Hydrogen economy

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A hydrogen economy is a hypothetical economy in which energy is stored and transported as hydrogen (H2). Various hydrogen economy scenarios can be envisaged using hydrogen in a number of ways. A common feature of these scenarios is using hydrogen as an energy carrier for mobile applications (vehicles, aircraft).

In the context of a hydrogen economy, hydrogen is an energy storage medium, not a primary energy source (see nuclear fusion for an entirely separate discussion of using hydrogen as an atomic energy source). Nevertheless, controversy over the usefulness of a hydrogen economy have been confused by issues of energy sourcing, including fossil fuel use, greenhouse warming, and sustainable energy generation. These are all separate issues, although the hydrogen economy impacts them all (see below).

Proponents of a hydrogen economy suggest that hydrogen is an environmentally cleaner source of energy to end-users, particularly in transportation applications, without release of pollutants (such as greenhouse gasses) at the point of end use; and that these advantages may hold similarly with use of hydrogen produced with energy from fossil fuels, if carbon capture or carbon sequestration methods are utilized at the site of energy or hydrogen production.

Critics of a hydrogen economy argue that for many planned applications of hydrogen, direct use of energy in the form of electricity, chemical batteries and fuel cells, and production of liquid synthetic fuels from CO₂ (see methanol economy), might accomplish many of the same net goals of a hydrogen economy, while requiring only a small fraction of the investment in new infrastructure.

Contents 1 Rationale 2 Centralized vs. distributed generation 3 Fuel cells 4 Problems in implementation 4.1 Production 4.1.1 Electrolysis 4.1.2 High-temperature electrolysis (HTE) 4.1.3 Thermochemical production 4.1.4 "Well-to-tank" issues 4.2 Storage 4.3 Infrastructure 4.4 Cost 5 Alternatives to the hydrogen economy 6 Environmental concerns 7 Direct dangers in use 8 Examples and pilot programs 9 Conclusion 10 References 11 See also 12 Related 13 External links

[edit] Rationale

A hydrogen economy is proposed to solve the ill effects of using hydrocarbon fuels in transportation, and other end-use applications where the carbon is released to the atmosphere.

In the current economy, the transportation of people and goods (so-called mobile applications) is fuelled primarily by petroleum, refined into gasoline and diesel, and natural gas. However, the burning of these hydrocarbon fuels causes the emission of greenhouse gases and other pollutants. Furthermore, the supply of hydrocarbon resources in the world is limited, and the demand for hydrocarbon fuels is increasing, particularly in China, India and other developing countries.

In a hydrogen economy, hydrogen fuel would be manufactured from some primary energy source and used as a replacement for hydrocarbon-based fuels for transportation. The hydrogen would be utilized either by direct combustion in internal combustion engines or as fuel in proton exchange membrane fuel cells. As the primary energy source can then become a stationary plant which can use renewable, nuclear or coal-fired energy sources, this would ease the pressure on finite liquid and gas hydrocarbon resources. With suitable primary energy sources, greenhouse gas emissions can be reduced or eliminated.

Hydrogen has an excellent energy density by weight. The fuel cell is also more efficient than an internal combustion engine. The internal combustion engine is said to be 20-30% efficient, while the fuel cell is 75-80% efficient (not accounting for losses in the actual production of hydrogen, which would result in an overall efficiency of about 33%) and together with the electric motor and controller, the drive train overall efficiency approaches 40% with low idling losses.

[edit] Centralized vs. distributed generation

In a hydrogen economy, primary energy sources and feedstocks would be used to produce hydrogen gas as stored energy for use in various sectors of the economy. Producing hydrogen from primary energy sources other than coal, oil, and natural gas, would result in lower emissions of the greenhouse gases characteristic of the combustion of these fossil energy resources.

One key feature of a hydrogen economy is that in mobile applications (primarily vehicular transport) energy generation and use is decoupled. The primary energy source need no longer travel with the vehicle, as it currently does with hydrocarbon fuels. Thus the energy can be generated at large-scale, centralised facilities with improved efficiency and allowing the possibility of technologies such as carbon sequestration, which are otherwise impossible for mobile applications. Alternatively, distributed energy generation schemes (such as small scale renewables) can be used.

