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Home
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Frequently Asked Questions Don't see your question below? Please contact us. HYDROGEN AS AN ENERGY CARRIER Why is hydrogen used as a fuel? How does hydrogen compare with other fuels like gasoline and diesel? PRODUCTION How is hydrogen produced? How does an electrolyzer produce hydrogen from water? How much water is used to make hydrogen? How much water would the U.S. use to fuel the entire light-duty vehicle fleet (cars and small trucks) with hydrogen? How much energy is required to produce hydrogen via electrolysis of water? Doesn't it take too much energy to make hydrogen? Is it worth doing? How much hydrogen is produced each year? How much hydrogen does the U.S. use? How much does hydrogen cost? VEHICLES Will I ever be able to buy a hydrogen-powered vehicle? What happens to the tank in my car if I get rear-ended? SAFETY Is hydrogen safe? Is hydrogen harmful to breathe? Did hydrogen cause the Hindenburg accident? How is burning hydrogen different than the reaction in the H-bomb? HYDROGEN AS AN ENERGY CARRIER
U.S. Department of Energy National Hydrogen Association PRODUCTION How is hydrogen produced? One of the great advantages of hydrogen is that it can be made from a variety of domestic feedstocks like water, biomass, coal and natural gas. Because hydrogen exists in many different forms, in any one region, there are a variety of local feedstocks from which the hydrogen can be extracted. Today, over 95% of the hydrogen produced in the U.S. comes from steam reforming natural gas. As hydrogen moves from its role primarily as an industrial gas to a consumer purchased fuel, we expect other production technologies to add to the mix so that hydrogen is produced using the most cost-effective and environmentally sound method available for a specific region. Some options are: renewable or nuclear electricity and electrolysis; gasification of biomass and other hydrocarbons like coal; and using nuclear reactor heat for high-temperature electrolysis or thermo-chemical production methods. For more information, please view our fact sheets. Source National Hydrogen Association How does an electrolyzer produce hydrogen from water?  An
electrolyzer uses an electric current to separate water into its components-hydrogen
and oxygen. The electricity enters the water at the cathode, a negatively
charged electrode, passes through the water and exists via the anode,
the positively charged electrode. The hydrogen is collected at the
cathode and oxygen is collected at the anode.Source U.S. Department of Energy How much water is used to make hydrogen? Electrolysis does not require significant amounts of water. The hydrogen extracted from a gallon of water using a hydrogen generator could drive a hydrogen fuel cell vehicle as far as gasoline vehicles travel today on a gallon of gasoline. Source Hydrogenappliances.com How much water would the U.S. use to fuel the entire light-duty vehicle fleet (cars and small trucks) with hydrogen? Conversion of the current U.S. light-duty fleet (some 230 million vehicles) to fuel cell vehicles would require about 100 billion gallons of water/year to supply the needed hydrogen (1). For comparison, the U.S. uses about 300 billion gallons of water/year for the production of gasoline (2), about three times the amount needed for hydrogen, and about 70 TRILLION gallons of water/year for thermoelectric power generation (3). Domestic personal water use in the United States is about 4800 billion gallons/year. Sources: Turner, John A., "Sustainable Hydrogen Production" Science, Vol 305, Issue 5686, 972-974, 13 August 2004 1) For an estimate of the amount of water needed for hydrogen-powered fuel cell vehicles, assume a vehicle fuel economy of 60 miles per kg of H2, that vehicle miles traveled = 2.6 X 10^12 miles/year (found at http://www.bts.gov/ publications/national_transportation_statistics/ 2002/html/table_automobile_profile.html), and that 1 gallon of water contains 0.42 kg of H2. Total water required for the U.S. fleet = (2.6 X 10^12 miles/year)(1 kg of H2/60 miles)(1 gal H2O/0.42 kg of H2) = 1.0 X 10^11 gallons of H2O/year. This represents the water used directly for fuel. If one considers all water uses along the chain; for example, from construction of wind farms to the electrolysis systems (life cycle assessment), then the total water use would be in the range of 3.3 X 10^11 gallons H2O/year. 2) This is a life cycle analysis (M. Mann and M. Whitaker, unpublished data). The United States used about 126 billion gallons of gasoline in 2001 [see link above]. 