Performance of a PEMFC system integrated with a biogas chemical looping reforming processor: A theoretical analysis and comparison with other fuel processors (steam reforming,partial oxidation and auto-thermal reforming)

In this work, the performance of a PEMFC (proton exchange membrane fuel cell) system integrated with a biogas chemical looping reforming processor is analyzed. The global efficiency is investigated by means of a thermodynamic study and the application of a generalized steady-state electrochemical model. The theoretical analysis is carried out for the commercial fuel cell BCS 500W stack. From literature, chemical looping reforming (CLR) is described as an attractive process only if the system operates at high pressure. However, the present research shows that advantages of the CLR process can be obtained at atmospheric pressure if this technology is integrated with a PEMFC system. The performance of a complete fuel cell system employing a fuel processor based on CLR technology is compared with those achieved when conventional fuel processors (steam reforming (SR), partial oxidation (PO) and auto-thermal reforming (ATR)) are used. In the first part of this paper, the Gibbs energy minimization method is applied to the unit comprising the fuel- and air-reactors in CLR or to the reformer (SR, PO, ATR). The goal is to investigate the characteristics of these different types of reforming process to generate hydrogen from clean model biogas and identify the optimized operating conditions for each process. Then, in the second part of this research, material and energy balances are solved for the complete fuel cell system processing biogas, taking into account the optimized conditions found in the first part. The overall efficiency of the PEMFC stack integrated with the fuel processor is found to be dependent on the required power demand. At low loads, efficiency is around 45%, whereas, at higher power demands, efficiencies around 25% are calculated for all the fuel processors. Simulation results show that, to generate the same molar flow-rate of H₂ to operate the PEMFC stack at a given current, the global process involving SR reactor is by far much more energy demanding than the other technologies. In this case, biogas is burnt in a catalytic combustor to supply the energy required, and there is a concern with respect to CO₂ emissions. The use of fuel processors based on CLR, PO or ATR results in an auto-thermal global process. If CLR based fuel processor is employed, CO₂ can be easily recovered, since air is not mixed with the reformate. In addition, the highest values of voltage and power are achieved when the PEMFC stack is fed on the stream coming from SR and CLR fuel processors. When a H₂ mixture is produced by reforming biogas through PO and ATR technologies, the relative anode overpotential of a single cell is about 55 mV, whereas, with the use of CLR and SR processes, this value is reduced to ∼37 and 24 mV, respectively. In this way, CLR can be seen as an advantageous reforming technology, since it allows that the global process can be operated under auto-thermal conditions and, at the same time, it allows the PEMFC stack to achieve values of voltage and power closer to those obtained when SR fuel processors are used. Thus, efforts on the development of fuel processors based on CLR technology operating at atmospheric pressure can be considered by future researchers. In the case of biogas, the CO₂ captured can produce additional economical benefits in a ‘carbon market’.     

Hydrogen production by reforming of liquid hydrocarbons in a membrane reactor for portable power generation—Experimental studies

One of the most promising technologies for lightweight, compact, portable power generation is proton exchange membrane (PEM) fuel cells. PEM fuel cells, however, require a source of pure hydrogen. Steam reforming of hydrocarbons in an integrated membrane reactor has potential to provide pure hydrogen in a compact system. Continuous separation of product hydrogen from the reforming gas mixture is expected to increase the yield of hydrogen significantly as predicted by model simulations. In the laboratory-scale experimental studies reported here steam reforming of liquid hydrocarbon fuels, butane, methanol and Clearlite^® was conducted to produce pure hydrogen in a single step membrane reformer using commercially available Pd–Ag foil membranes and reforming/WGS catalysts. All of the experimental results demonstrated increase in hydrocarbon conversion due to hydrogen separation when compared with the hydrocarbon conversion without any hydrogen separation. Increase in hydrogen recovery was also shown to result in corresponding increase in hydrocarbon conversion in these studies demonstrating the basic concept. The experiments also provided insight into the effect of individual variables such as pressure, temperature, gas space velocity, and steam to carbon ratio. Steam reforming of butane was found to be limited by reaction kinetics for the experimental conditions used: catalysts used, average gas space velocity, and the reactor characteristics of surface area to volume ratio. Steam reforming of methanol in the presence of only WGS catalyst on the other hand indicated that the membrane reactor performance was limited by membrane permeation, especially at lower temperatures and lower feed pressures due to slower reconstitution of CO and H₂ into methane thus maintaining high hydrogen partial pressures in the reacting gas mixture. The limited amount of data collected with steam reforming of Clearlite^® indicated very good match between theoretical predictions and experimental results indicating that the underlying assumption of the simple model of conversion of hydrocarbons to CO and H₂ followed by equilibrium reconstitution to methane appears to be reasonable one.     

