determined by filtering out various harmful signals. The new power management strategy is applied to a 1-kW stationary fuel cell/battery hybrid system. Results show that the fuel cell hybrid system can run much smoothly with prolonged lifetime.

A Stand-Alone Hybrid Photovoltaic, Fuel Cell, and Battery System: Case Studies in Jordan

The main purpose of this study is to investigate the feasibility of using a hybrid photovoltaic (PV), fuel cell (FC), and battery system to power different load cases, which are intended to be used at the Al-Zarqa governorate in Jordan. All aspects related to the potentials of solar energy in the Al-Hashemeya area were studied. The irradiation levels were carefully identified and analyzed and found to range between 4.1 and 7.6 kWh/m2/day; these values represented an excellent opportunity for the photovoltaic solar system. homer (Hybrid Optimization model for Multiple Energy Resources) software is used as an optimization and sizing tool to discuss several renewable and nonrenewable energy sources, energy storage methods, and their applicability regarding cost and performance. Different scenarios with photovoltaic slope, diesel price, and fuel cell cost were done. A remote residential building, school, and factory having an energy consumption of 31 kWh/day with a peak of 5.3 kW, 529 kWh/day with a maximum of 123 kW and 608 kWh/day with a maximum of 67 kW, respectively, were considered as the case studies' loads. It was found that the PV-diesel generator system with battery is the most suitable solution at present for the residential building case, while the PV-FC-diesel generator-electrolyzer hybrid system with battery suites best both the school and factory cases. The load profile for each case was found to have a substantial effect on how the system's power produced a scheme. For the residential building, PV panels contributed by about 75% of the total power production, the contribution increased for the school case study to 96% and dropped for the factory case to almost 50%.

Enhanced Electricity Generation and H2O2 Production in a Photocatalytic Fuel Cell and Fenton Hybrid System Assisted with Reverse Electrodialysis.

A novel integrating system coupled with photocatalytic fuel cell and Fenton system assisted by reverse electrodialysis (PREC) is proposed. The results demonstrate that H2O2 concentration increased continuously in the reaction process to finally reach 960 mg/L and the current became stable at around 5.2 mA. The salinity-driven potential derived from the high concentration and low concentration cells in the hybrid system was 0.72 and 0.90 V respectively, at the salinity ratio of 50 and 100. The hybrid system has an energy recovery of 16%, a cathodic efficiency of 51%, and the maximum power of 76 W/m2 at a salinity ratio of 50, with a 100 Ω external resistance. It is proved that PREC-Fenton possessed great potential in industrial wastewater treatment.

Fast identification of power change rate of PEM fuel cell based on data dimensionality reduction approach

The efficiency, reliability and lifespan of the fuel cell are strongly affected by the dynamic load variation of its output, which renders it desperate to investigate the influence of the power change rate on the fuel cell. In this study, three data dimensionality reduction algorithms are applied to identify the power change rate of the fuel cell in a less time-consuming way. To achieve that, the cell voltages of the stack as high-dimensional dataset is instantly projected onto the one-dimensional eigenvector space by principal component analysis (PCA), Fisher discriminant analysis (FDA) and locally linear embedding (LLE), respectively. The eigenvalue of one-dimensional eigenvector has the potential for instantly identifying the power change rate of the fuel cell and can be used as a feedback parameter in the control, which can improve the dynamic response, reliability, and lifespan of the fuel cell stack. According to the performance indicators of the algorithms including monotonicity, linearity and program execution time, the result shows that the PCA algorithm is the best-matched method for the real-time control of the fuel cell system. In the end, this study discussed some potential applications of this method in the fuel cell system, be it to be used alone or in a vehicular fuel cell hybrid system.

