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Research Opportunities and Challenges in
the Energy Sector
Alexis T. Bell,
University of California, Berkeley
Energy usage in the United States presently is largely from fossil fuels-
petroleum, natural gas, and coal. Petroleum is used to produce transportation and
heating fuels and to a smaller degree it is a source of chemicals and lubricants.
Natural gas is used to produce electricity along with domestic and industrial heat-
ing. Coal is largely used to produce electricity.
In the 21st century this pattern of energy usage probably will not change
significantly. The main reason is that carbon-based fuels will remain plentiful
and low in cost. Examination of the reserve supply of fossil fuels indicates a
substantial amount of petroleum still in the ground and accessible. At present
consumption rates, and analyzing only proven reserves for fossil fuels, it is antici-
pated that oil reserves will last for at least another 40 years, supplies of gas another
70 years, and coal supplies 200 years. If likely reserves that have not yet been
discovered are included, fossil fuels will be plentiful for decades to come.
In light of the supply predictions, what are the drivers for changing the
nation's primary fuel sources? The first is a desire to reduce the nation's depen-
dence on imported petroleum. The second driver is the need for clean-burning
fuels, including gasoline containing less sulfur and diesel fuels that produce less
soot, which would reduce the impact of vehicle emissions and other combustion
sources on human health. A third and very significant motivator is the increasing
concern about man-made carbon dioxide emissions being released into the
atmosphere.
The extent to which man-made carbon dioxide emissions contribute to global
warming is still an issue of considerable debate. Analysis indicates that while the
contribution to the total amount of this gas in the atmosphere from anthropogenic
sources amounts to 3 to 4 percent, the problem is that carbon dioxide remains in
13
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4
ENERGY AND TRANSPORTATION
the atmosphere for a very long time and thus accumulates. If currently projected
rates of fuel consumption continue, a doubling of carbon dioxide in the atmo-
sphere is anticipated by the end of this century. Even though the question of
whether man-made carbon dioxide emissions are responsible for global warming
is still unresolved, there is a growing global consensus that these man-made
carbon dioxide emissions must be reduced.
Options for reducing man-made carbon dioxide emissions include improve-
ments in the efficient use of carbon-based fuels. This goal could be achieved by
moving to lighter-weight vehicles that consume less fuel and also by switching
from gasoline to diesel fuel. With a threefold increase in efficiency, it is esti-
mated that a two and one-half to threefold decrease in the amount of carbon
emitted per mile driven would result.
Another means to reduce man-made carbon dioxide emissions is sequestra-
tion in the land or the ocean. When carbon dioxide is produced locally it may be
possible to efficiently separate it from other gases, concentrate it, and dispose of
it. A number of complex scenarios may be envisioned to accomplish this dis-
posal, from pumping it into the ocean, to displacing methane in coal mines, to
storage in depleted hydrocarbon reservoirs.
FUELS WITH HIGHER HYDROGEN CONTENT
One of the most promising means to mitigate carbon dioxide emissions is to
either reduce the use of carbon-based fuels and/or increase the hydrogen content
of the fuels that are used. Looked at historically, it is clear the trend in fuel use
over the past 150 years has been toward fuels with progressively higher hydrogen-
to-carbon content, starting with wood, moving to coal and petroleum, then to
methane. If this trend continues, we will eventually move toward a nonfossil-
based hydrogen economy.
Over the past decade, natural gas usage increased by 20 percent, petroleum
utilization increased by 12 percent, and coal use decreased by 6 percent. This
trend indicates that for the near term at least there is already a noticeable increase
in the use of more hydrogen-rich fuels.
Natural Gas
Natural gas has a high hydrogen-to-carbon content and is plentiful world-
wide. It can be brought to market in four different ways pipelines, liquefied
natural gas, conversion to electricity, or conversion to liquid products that can be
pipelined. It is also possible to envision in the near future a natural gas refinery
for which natural gas will serve as the principal feedstock. This type of facility
would provide an effective means to use natural gas to produce electricity and
liquid fuels while also allowing for the recovery of carbon dioxide on site that
then could be sequestered.