Hydrogen production by reforming of liquid hydrocarbons in a membrane reactor for portable power generation—Model simulations

One of the most promising technologies for lightweight, compact, portable power generation is proton exchange membrane (PEM) fuel cells. PEM fuel cells, however, require a source of pure hydrogen. Steam reforming of hydrocarbons in an integrated membrane reactor has potential to provide pure hydrogen in a compact system. In a membrane reactor process, the thermal energy needed for the endothermic hydrocarbon reforming may be provided by combustion of the membrane reject gas. The energy efficiency of the overall hydrogen generation is maximized by controlling the hydrogen product yield such that the heat value of the membrane reject gas is sufficient to provide all of the heat necessary for the integrated process. Optimization of the system temperature, pressure and operating parameters such as net hydrogen recovery is necessary to realize an efficient integrated membrane reformer suitable for compact portable hydrogen generation. This paper presents results of theoretical model simulations of the integrated membrane reformer concept elucidating the effect of operating parameters on the extent of fuel conversion to hydrogen and hydrogen product yield. Model simulations indicate that the net possible hydrogen product yield is strongly influenced by the efficiency of heat recovery from the combustion of membrane reject gas and from the hot exhaust gases. When butane is used as a fuel, a net hydrogen recovery of 68% of that stoichiometrically possible may be achieved with membrane reformer operation at 600 °C (873 K) temperature and 100 psig (0.791 MPa) pressure provided 90% of available combustion and exhaust gas heat is recovered. Operation at a greater pressure or temperature provides a marginal improvement in the performance whereas operation at a significantly lower temperature or pressure will not be able to achieve the optimal hydrogen yield. Slightly higher, up to 76%, net hydrogen recovery is possible when methanol is used as a fuel due to the lower heat requirement for methanol reforming reaction, with membrane reformer operation at 600 °C (873 K) temperature and 150 psig (1.136 MPa) pressure provided 90% of available combustion and exhaust gas heat is recovered.     

Hydrogen production by methanol reforming in a non-thermal atmospheric pressure microplasma reactor

On board reforming of hydrocarbons for fuel cell feed has become an attractive research topic due to the low energy densities of batteries. The implementation of a microplasma as a means for reforming the liquid fuel methanol is explored in this work. Hydrocarbon reforming is commonly accomplished through catalysis, but catalysts have a number of limitations such as poisoning, coking, coarsening, long start-up times and excessive costs. Published studies have shown the viability of plasma reforming but none have succeeded in achieving suitable system efficiencies for portable applications. Non-thermal microplasmas are particularly attractive for reforming due to their extremely high electron and power densities and the scale of microplasma devices make them well suited for portable applications. This study describes experimental microplasma reactors reforming methanol. The reactors are based on the microhollow cathode discharge (MHCD) structure fabricated with microelectromechanical systems (MEMS) fabrication techniques. Through modeling the reaction for all five experiments, conversions within the microchannel were found to be nearly 100%. Despite the variations in the five experiments due to input electrical power, flow rate and concentration, the model was validated in each test. The experiments discussed in this work show the promise of a portable, non-thermal microplasma reformer that generates hydrogen for fuel cells for portable power.     

Hydrogen production by sorption enhanced steam reforming of oxygenated hydrocarbons (ethanol, glycerol, n-butanol and methanol): Thermodynamic modelling