Aside from the energy generation, hydrogen production could be centralised, distributed or a mixture of both. While generating hydrogen at cantralised primary energy plants promises higher hydrogen production efficiency, difficulties in high-volume, long range hydrogen transportation (due to factors such as hydrogen damage and the ease of hydrogen diffusion through solid materials) makes electrical energy distribution attractive within a hydrogen economy. In such a scenario, small regional plants or even local filling stations could generate hydrogen using energy provided through the electrical distribution grid. While hydrogen generation efficiency is likely to be lower than for centralised hydrogen generation, losses in hydrogen transport can make such a scheme more efficient in terms of the primary energy used per kilogram of hydrogen delivered to the end user.

The proper balance between hydrogen distribution and long-distance electrical distribution is one of the primary questions that arises in the hydrogen economy.

[edit] Fuel cells

Main article: Fuel cell

One of the main offerings of a hydrogen economy is that fuel cells can replace internal combustion engines and turbines as the primary way to convert chemical energy into kinetic or electrical energy. The reason to expect this changeover is that fuel cells, being electrochemical, are usually (and theoretically) more efficient than heat engines. Currently, fuel cells are more expensive to produce than common internal combustion engines, but are becoming cheaper as new technologies and production systems develop.

Some types of fuel cells work with hydrocarbon fuels while all can be operated on pure hydrogen. In the event that fuel cells become price-competitive with internal combustion engines and turbines, large gas-fired power plants are expected to be first to adopt the new technology^{[citation needed]}. Such commercialisation would be an important step in driving down the cost of fuel cell technology.

Much of the interest in the hydrogen economy concept is focussed on the use of fuel cells in cars. The cells can have a superior power-to-weight ratio, are much more efficient than internal combustion engines, and produce no harmful emissions. If a practical and engineerable method to store and carry hydrogen is introduced and fuel cells become cheaper, they can be economically viable to power hybrid fuel cell/battery vehicles, or purely fuel cell-driven ones. The economic viability of fuel cell powered vehicles will improve as the hydrocarbon fuels used in internal combustion engines become more expensive, due to the depletion of easily accessible reserves or economic accounting of environmental impact through such measures as carbon taxes.

[edit] Problems in implementation

Since hydrogen is an energy transfer medium, not an energy source, it requires other fuels or energy sources to produce, and each of these has energy conversion efficiencies, which may pose limitations on their use in hydrogen manufacture, vs. more direct use. In addition, a hydrogen economy would impose high initial infrastructure costs associated with distribution and use, even if clean primary energy sources to make hydrogen were identified and utilized.

[edit] Production

Main article: Hydrogen production

Molecular hydrogen is not available in convenient natural reservoirs, though it is an atmospheric trace gas having a mixing ratio of 500 parts per billion by volume (Novelli, 1999) in addition to being produced by microbes and consumed by methanogens in a rapid biological hydrogen cycle. Most hydrogen on earth is locked in water. Hydrogen can be produced using fossil fuels via steam reforming or partial oxidation of natural gas and by coal gasification. It can also be produced via electrolysis using electricity and water, consuming approximately 50 kilowatt hours of electricity per kilogram. Nuclear power can provide the energy for hydrogen production by a variety of means [1], but has other disadvantages which may or may not be decisive. Solar power has also been considered, but is location-dependent.

The actual environmental impacts associated with hydrogen production can be compared with alternatives, taking into account not only the emissions and efficiency of the hydrogen production process but also the efficiency of the hydrogen conversion to electricity in a fuel cell.

Moreover, most 'green' sources produce rather low-intensity energy (which can be scaled up, albeit at a slight efficiency cost), not the prodigious amounts of energy required for extracting significant amounts of hydrogen, like high-temperature electrolysis.

There is concern about the energy-consuming process of manufacturing the hydrogen. Manufacturing hydrogen requires a hydrogen carrier such as a fossil fuel or water. The former consumes the fossil resource and produces carbon dioxide, while electrolyzing water requires electricity, which is mostly generated at present using conventional fuels (fossil fuel or nuclear power). While alternative energy sources like wind and solar power could also be used, they are still more expensive given current prices of fossil fuels and nuclear energy. In this regard, hydrogen fuel itself cannot be called truly independent of fossil fuels (or completely non-polluting), unless a totally nuclear or renewable energy option were considered.

[edit] Electrolysis

When the energy supply is chemical, it will always be more efficient to produce hydrogen through a direct chemical path. But when the energy supply is mechanical (hydropower or wind turbines), hydrogen can be made via electrolysis of water. In the current market the electricity consumed is more valuable than the hydrogen produced, which is why only a tiny fraction of hydrogen is currently produced this way.

