potential for automotive fuel cells, the desire to maintain combustion stability in supersonic aircraft engines, and the possibility of enhancing lean-premixed flame stability has increased interest in reforming of hydrocarbon fuels for production of hydrogen. Fuel reforming uses a fuel rich mixture to convert a hydrocarbon (such as straight gasoline) or oxygenated fuel (such as methanol) into H2 and CO or CO2 through some combination of partial oxidation and steam reforming reactions. Although fuel-reforming technology has existed in the petrochemical industry for many years, petrochemical reformers have been designed for large steady-state systems. With the recent interest in fuel cells for hybrid electric vehicle applications and in hydrogen fuel for high-speed civil transport, the need has arisen for smaller fuel reformers to produce hydrogen both with rapid response and over wide operating windows. At the University of Maryland at College Park, we are developing a program to investigate the coupling of heterogeneous surface reactions and flow fields in H2 reactors. Our goals are to determine optimal design strategies, both in terms of catalyst structure and surface geometry, for developing fast-response and high-performance fuel reformers in transportation applications.
The demands on a fuel reformer will in part depend on the application for which H2 is being generated. For gas turbine combustion stability enhancement, the reformer will need to avoid excessive temperature rises. To this end, particular reformer designs will not need to worry about exhaust concentrations of CO and CO2. A schematic is shown here or a reformer for a gas turbine combustor
Schematic of a fuel reformer for enhancing combustor stability
On the other hand, reformers used for fuel cell applications, particularly proton-exchange membrane applications, will be highly concerned about minimizing CO in the exhaust (as CO in concentrations greater than 20 ppm is a poison for anode catalysts in PEM fuel cells). Thus, a reformer for fuel cells will incorporate a downstream water-gas shift reactors which uses additional H2O to react with CO to form more H2 and CO2. The water-gas shift reactor, which is an area of current research, will also increase the exit H2 mole fraction, which is important for maintaining high fuel cell efficiencies. A schematic of a staged fuel cell reformer is shown here.
Schematic of a fuel reformer with a water-gas shift reactor for fuel cell applications
The reactions involved in conversion of hydrocarbon fuels to H2 are three-fold: partial oxidation, steam reforming, and the water-gas shift reaction. These reactions are summarized in Appendix A for n-heptane. Designers of fuel reformers will choose some combination of partial oxidation and steam reforming depending upon the availability of steam and heat for the specific application. For applications with a substantial waste heat and the need for high H2 exit concentrations, steam reforming should be the primary reaction. However, the indirect heating of the catalyst required for steam reforming will cause the reactor to have slow response times during transient operating conditions such as start-up (unless transient manipulation of H2O/air split is used). In applications where fast response and limited reactor size is critical, the highly exothermic partial oxidation reactions are beneficial because the heat improves reactor response times and fuel conversion rates. However, some steam reforming must offset exothermic oxidation reactions to keep reactor temperatures within substrate and catalyst temperature limits. Some recent development efforts have used H2O/air splits such that the reformer will operate in a so-called autothermal mode, where the heat required and the heat generated are nearly equal. The operating temperatures in autothermal mode tend to be high enough that there is still a substantial time for heating during start-up, and thus there is a need to develop reactors which provide more rapid start-up. Our work at the University of Maryland plans to investigate these issues by investigating reforming catalyst additives and alternative surface geometries for improving reactor response and performance at low inlet temperatures.
The above plot shows the operating bounds of a fuel reformer operating on a kerosene-like fuel. Higher H2O inlet concentrations cause the reactor temperature to drop below the limit where catalysts can be expected to be active (around 600 K) and lower H2O inlet concentrations cause the reactor temperature to rise above catalyst temperature limits. For gas turbine applications where H2 production can improve combustor stability and lower emissions, exit mole fractions of H2 do not need to be high and a designer would favor a lower H2O/air split. With stoichiometries for H2 and CO production, an H2O mass < 20% of the fuel mass can provide H2 exit mole fractions as high as 33%. Such H2 exit concentrations can enhance downstream flame stability both for lean and high-speed combustor applications. For fuel cell applications, higher H2O/air-split would be desirable to produce higher H2 exit concentrations with stoichiometries for H2 and CO2, since even low CO concentrations will poison fuel cell anodes. For such operating conditions, H2 exit mole fractions above 50% can be achieved before reactor temperatures begin to drop below expected catalyst light-off temperatures.