Thermodynamic analysis of steam reforming of different oxygenated hydrocarbons (ethanol, glycerol, n-butanol and methanol) with and without CaO as CO₂ sorbent is carried out to determine favorable operating conditions to produce high-quality H₂ gas. The results indicate that the sorption enhanced steam reforming (SESR) is a fuel flexible and effective process to produce high-purity H₂ with low contents of CO, CO₂ and CH₄ in the temperature range of 723-873 K. In addition, the separation of CO₂ from the gas phase greatly inhibits carbon deposition at low and moderate temperatures. For all the oxygenated hydrocarbons investigated in this work, thermodynamic predictions indicate that high-purity hydrogen with CO content within 20 ppm required for proton exchange membrane fuel cell (PEMFC) applications can be directly produced by a single-step SESR process in the temperature range of 723-773 K at pressures of 3-5 atm. Thus, further processes involving water-gas shift (WGS) and preferential CO oxidation (COPROX) reactors are not necessary. In the case of ethanol and methanol, the theoretical findings of the present analysis are corroborated by experimental results from literature. In the other cases, the results could provide an indication of the starting point for experimental research. At P = 5 atm and T = 773 K, it is possible to obtain H₂ at concentrations over 97 mol% along with CO content around 10 ppm and a thermal efficiency greater than 76%. In order to achieve such a reformate composition, the optimized steam-to-fuel molar ratios are 6:1, 9:1, 12:1 and 4:1 for ethanol, glycerol, n-butanol and methanol, respectively, with CaO in the stoichiometric ratio to carbon atom.     

Experimental evaluation of methanol steam reforming reactor heated by catalyst combustion for kW-class SOFC

The distributed power generation of methanol steam reforming reactor combined with solid oxide fuel cell (SOFC) has the characteristics of outstanding economic advantages. In this paper, a methanol steam reforming reactor was designed which integrates catalyst combustion, vaporization and reforming. By catalyst combustion, it can achieve stable operation to supply fuel for kW-class SOFC in real time without additional heating equipment. The optimal operating condition of the reforming reactor is 523–553 K, and the steam to carbon ratio (S/C) is 1.2. To study the reforming performance, methanol steam reforming (MSR), methanol decomposition (MD), water-gas shift (WGS) were considered. Operating temperature is the greatest factor affecting reforming performance. The higher the reaction temperature, the lower the H₂ and CO₂, the higher the CO and the methanol conversion rate. The methanol conversion rate is up to 95.03%. The higher the liquid space velocity (LHSV), the lower the methanol conversion rate, the lowest is 90.7%. The temperature changes of the reforming reactor caused by the load change of stack takes about 30 min to reach new balance. Local hotspots within the reforming reactor lead to an excessive local temperature to test a small amount of CH₄ in the reforming gas. The methanation reaction cannot be ignored at the operating temperature. The reforming gas contains 70–75% H₂, 3–8% CO, 18–22% CO₂ and 0.0004–0.3% CH₄. Trace amounts of C₂H₆ and C₂H₄ are also found in some experiments. The reforming reactor can stably supply the fuel for up to 1125 W SOFC.     

Thermally integrated fuel processor design for fuel cell applications

Effective thermal integration could enable the use of compact fuel processors with PEM fuel cell-based power systems. These systems have potential for deployment in distributed, stationary electricity generation using natural gas. This paper describes a concept wherein the latent heat of vaporization of H₂O is used to control the axial temperature gradient of a fuel processor consisting of an autothermal reformer (ATR) with water gas shift (WGS) and preferential oxidation (PROX) reactors to manage the CO exhaust concentration. A prototype was experimentally evaluated using methane fuel over a range of external heat addition and thermal inputs. The experiments confirmed that the axial temperature profile of the fuel processor can be controlled by managing only the vapor fraction of the premixed reactant stream. The optimal temperature profile is shown to result in high thermal efficiency and a CO concentration less than 40 ppm at the exit of the PROX reactor.     

Thermodynamic analysis of solid oxide fuel cells operated with methanol and ethanol under direct utilization,steam reforming,dry reforming or partial oxidation conditions

There is increasing interest in developing solid oxide fuel cells (SOFC) for portable applications. For these devices it would be convenient to directly use a liquid fuel such as methanol and ethanol rather than hydrogen. The direct utilization of alcohol fuels in SOFC involves several processes, including the deposition of carbon, which can lead to irreversible deactivation of the fuel cell. Several publications have addressed the thermodynamic analysis of the reforming of methanol (MeOH) and ethanol (EtOH) in SOFC, but none have considered the direct utilization of these fuels. The equilibrium compositions, the carbon deposition boundaries, and the electromotive forces for the direct utilization and partial oxidation of methanol and ethanol in SOFC as a function of the fuel utilization are obtained in this study. In addition, the minimum amounts of H₂O, and CO₂ for direct and indirect reforming with MeOH and EtOH to avoid carbon formation are calculated.     

