Fuel Cell Basics

Fuel cells are the electrochemical devices that convert chemical energy from various fuels into electrical energy. In contrast to conventional energy converters based on combustion of fuels, the intermediate step of production of kinetic energy is excluded in fuel cells. As a result fuel cells work more efficiently. As there is no combustion involved in the process they emit less amount of pollutants. In order to obtain continuous power from the fuel cells the oxidants and reductants must be supplied continuously. Particularly of interest are those fuel cells which use common fuels and hydrogen to produce power. Fuel cell stacks are constructed using a number of fuel cells or unit cells. Each unit cell mainly consists of an anode (negative electrode), cathode (positive electrode) and electrolyte. The working principle of a fuel cell can be summarized as follows. Fuel is supplied at anode and oxidant is supplied at cathode. Electrochemical reactions take place at the electrodes. The ions of the reductant travel to cathode through the electrolyte while the electrons travel through the external circuit, delivering electrical power.
There are many different types of fuel cells. They are differentiated on the basis of the electrolyte they use. Accordingly the common types of fuel cells are:
Proton Exchange Membrane Fuel Cell (PEFC or PEMFC),
Solid Oxide Fuel Cell (SOFC), Molten Carbonate Fuel Cell (MCFC), Direct Methanol Fuel Cell (DMFC), Phosphoric Acid Fuel Cell (PAFC) and
Alkaline Fuel Cell (AFC).

A brief comparison of these types is given in the table 1 below.
Table 1: Comparison of common types of fuel cells

Criterion		PEFC	SOFC	MCFC	DMFC	PAFC	AFC
Electrolyte		Ion exchange membrane (fluorinated sulfonic acid polymer or similar)	Solid non-porous metal oxide (Perovskites-ceramics, stabilised ZrO2 )	Immobilized liquid molten carbonate in LiAlO2	Ion exchange membrane	Immobilized liquid phosphoric acid in SiC	Concentrated KOH in matrix (usually asbestos)
Electrodes		Carbon	Ni-ZrO2 cermet (anode), Sr-doped LaMnO3 (cathode)	Nickel (anode) and nickel oxide (cathode)	Carbon	Carbon	Ni, Ag, metal oxides, spinels, nobal metals
Catalyst		Platinum based	Electrode material	Electrode material	Platinum based	Platinum	Platinum
Interconnect		Carbon or metals	Nickel ceramic / steel	Stainless steel or nickel	Carbon or metals	Graphite	Metal
Operating temperature		60 – 80 °C 120 - 160 °C	600 – 1000 °C	600 – 700 °C	50 – 120 °C	150 - 220 °C	65 – 220 °C
Impact of feed gas on fuel cell components	H2	Fuel	Fuel	Fuel	Fuel (in CH3OH)	Fuel	Fuel
	CO	Poison (> 50 ppm)	Fuel	Fuel	N/A	Poison (> 0.5 %)	Poison
	CH4	Diluent	Fuel	Diluent	N/A	Diluent	Poison
	CO2 & H2O	Diluent	Diluent	Diluent	N/A	Diluent	Poison
	S (H2S & COS)	N/A	Poison (<1 ppm)	Poison (<0.5 ppm)	N/A	Poison (<50 ppm)	Poison

Types of fuel cells

Fuel cells are generally classified according to the electrolyte used. There are five primary types of fuel cells.

Phosphoric Acid Fuel Cell (PAFC)

The PAFC uses liquid phosphoric acid as the electrolyte. The phosphoric acid is contained in a Teflon bonded silicone carbide matrix. The small pore structure of this matrix preferentially keeps the acid in place through capillary action. Some acid may be entrained in the fuel or oxidant streams and addition of acid may be required after many hours of operation. Platinum catalyzed, porous carbon electrodes are used on both the fuel (anode) and oxidant (cathode) sides of the electrolyte. Fuel and oxidant gases are supplied to the backs of the porous electrodes by parallel grooves formed into carbon or carbon-composite plates. These plates are electrically conductive and conduct electrons from an anode to the cathode of the adjacent cell. The byproduct water is removed as steam on the cathode (air or oxygen) side of each cell by flowing excess oxidant past the backs of the electrodes. This water removal procedure requires that the system be operated at temperatures around 375°F (190°C). The PAFC reactions that occur are Anode: H2 → 2H+ + 2e- Cathode: 1/2 O2 + 2H+ + 2e- → H2O At the anode, hydrogen is split into two hydrogen ions (H+), which pass through the electrolyte to the cathode, and two electrons which pass through the external circuit (electric load) to the cathode. At the cathode, the hydrogen, electrons and oxygen combine to form water.

Alkaline Fuel Cell (AFC)

Molten Carbonate Fuel Cell (MCFC)

The MCFC uses a molten carbonate salt mixture as its electrolyte. The composition of the electrolyte varies, but usually consists of lithium carbonate and potassium carbonate. At the operating temperature of about 1200°F (650°C), the salt mixture is liquid and a good ionic conductor. The electrolyte is suspended in a porous, insulating and chemically inert ceramic (LiA102) matrix. The MCFC reactions that occur are Anode: H2 + CO32- → H2O + CO2 + 2e- Cathode: O2 &rarr 2CO2 + 4e- → 2CO32- The anode process involves a reaction between hydrogen and carbonate ions (CO3=) from the electrolyte which produces water and carbon dioxide (CO2) while releasing electrons to the anode. The cathode process combines oxygen and CO2 from the oxidant stream with electrons from the cathode to produce carbonate ions which enter the electrolyte. The need for CO2 in the oxidant stream requires a system for collecting CO2 from the anode exhaust and mixing it with the cathode feed stream.

Solid Oxide fuel Cell (SOFC)

The SOFC is based upon the use of a solid ceramic as the electrolyte. The preferred material, dense yttria-stabilized zirconia, is an excellent conductor of negatively charged oxygen (oxide) ions at high temperatures. The anode is a porous nickel/zirconia cermet while the cathode is magnesium-doped lanthanum manganate. The SOFC reactions that occur are Anode: H2 + O2- → H2O + 2e- CO + O2- → CO2 + 2e- CH4 + 4e- → 2H2O + CO2 + 8e- Cathode: O2 + 2e- → O2- hydrogen or carbon monoxide (CO) in the fuel stream reacts with oxide ions (O=) from the electrolyte to produce water or CO2 and to deposit electrons into the anode. The electrons pass outside the fuel cell, through the load, and back to the cathode where oxygen from air receives the electrons and is converted into oxide ions which are injected into the electrolyte. It is significant that the SOFC can use CO as well as hydrogen as its direct fuel.