Our research is looking at the basic performance of reforming catalysts in sub-scale reactors. The experimental observations will indicate the viability of achieving rapid start-up and minimization of reactor volume and expense. The study will not investigate some systems integration issues such as managing fuel sulfur content, but results will lay the foundation for which to address systems issues in a more comprehensive design effort. The study will look at how catalysts, such as nickel-based catalysts with additives to improve light-off and avoid surface carbon build-up, for fuel reforming perform in a simple flow configuration. A parallel flat-plate reactor will investigate the performance of selected catalysts, which have demonstrated good thermal stability in preliminary oven cycling tests, as a function of inlet temperature, velocity, and H2O/air split. The experimental results from the performance mapping tests will then be used to validate reduced chemistry models for the catalytic destruction of heavier hydrocarbons. This study will provide valuable information for actual design of integrated catalytic reforming reactors that can be developed for gas turbine and/or fuel cell applications.
The objectives of our research in fuel reforming center on developing a fundamental catalyst performance data-base for single-component alkane fuels and validating a reduced chemical mechanisms for designing actual reformers with low residence times and high fuel conversion. Experiments will be used to examine catalyst/substrate compositions and surface mass transfer enhancements for achieving the high fuel conversion and catalyst performance with actual multi-component fuels. We are seeking to map out the operating conditions of selected catalysts where reactors can achieve high conversion, negligible carbon surface deposition, and thermal stability. The experimentally determined catalyst operating will demonstrate the feasibility of fuel reforming for different applications and the conditions necessary to ensure reliable H2 production from large hydrocarbons. The study will provide information on the possibility for fuel reformers as a means for stabilizing low temperature flames, for recycling heat in ultra-low emissions power cycles, and for providing H2 for fuel cells.
For more information, send e-mail to gsjackso@eng.umd.edu
Back to Reacting Flow Laboratory's home page
--------------------------------------------------------------------------------
Appendix A: Discussion of Global Reactions in Liquid Fuel Reforming for H2 Production
This appendix reviews global reactions in fuel reformers. The reaction products are shown as a function of the H2 selectivity (i.e., hH2). Heats of reaction given below are calculated from heats of formation at 298 K (with liquid values where appropriate) and are given as a function of hH2. It should be noted that the heats of reaction and thus temperature rise across the reactor can depend strongly on hH2 when inlet stoichiometries are set for H2 and CO formation. On the other hand, when inlet stoichiometries are set for H2 and CO2 formation, reactor temperature rises are only a weak function of hH2.
As shown in the global chemical reactions below, partial oxidation reactions are exothermic and can be utilized to keep catalyst temperatures high enough to sustain reactions. When stoichiometries are set to produce H2 and CO care must be taken not to have sudden temperature increases which will favor the formation of carbon and H2O rather than H2. On the other hand, for H2 and CO2 stoichiometries, heat release rates can be quite high and temperatures are difficult to control without the addition of H2O in the inlet. With air as the oxidizer, pure partial oxidation can only produce up to 0.28 mole fraction H2 in the exit stream with C7H16 (gasoline-like) feeds and no solid carbon formation.
Steam reforming reactions are highly endothermic but H2 exit mole fractions with steam reforming are much higher, up to 0.75 for C7H16. Higher exit H2 concentrations hoowever are only achievable with large amounts of heat input per mole of reactant. Required indirect heating of the reactor implies slow response and poor start-up. This has led some fuel reformer developers to pursue compromises between steam reforming and partial oxidation for applications where response times are critical. The compromises involve running the reactor with inputs of steam and air in a mode where the net reaction is nearly “autothermal”.
Global partial oxidation reactions generate substantial heat and risk the formation of H2O and CO.
Stoichiometry for H2 and CO
C7H16 + 3.5 O2 => (7hH2)CO + (7-7hH2)C(s) + (8hH2) H2 + (8-8hH2) H2O
DHR,298K = (-2062.4+1582.4hH2)kJ/mole
Stoichiometry for H2 and CO2 (hH2 > 1/8)
C7H16 + 7.0 O2 => (8-8hH2)CO + (8hH2-1) CO2 + (8hH2) H2 + (8-8hH2) H2O
DHR,298K = (-2553.2+23.1hH2)kJ/mole
Global steam reforming reactions require substantial heat input but produces primarily CO2 and H2.