Micro methanol reformer combined with a catalytic combustor for a PEM fuel cell

This paper presents the development of a micro methanol reformer for portable fuel cell applications. The micro reformer consists of a methanol steam reforming reactor, catalytic combustor, and heat exchanger in-between. Cu/ZnO was selected as a catalyst for a methanol steam reforming and Pt for a catalytic combustion of hydrogen with air. Porous ceramic material was used as a catalyst support due to the large surface area and thermal stability. Photosensitive glass wafer was selected as a structural material because of its thermal and chemical stabilities. Performance of the reformer was measured at various test conditions and the results showed a good agreement with the three-dimensional analysis of the reacting flow. Considering the energy balance of the reformer/combustor model, the off-gas of fuel cell can be recycled as a feed of the combustor. The catalytic combustor generated the sufficient amount of heat to sustain the steam reforming of methanol. The conversion of methanol was 95.7% and the hydrogen flow of 53.7 ml/min was produced including 1.24% carbon monoxide. The generated hydrogen was the sufficient amount to operate 4.5 W polymer electrolyte membrane fuel cells.     

Combustion chemistry aspects of alternative fuels reforming for high-temperature fuel cell applications

Solid-oxide fuel cells (SOFC) constitute a particularly attractive technology for sustainable, combined heat and power generation, both at domestic and district levels. The elevated operating temperature of SOFC systems, allows the utilization of a wide spectrum of conventional and alternative fuels, through suitable reforming processes. The high temperatures and fuel rich conditions prevailing in SOFC reformers, enhance syngas yield and reforming efficiency but may give rise to unwanted effects, such as ignition, soot and coke formation and deposition. The above phenomena cannot be described via thermodynamic considerations and can only be effectively tackled through a detailed chemical kinetic approach. The present study provides a comparative assessment of SOFC reformer operation on conventional and alternative hydrocarbon fuels in terms of syngas yield, thermal efficiency and pollutants formation. In particular, the reforming of methane, a typical biogas (comprising of 60% CH₄ and 40% CO₂), methanol and ethanol is numerically assessed by utilizing a recently developed and validated comprehensive detailed kinetic mechanism for C₁–C₆ hydrocarbons, augmented with a PAH model. Chemical aspects of the fuel reforming process are investigated through rate-of-production path and sensitivity analyses. The study supports design guidelines aiming towards identification of optimum operating conditions, for specific applications and fuels. The analysis reveals that the extent of coupling between syngas formation and molecular growth processes is strongly dependent on fuel and operating conditions choice and identifies windows of efficient operation, for each case.     

Fuel processors for fuel cell APU applications

The conversion of liquid hydrocarbons to a hydrogen rich product gas is a central process step in fuel processors for auxiliary power units (APUs) for vehicles of all kinds. The selection of the reforming process depends on the fuel and the type of the fuel cell.For vehicle power trains, liquid hydrocarbons like gasoline, kerosene, and diesel are utilized and, therefore, they will also be the fuel for the respective APU systems.The fuel cells commonly envisioned for mobile APU applications are molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and proton exchange membrane fuel cells (PEMFC). Since high-temperature fuel cells, e.g. MCFCs or SOFCs, can be supplied with a feed gas that contains carbon monoxide (CO) their fuel processor does not require reactors for CO reduction and removal. For PEMFCs on the other hand, CO concentrations in the feed gas must not exceed 50 ppm, better 20 ppm, which requires additional reactors downstream of the reforming reactor.This paper gives an overview of the current state of the fuel processor development for APU applications and APU system developments. Furthermore, it will present the latest developments at Fraunhofer ISE regarding fuel processors for high-temperature fuel cell APU systems on board of ships and aircrafts.     

A 75-kW methanol reforming fuel cell system

A 75-kW methanol reforming fuel cell system, which consists of a fuel cell system and a methanol auto-thermal reforming fuel processor has been developed at Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS). The core of the fuel cell system is a group of CO tolerant PEMFC stacks with a double layer composite structured anode. The fuel cell stacks show good CO tolerance even though 140 ppm CO was present in the reformate stream during transients. The auto-thermal reforming (ATR) fuel cell processor could adiabatically produce a suitable reformate without external energy consumption. The output of hydrogen-rich reformate was approximately 120 N m³ h⁻¹ with a H₂ content near 53% and the CO concentrations generally were under 30 ppm. The fuel cell system was integrated with the methanol reforming fuel processor and the peak power output of the fuel cell system exceeded 75 kW in testing. The hydrogen utilization approached 70% in the fuel cell system.     