Proton Exchange Membrane Fuel Cell (PEFC)

The PEFC uses as its electrolyte a polymer membrane. This membrane is an electronic insulator, but an excellent conductor of hydrogen ions. The materials used to date consist of a fluorocarbon polymer backbone, similar to Teflon, to which are attached sulfonic acid groups. The acid molecules are fixed to the polymer and cannot "leak" out, but the protons on these acid groups are free to migrate through the membrane. With the solid polymer electrolyte, electrolyte loss is not an issue with regard to stack life. The anode and cathode are contacted on the back side by flow field plates made of graphite in which channels have been formed. The ridges between the channels make electrical contact with the backs of the electrodes and conduct the current to the external circuit. The channels supply fuel to the anode and oxidant to the cathode. The electrode reactions in the PEFC are analogous to those in the PAFC. As the PEFC operates at about 175°F (80°C), the water is produced as liquid water and is carried out of the fuel cell by excess oxidant flow. Anode: H2 → 2H+ + 2e- Cathode: 1/2 O2 + 2H+ + 2e- → H2O
A comparision types of fuel cell is summerized below.

Criteria	PAFC	MCFC	SOFC	PEFC
Electrolyte	Phosphoric Acid	Molten Carbonate Salt	Ceramic	Polymer
Operating Temperature	375°F (190°C)	1200°F (650°C)	1830°F (1000°C)	175°F (80°C)
Fuels	Hydrogen(H2) Reformate	H2/CO/ Reformate	H2/CO2/CH4 Reformate	H2 Reformate
Reforming	External	External/Internal	External/Internal	External
Oxidant	O2/Air	CO2/O2/Air	O2/Air	O2/Air
Efficiency	40-50%	50-60%	45-55%	40-50%

Components of Fuel Cell

A fuel cell consists of mainly four components, anode, cathode, electrolyte and a catalyst. Anode is the negative post of the cell. It conducts the electrons that are freed from the input fuel molecules so that they can be used in an external circuit. It has channels etched into it that disperse the fuel equally over the surface of the catalyst. Cathode is the positive post of the cell. It also has channles etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit. The electrodes are made of metal, nickel or carbon nanotubes, and are coated with a catalyst for higher efficiency. The electrolyte conducts only positively charged ions and blocks electrons. Differet types of electrolytes used are given in the table above. The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum, nano iron powders or palladium. Carbon paper separates them from the electrolyte. A typical fuel cell produces only about 0.86 volts. To create enough voltage, the cells are layered and combined in series and parallel circuits to form a fuel cell stack. The number of cells used is usually greater than 45 but varies with design.

Applications of Fuel Cell

First application of a fuel cell can be traced back to early 1960´s, for Apollo space program. Following the success in space program they can now be used in two types of applications, stationary and mobile applications. Some of the applications are listed below. 1. Space applications 2. Stationary power installations for factories, hospitals, banks 3. Diverse military applications 4. Domestic power supply 5. Mobile phones, laptops and other electronic applications 6. Transportation, particularly cars and buses, but also in scooters, boats, trains, planes 7. In highway road signals Proton Exchange Membrane Fuel Cell

From Roads2HyCom Hydrogen and Fuel Cell Wiki - A Reliable Source of Information - Edited by Technology Experts Only

A proton exchange membrane fuel cell (PEMFC) is a versatile fuel cell for diverse applications. The typical components are:

• ion exchange membrane (e.g. Nafion, see materials for FCs), subject to durability issues,
• electrically conductive porous backing layer (gas diffusion layer), providing the pathway for electrons, assuring mechanical support and lead product water away from the electrodes (i.e. with Teflon-like material),
• electro-catalyst layer between membrane and backing layer (electrodes, e.g. made with platinum, see materials for FCs), with a strong impact on stack costs,
• cell connectors and flowplates delivering fuel and oxidant to anode and cathode.

Possible designs are tubular or planar, with the planar bipolar type being the most favourite design for manufacturing and packaging reasons.

Contents [hide] 1 Metrics Table 2 Summary 3 Costs 4 High Temperature PEM Fuel Cell 5 Key Issues 6 Data Lacking 7 Related Components 8 References 9 Notes

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Metrics Table

METRIC	SUB-METRIC	UNITS	RATING	DATA	SECTOR
Technology Accessibility	Compatibility with existing consumer technologies	0-4	4	-	Transport
			2	-	Stationary
			N/A	-	Portable
	Number of companies selling the technology	number	-	3+	all
	Probability of market co-existence with current (competing) technology	0-4	N/A	-	all
Global Environmental Impact	GHG- emissions at full load	0-4	4	(when setting system boundary to PEFC)	all
	GHG- emissions at part load	0-4	4	(when setting system boundary to PEFC)	all
Local Environmental Impact	Air quality impact (consider NOx, PM, CO, NMHC)	0-4	4	(<1ppm)	Stationary
	Noise or perception of noise from the technology (SPL, loudness,etc.)	dB(A), sone	-	60dB(A) @ 1m	Stationary
	Design / product appearance impact	0-4	N/A	-	all
Efficiency	Part load efficiency of technology	%	-	40-70 %	Transport
			-	N/A	Stationary
			-	60%	Portable
	Full load efficiency of technology	%	-	50%	Transport
			-	45-50 %	Stationary
				30 % (max. 34 % at 22 A)[1]
			-	55%	Portable
	Efficiency of auxiliary components	%	-	not applicable	all
Capacity & Availability	Capacity to meet user’s needs	0-4	3	(Range, Max. Power)	Transport
			N/A	-	Stationary
			N/A	-	Portable
	Number of hours per year during which technology is available	hours/year	-	90% (vehicle availability)	Transport
			-	N/A	Stationary
			-	N/A	Portable
	Durability of technology	hours	-	>2000h 6% degradation in 1000h	Transport
			-	>18000h	Stationary
			-	N/A	Portable
Cost (click here for more datails)	Capital investment for technology	€	-	15200 € (80kW)	Transport
			-	5900 € (1.2 kW) (Nexa)	Stationary
			-	N/A	Portable
			-	2575-3900 €/kW[2]	all
	Cost of ownership for consumers (e.g. Maintenance)	€ / year	-	0.019-0.027 €/kWh[3]	all
	Specific cost of technology	€ / kW	-	target 50 $/kW, today 500 $/kW	Transport
			-	4000 € / kW (NedStack), 3120-4700 $/kW [4]	Stationary
			-	3000 GBP /100W (Voller)	Portable
			-	1522 €/kW[5]	all
Safety	Technology breakdown (including misuse)	no. / year		N/A	all
	Severity of failure	0-4	N/A	-	all

