Hydrogen and AAs

September 9, 2007

in Daily updates, Science, The environment

Steel bridge struts

At a party this weekend, I had a conversation with someone who believed that the energy needs of the future would be solved by hydrogen. Not hydrogen as the input for nuclear fusion, but hydrogen as a feedstock for fuel cells and combustion engines. It’s not entirely surprising that some people believe this. For years, car companies have been spouting off about hydrogen powered vehicles that will produce only water vapour as emissions. The Chevron game mentioned earlier lets you install ‘hydrogen’ electricity generating capacity. The oversight, of course, is that hydrogen is just an energy carrier. You might as well say that the energy source of the future will be AA batteries.

AA batteries are obviously useful things. They provide 1.5 volts of power that you can carry around with you and use to drive all manner of gadgetry, but they are hardly an energy system unto themselves. The chemicals inside them that create their electrical potential had to be extracted, processed, and combined into a usable form. Inevitably, this process required more energy than is in the batteries at the end. The loss of potential energy is a good trade-off, because we get usable and portable power, but there is no sense in which we can say that AA batteries are an energy system.

A similar trade-off may well eventually be made with hydrogen. We may break down hydrocarbons, sequester the CO2 produced in that process, and use the hydrogen generated as fuel for cars. Alternatively, we might use gobs of electricity to electrolyse water into hydrogen and oxygen. Then, we just need to find a way to store a decent amount of hydrogen safely in a tank small, durable, and affordable enough to put in vehicles; build fleets of vehicles with affordable fuel cells or hydrogen powered internal combustion engines; and develop an infrastructure to distribute hydrogen to all those vehicles.

When you think about it, hydrogen seems less like a solution in itself, and more like the possible end-point of solving a number of prior problems. As far as ground vehicles go, it seems a safer bet to concentrate on improvements to rechargeable battery technology.

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{ 11 comments… read them below or add one }

Anon September 10, 2007 at 8:12 am
Litty September 10, 2007 at 10:26 am

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Hydrogen Skeptic September 10, 2007 at 10:44 am

“The hydrogen fuel cell costs nearly 100 times as much
per unit of power produced as an internal-combustion engine.
To be price competitive, “you’ve got to be at a nickel a watt, and
we’re at $4 a watt,’’ says Tim R. Dawsey, a research associate
at Eastman Chemical Company, which makes polymers for fuel
cells. Hydrogen is also about five times as expensive, per unit
of usable energy, as gasoline.”

“Hydrogen could come from the methane in natural gas,
methanol or other hydrocarbon fuel. Natural gas can be reacted
with steam to make hydrogen
and carbon dioxide. Filling fuel cells, however, would preclude
the use of natural gas for its best industrial purpose today: burning
in high-efficiency combined-cycle turbines to generate electricity.
That, in turn, might again lead to more coal use. Combined-
cycle plants can turn 60 percent of the heat of burning
natural gas into electricity; a coal plant converts only about 33
percent. Also, when burned, natural gas produces just over half
as much carbon dioxide per unit of heat as coal does, 117
pounds per million Btu versus 212. As a result, a kilowatt-hour
of electricity made from a new natural gas plant has slightly
over one fourth as much carbon dioxide as a kilowatt-hour
from coal. (Gasoline comes between coal and natural gas, at
157 pounds of carbon dioxide per million Btu.) In sum, it seems
better for the environment to use natural gas to make electricity
for the grid and save coal, rather than turning it into hydrogen
to save gasoline.”

“When natural gas is cracked for hydrogen, about 40 percent
of the original energy potential is lost in the transfer, according
to the DOE Office of Energy Efficiency and Renewable
Energy. Using electricity from the grid to make hydrogen by electrolysis
of water causes a loss of 78 percent.”

“In contrast, pumping a gallon of oil out of the
ground, taking it to a refinery, turning it into gasoline and getting
that petrol to a filling station loses about 21 percent of the
energy potential. Producing natural gas and compressing it in a
tank loses only about 15 percent.”

“For the conventional
gasoline internal-combustion engine, 85 percent of the energy
in the gasoline tank is lost; thus, the whole system, well to tank
combined with tank to wheels, accounts for a total loss of
88 percent… The fuel cell converts about 37 percent of the hydrogen’s
energy value to power for the wheels. The total loss, well to
wheels, is about 78 percent if the hydrogen comes from steamreformed
natural gas. If the source of the hydrogen is electrolysis
from coal, the loss from the well (a mine, actually) to tank
is 78 percent; after that hydrogen runs through a fuel cell, it loses
another 43 percent, with the total loss reaching 92 percent.”

“In a car that employs an electric motor to turn the wheels, a
kilowatt-hour used to recharge batteries will propel the auto
three times as far as if that same kilowatt-hour were instead
used to make hydrogen for a fuel cell.”