Performance comparison of autothermal reforming for liquid hydrocarbons,gasoline and diesel for fuel cell applications

This paper discusses the reforming of liquid hydrocarbons to produce hydrogen for fuel cell applications, focusing on gasoline and diesel due to their high hydrogen density and well-established infrastructures. Gasoline and diesel are composed of numerous hydrocarbon species including paraffins, olefins, cycloparaffins, and aromatics. We have investigated the reforming characteristics of several representative liquid hydrocarbons. In the case of paraffin reforming, H₂ yield and reforming efficiency were close to thermodynamic equilibrium status (TES), although heavier hydrocarbons required slightly higher temperatures than lighter hydrocarbons. However, the conversion efficiency was much lower for aromatics than paraffins with similar carbon number. We have also investigated the reforming performance of simulated commercial diesel and gasoline using simple synthetic diesel and gasoline compositions. Reforming performances of our formulations were in good agreement with those of commercial fuels. In addition, the reforming of gas to liquid (GTL) resulted in high H₂ yield and reforming efficiency showing promise for possible fuel cell applications.     

Selection of appropriate primary fuel for hydrogen production for different fuel cell types: Comparison between decomposition and steam reforming

In order to select a proper hydrogen production system being compatible with fuel cell, a variety of interesting primary fuels such as light hydrocarbons and alcohols were tested in the decomposition (D) and the steam reforming (SR) processes by thermodynamic approach. The reaction performances of the systems particularly under thermally self-sustained condition were focused on. To obtain self-sustained condition, two approaches, splitting feed and splitting gas product streams to the burner for heat supply to endothermic hydrogen processor, are investigated. Our results revealed that splitting gas product gave higher carbon capture than splitting feed but lower in hydrogen yield. As expected, steam reforming provides higher hydrogen production, however, lower in hydrogen purity and carbon capture comparing to decomposition process. By considering primary fuels, D-alcohols could be applied to MCFC and SOFC, among these, D-C₂H₅OH was preferable because it gives the highest ratio of H₂/CO. For D-light hydrocarbon systems, which is operated at 1100 K providing 97% hydrogen purity, is suitable to be connected to MCFC, SOFC and also PEMFC.     

Carbon monoxide clean-up of the reformate gas for PEM fuel cell applications: A conceptual review

The removal of CO from hydrocarbon- and methanol-derived hydrogen can be performed by a series of methods to achieve the 10 ppm CO limit required for proton exchange membrane fuel cell (PEMFC) applications. The fuel processing includes reforming of the feed followed by water-gas shift (WGS) and a final CO removal with the latter decreasing the CO concentration below the desirable level. Pressure swing adsorption (PSA), membrane separation, selective methanation (SMET) and preferntial oxidation (PROX) are the applicable techniques as the final clean-up step. The appropriate method depends on the scale but for small scale portable fuel processors, catalytic processes are more appropriate due to the operating conditions close to that of PEMFC. The PROX appears to be the best due to rapid reaction rate and mild operation conditions which renders intensification of the processes possible. Extensive research and development efforts are underway to increase catalyst activity and improve the temperature window of the reaction.     

Combined thermal characteristics analysis of steam reforming and combustion for 5 kW domestic PEMFC system

A natural gas-based steam reformer for a domestic polymer electrolyte membrane fuel cell (PEMFC) system is thermodynamically analyzed with a special focus on the heat supply mechanism, which is critical to the endothermic steam reforming process. The interdependence of the reforming and combustion processes is evaluated through a characteristic study of heat transfer from the heat source to the reforming zone. Premixed combustion patterns may be affected by the inclusion of controlling means such as a metal fiber screen or burner placement. In this study, we attempted to enhance reforming performances of a reformer embedded in a 5 kW in-house PEMFC through modification of the combustion pattern by varying the type and placement of the burner and other operating conditions. Reforming input conditions such as steam-carbon ratio (SCR) and fuel distribution ratio (FDR) are also analyzed to quantify the overall performance such as thermal efficiency and fuel conversion rate. In our experiments involving three types of combustors—cylindrical metal fiber burner, flat type metal fiber burner and nozzle-mixing burner—the operating conditions are set so that the SCR and FDR are in the range 3.0–4.0 and 0.4–0.7, respectively. It is found that the cylindrical metal fiber burner at an appropriate location could improve thermal efficiency up to 79% by 10%, compared to other devices. This maximum thermal efficiency output is obtained with 0.63 FDR, which eventually yields 99% hydrogen conversion rate when using a cylindrical metal fiber burner, while the other burners produce 95% conversion. These outputs substantiate that the overall efficiency is strongly affected by an appropriate control for uniform temperature distribution on the catalyst layer.     