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RESEARCH OPPORTUNITIES AND CHALLENGES IN THE ENERGY SECTOR 15
One of the ways in which natural gas could be converted to liquid products is
by Fischer-Tropsch synthesis. In this process, methane is reformed with steam
and oxygen to produce a synthesis gas that is a mixture of carbon monoxide and
hydrogen. The synthesis gas is then reacted over a catalyst to produce a variety of
fuels. However, recently the most emphasis has been on the production of high-
cetane, sulfur-free diesel fuel. Fischer-Tropsch fuels can be produced at the
equivalent of $14 to $20 a barrel of oil, and plants with capacities of 10 to 100,000
barrels a day have either been built or designed.)
Another liquid fuel that can be produced in a natural gas refinery is methanol.
Methanol is itself a high-octane fuel used in racecars, and it is sulfur free. It can
be reformed readily to hydrogen and carbon dioxide, and the hydrogen can be
used for fuel cells. Direct methanol fuel cells convert methanol into protons, free
electrons, and carbon dioxide, thus providing a safe and simple-to-use energy
source.2 The byproducts of this type of fuel cell steam and carbon dioxide-
are produced in such small amounts that these fuel cells are particularly environ-
mentally friendly. However, methanol, while readily degradable, presents prob-
lems. It has half the energy content of gasoline on a per-volume basis and has a
much higher acute toxicity than gasoline. To use methanol as a common fuel
would require modifications in the storage and delivery infrastructure.
An alternative to methanol that possibly may be more attractive is dimethyl
ether, which is produced by coupling two methanol molecules. Dimethyl ether
provides a good substitute for liquefied petroleum gas. It burns very cleanly, it is
a high-cetane sulfur-free smokeless diesel fuel, it can be easily reformulated to
hydrogen and carbon dioxide, and it can readily be converted to gasoline using
zeolites. Balanced against these benefits is the fact that dimethyl ether is very volatile
and, similar to methanol, would require a new storage and delivery infrastructure.
Biomass presents another option for mitigation of carbon dioxide in the
atmosphere. The basic concept is to grow plants to provide cellulose that can be
converted to ethanol with known technology and then concentrate the ethanol
produced up to 100 percent and use it as a fuel. It is estimated that use of biomass
could be a carbon dioxide-neutral technology, meaning that as much carbon dioxide
is consumed as is returned to the atmosphere. It has been estimated that there is
sufficient land mass available in the United States to replace the 1.3 x 10~i gallons
per year of gasoline used in 20003 without substantially impacting land other-
iG.N. Choi, S.J. Kramer, S.S. Tram, J.M. Fox III. July 9-11, 1996. "Economics of a Natural Gas
Based Fischer-Tropsch Plant." First Joint Power and Fuel Systems Contractors' Conference. Pitts-
burgh, PA.
2One issue to consider with direct methanol fuel cells is their relative efficiency compared to indi-
rect methanol fuel cells. Direct methanol fuel cell anode catalysis is currently poor and requires a high
overpotential. When comparing an indirect methanol fuel cell (reforming of methanol to hydrogen
and carbon dioxide, feeding the hydrogen to a fuel cell) and a direct methanol fuel cell, the efficiency
on an indirect methanol fuel cell system is much higher, thus the carbon dioxide emissions are lower.
3"Worried Drivers," ExxonMobil Corporation, Houston, TX, 2001.
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ENERGY AND TRANSPORTATION
wise used for agriculture. As with other fuels, ethanol would require change in
the fuel infrastructure.
Hydrogen
Hydrogen in many respects may be the ultimate fuel. It is completely carbon
free and sulfur free. It can be used for spark injection engines and can be com-
bined with natural gas and burned in such engines as well. It is an ideal fuel for
fuel cells, although problems with storage and distribution would require an
entirely new infrastructure.
There are a number of significant issues regarding hydrogen production and
bringing it to market. Current technology requires a high water-to-methane ratio
to avoid carbon deposition on the catalyst used for the reforming of methane.