[edit] High-temperature electrolysis (HTE)

When the energy supply is in the form of heat (solar thermal or nuclear), hydrogen can be generated through high-temperature electrolysis (HTE). In contrast with low-temperature electrolysis, HTE of water converts more of the initial heat energy into chemical energy (hydrogen), potentially doubling efficiency, to about 50%. Because some of the energy in HTE is supplied in the form of heat, less of the energy must be converted twice (from heat to electricity, and then to chemical form), and so less energy is lost. HTE has been demonstrated in a laboratory, but not at a commercial scale.

HTE processes are generally only considered in combination with a nuclear heat source, because the other non-chemical form of high-temperature heat (concentrating solar thermal) is not consistent enough to bring down the capital costs of the HTE equipment. Research into HTE and high-temperature nuclear reactors may eventually lead to a hydrogen supply that is cost-competitive with natural gas steam reforming.

Some prototype Generation IV reactors have coolant exit temperatures of 850 to 1000 degrees Celsius, considerably hotter than existing commercial nuclear power plants. General Atomics predicts that hydrogen produced in a High Temperature Gas Cooled Reactor (HTGR) would cost $1.53/kg. In 2003, steam reforming of natural gas yielded hydrogen at $1.40/kg. At 2005 gas prices, hydrogen cost $2.70/kg. Hence, just within the United States, a savings of tens of billions of dollars per year is possible with a nuclear-powered supply. Much of this savings would translate into reduced oil and natural gas imports.

One side benefit of a nuclear reactor that produces both electricity and hydrogen is that it can shift production between the two. For instance, the plant might produce electricity during the day and hydrogen at night, matching its electrical generation profile to the daily variation in demand. If the hydrogen can be produced economically, this scheme would compete favorably with existing grid energy storage schemes. What is more, there is sufficient hydrogen demand in the United States that all daily peak generation could be handled by such plants.

[edit] Thermochemical production

Some thermochemical processes, such as the sulfur-iodine cycle, can produce hydrogen and oxygen from water and heat without using electricity. Since all the input energy for such processes is heat, they can be more efficient than high-temperature electrolysis. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient. High temperature (950-1000°C) gas cooled nuclear reactors have the potential to split hydrogen from water by thermochemical means using nuclear heat.

None of the thermochemical hydrogen production processes have been demonstrated at production levels, although several have been demonstrated in laboratories.

[edit] "Well-to-tank" issues

An accounting of the energy utilized during a thermodynamic process, known as an energy balance, can be applied to automotive fuels. With today's technology, the manufacture of hydrogen via steam reforming can be accomplished with a thermal efficiency of 75 to 80 percent. Additional energy will be required to liquify or compress the hydrogen, and to transport it to the filling station via truck or pipeline. The energy that must be utilized per kilogram to produce, transport and deliver hydrogen (i.e., its well-to-tank energy use) is approximately 50 megajoules. Subtracting this energy from the enthalpy of one kilogram of hydrogen, which is 141 megajoules, and dividing by the enthalpy, yields a thermal energy efficiency of roughly sixty percent (Kreith, 2004). Gasoline, by comparison, requires less energy input, per gallon, at the refinery, and comparatively little energy is required to transport it and store it owing to its high energy density per gallon at ambient temperatures. Well-to-tank, the supply chain for gasoline is roughly 80 percent efficient (Wang, 2002).

Another pathway proposed for hydrogen production, that of distributed electrolysis, would take advantage of existing infrastructure to transport electricity to small, on-site electrolyzers located at filling stations. Hydrogen can be produced through electrolysis of water, which is roughly 70 percent efficient (using the lower heating value for hydrogen). However, accounting for the energy used to produce the electricity (i.e., enlarging the system boundary) and accounting as well for transmission losses will reduce this efficiency. Natural gas combined cycle power plants, which account for almost all builds of new electricity plants in the United States, generate electricity at efficiencies of 60 percent or greater. Increased demand for electricity, whether due to hydrogen cars or other demand, would have the marginal impact of adding new combined cycle power plants. On this basis, distributed production of hydrogen would be roughly 40 percent efficient. However, if the marginal impact is referred to today's power grid, with an efficiency of roughly 40 percent owing to its mix of fuels and conversion methods, the efficiency of distributed hydrogen production would be roughly 25 percent. (Note that, analogous to hydrogen production from a fossil fuel, gasoline must be refined from crude oil, the "primary energy resource" (Nakicenovic, 1998).) The distributed production of hydrogen in this fashion will generate air emissions of pollutants and carbon dioxide at various points in the supply chain, e.g., electrolysis, transportation and storage. Such externalities as pollution must be weighed against the potential advantages of a hydrogen economy. Other fuel cell technologies based on the exchange of metal ions (i.e. zinc-air fuel cells) are typically more efficient at energy conversion than hydrogen fuel cells, but the widespread use of any electrical energy->chemical energy->electrical energy systems would necessitate the production of electricity.

