The “Hydrogen Economy” is an oft-discussed topic with supporters
and detractors on both sides. The push to use hydrogen as an energy source has
even been part of a $1.2 billion presidential initiative, announced in the 2003
State of the Union Address. As it is rapidly becoming apparent that energy is
one of the most important issues facing our world today, it is important that
we consider hydrogen in tandem with other technologies as an alternative to
the once-abundant hydrocarbon resources on which our society depends.
To date, geologists have been the key to finding abundant and affordable energy.
Discoveries of oil and natural gas have kept up with demand, but the fossil-fuel
economy is starting to show some wear. As worldwide consumption continues to
grow and major finds become more elusive, and as concern mounts over anthropogenic
carbon dioxide and major unknowns about its impact on global climate change,
human-kind finds itself faced with the following challenge: how to continue
to power this society, particularly in the face of the rapidly growing economies
of emerging nations like India and China, and yet answer questions of sustainability,
energy security, geopolitics and the global environment.
The major issue facing United States and most other countries in the world is
how to supply transportation fuel. Hydrogen, as part of a sustainable energy
supply, can meet the challenge of a domestically produced energy carrier that
can replace gasoline, and can additionally address carbon dioxide and other
emissions.
To fully understand the viability of hydrogen as our primary chemical energy
carrier, we need to see how it fits into a future energy system. With current
fossil-fuel-based energy systems expected to last a scant 200 years or so, we
should consider the possibility of energy systems that would be viable for millennia.
We must consider four major criteria in any discussion of a millennia-long energy
system: how long the proposed energy system will last; whether or not the technology
to exploit it exists; whether it can meet the energy needs of the nation today
and into the future; and whether the system will ultimately yield more energy
than it took to build it.
Solar, wind, biomass, geothermal, hydropower and wave energy are systemic to our planet. These energy systems have
been around for billions of years and will likely remain viable for billions
of years to come — certainly sustainable on a millennial time scale. Studies
have also shown that both wind and solar energy systems produce more energy
in their lifetimes than it takes to manufacture them; the energy payback time
for wind is four to six months and for solar, it’s three to four years.
But none of these systems alone will solve our transportation fuel demand. That’s
where the Hydrogen Economy comes into play.
Using electricity and water as feedstocks, hydrogen can be produced via a commercial
process called electrolysis that separates out the hydrogen from H2O. The hydrogen
represents stored energy that can be released via a chemical reaction, just
like gasoline. The vision then is to replace our oil imports with electricity
production followed by electrolysis of water to produce hydrogen, and use that
hydrogen to power our transportation infrastructure. Producing the hydrogen
itself will require electricity from other renewable sources as well.
Photovoltaic and wind systems can conceivably provide all U.S. electricity needs
(with major modification to our grid), eliminating our use of coal, oil and
natural gas for electricity generation. It is illustrative to point out that
to supply all the electrical needs of the United States using current solar-cell
technology would require about 15,500 square kilometers (6,000 square miles)
of panels taking up about 31,000 square kilometers of land area (assuming 50
percent coverage). To generate the electricity necessary to produce enough hydrogen
to fuel 300 million future hydrogen-powered vehicles would require an additional
array of similar size. This represents about 0.7 percent of U.S. land area,
and while much of this required coverage could be met with existing structures,
such as homes, buildings and parking lots, it is by no means necessary for photovoltaics
do it all.
While hydrogen can be burned in a modified internal-combustion engine, its maximum
benefits are realized with a fuel cell. A fuel cell is a device similar to a
battery in that it converts chemical energy to electrical energy directly. In
a battery, all the chemical components are stored inside the battery; in a fuel
cell, the chemicals (hydrogen and air) are fed from external resources. When
that hydrogen is used, the outputs are electricity, heat and water. Unlike the
fossil-fuel economy, with a hydrogen economy, you get your feedstock (water)
back in real time.
Every major automotive manufacturer is developing and testing fuel-cell vehicles;
more than 50 fuel-cell-powered buses are currently in service around the world.
Significant challenges remain as to the cost, range and refueling of these vehicles,
but the conclusion is clear; these are zero-emission vehicles operating on a
fuel that can be sustainably produced using indigenous energy resources.
According to a report by the Intergovernmental Panel on Climate Change, to stabilize
the carbon-dioxide level in our atmosphere at 450 parts per million (ppm) —
we are currently at 380 ppm — we would need to be generating about 10 terawatts
of carbon-dioxide-emission-free energy by 2030. If the new paradigm is carbon-dioxide-emission-free
energy generation, then nuclear is in the lead, followed by hydropower and then
wind and solar. But with growth rates of 30 percent or better, only wind and
solar have the potential to have a global impact simultaneously on emissions
and energy supply. Combine those technologies with a simultaneous development
of a hydrogen economy, and we have an energy system based on two of the most
abundant resources on the planet: sunshine and water.
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