User:Iain.mcclatchie/Hydrogen economy
This is the April 1, 2005 version of the Hydrogen Economy article. I've copied it here so that I can attempt a merge of the good work that's been done on that article since then, as well as merge in the data I've collected in the meantime. Iain McClatchie 01:11, 26 August 2005 (UTC)
A hydrogen economy is a hypothetical future economy in which the primary form of stored energy for mobile applications and load balancing is hydrogen.
In modern western economies, both the primary source of energy and the primary form of stored and transported energy is hydrocarbon fossil fuels. Because pumping the hydrocarbons out of the ground is currently inexpensive (about one U.S. dollar per barrel in Saudi Arabia in 2004), the price of energy comes from the costs of refining and distribution, and from taxation and profits by the various governments and companies in the custody chain between producer and consumer. The price of crude delivered to a refinery in the U.S. is about $50 a barrel in late 2004.
Sources[edit]
As of 2004, hydrogen production is a large industry. Globally, about 50 million metric tons of hydrogen are produced each year. About half of worldwide hydrogen production is used to produce ammonia-based fertilizers, and most of the rest is used in oil refineries. 48% of hydrogen is produced from natural gas, 30% is from oil, and 18% is from coal. Electrolysis accounts for about 4%, because electrolysis only makes sense when the cost of electricity is lower than the cost of the hydrocarbon fuel that could produce that electricity. A massive increase in hydrogen production (via electrolysis) will only happen if the demand is there and the alternative electrical supply booms and takes electricity prices below hydrocarbon prices.
Production of hydrogen from hydrocarbons or plain carbon (coal) is via high temperature steam and catalysts, via the Fischer-Tropsch process and the water gas shift reaction. Essentially, the oxygen atom is stripped from the water (steam) to oxidize the carbon, liberating the hydrogen formerly bound to the carbon and oxygen. The byproduct CO2 (a greenhouse gas) is usually released into the atmosphere, but there is some research into interning it underground or undersea.
Electricity from dams has been cheaper than electricity from oil- and gas- burning turbines in many parts of the world for a long time. The United States has built dams on nearly every river that can sensibly be dammed; this resource is almost completely built out. In order to mitigate some of the unexpected evironmental damage, the U.S. is currently destroying dams faster than it is building them, but the rate of change is not large.
Like hydroelectric production, geothermal electric production has been cost-competitive, and in use, for years. Geothermal resources are not as widespread as hydraulic resources, nor typically near population centers, and so geothermal is not currently well built out.
Nuclear electric production was once thought to be the next oil. Walter Marshall famously declared that it would be "too cheap to meter". It now appears that nuclear electric production is about as expensive as hydrocarbon-based production. Nuclear production is as high as it is in France, the U.S., and Japan principally because it was viewed by legislators as bootstrapping a domestic industry and also as being less dependent on volatile foreign supplies, and thus a stabilizing influence on the domestic economies.
Wind power appears to be the next booming supply of energy. Proponents like to point out that it is the fastest growing source of energy (in late 2004), but this is relative to a small installed base. In small parts of the world with strong steady winds near population centers (i.e. Denmark), wind power is already price competitive, and is being built out. As wind turbine prices come down and the technology for siting them in difficult conditions (primarily offshore) matures, wind electric production is expected to grow to supply a significant portion of the world electric demand.
Solar electric (photovoltaic) production is not currently competitive with utility-scale generation from any of the above-mentioned sources. It is interesting primarily because it can be practically located close to the demand in many parts of the world. Because it costs so much to move electricity, production that is close to the demand is worth more than remote production. Even with this advantage, photovoltaic production is currently only competitive when supported by large subsidies or when its use allows a grid connection to be eliminated entirely.
There are many other alternative energy supplies under development. Tides, ocean currents and deep ocean thermal gradients have all been proposed as sources of energy to be tapped. A few significantly large tidal generators have been built, but they form navigation hazards and no forseeable buildout would be expected to supply significant amounts of power on a worldwide scale.
Large scale biomass programs, like midwest ethanol added to Californian gasoline, appear to consume more energy than they produce and are only cost effective for the producers due to favorable tax and subsidy policies.
