Economic feasibility of advanced technology for hydrogen production from fossil fuels

Hydrogen synthesis gas, an important feedstock and energy component in the chemical and refining industries, is currently generated primarily from carbon fuels by one of the three well-known technologies: (1) steam reforming of light hydrocarbons, (2) partial oxidation of heavy hydrocarbons, (3) gasification of coal or other solid carbon compounds. Each of these three technologies has its own characteristics such as H₂:CO ratio without shifting; impurity levels of N₂, Ar, CH₄, H₂S, and COS; thermal efficiency; optimum operating pressure; and capital cost intensity. This paper compares the compositions and costs of these different hydrogen synthesis gas processes to provide a guide for the most economical utilization of carbon fuel resources. The major considerations in the economic selection are: relative feedstock cost over the life of the facility; the size of the facility; and co-production of products to achieve improved thermal efficiency and economy of scale.     

Hydrogen quality from decarbonized fossil fuels to fuel cells

Increased focus on curbing carbon dioxide (CO₂) emissions and a limited and unstable supply of fossil fuel resources make diversification of energy resources a priority. Hydrogen has emerged as a promising energy vector for solving these issues. However, there are numerous challenges related to production, distribution and end use of hydrogen. Of particular importance is the link between hydrogen purity requirements for use in fuel cells and the capabilities of production. Impurities can adversely affect fuel cell performance and durability, and the fuel composition must therefore be carefully controlled. However, impurity specifications should be balanced against production and purification costs. This paper examines the effects of impurities on fuel cell performance and assesses the capabilities of hydrogen production from decarbonized fossil fuels to meet the purity requirements dictated by use in fuel cells. While carbon monoxide, hydrogen sulfide and ammonia impurities are shown to most negatively affect fuel cell performance, these species are also the most easily removed during purification. In hydrogen production from decarbonized fossil fuels, inert gases are the most limiting species in the separation. If inert gas specifications were relaxed, then carbon monoxide would become the most limiting factor.     

Highly purified hydrogen production from ammonia for PEM fuel cell

Liquid ammonia is an attractive hydrogen carrier because of high storage capacity. According to ISO14687-2, an acceptable ammonia concentration in hydrogen for polymer electrolyte membrane (PEM) fuel cell vehicles is 0.1 ppm. When ammonia is used as the hydrogen carrier, about 1000 ppm of ammonia included in gas generated by ammonia decomposition at 773–823 K and 0.1 MPa has to be reduced to less than 0.1 ppm. Although several types of ammonia absorption materials are investigated as ammonia remover, the target value cannot be achieved by static adsorption methods. However, we have succeeded in that the ammonia concentration is reduced down to 0.01–0.02 ppm by using Li-exchange X-type zeolite (Li-X) as the absorbent and dynamic adsorption methods. Furthermore, Li-X is simply recycled by heating at 673 K. Therefore, Li-X is a durable and recyclable ammonia removal material for the highly purified hydrogen production from ammonia for PEM fuel cells.     

Extraction of hydrogen from fossil fuels with production of solid carbon materials

Fossil fuels can be considered as hydrogen ores for CO₂-free energy, and carbon ores for carbon construction materials. This paper discusses methods for extraction of hydrogen from fossil fuels without carbon oxidation, with co-production of high value solid carbon material products.     

Replacement of fossil fuels by hydrogen

Up to the end of the century, an export business for photovoltaic solar power stations with an accumulated total power of more than 300 gigawatts could be build up. The profit from the export of these solar-electrical power stations could finance the, at that time, accumulated total costs for the project of $200 billion(US). Included in this financial investment would also be the construction of so-called solar plantation families. After the year 2000, a total of 10 plantation families (each with 10 family members) situated in suitable deserted zones of the world would be capable of reproducing themselves. With this aim, each plantation would use its output of electrical energy to produce solar cells and materials for the construction of 10 new plantations within a decade. This highly technological growth process for identical solar plantation units could be completed in the fourth generation of each plantation family, i.e. about 50 years after the start of construction of the first plantation. From this time on, all 10 plantation families could together, by using their electrical energy for the electrolysis of water, generate an amount of hydrogen per year which would represent four to five times the energy of the world's present annual consumption of oil.     

Thermodynamic analysis of fossil fuels reforming for fuel cell application

At present, the infrastructure of hydrogen production, storage and transportation is poor. Fuel reforming for hydrogen production from liquid fossil fuels such as kerosene, petrol and diesel is of great significance for wide application of on-board fuel cell and distributed energy resources. In this work, the produced and heat released of kerosene, petrol and diesel reformed by different reforming methods (autothermal reforming, partial oxidation, steam reforming) were studied by means of thermodynamic analysis. Based on the thermodynamic analysis, the effect of reforming methods on the system's ideal thermal efficiency are analysed. The results show that the hydrogen concentration of syngas obtained from steam reforming is highest regardless of the fuel types. The hydrogen yielded by per unit volume of diesel is largest under same reforming method. Autothermal reforming has the largest ideal thermal efficiency among three reforming methods.     