Summary

A PEMFC is easy to handle and operate at low temperature. It is the most widely used fuel cell in transport applications: since 2000, more than 90% of all fuel cell vehicles on the road have been equipped with a PEMFC. The low temperature of operation and high power density, both at its operating temperature as well as during start-up, make it the most suitable fuel cell for transport applications. However, the transport applications also face problems concerning cooling systems. The large research and development efforts put into the PEMFC have made the PEMFC an attractive candidate for stationary applications as well. When setting the system boundaries to the stack itself, GHG emissions are negligible during hydrogen operation. During operation with reformate, other emissions, namely CO, CO2, NOx and SO2, are present but at a very low level. Published data regarding noise usually is difficult to assess, as only FC system noise levels are available. A published value for noise emission is 60dB @ 1m for a stationary system. Due to the absence of moving mechanical parts, noise should be well under control for most FC stack types. Efficiency data is well documented for PEMFC, indicating that it is higher than efficiency of competing technologies. The part load efficiency is 40-70% and a full load efficiency is 50-55%, although the measuring procedure for efficiency is mostly not communicated. The full load efficiency for stationary sector is 45 to 50%, 55% is a value given for portable PEMFC stacks. Concerning the stack performances, cell power densities of 0.5 W/cm2 at a cell voltage of 0.7 V can be considered as state-of-the-art for PEMFC operating at 80°C or lower and at a pressure of 1.5 bar g. The power density of stacks especially for those developed for transport applications, is typically above 1 – 1.5 kW/l with a power density of 0.88-0.94 kW/kg. In terms of performance (range, max. power), a PEMFC in the transport sector (FC vehicle) has different power development properties than ICE-powered vehicles. This is due to the electric drivetrain and the electric motor. Its strong side is low speed operation, where the electric motor can deliver high torque and thus deliver very good performance. Current hybrid vehicles use their electric converters mainly in low speed / low torque requirements. Results from demonstration projects indicate a durability of the technology for transport and stationary sectors of more than 2000 (under real drive cycle testing conditions) and more than 18000 hours respectively.
Read more: Introduction to PEFC Operation

Costs

According to available cost data, a PEMFC stack costs around 15,200EUR (for 80 kW, in 2005). A reasonable high volume manufacturing (500,000 unit per year) cost estimate has been by TIAX for Ballard: this cost, for 2005, is 73 USD/kW. Cost data for typical stationary systems with 10 kW and 200 kW respectively are shown in the following table:

	10 kW system	<200 kW system
Package costs [$/kW]	4700	3120
Total installed cost [$/kW]	5500	3800
Operating and maintenance cost [$/kWh]	0.033	0.023

A further study called "Mass Production cost of PEM fuel cell by learning curve" from the 29th International Journal of Hydrogen Energy states the cost per unit of energy to be 1522 €/kW, whereas an article about the GM HydroGen3 gives a figure of 500 $/kW for a transportation system, and a target value of 50 $/kW. Read more: Hydrogen Pathway Cost Analysis

High Temperature PEM Fuel Cell

Volkswagen is developing a high temperature PEM fuel cell. In these cells, the membrane is saturated with phosphoric acid instead of water. To prevent the phosphoric acid from being washed out by the product water, the electrodes are coated with a special paste. By using phosphoric acid instead of water, the operating temperature of the cell can be raised to 160° C because of the higher boiling point of the acid. Therefore the cooling system can be dimensioned smaller. A further advantage of this cell type is that no humidification is needed for the fuel gases. So the whole fuel cell system is smaller than previous systems. According to Volkswagen, the cell has a power of 0.9 W/cm2 , with a cell degradation of 6 % per 1000 hours of operation.

Key Issues

The key issue of PEMFC technology concerns costs, mainly due to the platinum loading, which remains at an unacceptable level for PEMFC mass market penetration despite major efforts to reduce its amount. Current manufacturing processes are far from mass production technologies and thus result in high production costs. Engineering efforts will probably lead to a solution to this problem. Durability is also a key issue, whereas it only partly depends on the stack itself. While failure because of poor isolation of MEAs or because of dehydration can be traced back to stack design, deteriorating performance following membrane poisoning is an issue of fuel conditioning (e.g. CO removal from reformate gas) and must be addressed there. PEMFC behaviour at temperatures and pressures below or above regular operating conditions (cold-start response, failure of cooling systems) also needs to be investigated in more detail as too little information is available. Other key issues, in particular related to the automotive applications, are the following:

• Tolerance of sub-zero conditions with a fast start-up from sub-zero conditions
• Reduced or even eliminated external humidification requirements
• Increased operating temperature

Data Lacking

Although much data is available about the technology for the transport sector, in the field of stationary and portable application, less data could be collected so far. Reliable data on costs - either current costs, prospects or well-founded learning curves - would also be highly desirable.

Related Components

• Water and Air Management (Thermal Management)

• Heat Exchanger (Thermal Management)

• Reformer Technology (Fuel and Oxidant Conditioning)

• Compressors (Fuel and Oxidant Conditioning)

References

• J. Haubrock , G. Heideck , Z. Styczynski
  Electrical Efficiency Losses Occurred By The Air Compressor For PEMFC
  WHEC 16, Lyon France, 13 - 16 June 2006

• Bent Sørensen
  Comparison Between Hydrogen Fuel Cell Vehicles And Bio-Diesel Vehicles
  WHEC 16, Lyon France, 13 - 16 June 2006

• Renaut Mosdale, Annette Mosdale
  High Efficiency Portable Fuel Cells
  WHEC 16, Lyon France, 13 - 16 June 2006

• Ferraro Marco, Sergi Francesco, Cretì Pasquale, Dispenza Giorgio, Matera Fabio, Sapienza Cristoforo, Andaloro Laura and Antonucci Vincenzo
  Evaluation Of An UPS System Based On Direct Hydrogen PEM Fuel Cell
  WHEC 16, Lyon France, 13 - 16 June 2006

• Keith Wipke, Cory Welch, Holly Thomas, Sam Sprik, Sigmund Gronich, John Garbak
  Controlled Hydrogen Fleet And Infrastructure Demonstration And Validation Project: Fall 2006 Progress Update
  The 22nd International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exposition (EVS-22), Yokohama, Japan, Oct. 23-28, 2006

• Wolfgang Friede, Mark Kammerer, Naoya Kodama, Kevin Harris
  Fuel Cell Hybrid Midibuses for Niche Applications
  The 22nd International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exposition (EVS-22), Yokohama, Japan, Oct. 23-28, 2006

• Mikio Kizaki, Yoshiyuki Miki, Hideaki Mizuno, Tsuyoshi Takahashi, Nobuyuki Oogami
  Development of Fuel Cell Hybrid Vehicles in TOYOTA
  The 22nd International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exposition (EVS-22), Yokohama, Japan, Oct. 23-28, 2006