“Fuel-cell vehicles emit no greenhouse gases themselves, but the
creation of the hydrogen fuel can be responsible for more
emissions overall than conventional gasoline internalcombustion
engines are.”

“Given
hydrogen’s low density, it is far harder to deliver than, for instance,
natural gas. To move large volumes of any gas requires
compressing it, or else the pipeline has to have a diameter similar
to that of an airplane fuselage. Compression takes work, and
that drains still more energy from the total production process.
Even in this instance, managing hydrogen is trickier than dealing
with other fuel gases. Hydrogen compressed to about 790
atmospheres has less than a third of the energy of the methane
in natural gas at the same pressure, points out a recent study by
three European researchers, Ulf Bossel, Baldur Eliasson and
Gordon Taylor.”

“A related problem is that a truck that could deliver 2,400
kilos of natural gas to a user would yield only 288 kilos of hydrogen
pressurized to the same level, Bossel and his colleagues
find. Put another way, it would take about 15 trucks to deliver
the hydrogen needed to power the same number of cars that
could be served by a single gasoline tanker. Switch to liquid hydrogen,
and it would take only about three trucks to equal the
one gasoline tanker, but hydrogen requires substantially more
effort to liquefy.”

Scientific American 2004

Hydrogen Skeptic September 10, 2007 at 10:55 am

“Storage devices should hold sufficient hydrogen to sup­port today’s minimum acceptable travel range—300 miles—on a tank of fuel in a volume of space that does not compromise passenger or luggage room. They should release it at the re­quired flow rates for acceleration on the highway and operate at practical temperatures. They should be refilled or recharged in a few minutes and come with a competitive price tag. Current hydrogen storage technologies fall far short of these goals.”

“Even at 10,000 psi, the best achievable energy density with current high-pressure tanks (39 grams per liter) is about 15 percent of the energy content of gasoline in the same given volume. Today’s high-pressure tanks can contain only about 3.5 to 4.5 percent of hydrogen by weight.. Also, the current cost of such tanks is 10 or more times higher than what is competitive for autos.”

Scientific American 2007

Tristan Laing September 11, 2007 at 1:10 am

for cars, not hydrogen, but compressed air. First compressed air cars will be in Canada next year. Will blow the market open.

for boats, not hydrogen, but lead acid batteries. I can’t believe there’s a dude who is using solar panels to make hydrogen to power a motor to drive his sailboat. It’s a boat! Batteries are heavy! It’s a perfect combination.

Milan September 11, 2007 at 8:33 am

Tristan,

Compressed air for mobile energy storage

I haven’t heard anything about this since that post was written. I wonder whether things are still moving forward.

. November 22, 2007 at 10:00 am

Dream of hydrogen car goes down in flames

By Joseph Romm

Ballard — the Canadian fuel-cell company that once hoped to be the “Intel Inside of the hydrogen car revolution — has sold off its automotive fuel-cell business to Daimler and Ford.

You can listen to a good CBC radio story on it, which includes an interview of me (click on “Listen to the Current,” Part 2). You can read Toronto Star columnist Tyler Hamilton on the story here. A Financial Post post piece headlines the story bluntly: “Hydrogen highway hits dead end: Ballard’s talks with potential buyers is admission that dream of hydrogen fuel car is dead: analyst.”

. August 30, 2008 at 9:38 pm

WATER AS FUEL – Using hydrolysis to produce hydrogen and oxygen from water requires more energy than the amount you get back by “combusting” the hydrogen to power a vehicle. This energy deficeit [sic] makes “onboard hydrolysis” vehicles infeasible. (Hydrogen gas and fuel cell powered vehicles already exist that use methods other than “onboard hydrolysis”.)

. August 30, 2008 at 9:42 pm

Electrolysis of Water

By providing energy from a battery, water (H2O) can be dissociated into the diatomic molecules of hydrogen (H2) and oxygen (O2). This process is a good example of the the application of the four thermodynamic potentials.

. September 9, 2009 at 11:24 am

Hydrogen

While not generally considered a biofuel, I discussed hydrogen in my “Pretenders” piece so I will address it here as well. In my opinion, the most interesting realistic option for hydrogen is as energy storage for excess power. For instance, let’s say you have a neighborhood in which most houses have enough solar panels to produce excess electricity at mid-day. Once the batteries are charged, what else can you do with that excess electricity? If it can’t be diverted to someplace that has a need, then it may make sense to electrolyze water to produce hydrogen. This is not a very efficient process, and not something you would do under normal circumstances, but in this case it could be the best storage option.

Once the hydrogen is produced, it could either be used to fuel stationary fuel cells for the neighborhood when the solar panels aren’t producing, or it could be compressed and used to fuel hydrogen combustion engines.

Milan December 19, 2009 at 6:20 am

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