Investigation of hydrogen production from boron compounds for pem fuel cells

This paper presents a comprehensive study of hydrogen production from sodium borohydride (NaBH₄), which is synthesized from sodium tetraborate (Na₂B₄O₇) decomposition, for proton exchange membrane (PEM) fuel cells. For this purpose, Na₂B₄O₇ decomposition reaction at 450–500 °C under hydrogen atmosphere and NaBH₄ decomposition reaction at 25–40 °C under atmospheric pressure are selected as a common temperature range in practice, and the inlet molar quantities of Na₂B₄O₇ are chosen from 1 to 6 mol with 0.5 mol interval as well. In order to form NaBH₄ solution with 7.5 wt.% NaBH₄, 1 wt.% NaOH, 91.5 wt.% H₂O, the molar quantities of NaBH₄ are determined. For a PEM fuel cell operation, the required hydrogen production rates are estimated depending on 60, 65, 70 and 75 g of catalyst used in the NaBH₄ solution at 25, 32.5 and 40 °C, respectively. It is concluded that the highest rate of hydrogen production per unit area from NaBH₄ solution at 40 °C is found to be 3.834 × 10⁻⁵ g H₂ s⁻¹ cm⁻² for 75 g catalyst. Utilizing 80% of this hydrogen production, the maximum amounts of power generation from a PEM fuel cell per unit area at 80 °C under 5 atm are estimated as 1.121 W cm⁻² for 0.016 cm by utilizing hydrogen from 75 g catalyst assisted NaBH₄ solution at 40 °C.     

PEM electrolysis for production of hydrogen from renewable energy sources

PEM electrolysis is a viable alternative for generation of hydrogen from renewable energy sources. Several possible applications are discussed, including grid independent and grid assisted hydrogen generation, use of an electrolyzer for peak shaving, and integrated systems both grid connected and grid independent where electrolytically generated hydrogen is stored and then via fuel cell converted back to electricity when needed. Specific issues regarding the use of PEM electrolyzer in the renewable energy systems are addressed, such as sizing of electrolyzer, intermittent operation, output pressure, oxygen generation, water consumption and efficiency.     

Pure hydrogen production by PEM electrolysis for hydrogen energy

Last years hydrogen as energy carrier becomes one of the best solutions of energy and ecological problems. Intensive development of fuel cells, especially based on proton exchange membrane (PEM), where pure hydrogen is needed, stimulates electrolyzers development for the future application in hydrogen energy and technology. From point of view of the authors PEM electrolysis is very perspective for this goal. Advantages and possible fields of applications of this type of electrolyzers in comparison with another one are reviewed. Some results achieved up to now in PEM electrolysis, including last achievement of the authors, are summarized.     

Integration of direct carbon and hydrogen fuel cells for highly efficient power generation from hydrocarbon fuels

In view of impending depletion of hydrocarbon fuel resources and their negative environmental impact, it is imperative to significantly increase the energy conversion efficiency of hydrocarbon-based power generation systems. The combination of a hydrocarbon decomposition reactor with a direct carbon and hydrogen fuel cells (FC) as a means for a significant increase in chemical-to-electrical energy conversion efficiency is discussed in this paper. The data on development and operation of a thermocatalytic hydrocarbon decomposition reactor and its coupling with a proton exchange membrane FC are presented. The analysis of the integrated power generating system including a hydrocarbon decomposition reactor, direct carbon and hydrogen FC using natural gas and propane as fuels is conducted. It was estimated that overall chemical-to-electrical energy conversion efficiency of the integrated system varied in the range of 49.4–82.5%, depending on the type of fuel and FC used, and CO₂ emission per kW_elh produced is less than half of that from conventional power generation sources.     

Separation of hydrogen from hydrogen/ethylene mixtures using PEM fuel cell technology

This article is a study of the feasibility of electrochemically separating hydrogen from hydrogen/ethylene mixtures. Experimental results are presented for the performance of the anode of a proton exchange membrane (PEM) fuel cell that is used to separate hydrogen/ethylene mixtures. Experiments were performed using a single cell PEM fuel cell. The experimental results show that, to a large extent, the ethylene reacts with the hydrogen in the anode chamber to form ethane. In spite of this reaction, it is still possible to separate a significant portion of the hydrogen and options for improving the separation efficiency are discussed. A zero-dimensional mathematical model of the hydrogen separation and hydrogenation process has been developed and it has been shown that this model gives generally good agreement with the experimental results.     