• H. G. Düsterwald, J. Günnewig, R. Heuss, P. Radtke,
  DRIVE - The Future of Automotive Power
  VDI-Berichte Nr. 1972, 2006

• F. N. Büchi, A. Delfino, P. Dietrich, S. A. Freunberger, R. Kötz, Daniel Laurent, Pierre-Alain Magne, David Olsommer, Dr. Gino Paganelli, Akinori Tsukada, Pierre Varenne, Daniel Walser
  Electrical Drive-train Concept with Fuel Cell System and Supercapacitor - Results of the „Hy-LIGHT" - vehicle
  VDI-Berichte Nr. 1972, 2006

• J. Schindler
  Bewertung von alternativen Kraftstoffen und Antrieben: Ergebnisse von Well-to-Wheel Analysen
  VDI-Berichte Nr. 1975, 2006

• N.N.
  Manual: Ballard Fuel Cell Power Module: Mark 902
  Ballard Power Systems

• B. Gnörich, L. Schlecht
  Wege zur Markteinführung alternativer Fahrzeugantriebe: Eine technisch-ökonomische Analyse
  Aachen & Berlin, December 2004

• N.N.
  Brennstoffzellenantriebsentwicklung: Input aus dem Forschungsfahrzeug F600 HYGENIUS
  DaimlerChrysler, 17 July 2006

• N.N.
  Manual: HyPM Fuel Cell Power Modules 500 Series
  Hydrogenics corporation

• N.N.
  Manual: Ballard Fuel Cell Power: Mark 1030, Mark9 SSL
  Ballard Power Systems

• N.N.
  Manual: Fuel Cell Products for Uninterruptible Power
  GenCore Systems

• N.N.
  Report: GM Well To Wheel Analysis of Energy Use and Greenhouse Gas Emissions of Advanced Fuel / Vehicel Systems - A European Study
  L-B-Systemtechnik GMBH, Ottobrunn, Germany
  27 September 2002

• Jack Frost
  Hydrogen and Fuel Cells for Automotive Applications
  ImechE, London, 7 November 2006

• N.N.
  Manual: Membrane Electrode Assemblies for High Temperature PEM
  PEMEAS Fuel Cell Technologies

• N.N.
  Produktdatenblatt: CS 9782.050
  Rittal

• Jens Burfeind
  Betriebliche Aspekte von Hochtemperatur-PEM-Brennstoffzellen
  May 2006

• N.N.
  Fuel Cell Handbook, 7th Edition
  EG&G Technical Services, Inc., U.S. Department of Energy, 2004

• N.N.
  Volkswagen Forschung: Weltpremiere der VW-Hochtemperatur-Brennstoffzelle
  Volkswagen AG, Oktober 2006

• R. Friesen
  Draft Fuel Cell Economic Analysis
  UCI Advanced Power and Energy Program, 2004; [4]

• N.N.
  The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs (2004)
  National Academy of Engineering (NAE), Board on Energy and Environmental Systems (BEES), page 32, [5]

• H. Tsuchiya, O. Kobayashi
  Mass Production cost of PEM fuel cell by learning curve
  International Journal of Hydrogen Energy 29, 985 (2004)

Notes

1. ↑ Back-up power generated based on PEFC with rated power of 1 kW, System realized at University of Cassino, Italy
2. ↑ Draft Fuel Cell Economic Analysis, R. Friesen, UCI Advanced Power and Energy Program, 2004; [1]
3. ↑ The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs (2004), National Academy of Engineering (NAE), Board on Energy and Environmental Systems (BEES), page 32, [2]
4. ↑ The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs (2004), National Academy of Engineering (NAE), Board on Energy and Environmental Systems (BEES), page 32, [3]
5. ↑ H. Tsuchiya, O. Kobayashi, Mass Production cost of PEM fuel cell by learning curve, International Journal of Hydrogen Energy 29, 985 (200

2.On-site Hydrogen Generators from Hydrocarbons

From Roads2HyCom Hydrogen and Fuel Cell Wiki - A Reliable Source of Information - Edited by Technology Experts Only

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Introduction

The aim of the WP1 task 1.3 is to assess the various pathways to bring hydrogen fuel to the consumer. Among all these various pathways, the on-site hydrogen production from fossil fuels is the most attractive one (refer figure below). The objective of this report is to evaluate more precisely the various technologies and associated economics of on-site hydrogen production. This transition pathway gives rise to CO2 emissions but the advantages due to the price and commercial status of the technology are such compared with the CO2 free technologies that this pathway will play a major role in the initial development of the hydrogen filling stations. The main candidate hydrocarbons are natural gas and LPGs and possibly at a later stage, GTL diesel and biogas.

State of the Art

Technology Status of Small Scale Hydrogen Production from Hydrocarbons

Steam reforming is essentially the only technology used commercially for the small scale production of hydrogen from hydrocarbons. Custom made small scale reformers have been offered since the 1950's by a small number of dedicated vendors and by larger engineering companies on a special order basis. The number of small scale reformers in the world, between 50 and 5000 Nm3/h, can be estimated to be around 1500[2]. In the 50 to 600 Nm3/h range, they compete in the industrial gas market with hydrogen deliveries and electrolyzers. Due to their relatively high prices the small on-site generators occupy only a small fraction of that market. They usually operate on natural gas, LPGs and methanol, which are the feed-stocks for which there is a widespread distribution infrastructure. Large scale reformers also operate on naphtha in petrochemical plants. Heavier feeds are not suitable for steam reforming because of their higher sulfur content and propensity to cause carbon fouling of the catalysts. Most of the small scale reformers currently offered are derived from the well established large scale steam reforming processes. However, spurred by the perspectives generated by the development of the hydrogen economy and fuel cells, a number of new players have begun to enter the market with less expensive and innovative units developed often as scale-up versions of fuel processors for fuel cells. This trend is continuing today and new technologies have emerged and continue to develop. HyRadix, USA, is one of the newcomers that offers a product with a technology not based on steam reforming but on catalytic autothermal reforming. This report aims at presenting a snapshot of the current situation of small scale reforming in terms of technology, markets and players. Commercial Technologies for Hydrogen Production from Hydrocarbons As mentioned above, nearly all small scale reformers available today are down-scaled versions of the large scale steam reforming technology. Only Hyradix USA offers catalytic auto-thermal reforming, which is a novel technology as an alternative to steam reforming. Steam reforming is more amenable to down-scaling than the other two major large scale technologies for converting hydrocarbons into hydrogen which are partial oxidation, and autothermal reforming. Partial oxidation which is a non catalytic thermal process, leads to a syngas with a lower H/C ratio and produces some soot which would be very difficult to handle at the lower scale. Autothermal reforming combines a partial oxidation step and a steam reforming step. Excellent reviews of the established industrial processes for the production of hydrogen from hydrocarbon are regularly published[3]. We present here a very brief reminder in order to highlight better the specificities of the small scale reformers. We consider here only the industrial processes that are used to produce hydrogen specifically and do not discuss the processes that produce hydrogen as a by-product, such as some petroleum refining processes and the acetylene plasma process, e.g. These processes account for at least one third of the hydrogen produced in the world but most of that hydrogen is used "in-house" where it is produced, without entering the hydrogen market. Besides, none of these processes that yield by-product hydrogen is considered for the small scale production of hydrogen.