Stoichiometry for H2 and CO2
C7H16 + 7.0 H2O => (7-7hH2)CO + (22hH2-15) C(s) + (15hH2) H2 + (15-15hH2) H2O
DHR,298K = (2062.4-5061.6hH2)kJ/mole
Stoichiometry for H2 and CO2 (hH2 > 15/22)
C7H16 + 14.0 H2O => (22-22hH2)CO + (22hH2-15) CO2 + (22hH2) H2 + (22-22hH2) H2O
DHR,298K = (1408.3+63.5hH2)kJ/mole
Water-gas shift reaction converts CO and H2O to CO2 and H2 with a small amount of heat release.
CO + H2O => CO2 + H2 DHR,298K = +2.9 kJ/mole
next
Diagram of the integrated diesel fuel reforming flow
process (above), and schematic of the system
installation (below).
Air
Fuel
Water
Air
Exhaust
Autothermal
Reformer Regenerable
Desulfurizer
Guard
Desulfurizer
High
Temperature
Shift Reactor
Low
Temperature
Shift Reactor
Selective
Oxidizer
Water
Preheater
Multi Stream Steam Generator
Simulated
Fuel Cell
Spent Fuel
Burner
Air
Heater
ATR
Turbocompressor
Fuel Cell
Turbocompressor
Fuel
Vaporizer
To Regen
To Regen Burner
Burner
To Selective
Oxidizer
Fuel
Steam
Superheaters
Air and Spent Reformate
Recuperators
How the Process Works
The Integrated Fuel Processor takes in diesel
fuel, air, and water. It reacts these components
to make a gas mixture containing about 30%
hydrogen and various inert gases from the air –
like carbon dioxide, steam, and nitrogen. This
mixture is fed to a catalytic burner (similar to
flameless kerosene space heaters used in many
home garages or shops) that is used to simulate
a fuel cell. The burner reacts about 80% of the
hydrogen with added air to make heat and
water, simulating a fuel cell that has about an
80% conversion rate. A second catalytic burner
reacts the rest of the hydrogen with yet more air
to convert all the hydrogen to steam. The
system then vents an inert mixture of carbon
dioxide, steam, and nitrogen. The entire
process is show in the illustration at right.
The hydrogen that is made exists for about
15 seconds before it moves to the end of the
process where it is oxidized. There is no
intermediate storage of hydrogen or other
gases in the process. The amount of pure
hydrogen gas that exists at any instant is
about 46 cubic feet – one-fourth of the
amount in a typical laboratory gas cylinder.
The very low inventory of hydrogen does not
present an extraordinary hazard.
Safety Features
The system is designed to be inherently safe.
A Hazardous and Operability analysis was
performed to identify and resolve potential
safety concerns with the design of the process.
Because the system only uses diesel fuel, air
and water as feeds, there is no possibility that
hydrogen – or any other hazardous gas – will
leak, unless the process is running. A process
control computer dedicated to this system
Reforming Diesel Fuel to Hydrogen
The INEEL is participating with SOFCo EFS in its 500 kWe Integrated Fuel Processor Program --
part of the Ship Service Fuel Cell Program of the US Navy – to design, fabricate and test a first
generation integrated fuel processor for producing hydrogen-rich gas from NATO-76 diesel fuel,
as part of a fuel cell electric power generation system. The process utilizes technology developed
by SOFCo EFS, and when completed, the processes could provide clean electric power on Navy
ships or as a stand-alone power system in remote areas such as Yellowstone National Park.
Technical Contacts
Bob Carrington
Phone - 208-526-5041
Email - carrra@inel.gov
Ray Anderson
Phone - 208-526-1623
Email - anderp@inel.gov
Management Contact
Bruce Reynolds
Phone - 208-526-1992
E-mail - reynba@inel.gov
tracks about 150 measurements – 50 of which
can trip an automatic shutdown. Unless all
these conditions are as intended, the computer
will not allow either diesel fuel or air into the
process. The control system must verify that the
process is working properly several times per
second to allow the process to continue to
operate. Without this verification the process
will automatically shutdown to a safe condition
within two to five seconds.