Sustainable hydrogen production options from food wastes

In this study, two thermochemical processes, namely steam gasification and supercritical water gasification (SCWG), were comparatively studied to produce hydrogen from food wastes containing about 90% water. The SCWG experiments were performed at 400 and 450 °C in presence of catalyst (Trona, K₂CO₃ and seaweed ash). The maximum hydrogen yield was obtained at 450 °C in presence of K₂CO₃ catalyst. In second process, hydrothermal carbonization was used to convert food wastes into a high-quality solid fuel (hydrochar) that was further gasified in a dual-bed reactor in presence of steam. The steam gasification of hydrochar was carried out with and without catalysts (iron?ceria catalyst and dolomite). The maximum hydrogen yield obtained from steam gasification process was 28.08 mmol/g dry waste, about 7.7 times of that from SCWG. This study proposed a new concept for hydrogen production from wet biomass, combination of hydrothermal carbonization following steam gasification.     

Design considerations for miniaturized PEM fuel cells

In this paper, we consider the design of a miniaturized proton-exchange membrane (PEM) fuel cell for powering 0.5–20 W portable telecommunication and computing devices. Our design is implemented on a silicon substrate to take advantage of advanced silicon processing technology in order to minimize production costs. The reduced length scales afforded by silicon processing allow us to consider designs that would be prohibited by excessive Ohmic losses in larger systems. We employ a mathematical model to quantify the effects of the secondary current distribution on two competing cell designs. In addition to the design of the cell itself, we discuss key integration issues and engineering trade-offs relevant to all miniaturized fuel cell systems: air movement, fuel delivery and water balance, thermal management and load handling.     

Technical cost analysis for PEM fuel cells

The present cost of fuel cells estimated at about $200 kW⁻¹ is a major barrier for commercialization and use in automotive applications. In the United States the target costs for fuel cell systems for the year 2004 as formulated by PNGV are $50 kW⁻¹. Lomax et al. have estimated the costs of polymer electrolyte membrane (PEM) fuel cells to be as low as $20 kW⁻¹. These estimates are based on careful consideration of high volume manufacturing processes. Recently, Arthur D. Little (ADL) has estimated the cost of a fuel cell system for transportation at $294 kW⁻¹. This estimate considers a fuel processor and directly related balance of plant components. The difference of the cost estimates results from the vastly different design assumptions. Both of these estimates are based on considering a single high volume of production, 500,000 fuel cells per year. This work builds on these earlier estimates by employing the methods of technical cost modeling and thereby including explicit consideration of design specifications, exogenous factor cost and processing and operational details. The bipolar plate is analyzed as a case study. The sensitivity of the costs to uncertainty in process conditions are explored following the ADL design. It is shown that the PNGV targets can only be achieved with design changes that reduce the quantity of material used. This might necessitate a reduction in efficiency from the assumed 80 mpg.     

Metallic bipolar plates for PEM fuel cells

Metallic bipolar plates for Polymer electrolyte membrane (PEM) fuel cells with and without coatings were tested in single cell tests. Current–voltage curves, lifetime curves and the contamination with metal ions were measured. Additionally the surface of the plates was analyzed by several methods. So far the investigations revealed that principally stainless steel covered with a thin coating is suitable as material for bipolar plates in PEM fuel cells. Cell performance is the same as in PEM fuel cells with graphite bipolar plates. Concerning the cost it has to be considered that not only the material itself but also the coating process has to be evaluated.     

High temperature PEM fuel cells

There are several compelling technological and commercial reasons for operating H₂/air PEM fuel cells at temperatures above 100 °C. Rates of electrochemical kinetics are enhanced, water management and cooling is simplified, useful waste heat can be recovered, and lower quality reformed hydrogen may be used as the fuel. This review paper provides a concise review of high temperature PEM fuel cells (HT-PEMFCs) from the perspective of HT-specific materials, designs, and testing/diagnostics. The review describes the motivation for HT-PEMFC development, the technology gaps, and recent advances.

HT-membrane development accounts for 90% of the published research in the field of HT-PEMFCs. Despite this, the status of membrane development for high temperature/low humidity operation is less than satisfactory. A weakness in the development of HT-PEMFC technology is the deficiency in HT-specific fuel cell architectures, test station designs, and testing protocols, and an understanding of the underlying fundamental principles behind these areas. The development of HT-specific PEMFC designs is of key importance that may help mitigate issues of membrane dehydration and MEA degradation.