• Basic chemical reactions

There are three basic set of reactions/operations that permit hydrogen to be obtained from hydrocarbons.

1. Steam reforming + shift + H2/CO2 separation

CnHm + n H2O → n CO + (n + m/2) H2 + ∆H (endothermic)

CO + H2O → CO2 + H2 H2 + CO2 → H2 (separation)

2. Partial oxidation (thermal) + shift + H2/CO2 separation

CnHm + n/2 O2 → n CO + m/2 H2 - ∆H (exothermic) CO + H2O → CO2 + H2 H2 + CO2 → H2 (separation)


3. Decomposition CnHm → n C + m/2 H2 - ∆H (exothermic) n C + m/2 H2 → H2 (separation)

In the late fifties, Haldor Topsoe introduced the autothermal reforming which uses partial oxidation as a first step to provide the heat for the endothermic steam reforming.

• Large scale processes

1. Steam reforming Most of "on purpose" hydrogen (over 90%) is manufactured today via the steam reforming of natural gas[4]. Industrial experience (since 1930) shows that this technology is reliable and mature. The global conversion occurs in three steps: Steam methane reforming -SMR- is the endothermic conversion of methane and water vapour into hydrogen and carbon monoxide. The required heat for the reaction is provided by natural gas combustion eventually supplemented by combustion of the purge gas from the hydrogen purification step. The process typically is carried out at temperatures of 700 to 900°C and pressures of 10 to 40 bars in order to maximize output despite the thermodynamically adverse effect of increasing the pressure.
The reaction takes place in presence of a nickel catalyst, supported on low surface area alumina or ceramic aluminates (12-25 wt% Ni). This catalyst is very sensitive to sulphur. Sulphur is removed, usually by HDS, ahead of the reforming reactor. Excess steam is required to avoid coking of the reforming catalyst and reactor tubes, typically a steam-to-carbon mass ratio of 3. Reactor furnaces may contains several hundred tubes up to 15 m high and 10 cm ID, which makes steam reforming a very capital intensive process. Four main furnace designs exist: top, side, radiant and terrace fired (figure). In the second step, CO produced in the first step is converted to CO2 with the concomitant production of hydrogen by the mildly exothermic water gas shift reaction Two successive beds of shift catalysts are used: a high temperature shift with a HTS catalyst at 400°C, 89 wt% Fe2O3 + 9 wt% Cr2O3, unsupported,
and a LTS catalyst at 250°C, typically 35 wt% CuO + 65 wt% ZnO + promoters. This catalyst is prone to poisoning. A recent trend is to replace the HTS catalyst by a copper containing MTS catalyst. An initial prereforming step (milder conditions) is sometimes added prior reforming in order to take care of the higher hydrocarbons. The third and final step consists in the separation of H2 and CO2 by pressure swing adsorption (PSA) technology, which can produce hydrogen in concentrations up to 99.999%. The PSA processes have started replacing the methanation / decarbonatation processes at the end of the seventies.

2. Partial oxidation :For liquid feed-stocks with final boiling points higher than 240°C, the steam reforming process is not adapted because of the propensity of the nickel catalyst to coke. Partial oxidation processes, that are thermal processes which do not use catalysts in the initial syngas production step, can be used then. These processes can also handle solid hydrocarbons such as coke and coal, in which case they are called gasification processes. Partial oxidation/gasification processes are very flexible in terms of feedstocks, from natural gas to coal, but they are more capital intensive than steam reforming, especially due to the oxygen plant, and they have a lower efficiency for hydrogen production. They yield a syngas with a lower H2/CO ratio which is more adapted to chemical synthesis than the syngas produced by steam reforming (except ammonia). For these reasons, only partial oxidation processes are considered in Gas To Liquids projects, which involve a Fischer-Tropsch[6] conversion. There are about 500 gasification plants in the world today[7]. Most of them produce syngas for clean electricity production. Whenever light hydrocarbons are available, POX is less attractive than SMR for large volume hydrogen production, as confirmed by the fact that 90% of the "on purpose" hydrogen production is by SMR. However, a number of potential advantages of POX over SMR have been perceived by the suppliers of small scale hydrogen production units: lower capital cost and faster response time to hydrogen demand. The arguments will be detailed in section 3 as well as the outcome of the attempts to develop small scale hydrogen production units based on partial oxidation.

POX and ATR reactor.

Source: ConocoPhillips

3. Autothermal reforming Autothermal reforming is a combination of partial oxidation and steam reforming where the necessary reforming heat demand is supplied by the partial oxidation. Steam is added to the feed streams to prevent carbon formation, and allow safe premixing of methane. The furnace system is simple and more compact than a steam reformer and it is therefore less costly. The upper part of the reactor is similar to a partial oxidation reactor (figure). It is followed by a catalytic steam reforming section. Shift and PSA are the next step of the process.

4. Decomposition In principle, hydrogen could be obtained from methane by simple decomposition. However, the reaction is very endothermic with a high activation energy barrier to overcome. In the fifties UOP (Honeywell Company) built a natural gas pyrolysis pilot plant but the process never became commercial. Today, to our knowledge, there is only one plant in the world that practices the natural gas decomposition. It is operated by Cancarb in Alberta for carbon black production. The hydrogen co-produced is used as heating fuel for the process. Pyrolysis at very short contact times (~15 ms) kinetically yields a high fraction of acetylene in place of 100% carbon black. This is the principle of the plasma acetylene process that supplies large quantities of hydrogen in the hydrogen pipeline network in the Ruhr area. The methane decomposition pathway has been touted as a route to obtain hydrogen without the concomitant production of CO2 but the high energy requirements limit the interest of the process to situations where large quantities of clean free energy are available, namely solar energy (see the "Emerging Technologies" section). Small Scale Commercial Technologies and Vendors

• New market prospects and incentives for innovation

Custom made small scale reformers have been offered since the 1950's by a small number of dedicated vendors and by larger engineering companies on a special order basis. Between 50 to 600Nm3/h range, they compete in the industrial gas market with hydrogen deliveries and electrolyzers. Due to their relatively high prices they occupy only a very small fraction of that market. They usually operate on methanol, LPGs and natural gas, and, which are the feedstocks for which there is a widespread distribution infrastructure. Their market share situation has been stable, if not dormant, for years but the prospects introduced by the forthcoming hydrogen "economy" and fuel cell markets have motivated many newcomers involved in the design of fuel processors for fuel cells. These new players have tried to compete as well in the industrial gas market and take advantage of the innovations introduced on this occasion. The design of fuel processors introduces indeed many challenges.