Development of multi-layered microreactor with methanol reformer for small PEMFC

A glass multi-layered microreactor with a methanol reformer that could provide power to portable electronic devices was developed to supply hydrogen to a small proton exchange membrane fuel cell (PEMFC). The microreactor consisted of four units: a methanol reformer with a catalytic combustor, a CO remover and two vaporizers. The dimensions of the microreactor were estimated by thermal simulation in order to achieve the required reaction temperature of each unit.In this study, the glass multi-layered microreactor was produced using anodic bonding. The number of glass pieces of which the microreactor was composed was 13. The experimental temperature of each unit, as well as the heat loss, for a methanol reformer of temperatures at 280 °C was measured and compared with the results from thermal simulation.     

A numerical study on methanol steam reforming reactor utilizing engine exhaust heat for hydrogen generation

Internal combustion engines are used in most vehicles around the world to power the transport sector. Efficiency improvement, emission reduction, and utilization of alternative fuels are the main aspects of current IC engine research. Hydrogen-enhanced combustion proved to be one of the efficient ways to achieve such goals. But the problem lies in the storage of hydrogen for the transportation sector, and on-board fuel reforming is a promising option for solving this issue. It deals with transforming a suitable liquid fuel (methanol) into an H₂-rich gas using a catalytic conversion process. For sustaining the reforming reaction, the required heat energy is taken from engine exhaust waste heat, this process is known as thermochemical recuperation. Number of studies on the reformers utilized for on-board hydrogen generation using engine exhaust heat are limited in the literature. The present study investigates the performance of a reactor that uses the exhaust gas heat energy for sustaining the reforming reaction. A numerical analysis was performed over a selected reactor where exhaust gases were flowing at one side, while on the other, the reforming reaction was taking place with the help of heat provided by high-temperature exhaust gases. A packed bed-type reactor was chosen for the current study and a parametric study was conducted where the effects of various operating parameters on both reacting and heating sides on the reactor's performance were investigated. It was found that temperature was the most influential inlet parameter among others. Steam/Carbon ratio and flow configuration had a negligible effect on the hydrogen yield as well as methanol conversion. Reactant inlet velocity increment revealed a significant drop in methanol conversion as it reduces the residence time for reforming reaction in the catalyst zone.     

Integrated fossil fuel and solar thermal systems for hydrogen production and CO2 mitigation

In most current fossil-based hydrogen production methods, the thermal energy required by the endothermic processes of hydrogen production cycles is supplied by the combustion of a portion of the same fossil fuel feedstock. This increases the fossil fuel consumption and greenhouse gas emissions. This paper analyzes the thermodynamics of several typical fossil fuel-based hydrogen production methods such as steam methane reforming, coal gasification, methane dissociation, and off-gas reforming, to quantify the potential savings of fossil fuels and CO₂ emissions associated with the thermal energy requirement. Then matching the heat quality and quantity by solar thermal energy for different processes is examined. It is concluded that steam generation and superheating by solar energy for the supply of gaseous reactants to the hydrogen production cycles is particularly attractive due to the engineering maturity and simplicity. It is also concluded that steam-methane reforming may have fewer engineering challenges because of its single-phase reaction, if the endothermic reaction enthalpy of syngas production step (CO and H₂) of coal gasification and steam methane reforming is provided by solar thermal energy. Various solar thermal energy based reactors are discussed for different types of production cycles as well.     

Optimization and efficiency analysis of methanol SOFC-PEMFC hybrid system

In order to improve the power generation efficiency of fuel cell systems employing liquid fuels, a hybrid system consisting of solid oxide fuel cell (SOFC) and proton exchange membrane fuel cell (PEMFC) is proposed. Utilize the high temperature heat generated by SOFC to reform as much methanol as possible to improve the overall energy efficiency of the system. When SOFC has a stable output of 100 kW, the amount of hydrogen after reforming is changed by changing the methanol flow rate. Three hybrid systems are proposed to compare and select the best system process suitable for different situations. The results show that the combined combustion system has the highest power generation, which can reach 350 kW and the total electrical efficiency is 57%. When the power of the tail gas preheating system is 160 kW, the electrical efficiency can reach 75%. The PEM water preheating system has the most balanced performance, with the electric power of 300 kW and the efficiency of 66%.