Some alternative supplies would produce hydrogen thermochemically, as is done from hydrocarbon sources now, rather than going through the intermediate form of shaft power. Some researchers are working on high-temperature hydrogen production in nuclear power plant cores. Others are working on direct solar production of hydrogen through cyanobacteria or organometallic substrates.
Recently announced developments show that the use of very high temperature water as a feedstock for electrolysis greatly increases the electrical efficiency of the system. As proposed gas–cooled pebble–bed nuclear reactors produce high temperatures and would be used as a gas source for turbines to drive electrical generators this could result in a cost effective mechanism for producing hydrogen. Note also that solar towers heated by sun-following mirrors (heliostats) offer similar potential in some locations (such as the desert southwest of the United States). The latter could be particularly attractive where electricity demand lags solar production — hydrogen produced in the mid morning (a time of high production and lower demand) could be saved and used to produce electricity in the late afternoon and evening (a time of low production and high demand).
Transmission[edit]
By far the cheapest way to move energy around the planet is in the form of oil in a pipeline or supertanker, or coal on a barge or rail car. (Uranium in a high-security armored rail car is even better, but unpopular.) Natural gas pipelines (and LNG tankers) are much more expensive, in comparison, which explains why natural gas from Alaska's North Slope is currently reinjected into the ground rather than shipped to the lower 48 states where it would be worth a fortune. Electric power lines cost so much for the energy moved that power stations are generally located within a hundred miles of the loads they serve, so that energy can be moved as coal, oil or gas rather than as electricity. For example, California burns an average of about 30 gigawatts of electricity, and has a north-south transmission capacity bottleneck (the 500 KV Path 15) of 5.4 gigawatts.
Hydrogen pipelines are unfortunately more expensive than even long-distance electric lines. They are more expensive not just because the electrolyzers and fuel cells cost so much, but because a pipeline carrying hydrogen is much more expensive than a wire carrying electricity. Hydrogen is about three times bulkier 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 only likely to expand with newer technology, as wires suspended in air can scale up voltage with marginal material costs, but high pressure pipes have material costs directly proportional to the amount of gas enclosed.
Storage[edit]
Currently, both hourly and seasonal national electric load balancing is done very cost-effectively by varying the output of hydroelectric and gas-fired generators, both of which have low base costs. In some cases water is pumped back up dams during off peak hours for even more load balancing. (See pumped-storage hydroelectricity or more generally grid energy storage.)
Although it is generally not referred to as load balancing, the varying rates of supply, refining, and consumption of hydrocarbons are also balanced by storing liquid hydrocarbons, generally in the familiar tank farms around refineries. Such storage is practical because the economic value of the hydrocarbons stored is very large compared to the cost of the tank.
Natural gas is also stored in large tanks, but these are much less common because natural gas is much more expensive to store, as it is a gas. Typically, if the gas would be stored for longer than a few months and a gas pipeline connection is available, it is cheaper to flare it off and buy more when needed. As a result, the primary form of storage for natural gas is within the distribution pipelines themselves.
Some attention has been given to the role of hydrogen distribution pipelines as a load balancing system for unpredictable energy supplies, like wind power. The most obvious competitor is hydroelectric pumped storage. The primary difficulty with using hydrogen stores as a load balancing system is that such use assumes that converting power to hydrogen and back is cheap, which it is not. Because water turbines and electric wires are so much cheaper than electrolysis plants, fuel cells, and hydrogen pipelines, pumped storage is much cheaper than hydrogen storage.
Hydrocarbons are also stored extensively at the point of use, be it in the gas tanks of cars or propane tanks hung on the side of barbeque grills. Hydrogen, in comparison, is quite expensive to store or transport with current technology. As a gas, it is very bulky compared to hydrocarbons storing the same energy, and tends to diffuse through any liner material intended to contain it. As a result, hydrogen tanks are heavier than natural gas tanks (increasing pressure makes the tanks smaller but not lighter, see pressure vessel). As a cryogenic liquid, hydrogen requires expensive and delicate vacuum isolation of some form. Bound into a hydride, the resulting storage is larger and heavier than hydrocarbons storing the same energy.