Table 1 below lists a few of these challenges and corresponding solutions offered by the fuel processor nascent industry. Table 1: Specific technological challenges encountered in the design of fuel processors and a few typical solutions implemented by the fuel processor industry

Challenge	solution
Physical size	Miniature heat exchangers
Efficiency (objective > 75%)	Pinch analysis, heat exchange reactors
Emissions (NOx, …), anode gas combustion	Catalytic burners, -
Response to transient fuel cell demands	Micro-channel reactors, -
Quick start-up	Catalytic partial oxidation, -
Non pyrophoric catalysts	Precious metal catalysts, -
Feedstock sulfur removal	Improved adsorbents or HDS at mild conditions
~zero level of CO in the reformate	PROX, membranes, -
Handling «tough» feedstocks: diesel, biogas	Thermal reforming, -
Cost	Standardization and mass production

At this time, the innovations introduced by the fuel cell processor industry have yet to be fully translated into commercial products. However, a few newcomers have begun to offer commercial units that carry a price tag well below those offered by the more established vendors. The new units also offer advantages in terms of footprint, efficiency, appearance and all the other features that are mandatory for the future hydrogen filling stations. However, only time will say whether they will have the reliability that the more traditional units have demonstrated over the years. Besides, the traditional vendors have reacted to the challenge and are working on improving their product line. All these factors may improve the competitiveness of the small scale reformers. They may therefore capture a larger bite of the hydrogen industrial gas market, before expanding on the hydrogen refuelling station market when hydrogen vehicles will begin to appear, which is still undetermined.

• Vendors

1. Traditional vendors Here is a short list of traditional dedicated vendors of small scale reformers. It is understood, as explained earlier, that other companies especially petroleum engineering companies, are able to and have supplied small scale reformers. The list is therefore not exhaustive. USA: Hydro-Chem/Linde, Pan American Enterprises Germany: Mahler, Caloric. Japan: MKK (Mitsubishi Kakoki Kaisha Ltd). 2. A few new players (since 2000) CarboTech has developed a compact reformer based on WS-Reformer-GmbH reformer technology (Floxâ) and their own PSA technology. CarboTech has delivered one unit to Repsol as a part of the EU-CUTE project for the H2-filling station in Madrid. Moreover, the company has also delivered a 100 Nm3.h-1 unit to Linde AG for the Munich Airport station. H2Gen is offering a compact reformer (53 Nm3/h) using sulphur resistant catalysts. Hydrogen is produced at a pressure of 15 bar and a purity of 99.999%.The unit has a small size of 2.13 m x 2.90m x 2.16 m, and a weight of 3175 kg[8] Harvest has supplied several steam compact regenerative reformers with capacities between 35 and 70 Nm3.h-1. Hygear (previously Hexion) has developed several steam reformers with PSA purification between 5 and 50 Nm3.h-1. HyRadix uses catalytic autothermal reforming at high-pressure (7 bar). Ultimate impurities are nitrogen and argon. Osaka Gas has supplied natural gas reformers for hydrogen filling stations and industrial customers . The efficiency is 70% HHV basis. Osaka Gas uses ruthenium steam reforming catalysts. The shift reactor is integrated with a HDS unit. The product purity is reported to be 99.999. Two HYSERVE-30 units have been in operation at a metal treating plant since January 2002. A durability of 90,000 hours was demonstrated that includes 1200 shut-down/start-up cycles and 25,000 load-change operations. Plug Power offers GenSite-H2 units with a production capacity of 8 Nm3.h-1 at a pressure of 10 bar. The unit provides hydrogen with a purity of 99.95% and CO-CO2 impurities of 10 ppm. A few examples, 30-100 Nm3/h, are provided below.

Emerging technologies (non-commercial)

Large Scale The large scale reforming and partial oxidation technologies are considered as mature technologies for which only slight incremental improvement can be made. It is also recognized that these technologies remain very capital intensive technologies for which alternatives should be found, especially in the context of the transportation of stranded gas (GTL). For this application, two novel syngas production routes have attracted considerable attention for the past 10 years and have been the object of pilot plant development. They are mentioned here because it was attempted to adapt these technologies to the small scale generation of hydrogen.

• Short contact time catalytic partial oxidation reactors

The short contact time catalytic partial oxidation, discovered in academia in 1992, raised the interest of several major companies - Shell, Haldor-Topsoe, ENI, ConocoPhillips - who evaluated the reaction at the pilot plant scale. In 2005, ConocoPhillips demonstrated their COPOX™ technology for producing the synthesis gas required for a 400 BBLD Fischer-Tropsch plant. However, a few of them, such as Shell and Haldor-Topsoe, announced that they had stopped the effort. Shell and UTC Fuel Cells had created a joint venture -Hydrogen Source- to develop the technology for fuel processors and on-site hydrogen generation. Hydrogen Source was dissolved in 2004.

• Oxygen Transport Membrane reactors

OTM offer the possibility of generating syngas from natural gas in GTL plants without the requirement of an expensive oxygen plant (up to 40% of the total cost of a GTL plan). The DOE and the US industry have spent several million $ on the scale up of the membranes before redirecting the R&D on smaller systems for on-site hydrogen generation and fuel processors.

• Plate reformers

Accentus (a subsidiary of AEA technology formerly the UK Atomic Energy Agency) has demonstrated a plate reformer for offshore GTL process[9]. The GTL Microsystems process employ Steam/Methane reforming and a proprietary metal substrate catalyst within the reactor channels. The technology improvement is claim to lead to an excellent heat transfer combined with a novel catalyst configuration and allows operation at a lower steam to methane ratio improving efficiency without catalyst deactivation or coking. Small Scale The US DOE and the European Commission support industry for the development of many alternatives to steam reforming for on-site hydrogen generators. A partial list of these emerging technologies is given below with the names of the industrial players involved.

