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Hydrogen
Frequently Asked Questions (FAQs)
Who
discovered hydrogen?
Henry Cavendish (1731–1810) was an English chemist and physicist who
spent several years studying the properties of hydrogen and carbon
dioxide. In 1776 he discovered that hydrogen was a separate substance.
He was the first chemist to produce water from hydrogen and oxygen and
to understand that the production of water was essentially related to
the loss of the combined weights of the gases.
Is hydrogen safe?
Most fuel uses proposed for hydrogen are for hydrogen in its gaseous
form and will not represent a radical departure from existing practices.
Furthermore, gaseous fuels have been used safely for many decades. In
the United States, "town gas," a mixture of hydrogen and
carbon monoxide, was widely used earlier in this century before it was
replaced by natural gas. In 1996, more than 476 billion m3
(17 trillion ft3) of natural gas was used in the U.S.
residential, commercial, and industrial sectors. The use of compressed
natural gas as a vehicle fuel is also increasing, again with an
excellent safety record. Gaseous hydrogen has many similarities to fuels
that are now used routinely, but there are some differences in the
properties of hydrogen compared to other commonly used gaseous fuels. As
with any fuel, safe handling depends on knowledge of its particular
physical, chemical, and thermal properties and consideration of safe
ways to accommodate those properties. Hydrogen, handled with this
knowledge, is a safe fuel.
Hydrogen has been and can be used safely if
appropriate codes, standards, and guidelines are followed. Industry has
produced, stored, transported, and used large amounts of hydrogen safely
and routinely by following standard practices that have been established
in the past 50 years. These practices can be emulated in nonindustrial
uses of hydrogen to attain the same level of safety and routine.
In general, hydrogen is neither more nor less
inherently hazardous than gasoline, propane, or methane. The potential
contribution of a particular property of hydrogen to a particular hazard
depends strongly on the specific conditions under which hydrogen is
released and/or confined.
For more information, consult the Sourcebook
for Hydrogen Applications (available from the National Hydrogen
Association).
Who was the first person to
successfully split water to produce hydrogen?
The first recorded splitting of water to produce hydrogen and oxygen was
accomplished by Sir William Grove in 1839. He also discovered the fuel
cell in the same year. He combined three fuel cells in series and
connected the cells to two electrodes in an acid solution, which
resulted in water splitting.
What does the future hold
for hydrogen fuel?
The ultimate goals are to produce cost-effective hydrogen from renewable
energy sources and to make it readily available for widespread use as a
clean energy carrier and fuel. To achieve this, scientists must develop
advanced technologies to safely produce, store, transport, use, and
detect hydrogen.
How much energy is
required to produce hydrogen via electrolysis of water?
The energy required to produce hydrogen via electrolysis (assuming 1.23
V) is about 32.9 kW-hr/kg. A kilogram is about 2.2 lb. For 1 mole (2 g)
of hydrogen the energy is about 0.0660 kW-hr/mole.
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.
How much hydrogen is produced
each year and how much does it cost?
Recent worldwide production numbers for hydrogen are:
| Origin |
Amount
in billions
Nm3/year |
Percent |
| Natural
gas |
240 |
48 |
| Oil |
150 |
30 |
| Coal |
90 |
18 |
| Electrolysis |
20 |
4 |
| Total |
500 |
100 |
Most of the hydrogen
produced today is consumed on site, such as at an oil refinery, and is
not sold on the market. From large-scale production, hydrogen costs
$0.32/lb if it is consumed on site. When hydrogen is sold on the market,
the cost of liquefying the hydrogen and transporting it to the user must
be added to the production cost. This can increase the selling price to
$1.00-1.40/lb for delivered liquid hydrogen. Some users who require
relatively small amounts of very pure hydrogen (such as the electronics
industry) may use electrolyzers to produce high-purity hydrogen at their
facilities. The cost of this hydrogen, which depends on the cost of the
electricity used to split the water, is typically $1.00–$2.00/lb.
If both hydrogen and
oxygen are flammable, then why doesn't water burn?
Hydrogen and oxygen will burn to form water if in an appropriate
mixture. Pure hydrogen by itself and pure oxygen by itself will not burn
(hydrogen needs an oxidizer and oxygen needs a reductant). Water (H2O)
is a stable chemical component that does not have the characteristics of
the elements that make up its composition (hydrogen and oxygen). This is
true of most chemical compounds.
Will I ever be able to
buy an H2-powered vehicle?
Every major automaker is developing fuel cell vehicles, although some
are focusing on other fuels with onboard reforming instead of hydrogen.
The successful development of advanced hydrogen storage systems will
accelerate the introduction of truly clean fuel cell vehicles.
If we use hydrogen for all
our energy needs, will we run out of oxygen?
The ultimate source of hydrogen is water—when producing hydrogen, we
would also produce oxygen, which would both be consumed in the same
ratio as produced. So there would be no depletion of oxygen from the
atmosphere.
Did hydrogen cause the Hindenberg
to blow up?
No. A recent study of
the accident implicates the paint used on the skin of the airship, which
contained the same component as rocket fuel.
If hydrogen comes from water,
then why can't we put water in our car?
Fuels are by nature reactive, but water is not very reactive. You would
need to have hydrogen or some other reactive fuel mixture, such as
gasoline or natural gas, to extract energy in a efficient manner.
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