Testing and Characterization Phase
The system will undergo a six-month start-up,
testing and characterization period, followed by
a series of formal tests for the Navy. In all,
about 500 hours of operation are anticipated
over the six-month period. While operating, the
system will use about 30 gallons of diesel fuel
per hour. Normal emissions from the operation
will consist of water vapor, carbon dioxide and
nitrogen. Sulfur that was introduced with the
fuel, and captured on regenerable sulfur
sorbent, will be periodically oxidized and
released to the atmosphere. While the amount
of Sulfur is small, it is equivalent to about 2.5
lbs – or less – per hour of operation, and is
below regulatory limits requiring control or
permits.
Subcontractor Atlas Mechanical is currently
installing the integrated fuel process system at
the INEEL’s Engineering Demonstration
Facility in Idaho Falls, Idaho.
The INEEL Engineering Demonstration Facility
(top photo) and the diesel reformer equipment
under construction (bottom photo).
next
Science News Share Blog Cite Print Email BookmarkCatalyst Support Structures Facilitate High-temperature Fuel Reforming
ScienceDaily (Jul. 30, 2005) — CHAMPAIGN, Ill. -- The catalytic reforming of liquid fuels offers an attractive solution to supplying hydrogen to fuel cells while avoiding the safety and storage issues related to gaseous hydrogen. Existing catalytic support structures, however, tend to break down at the high temperatures needed to prevent fouling of the catalytic surface by soot.
--------------------------------------------------------------------------------
See also:
Matter & Energy
Alternative Fuels
Fossil Fuels
Materials Science
Nature of Water
Petroleum
Civil Engineering
Reference
Catalytic converter
Catalysis
Combustion
Oil refinery
Now, researchers at the University of Illinois at Urbana-Champaign have developed porous support materials that can withstand the rigors of high-temperature reforming of hydrocarbon fuels.
"These novel materials show great promise for the on-demand reforming of hydrocarbons such as diesel fuel into hydrogen for portable power sources," said Paul Kenis, a professor of chemical and biomolecular engineering at Illinois and a corresponding author of a paper to appear in the August issue of the journal Advanced Functional Materials.
To be useful for hydrocarbon fuel reforming, a catalyst support must have a high surface area, be stable at high temperatures, and possess a low pressure drop.
"Our new materials satisfy all three key requirements," said Kenis, who also is a researcher at the Beckman Institute for Advanced Science and Technology. "They have a large surface area created by a network of interconnected pores. They can operate at temperatures above 800 degrees Celsius, which prevents the formation of soot on the catalytic surfaces. And they have a low pressure drop, which means it takes less pressure to push the fuel through the catalyst."
To fabricate the supports, the researchers begin by placing a polydimethylsiloxane (PDMS) mold onto a flat surface, forming a channel about 500 microns wide that is open at both ends. A slurry containing polystyrene spheres 50 nanometers to 10 microns in diameter is then allowed to flow into the channel from one end by capillary action.
"Once the slurry reaches the other end of the channel, the spheres begin to pack together as a result of solvent evaporation, and the packing process continues toward the inlet end," Kenis said. "After the packing process is completed, we remove any remaining solvent, which leaves a sacrificial template consisting of a bed of closely packed spheres."
Next, the researchers fill the spaces between the spheres with a low-viscosity, preceramic polymer-based liquid. After low-temperature curing, the mold is removed, leaving a stable, freestanding structure.
Lastly, the cured ceramic precursor is pyrolyzed at 1,200 degrees Celsius for two hours in an inert atmosphere. "The polystyrene spheres decompose during the pyrolysis process," Kenis said. "The end result is a silicon carbide or silicon carbonitride replica with a tailored structure of interconnected pores."
The overall size of the replica can be precisely tailored through the dimensions of the mold, Kenis said, while the pore size can be tailored independently by the size of spheres used in the sacrificial template.
To demonstrate the use of these materials as catalyst supports, the researchers coated samples of the porous structure with ruthenium. The structure was then incorporated within a stainless steel housing, where it successfully stripped hydrogen from ammonia at temperatures up to 500 degrees Celsius. In work not yet published, Kenis and his colleagues incorporated the structure in a ceramic housing, which enabled the successful decomposition of ammonia at operating temperatures up to 1,000 degrees Celsius.