This last form, hydride storage, is a leading contender for automotive storage. A hydride tank is about three times larger and four times heavier than a gasoline tank holding the same energy. For a standard car, that's about 45 gallons of space and 600 pounds versus 15 gallons and 150 pounds. A standard gasoline tank weighs a few dozen pounds and is made of steel costing less than a dollar a pound. Lithium, the primary constituent by weight of a hydride storage vessel, currently costs over $40 a pound.
End use[edit]
The underlying premise of a hydrogen economy is that fuel cells will replace internal combustion engines and turbines as the primary way to convert chemical power into motive and electrical power. The reason to expect this changeover is that fuel cells, being electrochemical, can be more efficient than heat engines. Currently, fuel cells are very expensive, but there is active research to bring down fuel cell prices.
Fuel cells work with hydrocarbon fuels as well as pure hydrogen. If and when fuel cells become cost-competitive with internal combustion engines and turbines, one of the first adopters will be large gas-fired powerplants. These are currently being built in large numbers by a highly competitive industry, their owners can work with operational constraints (tight temperature ranges, low shock, slow power ramps, etc), power to weight is not an issue, and even small efficiency gains are worth quite a lot. If reforming natural gas into hydrogen and then using that hydrogen in a fuel cell is somehow more efficient than burning the natural gas, gas-fired powerplants will do that instead. But there is no serious discussion of fuel-cell powerplants.
Much of the popular interest in hydrogen seems to attach to the idea of using fuel cells in automobiles. The cells can have a good power-to-weight ratio, are more efficient than internal combustion engines, and produce no damaging emissions. If cheap fuel cells can be had, they may make sense in an advanced hybrid automobile.
So long as methane is the primary source of hydrogen, it will make more sense to fill specialized car tanks with compressed methane and run the fuel cells directly off that. The resulting system uses the methane energy more efficiently, produces less total CO2, and requires less new infrastructure. A further advantage is that methane is much easier to transport and handle than hydrogen. Methane used for fuel cells cannot have traces of methyl mercaptan or ethanethiol, which are smelly chemicals injected into natural gas distributions to help users find leaks. The sulfur component of the odorant will destroy the membranes of the fuel cell. Since the technology for running internal combustion engines directly from methane is well developed, low polluting, and leads to long engine life, it is more likely that compressed natural gas (CNG) will be used for transportation in this way rather than in fuel cells for the near future.
Examples[edit]
Several domestic US 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.) Critics argue this "commitment" is merely a ploy to sidestep current calls for increased efficiency in gasoline and diesel fuel powered vehicles.
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: at present, it imports all the petroleum products necessary to power its automobiles and fishing fleet. But Iceland has large geothermal and hydroelectric resources, so much so 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 2000 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 aluminum-smelting industry. (Aluminum 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.
But neither directly replaces hydrocarbons. Plans call for Reykjavik's 80 busses to run on compressed hydrogen by 2005. Research on powering the nation's fishing fleet with hydrogen is underway. For practicality, Iceland may end up processing imported oil with hydrogen to extend it, rather than to replace it altogether.
See also[edit]
Further reading[edit]
- Jeremy Rifkin, The Hydrogen Economy, Penguin Putnam Inc, 2002, ISBN 1585421936
- Joseph J. Romm, The Hype about Hydrogen, Fact and Fiction in the Race to Save the Climate This book is very skeptical of the feasibility and economics of using either Hydrogen or fuel cells for transportation.
Links[edit]
- European Fuel Cell Forum - Papers by a set of fuel cell engineers, many concerning the hydrogen economy.
- 20 Hydrogen myths - Published by the Rocky Mountain Institute, a major hydrogen economy proponent.
- Transmitting 4,000MW of New Windpower from North Dakota to Chicago: New HVDC Electric Lines or Hydrogen Pipelines - Paper study comparing projected costs.
- FreedomCAR - U.S. hydrogen powered car initiative.
- PolyFuel - Commercial methanol fuel cell technology.