• Membrane reactors

One of the most original development over recent years is a new concept that integrates oxygen separation, steam reforming and POX into a single step. The Argonne national laboratory, in cooperation with Amoco, has pioneered in 1997 the use of membrane technology that selectively extracts pure oxygen from air. By providing oxygen at low cost, the membrane process could lower the cost of H2 production. Praxair (in collaboration with BP, Statoil, Sasol) is developing a small scale system that combines an ATR based oxygen membrane with a water-gas shift reactor incorporating a hydrogen membrane. Praxair is developing a Pd-Ag hydrogen membrane supported on a ceramic material (Figure). Control of the pore size and porosity of the ceramic substrate is critical to ensuring that the Pd-Ag coating is leak-free. To reach significant hydrogen fluxes porous ceramic substrate and thin film membranes are needed. Hydrogen flux also increases with increased partial pressure and operating temperature. Several designs were tested with substrate pore sizes between 50 and 5 mm, and membrane film thicknesses of 15-8 microns. Membrane Reactor Technology (MRT) has started the development of a fluidized-bed ATR reactor with in-situ separation of hydrogen by a planar Pd-membrane. A 50 Nm3.h-1 (2 m x 4.6 m x 2.1 m) prototype has been built that produces hydrogen at 7 bar with a purity of 99.99%. The unit converts grid NG (20 Nm3/h) with an efficiency of 82% (HHV). Mitsubishi Heavy Industries has developed a steam reformer of natural gas equipped with palladium membranes for hydrogen separation (refer Figure below). The natural gas, mixed with steam and preheated by the exhaust gas from the burner, is converted to mainly hydrogen and CO2 in the catalyst bed. The hydrogen is separated inside the membrane and withdrawn from the reformer at atmospheric pressure.

• Plate-type, microchannel and heat exchanger reformers

Plate-type reformers are smaller and lighter than steam reformers. This design of reformer uses several plates. For each plate, one side is coated with steam reforming catalysts and is supplied with methane and steam, and on the other side of the plate, the methane undergoes catalytic combustion, providing the necessary heat for the endothermic steam reforming. They have demonstrated heat transfer rates higher than 20-200 kW.m-2 in laboratory tests and up to 50 kW.cm-3 reactor volume. The residence time is in order of milliseconds compared to about 1 second for conventional reformers. Advantages of the plate design are compactness, standardized design (lower cost), better heat transfer (and therefore better conversion efficiency), fast start-up (lower thermal inertia than packed catalyst bed), and easier integration with PEM fuel cells when running at 600°C (figure a and b). The plate reformers were developed for the integration with fuel cells. The following companies are actively working in this area:
Ztek is using a special type of plate reformer where the plates are used as heat transfer medium. They have built an 18 Nm-3.h-1 prototype that produces hydrogen with a purity of 99.99%, and operated it for 8000 hrs[12] Velocys has developed a micro-channel reformer concept that has been applied for syngas production. This concept can also with small modifications be used for small-scale hydrogen production. ChevronTexaco with Modine, a heat exchanger company, has developed an ATR based hydrogen process that was put in operation in February 2005 at the Hyundai-Kia American Center, in Chino, California. The unit produces hydrogen from natural gas, using ChevronTexaco Technology Ventures proprietary autothermal reforming technology with close loop integration of steam reforming and catalytic combustion over a heat exchanger specifically designed (figure). The unit is claimed to be capable of producing hydrogen from corn-based ethanol.

• Methane decomposition

1. Catalytic decomposition of methane The catalytic decomposition of methane is an environmentally attractive approach to CO2-free hydrogen production[13]. In this process, methane is broken down to hydrogen and carbon, sometimes in the presence of a catalyst at 800-1200oC, according to the reaction: CH4 → C(s) + 2 H2 The reaction is endothermic (75,6 kJ.mol-1) and requires an energy input. Various transition metal catalysts have been used to reduce the temperature of the decomposition. Frequent regeneration of the catalyst is required to removed accumulated carbon, but relatively low capital costs are projected because of the system simplicity. 2. Plasma reformers The plasma technology is already used for wastes destruction and acetylene synthesis and can be applied for producing hydrogen from hydrocarbons fuels. Plasma processes have the advantages of rapid startup, small reactor size and short response times to demand compared with catalytic systems characterized by higher inertia. These advantages would be particularly attractive for fuel processors and have motivated a lot of R&D activities. They also well adapted to handle a large variety of feed-stocks (natural gas, gasoline, alcohols, diesel and biomass). Currently, several plasma concepts are under development for small-scale hydrogen production. MIT (worked with BP Amoco, Texaco[14]) has tested several designs including partial oxidation of diesel[15] (figure 7). A stream of 40% hydrogen can be obtained after the shift reaction. Power conversion efficiencies of 70-80% and start-up times of 90 seconds are claimed. Disadvantages of plasma reforming include the degradation of the anode that needs to be replaced every 1000 hours[16] and electrical power consumption.

• Reformers with cyclic regeneration of solid materials

Sorbent-enhanced reforming The aim of sorbent-enhanced reforming is to help the kinetics and thermodynamics and simplify the reforming process by the continuous removal of the carbon dioxide from the reaction zone[17]. In one step, it is possible to obtain a stream of 95% pure hydrogen without the recourse to a shift reaction. This can either be done by using an internal adsorbent such as calcium oxide. Because absorption is exothermic and steam reforming is endothermic, the energy requirement is significantly reduced by combining these reactions. The adsorbent has to be regenerated once fully converted into a carbonate. Potential advantages of this concept are simpler design (no shift reactor and less constraint on or no PSA), low reaction temperatures (below 500°C), reduced clean-up cost, and CO2 capture. Sorbent materials should satisfy the following conditions: high CO2 uptake, rapid kinetics, stability at high steam concentration, regenerable and low cost. ECN[18], ChevronTexaco with Cabot[19], IFE Norway and ZSW Germany are working on the development of new sorbent materials.

• Autothermal Cyclic Reformer (ACR)

General Electric Global Research is developing an Autothermal Cyclic Reformer (ACR) for hydrogen filling stations. ACR uses steam reforming operating in a 3-steps cycle: (step 1 - Reforming) steam reforming of the fuel in a Ni catalyst bed, (step 2 - Air Regeneration) heating the catalyst bed through oxidation of the Ni catalyst, and (step 3 - Fuel Regeneration) reducing the catalyst to the metallic state. The heat required for the endothermic reforming step is provided during the exothermic air regeneration step. The ACR process consists of two reactors cycling between the reforming and regeneration (air and fuel) steps (figure). The product stream is 70% hydrogen rich. CO concentrations at inlet and outlet of the shift reactor are 13-20% and 1.25% respectively. Praxair has developed a 3-bed PSA for integration with the ACR reactor. Preliminary tests show a hydrogen purity of 99.996% and 75% recovery at 120 psig[20]