In summary, the so-called production problem is seen to be a combination of two different problems: one of producing hydrogen efficiently from energy sources, and the other of locating suitable (renewable or at least less polluting) energy sources to do it.

[edit] Storage

Main article: Hydrogen storage

Although molecular hydrogen has excellent energy density on a mass basis, as a gas at ambient conditions it has poor energy density per volume. As a result, if it is to be stored and used as fuel onboard the vehicle, molecular hydrogen must be pressurized or liquefied to provide sufficient driving range. Increasing gas pressure improves the energy density per volume, making for smaller, but not lighter container tanks (see pressure vessel). Achieving higher pressures necessitates greater use of external energy to power the compression. Alternatively, higher volumetric energy density liquid hydrogen may be used. However liquid hydrogen is cryogenic and boils at 20.268 K (–252.882 °C or -423.188 °F). Cryogenic storage cuts weight but requires large liquification energies. The liquefaction process, involving pressurizing and cooling steps, is energy intensive. The liquefied hydrogen has lower energy density per volume than gasoline by approximately a factor of four. Storage tanks must also be well insulated to minimize boil off. Ice may form around the tank and help corrode it further if the insulation fails. Insulation for liquid hydrogen tanks is usually expensive and delicate.

The mass of the tanks needed for compressed hydrogen reduces the fuel economy of the vehicle. Because it is a small, energetic molecule, hydrogen tends to diffuse through any liner material intended to contain it, leading to the embrittlement, or weakening, of its container.

Distinct from storing molecular hydrogen, hydrogen can be stored as a chemical hydride or in some other hydrogen-containing compound. Hydrogen gas is reacted with some other materials to produce the hydrogen storage material, which can be transported relatively easily. At the point of use the hydrogen storage material can be made to decompose, yielding hydrogen gas. As well as the mass and volume density problems associated with molecular hydrogen storage, current barriers to practical storage schemes stem from the high pressure and temperature conditions needed for hydride formation and hydrogen release. For many potential systems hydriding and dehydriding kinetics and heat management are also issues that need to be overcome.

The most common method of onboard hydrogen storage in today's demonstration vehicles is as a compressed gas at pressures of roughly 700 bar (70 MPa). Many people believe that the energy needed to compress hydrogen to these pressures presents a major barrier to a hydrogen economy. For example, if one considers the entire world using hydrogen just in their cars, then a large amount of energy would be needed simply to compress the hydrogen for storage, of the order of 30% of the total energy used for transport. If this energy was not recovered in any way, the net energy used to compress it would be wasted. Currently, vehicle fuel cells are very expensive, typically 100 times more expensive per kW output than conventional internal combustion engines. It further has been suggested that cars utilizing Li-ion or Li-polymer batteries for onboard energy storage are capable of being more efficient than hydrogen-fueled cars would ever be, and that they just need to be mass produced to become cost effective. There are also prototype designs for zinc-air fuel cells, which can function as large, rechargeable batteries, and are as efficient as any battery based system, but with ranges around 400 to 500 miles^{[citation needed]}. For long trips, the electrolyte can even be completely replaced/exchanged at filling stations, which then recharge and recycle the spent electrolyte.

[edit] Infrastructure

Since hydrogen causes hydrogen embrittlement of steel, it is not clear if hydrogen can simply be put into today's natural gas transmission systems. Proponents of the hydrogen economy envision local hydrogen sources. The challenges that large, rural high-efficiency hydrogen generators face are far more acute in an urban environment. Thus, some kind of transmission system will probably be required for cities.