The researchers also showed that the silicon carbide and silicon carbonitride structures are stable at temperatures as high as 1,200 degrees Celsius in air, thus showing their promise to perform fuel reforming at temperatures where fouling of the catalyst by soot does not occur.
While the demonstration was performed on a microscale reformer, the material could be used for large-scale reformers, Kenis said, with improvements in the fabrication processes.
###
The research team included Kenis, visiting faculty Dong-Pyo (Don) Kim, visiting graduate student In-Kyung Sung, and two Illinois graduate students Michael Mitchell and Christian. Funding was provided by the U.S. Department of Defense, Army Research Office, Korean National Research Lab, National Science Foundation and the University of Illinois.
Editor's note: To reach Paul Kenis, call 217-265-0523; e-mail: kenis@uiuc.edu.
Christian is the entire name of the graduate student named in the last paragraph.
Adapted from materials provided by University of Illinois at Urbana-Champaign.
Need to cite this story in your essay, paper, or report? Use one of the following formats:
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MLA University of Illinois at Urbana-Champaign (2005, July 30). Catalyst Support Structures Facilitate High-temperature Fuel Reforming. ScienceDaily. Retrieved October 28, 2007, from http://www.sciencedaily.com /releases/2005/07/050728062129.htm
Paul Kenis and his research team at Illinois have developed porous support materials that can withstand the rigors of high-temperature reforming of hydrocarbon fuels. (Photo by Kwame Ross)
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Rating: n/a Bookmark Save as PDF Print Email Blog It Digg It del.icio.us Slashdot It! Stumble It! - + Catalyst support structures facilitate high-temperature fuel reforming
The catalytic reforming of liquid fuels offers an attractive solution to supplying hydrogen to fuel cells while avoiding the safety and storage issues related to gaseous hydrogen. Existing catalytic support structures, however, tend to break down at the high temperatures needed to prevent fouling of the catalytic surface by soot.
Now, researchers at the University of Illinois at Urbana-Champaign have developed porous support materials that can withstand the rigors of high-temperature reforming of hydrocarbon fuels.
“These novel materials show great promise for the on-demand reforming of hydrocarbons such as diesel fuel into hydrogen for portable power sources,” said Paul Kenis, a professor of chemical and biomolecular engineering at Illinois and a corresponding author of a paper to appear in the August issue of the journal Advanced Functional Materials.
To be useful for hydrocarbon fuel reforming, a catalyst support must have a high surface area, be stable at high temperatures, and possess a low pressure drop.
“Our new materials satisfy all three key requirements,” said Kenis, who also is a researcher at the Beckman Institute for Advanced Science and Technology. “They have a large surface area created by a network of interconnected pores. They can operate at temperatures above 800 degrees Celsius, which prevents the formation of soot on the catalytic surfaces. And they have a low pressure drop, which means it takes less pressure to push the fuel through the catalyst.”
To fabricate the supports, the researchers begin by placing a polydimethylsiloxane (PDMS) mold onto a flat surface, forming a channel about 500 microns wide that is open at both ends. A slurry containing polystyrene spheres 50 nanometers to 10 microns in diameter is then allowed to flow into the channel from one end by capillary action.
“Once the slurry reaches the other end of the channel, the spheres begin to pack together as a result of solvent evaporation, and the packing process continues toward the inlet end,” Kenis said. “After the packing process is completed, we remove any remaining solvent, which leaves a sacrificial template consisting of a bed of closely packed spheres.”
Next, the researchers fill the spaces between the spheres with a low-viscosity, preceramic polymer-based liquid. After low-temperature curing, the mold is removed, leaving a stable, freestanding structure.
Lastly, the cured ceramic precursor is pyrolyzed at 1,200 degrees Celsius for two hours in an inert atmosphere. “The polystyrene spheres decompose during the pyrolysis process,” Kenis said. “The end result is a silicon carbide or silicon carbonitride replica with a tailored structure of interconnected pores.”
The overall size of the replica can be precisely tailored through the dimensions of the mold, Kenis said, while the pore size can be tailored independently by the size of spheres used in the sacrificial template.