Main Metrics

METRIC	SUB-METRIC	DATA / RATING	UNITS	Onsite Reformer
				Natural Gas				LPG	Bio-ethanol	Gasoline	Methanol
				SMR	POX	ATR	CPO
Technology Accessibility	Compatibility with existing technologies	Rating	0-4	4	1	3	1	3	1	1	2
	Number of producers	Data	number	15	4	4	1	5	4	4	4
	Possibility of extending existing raffineries	Rating	0-4	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Global Environmental Impact	GHG emissions associated with fuel production	Data	gCO2 eq / kg fuel	12000	12000	12000	12000	19300	N/A	21600	12200
	CO2 emissions associated with fuel production	Data	gCO2 / kg fuel	10600	10600	10600	10600	17000	N/A	19100	10800
Efficiency	Part load energy efficiency of technology	Data	%
	Full load energy efficiency of technology	Data	%	71-76	66-76	66-73	>75	80	84	80	75/80
	Energy efficiency of auxiliary facilities	Data	%	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Capacity & Availability	Measured fuel production / supply	Data	kg fuel / year	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
	Maximum fuel production / supply (capacity)	Data	kg fuel / year	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
	Number of hours per year energy is available (regular use - maintenance hours, expected repairs or failures)	Data	hours / year	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Cost (click here for more datails)	Capital investment for fuel production facilities	Data	€/capacity	905 €/kW (1502 US$/kg/d)[21]
	Operational / maintenance cost (labour, electric energy cost etc.)	Data	€/year	211904 €/yr (213871 US$/yr, 470 kg/d)[22]
	Decommisioning cost	Data	€/capacity	N/A
	Selling price of fuel produced	Data	€/kg	4.78 €/kg[23]

N/A: Not Available

Market/Diffusion

The hydrogen industrial gas market

As mentioned earlier, it is presently the main market for small-scale reformers. The figure below indicates what the potential markets are for the on-site hydrogen generators, between 30 and 800 Nm3/h, on the condition that their prices drop by a factor of about 4 compared with the prices of the traditional vendors listed in before. Today this target appears realistic in view of the latest prices offered by some by a few of the vendors of on-site fuel reformers. Now the on-site hydrogen production with reformers is on the verge to be able to compete with the hydrogen deliveries by truck.

The hydrogen filling market

There are 135,000 service stations in EU-25 in Europe. The wish of the European Commission for the market share of hydrogen in the transportation sector is 5 % by 2020 This corresponds to about 8000 filling stations with a capacity of 1000 Nm3 H2/h[24].About 200 hydrogen-filling stations have been built for demonstration purposes so far[25] more than one third of them based on reforming (figure).

Evolution of the number of refueling stations and H2 origin

Source: Gaz de France, 2005

In the medium term (2030), a significant fraction of hydrogen is expected to be produced by on-site reforming of natural gas and other hydrocarbons. The initial size of small-scale reformers for hydrogen filling stations should be between100 and 300 Nm3 H2/hr. This size is considered suitable for the early stages of the hydrogen economy (i.e. 2015), in line with the anticipated numbers of the first hydrogen vehicles. In a few areas where trucked-in hydrogen is expensive, on-site reforming is an attractive alternative right now. In the long-term it is expected that large-scale hydrogen production with CO2 capture and pipeline distribution will be the option of choice in densely populated areas.

The CHP market

The Strategic Research Agenda of the Hydrogen & Fuel Cell Platform of the European Commission foresees that by 2030, 25% of presently centralized power generation in Europe will be replaced by distributed energy systems, operating essentially on natural gas. The Deployment Strategy snapshot assumed that by 2020 the cumulated number of units, including fuel cells, sold could be between 400 000 and 800 000 representing 8 and 16 GWe of installed capacity. Although probably optimistic, these numbers are an indication that the size of the fuel processor market will be significant if stationary fuel cells develop as predicted. These units may or may not include a fuel processor depending whether they are PEMFCs or SOFCs. Fuel processors produce a reformate which is a mixture of H2, CO2 and eventually N2. They are integrated in fuel cells and cannot be considered small scale hydrogen generators. Small scale hydrogen generators for the CHP market will develop only for feeding local hydrogen grids if these grids are ever constructed.

Notes

1. ↑ D.R. Simbeck & E. Chang SFA Pacific, hydrogen supply cost estimate for H2 pathways: scoping analysis NREL report, July 2002, NREL/SR-540-32525.
2. ↑ Estimate based on the data published by Hydrochem/Linde, a vendor of small scale hydrogen plants.
3. ↑ R. J. Farrauto and C. H. Bartholomew, Fundamentals of industrial catalytic processors, 1997, Chapman and Hall.
4. ↑ G.H. Shahani et al. Hydrogen and Utility Supply Optimization. Hydrocarbon Processing, page 143, September 1998.
5. ↑ Rostrup-Nielsen: Catalytic Steam Reforming, Springer, Berlin 1984)
6. ↑ “Natural Gas To Liquids (Fischer-Tropsch)” , Pétrole et techniques n°415, July/August 1998.
7. ↑ J. Saint-Just, La production de gaz manufacturés, Gaz d’aujourd’hui, Septembre 2000, 10,50-54, 2000.
8. ↑ [1]
9. ↑ [2]
10. ↑ [3]
11. ↑ D.R. Simbeck & E. Chang SFA Pacific, hydrogen supply cost estimate for H2 pathways: scoping analysis NREL report, July 2002, NREL/SR-540-32525.
12. ↑ [4]
13. ↑ Muradov N., Catalysis today, 116, 281-288 (2006).
14. ↑ [5]
15. ↑ [6]
16. ↑ L Bromberg, DR Cohn, A Rabinovich, N Alexeev, Plasma Catalytic Reforming of Methane, IJHE, 24(1999) 1131-37
17. ↑ Hildenbrand N., Applied Catalysis A, general 303, 131-137 (2006).
18. ↑ H. T. J Reijers, D. F. Roskam-Bakker, J. W. Dijkstra, R. P. de Shmidt, A. de Groot, R. W. van den Brink, Hydrogen production, through sorption enhanced reforming,ECN, the Netherlands [7]
19. ↑ J Stevens, Development of a 50-kW Fuel Processor for Stationary Fuel Cell Applications Using Revolutionary Materials for Absorption-Enhanced Natural Gas Reforming, DOE hydrogen program, FY 2003, [8]
20. ↑ R. Kumar et al., Autothermal cyclic reforming based hydrogen generating and dispensing systems, DOE hydrogen program, FY 2004, [9]
21. ↑ D. Simbeck, E. Chang, Hydrogen Supply: Cost Estimate for Hydrogen Pathways - Scoping Analysis NREL/SR-540-32525, November 2002
22. ↑
23. ↑ Affordable hydrogen transportation system, WHEC 16, Lyon, France, June 2006
24. ↑ IEA, Hydrogen Implementing Agreement Task 16 Subtask C Final Report.
25. ↑ [10]

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