Hydrogen use would require the alteration of industry and transport on a scale never seen before in history. For example, the distribution of hydrogen fuel for vehicles in the U.S. would require an entirely new infrastructure costing hundreds of billions of dollars, or more. However, it is believed that future oil costs, poor alternatives and improvements in technology may make the transition economically viable in the future.

[edit] Cost

Hydrogen seems unlikely to be the cheapest carrier of energy over long distances in the near future. Advances in electrolysis and fuel cell technology have not addressed the underlying cost problem yet.

Hydrogen pipelines are more expensive than even long-distance electric lines. Hydrogen is about three times bulkier in volume than natural gas for the same energy delivered, and hydrogen accelerates the cracking of steel (hydrogen embrittlement), which increases maintenance costs, leakage rates, and material costs. The difference in cost is likely to expand with newer technology: wires suspended in air can utilize higher voltage with only marginally increased material costs, but higher pressure pipes require proportionally more material.

Setting up a hydrogen economy would require huge investments in the infrastructure to store and distrubute hydrogen to vehicles, in addition to the cost of the new vehicles themselves. In contrast, battery electric vehicles, which are currently at a similar stage of technological maturity, don't require infrastructure investments. Since hydrogen is likely to be produced with the same sources as electricity (fossil, nuclear, solar, wind) it may be less economical than a pure electricity economy. See The Hype about Hydrogen.

How would Hydrogen be produced? Energy would/could come from a multitude of sources i.e. Natural gas, nuclear, solar, wind, biomass, coal, other fossil fuels, and geothermal.

Natural Gas

Uses steam reformation. Requires 15.9 Million cubic feet of gas - that's 777,000 facilities and would cost $1 trillion dollars to cover 150 million tons of hydrogen gas annually, the estimate for consumption in 2040. $3.00 per GGE (Gallons of Gas Equivalent)

Nuclear

Provides energy for electrolysis of water. Would require 240,000 tons of unenriched uranium - that's 2,000 600-megawatt power plants, which would cost $840 billion, or about $2.50 per GGE.

Solar

Provides energy for electrolysis of water. Would require 2,500 kWh of sun per square meter, 113 million 40-kilowatt systems, which would cost $22 trillion, or about $9.50 per GGE.

Wind

Provides energy for electrolysis of water. At 7 meters per second average wind speed, it would require 1 million 2 MW wind turbines, which would cost $3 trillion dollars, or about $3.00 per GGE.

Biomass

Gasification plants would produce gas with steam reformation. 1.5 billion tons of dry biomass, 3,300 plants which would require 113.4 million acres of farm to produce the biomass. $565 billion dollars in cast, or about $1.90 per GGE

Coal

FutureGen plants use coal gasification then steam reformation. Requires 1 billion tons of coal or about 1,000 275-megawatt plants with a cost of about $500 billion, or about $1 per GGE.

Facts and figures from Popular Science

• DOE Cost targets : [2]

[edit] Alternatives to the hydrogen economy

Hydrogen is simply a method to store and transmit energy. Various alternative energy transmission and storage scenarios may be more economic, in both near and far term. These include:

Vegetable Oil

A vegetable oil economy would use plants to make oil from sunlight and CO2. Vegetable oil is safer to use and store than gasoline or diesel as it has a higher flash point. Vegetable oil works in diesel engines if it is heated first ^[1]. Transition to vegetable oil based transportation could be gradual and relatively easy. Some diesel engines already heat their fuel, others need a small electric heater on the fuel line. Gas stations can start with one pump for vegetable oil and add more as needed. Since CO2 is first taken out of the atmosphere to make the vegetable oil and then put back when it is burned in the engine, there is no net increase in CO2. So vegetable oil does not contribute to the problem of greenhouse gas. It is a true renewable energy that is also safe and easy to make, store, and use.

Compressed air

Solving many of the generation, transportation and storage problems which plague hydrogen, compressed air suffers from a low energy density.

The electrical grid plus batteries

The electrical grid and chemical storage battery pose viable long term alternatives to hydrogen in transmission. The solar cell might also be used in some areas to make energy locally for battery powered autos which in turn could supply energy in the evening. Of these technologies, only grid power is currently in a high state of technical development. Solar power suffers from a low power density to area, making it difficult to use in transport. High capacity batteries (chemical cells) have already seen use in commercial hybrid cars, but these have yet to be used in load-balancing. It is possible that a combination of battery and hydrogen power will be used in the future, although many think that hybrid cars running on battery power and green fuels is a more viable option. Both the EV1 and the Rav4 EV proved the technology and were highly popular vehicles.