To demonstrate the use of these materials as catalyst supports, the researchers coated samples of the porous structure with ruthenium. The structure was then incorporated within a stainless steel housing, where it successfully stripped hydrogen from ammonia at temperatures up to 500 degrees Celsius. In work not yet published, Kenis and his colleagues incorporated the structure in a ceramic housing, which enabled the successful decomposition of ammonia at operating temperatures up to 1,000 degrees Celsius.
The researchers also showed that the silicon carbide and silicon carbonitride structures are stable at temperatures as high as 1,200 degrees Celsius in air, thus showing their promise to perform fuel reforming at temperatures where fouling of the catalyst by soot does not occur.
While the demonstration was performed on a microscale reformer, the material could be used for large-scale reformers, Kenis said, with improvements in the fabrication processes.
Source: University of Illinois at Urbana-Champaign
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Fuels are produced in a number of ways. Fossil fuels, are extracted from the ground by various techniques, ranging from mining for coal, to drilling for oil. They then need to be refined to remove impurities and processed into particular grades of fuel for usage in various applications.
As the competition for fossil-based energy sources increases, in conjunction with a need to reduce carbon emissions and combat Climate Change, non-fossil and particularly renewable fuels are becoming an increasingly important part of our energy mix.
Technologies to produce low-carbon and renewable fuels include:
Process Fuels Produced Additional Information
Electrolysis Hydrogen The hydrogen is only renewable if renewable energy powers the electrolyser
Anaerobic Digestion Biogas Biogas is a renewable fuel produced by digesting organic materials
Hydrogen Biogas can be Reformed to produce hydrogen
Gasification Synthesis Gas (Syngas) Biomass (organic materials), and plastics can be gasified to produce Syngas, which is a mixture of Hydrogen and carbon monoxide. Syngas can be used directly in Solid Oxide Fuel Cells and Molten Carbonate Fuel Cells. As there are a lot of organic and plastic materials in waste, gasification enables the conversion of waste into energy.
Hydrogen Pure hydrogen can be separated from syngas by using a palladium membrane.
Synthetic Liquid Fuels (Synfuels) Syngas can be converted into ultra-clean liquid fuels, called synfuels, using the fisher-tropsch (FT) process. These fuels contain no sulphur and are suitable fuels for fuel cells. Solid Oxide Fuel Cells can use FT Fuels directly, and FT fuels can also be reformed to produce pure hydrogen for use in PEM and Alkaline Fuel Cells.
Fermentation Ethanol Ethanol is a light hydrocarbon fuel which can be used directly in combustion engines and high temperature fuel cells. It can also be reformed to produce Hydrogen for use in PEM and alkaline fuel cells. Certain companies are also developing Direct Ethanol Fuel Cells
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System Integration and Technology Sourcing for Renewable Hydrogen Projects
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Electrolyzer Basic
Compact electrolyzer for hydrogen production for FC Mini Car Junior and Fuel Cell Junior H2/Air.
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Anion exchange membrane for electrolysers
Tokuyama A006 Anion Exchange Membrane
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FC Book
Comprehensive introduction to solar hydrogen and fuel cell technology. Lab manual for student experiments on solar cells, electrolysis and fuel cells.
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FC Book
Comprehensive introduction to solar hydrogen and fuel cell technology. Lab manual for student experiments on solar cells, electrolysis and fuel cells.
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Hydrogen Fuel Cell Model Car — complete
Powered by water and sunlight, this hydrogen fuel cell model car provides a simple and effective demonstration of solar hydrogen technology. Th
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UK gets first installation of innovative fuel cell heating and power unit in a domestic property
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Hydrogen Production - Fact Sheet No. 2
Although hydrogen is the most abundant element in the universe, it is rarely found on earth in its elemental form
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Types and Applications of Fuel Cells
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Activity and Durability of Water-Gas Shift Catalysts Used for the Steam Reforming of Methanol
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The Tees Valley Renewable Revolution Celebrates a Successful First Year
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Hydrogen Production - Fact Sheet No. 2
Although hydrogen is the most abundant element in the universe, it is rarely found on earth in its elemental form
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Hydrogen Production from GENTEC venturi
To produce a constant and very cheap supply of ‘green’ hydrogen from tidal and wave energy hybrid device
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Powering with Hydrogen
Imagine a world powered almost entirely by an infinitely abundant and totally clean fuel. Hydrogen is just such a fuel: the most common element in the universe, it can be made from water and used to generate ordinary electricity for homes and cars. In such a world energy would come from an easily stored and domestically produced fuel. Electric power and transportation would be totally clean and entirely free of messy geopolitical problems. Peering into the glass, we could see people using "cHars"--run on powerful but silent fuel cells--as mobile power plants. Plugging the home into the family car in the evening would offset the peak loads created by heating, air conditioning, lighting, and recreation. At work, employees could receive a bonus check every month for contributing power to the office park "grid." Unlike fossil fuels used in today's cars and power plants, the only by-product of hydrogen power would be pure water.