A Dual-Mode Energy Management Strategy Considering Fuel Cell Degradation for Energy Consumption and Fuel Cell Efficiency Comprehensive Optimization of Hybrid Vehicle

The energy management strategy is the key to achieve fuel cell hybrid system operation with high-efficiency and low-energy cost. The widely used energy management strategies are established based on the fixed models of power sources energy consumption and efficiency. However, due to the gradual performance degradation of the fuel cell during the service period, some model parameters will change significantly and the fixed models will become increasingly inaccurate over time. Therefore, this paper established time-varying models of power sources energy consumption and efficiency by introducing the fuel cell degradation rate. On this basis, in order to reduce the energy consumption of the system, improve the fuel cell efficiency and relatively maintain the SOC level, a novel dual-mode energy management strategy, DMDEE, for hybrid vehicles was proposed. In order to improve the online operation speed of proposed energy management strategy, the optimal control rules were obtained by offline calculation first. Then through comparison experiments with other two energy management strategies, PMP and PF, it was verified that the proposed strategy can effectively reduce the system energy consumption and improve the efficiency of the fuel cell system, meanwhile could make the SOC regress after its deviating from ideal working area. In addition, the mode switching hysteresis control was also validated. Therefore, the effectiveness and superiority of the proposed energy management strategy in this paper has been verified.

Multi-Objective Optimization of Molten Carbonate Fuel Cell and Absorption Refrigerator Hybrid System

The multi-objective optimization of the hybrid system consisting of molten carbonate fuel cell and absorption refrigerator is carried out based on the nondominated sorting genetic algorithm II (NSGA-II). The operating current density, temperature, pressure of the molten carbonate fuel cell and the irreversibility parameter of the absorption refrigerator are selected as the decision variables, and the equivalent power, efficiency and ecological performance of the hybrid system are treated as the comprehensive optimization objective functions. The Pareto optimal solution set under the constraint conditions of decision variables is get. Two kinds of effective decision-making tools are used: TOPSIS and LINMAP. They are used to obtain relative optimum solution as well as the optimized operation condition. At last, the results of the multi-objective optimization are compared with those of the single objective optimization.

Compressor Instability Analysis Within a Hybrid System Subject to Cycle Uncertainties

The dynamic modeling of energy systems can be used for different purposes, obtaining important information both for the design phase and control system strategies, increasing the confidence during experimental phase. Such analysis in dynamic conditions is generally performed considering fixed values for both geometrical and operational parameters such as volumes, orifices, but also initial temperatures, pressure. However, such characteristics are often subject to uncertainty, either because they are not known accurately or because they may depend on the operating conditions at the beginning of the relevant transient. With focus on a gas turbine fuel cell hybrid system (HS), compressor surge may or may not occur during transients, depending on the aforementioned cycle characteristics; hence, compressor surge events are affected by uncertainty. In this paper, a stochastic analysis was performed taking into account an emergency shut-down (ESD) in a fuel cell gas turbine HS, modeled with TRANSEO, a deterministic tool for the dynamic simulations. The aim of the paper is to identify the main parameters that impact on compressor surge margin. The stochastic analysis was performed through the response sensitivity analysis (RSA) method, a sensitivity-based approximation approach that overcomes the computational burden of sampling methods. The results show that the minimum surge margin occurs in two different ranges of rotational speed: a high-speed range and a low-speed range. The temperature and geometrical characteristics of the pressure vessel, where the fuel cell is installed, are the two main parameters that affect the surge margin during an emergency shut down.

An Efficient Technique for Power Management in Hybrid Solar PV and Fuel Cell System

ABSTRACTIn this paper, a hybrid system with solar PV, fuel cell (FC), and battery energy storage system (BESS) for the efficient power-management scheme have been proposed. The combined system is designed for the load of 1.2 kW consist of 0.9 kW AC and 0.3 kW of DC load. A power-management scheme is implemented and the modeling of the PV array with maximum power point tracking technique is used here. This hybrid system is providing power to a mutual DC bus from where the AC and DC type of loads are taking the supply. The power-management scheme used in this paper depends on power sharing and regulation of voltage at DC bus. The hybrid system provides the advantage of the reduction in capacity of battery banks to be used as it is integrated with a fuel cell system.

Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).