Hydrogen production of greenhouse-neutral alcohol

Hydrogen in a full "hydrogen economy" has been envisioned as a way to make renewable energy available to automobiles which are not all-electric. A final theoretical alternative to hydrogen would do this by using hydrogen locally (captive use) to make liquid fuels from a CO₂ source. To be greenhouse-neutral, this source would be from air, biomass, or from CO₂ which would otherwise be scheduled to be released into the air from non-carbon-capture fuel-burning power plants (of which there are likely to be many in the future, since economic carbon capture and storage is site-dependent and difficult to retrofit). These alcohols would then act as greenhouse-neutral additional energy stores and carriers for transportation, but without disrupting present methods of liquid fuel transport and use. Rather than be transported from its production site, hydrogen may thus instead be used centrally/locally to produce renewable liquid fuels which may be cycled into the present transportation infrastructure directly, requiring almost no infrastructure change. See methanol economy and ethanol economy

Hybrid Strategy of Electricity and Synthetic Methane

Electricity can be more efficiently used in a storage battery than electrolysing water to hydrogen. For example, a storage battery may retain about 90% of the electricity used to charge it, and be able to provide about 90% of the electricity that it can store, resulting in a "round trip" efficiency of about 80%. This is compared with a 70% efficiency of electrolysis and perhaps 60% efficiency of a fuel cell, resulting in a round trip efficiency of only about 40% for hydrogen -- only about half the efficiency of batteries.

But batteries are expensive, and they wear out over time. The cost of energy storage in batteries is driven largely by the cost of the batteries themselves, and not the cost of the energy put into them. The cost of storing energy for any extended length of time is prohibitive when using batteries, even when compared with hydrogen storage.

On the other hand, the cost of energy storage of hydrogen could be reduced further by using the hydrogen (and carbon dioxide) to synthesize methane, using a Sabatier reactor. This process is about 80% efficient, reducing the round trip efficiency to about 20 to 30%, depending on the method of fuel utilization. This is even lower than hydrogen, but the storage costs drop by at least a factor of 3. Methane is 3.2 times denser energetically than hydrogen, is easier to store -- and an infrastructure (Natural Gas pipelines) are already in place. The advantage of methane storage is that it is very inexpensive, once one has accepted the high cost of conversion.

We can start to see how a hybrid strategy could be more effective than hydrogen alone. Short term energy storage (meaning the energy is used not long after it has been captured) is best accomplished with battery or even ultracapacitor storage. Longer term energy storage (meaning the energy is used weeks or months after capture) is best done with synthetic methane, which can be stored indefinitely at relatively low cost. The strategy dovetails well with the recent interest in Plug-in Hybrid Electric Vehicles, or PHEVs, which use a hybrid strategy of electrical and fuel storage for their energy needs. See Plug-in hybrid electric vehicle

Hydrogen storage is therefore only optimal in a narrow range of energy storage time, probably somewhere between a few days and a few weeks. This range is subject to further narrowing with any improvements in battery technology. It is always possible that some kind of breakthrough in hydrogen storage or generation could occur, but this is unlikely given the physical and chemical limitations of the technical choices are fairly well understood.

Chemical fuels

See alternative fuel

[edit] Environmental concerns

Hydrogen gas can be created through the natural gas steam reforming/water gas shift reaction method, outlined above. This creates carbon dioxide (CO₂), a greenhouse gas, as a byproduct. This is usually released into the atmosphere, although there has also been some research into interring it underground or undersea. The steam reformers in methane-based fuel cells convert hydrocarbons into either carbon dioxide or carbon monoxide (CO). [3]

Recently, there have also been some concerns over possible problems related to hydrogen gas leakage, (this has been pointed out in a paper published in Science magazine by a group of Caltech scientists). Molecular hydrogen leaks slowly from most containment vessels. It has been hypothesized that if significant amounts of hydrogen gas (H₂) escape, hydrogen gas may, due to ultraviolet radiation, form free radicals (H) in the stratosphere. These free radicals would then be able to act as catalysts for ozone depletion. A large enough increase in stratospheric hydrogen from leaked H₂ could exacerbate the depletion process. However, the effect of these leakage problems may not be significant. The amount of hydrogen that leaks today is much lower (by a factor of 10-100) than the estimated 10%-20% figure conjectured by some researchers; in Germany, for example, the leakage rate is only 0.1% (less than the natural gas leak rate of 0.7%). At most, such leakage would likely be no more than 1-2% even with widespread hydrogen use, using present technology. Additionally, present estimates indicate that it would take at least 50 years for a mature hydrogen economy to develop, and new technology developed in this period could further reduce the leakage rate.