With hydrogen the challenge isn't finding a supply, but extracting the hydrogen cheaply and cleanly.
The fuel cell promise
Despite nearly two decades of investment in alternative energy sources, the world remains reliant on fossil fuels. milar to today's gas stations, then stored on-board. Current methods of on-board storage pose problems, however. As a gas, hydrogen takes up too much space: 7 cubic feet for a car with a 350-mile range, according to one study. Storing hydrogen as a liquid is costly and requires energy. Finally, though hydrogen can be stored at high density in metal alloys called hydrides, those available at present would add too much to a vehicle's weight to be practical. New breakthroughs--possibly in carbon nanostructures, which could also store hydrogen--are needed before hydrogen can become the fuel of choice in transportation; in the meantime, car makers will most likely choose on-board reforming of conventional fuels.
Power to the people
received plenty of attention from carmakers, the ability to generate both electricity and heat also makes them attractive anywhere energy is used. In 2000, the market richly rewarded companies working on stationary fuel cells for businesses and homes, with several new fuel cell IPOs (initial public offerings of new company stock) riding high and more start ups in the works. Most plans call for stationary fuel cells using natural gas reforming. International Fuel Cell, a subsidiary of United Technologies, has commercialized a 200-kW natural gas fuel cell for office building use (enough energy to power 200 homes, or one large office building); these devices go for $1 million apiece, well above the cost of other generation technologies. Newer fuel-cell technologies along with competition and mass production could bring the price down to a range comparable to other power technologies (though it's important to bear in mind that the competition is also a moving target). Plug Power--a new company--and IFC are both working on small, 7-kW fuel cells for use in homes and small businesses--again relying on natural gas as the fuel. Larger fuel cells for electric power generation are also under development by such firms as Fuel Cell Energy and Siemens-Westinghouse. Because of their small size, fuel cells are also useful in places where methane, a potent greenhouse gas, would otherwise be vented into the atmosphere, such as at landfills and gas-drilling operations.
Although alternative energy research in the past has been driven by government investment, a great deal of excitement surrounding fuel cells has been generated by the electricity deregulation movement. Today, electric power is typically generated in centralized coal, nuclear and hydroelectric power plants and then sent into urban areas over costly high-voltage transmission lines. Such lines are unsightly, costly and inefficient--roughly eight percent of all US electricity is lost over the transmission and distribution system. Because fuel cells are modular, quiet and clean, they can be placed right in buildings, houses and factories, thus increasing efficiency while reducing the need for new power lines.
Furthermore, deregulation and shortfalls in power generation has meant a decline in the reliability of power and, in many areas, unheard of price spikes. Each of these factors has helped propel the movement toward distributed generation--power that is generated near or at the place where it is consumed, as could be the case with fuel cells.
Discussion
Who do you think should be responsible for finding alternative sources of energy for the transportation sector?
As with other alternative technologies, a major roadblock is costs, which generally can't come down without mass production. Advocates of fuel cells hope that the diverse array of possible fuel-cell applications will speed their adoption. One hope is that, in a deregulated energy market, more businesses and energy companies will turn to distributed generation. The first markets for fuel cells will be in isolated locations, as well as in industries that need high-quality, uninterruptible power such as hospitals, data-storage facilities and possibly e-commerce firms. Eventually, the hope is that quiet and clean fuel cells will be attractive for cogeneration, where the efficiency of combined heat and power generation could render them cost-effective even at a premium to other sources of power. So although a lot still depends on the ability to bring down costs, there is reason for optimism that a solid market for stationary fuel cells will emerge within the next few years. Moreover, the initial market doesn't need to be large to have an impact on the rate of technological change.