Electrolysis of water is an alternative, but if carbon-based fuels are used for elec-
tricity generation, double the amount of carbon dioxide is produced per mile when
compared to gasoline. Photovoltaic generation of hydrogen is attractive, but the
silicon technology required for making energy through electrolyzed water is at
present prohibitively expensive.
The use of fuel cells running on hydrogen produced by the reforming of a
liquid fuel has been much discussed as a fuel-efficient means of powering auto-
mobiles. While this technology has been demonstrated, approximately 100 to 150
grams of noble metal principally platinum would be required per car using
present technology. For reference, this is two orders of magnitude more precious
metal per car than is required for the catalytic converter. Since at present roughly
one half to one third of the world's supply of precious metals is being put into
automobiles for use in automotive conversion technologies, it is hard to envision
fuel cells as a widespread alternative for automobiles unless the requirements for
precious metals can be reduced by one to two orders of magnitude, or other cata-
lytic approaches are developed that do not require the use of precious metals.
An additional challenge to the use of fuel cells for automobiles is response
time. Currently, fuel cells have a response time of 15 seconds from 10 percent
power to 90 percent. In order to be viable, this response time must drop to 1 sec-
ond. Because they require liquid water to operate, a further challenge is to operate
fuel cells in subfreezing temperatures. In addition, the current cost per kilowatt-
hour for fuel cells must be reduced from $300 down to $45.
OPPORTUNITIES FOR THE CHEMICAL SCIENCES
To meet the challenges discussed above, research opportunities for the chemi-
cal sciences may be envisioned in four areas. First, in carbon dioxide sequestra-
tion, an understanding is required regarding how molecular carbon dioxide inter-
acts with various species present in coal mines or other geological formations
where carbon dioxide might be stored. It is particularly important to understand
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RESEARCH OPPORTUNITIES AND CHALLENGES IN THE ENERGY SECTOR 17
carbon dioxide flow in permeable underground formations, as well as the geology
and geochemistry of these formations, to ensure that large amounts of carbon
dioxide do not escape back into the atmosphere.
In order for methane to be used for energy, a number of developments must
take place. New catalysts for the conversion of methane to oxygenated products
are needed, particularly for transformation of methane to formaldehyde or
methanol without first converting methane to syngas. Highly effective catalysts
are also required to lower the reaction temperature and increase overall efficiency.
Photovoltaics also require significant research activity in the chemical
sciences. Low-cost methods are required for producing solar-grade silicon for
photovoltaic cells. Better solar cell materials are needed than the presently uti-
lized amorphous silicon. These materials must be more efficient without the use
of heavy metals such as cadmium, tellurium, indium, and lead, which present
significant environmental issues. An understanding of the degradation process of
photovoltaic cells is needed, as is an answer to why these materials lose their
effectiveness after prolonged exposure to the sun. Finally, there is a need to
develop catalysts for the efficient photochemical conversion of water.
A fourth area for research opportunities is in the development of fuel cells.
There is a need to develop electrode materials for methanol-based fuel cells. This
would allow for the use of liquid fuel directly without a reformer. Less expensive
alternatives to Nation are required for fuel cell membranes. Rapid-response
onboard reformers are also needed for potential use in conjunction with the fuel
cell to convert liquid fuel to hydrogen.
Requirements to Achieve these Goals
In order for the chemical sciences to take advantage of the research opportu-
nities outlined above and to achieve the goals set, two major requirements must
be met. First, public policies must be set that signal the need for development and
deployment of new technologies in the energy sector that meet four criteria:
and
1. Technologies that are carbon efficient;
2. Technologies that enable carbon dioxide sequestration;
3. Technologies that enable the use of natural gas to produce liquid fuels;
4. In the longer term, technologies that enable the use of biomass, solar
energy, and renewable sources of energy in general.
A second major requirement is a major commitment toward federal support
for energy-related research. In the 13-year period from 1985 to 1998, real dollar
U.S. investment in energy research dropped 36 percent. Worldwide there was a
33 percent drop. This commitment should not be a short-term one lasting 1 to 2
years but rather a sustained investment over several decades.
Representative terms from entire chapter:
natural gas