[edit] Direct dangers in use

Hydrogen has been feared in the popular press as a relatively more dangerous fuel, and hydrogen in fact has the widest explosive/ignition mix range with air of all the gases. Hydrogen also usually rapidly escapes after containment breach. Additionally, hydrogen flames are difficult to see, so may be difficult to fight. Most of these problems are offset in reality by the fact that hydrogen rapidly disperses by lifting off the scene due to buoyancy, and this is true to some extent of hydrogen fires. For example, it is often forgotten that in the most famous hydrogen fire, the LZ 129 Hindenburg disaster, 2/3 of passengers and crew survived (most deaths were from jumping). In a more recent event, an explosion of compressed hydrogen during delivery at the AEP Muskingum River Coal Plant caused significant damage and killed one person.[4]

[edit] Examples and pilot programs

Several domestic U.S. automobile manufactures have committed to develop vehicles using hydrogen. (They had previously committed to producing electric vehicles in California, a program now defunct at their behest.^{[citation needed]}) Critics argue this "commitment" is merely a ploy to sidestep calls for increased efficiency in gasoline and diesel fuel powered vehicles and diverts us from needed steps to address global warming, such as greater focus on conservation, green fuel production and other green technologies. The distribution of hydrogen for the purpose of transportation is currently being tested in very limited markets around the world, particularly in Iceland, Germany, California, Japan[5] and Canada, but the cost is very high.

Some hospitals have installed combined electrolyzer-storage-fuel cell units for local emergency power. These are advantageous for emergency use due to their low maintenance requirement and ease of location compared to internal combustion driven generators.

The North Atlantic island country of Iceland has committed to becoming the world's first hydrogen economy by the year 2050. Iceland is in a unique position. Presently, it imports all the petroleum products necessary to power its automobiles and fishing fleet. Iceland has large geothermal and hydroelectric resources, so much that the local price of electricity actually is lower than the price of the hydrocarbons that could be used to produce that electricity.

Iceland already converts its surplus electricity into exportable goods and hydrocarbon replacements. In 2002, it produced 2,000 tons of hydrogen gas by electrolysis-- primarily for the production of ammonia (NH₃) for fertilizer. Ammonia is produced, transported, and used throughout the world, and 90% of the cost of ammonia is the cost of the energy to produce it. Iceland is also developing an aluminium-smelting industry. Aluminium costs are primarily driven by the cost of the electricity to run the smelters. Either of these industries could effectively export all of Iceland's potential geothermal electricity.

Neither industry directly replaces hydrocarbons. Reykjavík has a small pilot fleet of city buses running on compressed hydrogen [6], and research on powering the nation's fishing fleet with hydrogen is under way. For more practical purposes, Iceland might process imported oil with hydrogen to extend it, rather than to replace it altogether.

The Reykjavík buses are part of a larger program, HyFLEET:CUTE [7], operating hydrogen fueled buses in eight European cities. HyFLEET:CUTE buses also operate in Beijing and Perth (see below).

A pilot project demonstrating a hydrogen economy is operational on the Norwegian island of Utsira. The installation combines wind power and hydrogen power. In periods when there is surplus wind energy, the excess power is used for generating hydrogen by electrolysis. The hydrogen is stored, and is available for power generation in periods when there is little wind.

A joint venture between NREL and Xcel Energy is combining wind power and hydrogen power in the same way in Colorado. [8]

A similar pilot project on Stuart Island (Washington) uses solar power, instead of wind power, to generate electricity. When excess electricity is available after the batteries are full, hydrogen is generated by electrolysis and stored for later production of electricity by fuel cell. [9]

The UK completed a fuel cell pilot program in December 2005. Started in January 2004, the program ran two Fuel cell buses on route 25 in London.

The Hydrogen Expedition is currently working to create a hydrogen fuel cell-powered ship and using it to circumnavigate the globe, as a way to demonstrate the capability of hydrogen fuel cells.