3) See http://water.usgs.gov/pubs/circ/2004/circ1268/ How much energy is required to produce hydrogen via electrolysis of water? The energy required to produce hydrogen at atmospheric pressure via electrolysis (assuming 1.23 V) is about 32.9 kWh/kg. A kilogram is about 2.2 lb. For 1 mole (2 g) of hydrogen the energy is about 0.0660 kWh/mole. Compressing or liquefying the hydrogen would take additional energy. One company produces hydrogen through electrolysis at about 7,000psi at an energy usage of about 60kWh/kg H2. Because a Watt is Voltage x Current, this is equivalent to Power x Rate x Time. The power in this case is the voltage required to split water into hydrogen and oxygen (1.23 V at 25?C). The rate is the current flow and relates directly to how fast hydrogen is produced. Time, of course, is how long the reaction runs. It turns out that voltage and current flow are interrelated. To run the water splitting reaction at a higher rate (generating more hydrogen in a given time), more voltage must be applied (similar to pushing down on the accelerator of a car; more gas is used to make the car go faster.) For commercial electrolysis systems that operate at about 1 A/cm2, a voltage of 1.75 V is required. This translates into about 46.8 kW-hr/kg, which corresponds to an energy efficiency of 70%. Lowering the voltage for electrolysis, which will increase the energy efficiency of the process, is an important area for research. Sources U.S. Department of Energy National Hydrogen Association Doesn't it take too much energy to make hydrogen? Is it worth doing? Like all fuels, it takes energy to produce hydrogen and deliver it to a vehicle. The amount of energy required depends on how the hydrogen is made. Some methods require more energy than others. While it may take more energy to produce and deliver hydrogen than it takes to produce and deliver gasoline or natural gas, the hydrogen fuel is used more efficiently in hydrogen vehicles. Most hydrogen internal combustion engines (ICEs) are about 25% more efficient than their gasoline counterparts and fuel cells are 100-200% (2-3 times) more efficient. In many cases, the overall "well-to-wheels" energy usage can be much lower for hydrogen vehicles than for gasoline or natural gas vehicles using a conventional internal combustion engine. Source National Hydrogen Association How much hydrogen is produced each year? The world economy currently consumes about 42 million tons of hydrogen per year. About 60 percent of this becomes feedstock for ammonia production and subsequent use in fertilizer (ORNL, 2003). Petroleum refining consumes another 23 percent, chiefly to remove sulfur and to upgrade the heavier fractions into more valuable products. Another 9 percent is used to manufacture methanol (ORNL, 2003), and the remainder goes for chemical, metallurgical and space purposes (Holt, 2003). Some recent worldwide hydrogen production totals are shown below:
Source U.S. Department of Energy How much hydrogen does the U.S. use? Each year, the United States uses more than 9 million tons (about 90 billion normal cubic meters, 3.2 trillion standard cubic feet) of hydrogen, 7.5 million tons of which are consumed at the place of manufacture. The remaining 1.5 million tons are considered to be "merchant" hydrogen, or hydrogen that is sold. Today, most of this hydrogen is used as a chemical, rather than a fuel, in a variety of commercial applications:
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Hydrogen
tanks, whether they are filled with gaseous or liquid hydrogen are
incredibly strong-MUCH stronger than the gasoline tanks found in
vehicles today. For example, this car was dropped on its back end
from 90 feet (reaching 52 mph as it hit the ground), with a hydrogen
tank secured in the trunk. The tank was undamaged and no hydrogen
was leaked.
The
fire that destroyed the Hindenburg in 1937 gave hydrogen a misleading
reputation. Hydrogen was used to keep the airship buoyant and was
initially blamed for the disaster. An investigation by Addison Bain
in the 1990s provided evidence that the airship's fabric envelope
was coated with reactive chemicals, similar to solid rocket fuel,
and was easily ignitable by an electrical discharge. The Zeppelin
Company, builder of the Hindenburg, has since confirmed that the
flammable, doped outer cover is to be blamed for the fire.
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