Once fuel cells are widely adopted, where and when does hydrogen come in? The challenge is to create an infrastructure for producing, transporting and distributing the hydrogen in a way that is itself clean. Today the US annually produces 8.5 billion kilograms of hydrogen for industry, usually through steam reforming of natural gas. After production, typically the hydrogen is transported in liquid form by chemical trucks. The high volume of hydrogen required by a hydrogen economy would require pipelines like those now used to pump natural gas around the country. Although they are expensive, two such pipelines already exist in Louisiana and Texas, supplying hydrogen for local industrial purposes.
Making, storing and moving hydrogen
Predicting the Future
"Yes, my friends," [said Cyrus Smith], "I believe that one day water will be used as a fuel--that the hydrogen and the oxygen which constitute it, separately or simultaneously, will provide an inexhaustible source of heat and light of an intensity unknown to petroleum. One day, instead of being fired with coal, steamships and locomotives will be propelled by these two compressed gases, which will burn in their engines with enormous energy. Thus there is nothing to fear. As long as the earth is inhabited it shall provide for the needs of its inhabitants, and they will never want for light or heat... Water is the coal of the future."
"That I'd like to see," said the sailor.
-- Jules Verne, The Mysterious Island, 1874
Assuming fuel cells and hydrogen work out, how long will it take? Building a hydrogen infrastructure will be an expensive proposition. The Argonne National Laboratory has estimated that the cost for building production facilities and pipelines sufficient to meet US energy needs could be as high as $300 billion, with distribution costing another $175 billion, coming to roughly $3.00 per gallon of gasoline equivalent. And that price doesn't account for operating the infrastructure, the cost of the feedstock itself (such as natural gas), or the cost of transporting and storing the hydrogen. The build-out of such a system would most likely take place very gradually, as the fuel-cell market takes shape. In California, for example, the California Fuel Cell Partnership, a public-private entity implementing the state's alternative vehicle program, has broken ground on the nation's first hydrogen fueling station, which it expects will power a dozen or more demonstration vehicles in 2001. As fuel cells go mainstream, such stations could proliferate.
Another major hurdle is finding a way to produce hydrogen that is itself clean. While hydrogen is inherently clean burning, steam reforming of natural gas releases more carbon dioxide into the atmosphere than combustion of the natural gas feedstock alone. Some analysts believe that carbon from fossil fuel sources of hydrogen could be sequestered. Since 1996 Norway's Statoil has reinjected carbon dioxide from natural gas extraction into reservoirs in rock thousands of feet beneath the ocean floor. This and other methods of carbon sequestration or storage carry substantial costs in terms of both money and energy. Other forms of sequestration, such as reinjection of carbon dioxide to aid in oil exploration, are more economical, but their environmental benefits are not yet fully understood.
Fossil fuels are not the only source of hydrogen, of course: hydrogen can be extracted from water as well. If the energy for this extraction process were itself derived from a renewable energy source, hydrogen and water would form a clean and renewable energy loop. Some possible ways of obtaining hydrogen from water are direct. For example, research is now being conducted on photobiological ways of producing hydrogen that rely on specially modified algae that can form hydrogen with very little carbon impact. It is also possible to produce hydrogen from water electrochemically using photovoltaic electrodes. Other renewable routes for producing hydrogen from water are indirect: they rely on electricity, which would be generated from wind, solar, hydro or biomass. Of course, renewable electricity sources themselves face many technological obstacles.
Whatever the route to hydrogen adoption, everything now hinges on the ability of fuel-cell researchers and manufacturers to build a product that can capture a meaningful slice of the market--the same problem alternative fuel advocates have been trying to crack since the energy crisis of the 1970s. This time around, the tea leaves appear to be pointing in the right direction, with dozens of companies pushing fuel-cell technology for a diverse portfolio of mass-produced applications. The question seems to be not whether fuel cells will become viable, but how large a market share they will command, and whether hydrogen--the ideal fuel from an environmental standpoint--will eventually come to power them.
Session 1
Session 2