Western Australia's Department of Planning and Infrastructure currently operates three Daimler Chrysler Citaro fuel cell buses as part of its Sustainable Transport Energy for Perth Fuel Cells Bus Trial in Perth. The buses are operated by Path Transit on regular Transperth public bus routes. The trial began in September 2004 and will conclude in September 2006. The buses' fuel cells use a proton exchange membrane system and are supplied with raw hydrogen from a BP refinery in Kwinana, south of Perth. The hydrogen is a byproduct of the refinery's industrial process. The buses are refueled at a station in the northern Perth suburb of Malaga.

[edit] Conclusion

Before the technical and economic challenges of implementing a "hydrogen economy" can be fully addressed, the fundamental problem of renewable energy production requires a solution. Even then, there are many problems to be solved before hydrogen can serve as a universal energy medium. These include difficulties with hydrogen production, transportation, storage, distribution and end use. It could take many decades to solve all of these problems, and even though the potentials are promising, hydrogen may never be the most economically feasible energy storage medium for all uses.

[edit] References

• Jeremy Rifkin (2002). The Hydrogen Economy. Penguin Putnam Inc. ISBN 1-58542-193-6. 
• Roy McAlister (2003). The Solar Hydrogen Civilization. American Hydrogen Association. ISBN 0-9728375-0-7. 
• Joseph J. Romm (2004). The Hype about Hydrogen, Fact and Fiction in the Race to Save the Climate. Island Press. ISBN 1-55963-703-X.  Author interview at Global Public Media.
• James Howare Kunstler (2006). The LONG EMERGENCY. Grove Press. ISBN 0-8021-4249-4.  Hydrogen economy = "laughable a fantasy" p. 115
• M. Wang (2002). "Fuel Choices for Fuel Cell Vehicles: Well-to-Wheels Energy and Emissions Impact". Journal of Power Sources 112: 307–321. 
• F. Kreith (2004). "Fallacies of a Hydrogen Economy: A Critical Analysis of Hydrogen Production and Utilization". Journal of Energy Resources Technology 126: 249–257. 
• Nakicenovic, et al. (1998). Global Energy Perspectives. Cambridge University Press.  Summary
• Novelli, P.C., P.M. Lang, K.A. Masarie, D.F. Hurst, R. Myers, and J.W. Elkins. (1999). "Molecular Hydrogen in the troposphere: Global distribution and budget". J. Geophys. Res. 104(30): 427-30. 

[edit] See also

• Future energy development
• Hydrogen car
• Grid energy storage
• Hydridic Earth theory
• The Hype about Hydrogen
• Hydrogen prize
• Low-carbon economy
• Renewable energy in Scotland

[edit] Related

• vegetable oil economy, zinc economy, methanol economy, ethanol economy, lithium economy or liquid nitrogen economy

[edit] External links

State:

• International hydrogen alliance-since 2003
• US-DOE
• US-EERE
• US-Department of Commerce 2003

Organizations:

• National Hydrogen Association
• Hydrogen Fuel - A new organization to study and discuss this alternative trend

News:

• Why a hydrogen economy doesn't make sense? - physorg.com
• The Truth About Hydrogen - Popular Mechanics
• Hydrogen Pathways Program - Hydrogen transportation research and graduate program at the Institute of Transportation Studies at UC Davis.
• Hydrogen Hopes - Scientific American Frontiers
• 20 Hydrogen myths - Published by the Rocky Mountain Institute, a major hydrogen economy proponent.
• [10] - "Twenty Myths Challenged" - A rebuttal to Amory Lovins paper by John Wilson, Phd.
• Transmitting 4,000MW of New Windpower from North Dakota to Chicago: New HVDC Electric Lines or Hydrogen Pipelines - Paper study comparing projected costs.
• Hydrogen Use - News about the use of hydrogen as a clean fuel.
• Hydrogen Economy - Outlines the future of the hydrogen economy as it is being built.
• www.physicstoday.org article - Summary of avenues of research into lower-cost hydrogen production, better storage, and lower-cost fuel cells.
• Bottling the hydrogen genie - Article from The Industrial Physicist.
• American Hydrogen Association non-profit association of individuals and institutions, technical and non-technical
• Scientific American Magazine (July 2006 Issue) A Power Grid for the Hydrogen Economy
• Article about government pressure on scientists who oppose the government's pro-hydrogen agenda
• Does a Hydrogen Economy Make Sense?
• Chewonki Renewable Hydrogen Project

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