Is the Hydrogen Economy "Dead in the Water"?
The hydrogen economy has been an interesting prospect for
scientists for over three decades. Particularly around the beginning of this
century, there was a lot of excitement generated for hydrogen, mostly as a
transportation fuel. But although progress has continued since its inception,
most of the hype and excitement has turned to batteries, biofuels, and electric
cars. What does this mean for the future of hydrogen?
Hydrogen as an Energy Carrier
Hydrogen is not a primary energy source. Since it is not
stored in an accessible form like fossil fuels, energy must be used to create
it (like a battery). This makes it an energy carrier or currency. Much like
money is a universal form for exchanging goods and services, hydrogen is a (potential)
universal form for energy exchange (hence the term 'hydrogen economy').
Current primary energy forms (fossil fuels and various sources of electricity)
can be converted to hydrogen through electrolysis of water or fossil fuel
reformation. Electrolysis uses electricity to split water molecules (H2O) into
oxygen gas (O2) and hydrogen gas (H2). Fossil fuel reformation uses
hydrocarbons, typically natural gas or syngas containing primarily methane
(CH4), and steam to form carbon dioxide (CO2) and hydrogen gas via a two-step
reaction. The fuel cell can then utilize hydrogen gas with oxygen to create
electricity, with water vapor as the only waste product.
Fuel Cell Operation. Image
Credit: Scotland's Renewable Energy Blog
Though the hydrogen economy could involve many industries,
the focus has been in transportation.
What's Right with Hydrogen
Hydrogen offers a number of advantages over other energy
alternatives, particularly for use in vehicles.
Most prominent is its versatility. Hydrogen can be generated
from all primary energy sources, making it theoretically more available than
biofuels which are limited by the abundance of raw materials. The process for
hydrogen is also more continuous than batteries which require substitution and
replacement, and makes the utilization of intermittent power sources (wind and
solar) more convenient.
On the flip side, hydrogen carries the convenience of
biofuels and gasoline as a fuel. Travelling long distances remains feasible with
refueling similar to today's gas station, as compared to the hours needed for recharging
a battery.
Image Credit:
Mercedes-Benz
Hydrogen promoters also label it a "clean" fuel since it
produces no greenhouse gases in combustion or fuel cell conversion. And who
wouldn't want to drive a vehicle that emits water vapor out the exhaust?
What's Wrong with Hydrogen
Unfortunately, hydrogen is not the bowl of cherries it
seems. It has a number of pitfalls
(OK, no more puns I promise).
Though it may be versatile, it's not inherently practical. Hydrogen
is odorless, colorless, and tasteless, making the detection of leaks difficult.
This, along with the fact that hydrogen is extremely volatile, is a major safety
concern. Storing hydrogen, due to its low energy density and small size, is
also extremely difficult. An acceptable storage system must be simultaneously
lightweight, compact, inexpensive, and safe; a tall hurdle to overcome.
Hydrogen is also relatively inefficient. Incorporating a
fuel cell into current vehicle manufacturing processes noticeably decreases its
energy efficiency. It is also incredibly expensive to build due to its
complexity. Fuel cell vehicles don't gain much for being lightweight (no
engine) either, after considering losses in the production cycle, storage
losses, and various other minor losses in the fuel cell system.
Since hydrogen is an energy carrier, it also cannot in
reality be considered clean. Though the vehicle has no emissions, the hydrogen
process is no more green than the means used to create it (as depicted in the adjacent cartoon). Even if produced completely by renewable power sources, the
grid displacement would ensure similar levels of carbon emission.
A Dead End?
As with many other new technologies, a barrier to
development is the chicken and egg conundrum, in which adequate infrastructure
(refueling stations) and products (cars) are both dependent on the other for
successful business. And while Germany has announced it will build 1,000
hydrogen fueling stations by 2020, the U.S. drive has gone noticeably cold
towards hydrogen. Adventurous entrepreneurs, such as Thomas D. Sullivan of Proton OnSite, are taking steps to
solve this problem by building clusters of refueling stations ahead of the game
in hopes that the market for fuel cell vehicles will grow in response.
But are these efforts in vain? Will hydrogen technology ever
pan out? That really depends on who you talk to. Some believe hydrogen will never
work, while others think it is the only true long term replacement for gasoline
powered cars. Regardless of opinion, most agree that hydrogen powered vehicles
are still decades away from making even a small impact on the transportation
market. What do you think?
Resources
C&EN
- Still Chasing the Hydrogen Economy
The
Guardian - Environment Blog
World
Energy Council - Fuel Cells
Materials
Research Society - Waiting for the Hydrogen Economy
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