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Economy
and society today are characterised by a high degree of mobility, and
indeed depend upon it. Without the free and cost-effective movement of
products and people, our global economic system would simply not work.
Demand for air transport is currently increasing by some 4 to 5% per year
and expectations with regard to the availability of efficient transportation
will undoubtedly continue to grow, especially in the newly emerging economies
of Asia and South America.
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While air
traffic has been on the increase for many decades now, the sustainability
of its growth is uncertain under today's technical conditions. Since the
Earth Summit held in Rio de Janeiro in 1992, the need to reduce carbon
dioxide emissions has been widely accepted, and at the Kyoto summit on
climate change in 1997, industrial countries agreed to reduce their emissions
by 5.2% by 2008/2012. Despite the stern warnings issued at these global
summits and subsequent measures to redress environmental degradation,
fossil fuel resources will eventually run out of their own accord.
Under such conditions, it is evident that improvements in conventional
aircraft and engine technology and in the efficiency of the air traffic
system will not fully off-set the effects of increased emissions resulting
from the projected growth in aviation.
 Search
for an alternative fuel |
Of
the possible alternative energy carriers, liquid hydrogen, currently
in use in rocket boosters and in some experimental land vehicles,
would seem to be among the most suitable for use in aircraft. It can
be produced from water by electrolysis using electrical energy from
renewable resources, and it releases only water and very small amounts
of nitrogen oxides upon combustion.
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With
that in mind, 35 partners from 11 European countries, representing
industry, research entities and universities have come together in
a comprehensive "system analysis" of liquid hydrogen fuelled
aircraft. According to project co-ordinator Heinz Guenter Klug of
EADS Airbus, all
of the partners, big and small, are playing important roles in what
he hopes will be a long-awaited success. Dubbed CRYOPLANE, the project
will assess the technical feasibility, safety, environmental compatibility
and economic viability of using liquid hydrogen as an aviation fuel.
Among the goals are the delineation of aircraft configurations for
all categories of commercial aircraft, from business jets to A3XX-type
very large long-range aircraft, as well as new concepts. Performance
and fuel efficiency will be quantified. The architecture of the new
liquid hydrogen fuel system and its potential synergies with other
aircraft systems will be assessed. New engine concepts will be defined,
with emphasis on minimising nitrogen oxide emissions. Aircraft-specific
safety aspects will be studied and a hydrogen-specific fire protection
system will be elaborated.
Finally, and perhaps most importantly, the CRYOPLANE project will
attempt to indicate possible strategies for making a smooth transition
to the new fuel. Airport infrastructure for fuel production and distribution
will be considered and ground and flight operations will be analysed. |
| An
unusual aircraft configuration |
| Four
litres of liquid hydrogen are required to store the same amount
of energy contained in just a single litre of kerosene. The necessarily
large volume of fuel will therefore require changes in the configuration
of the aircraft. In addition, holding tanks for liquid hydrogen
have to be either spherical or cylindrical in shape. Tanks on top
of the fuselage are a possible solution for big passenger aircraft.
The high-energy content of the new fuel in relation to its weight
will allow an increase in the payload fraction of the aircraft.
Safety can be expected to be at least equal to, and in certain respects
even significantly better, than that of kerosene-fuelled aircraft. |
| No
change without incentives |
| The
development of air traffic within a specific country depends in
large part on its economic power. In 1996, the USA, with only 4.6%
of the world's population, generated 41% of the world's air traffic,
while China and India with 37% of world population contributed only
3.4%. Thus, there is still a huge potential for growth in global
air traffic and, given the environmental constraints already mentioned,
someone is going to have to step in and close the gap.
The transition from fossil fuels to liquid hydrogen will not be
an easy one, says Klug. Liquid hydrogen is expensive to produce
and operators are likely to resist making the switch if there are
no convincing economic reasons to do so. The new aircraft will have
to be accompanied by new emission regulations, depending on how
it is decided to implement the Kyoto agreement. An emission charge,
for example, could provide the economic motivation for switching
to clean energy sources. While this need not make the cost of buying
a plane ticket prohibitively more expensive, it will provide the
incentive to airline operators.
Once the system analysis is complete, technology development and
ground and flight testing are expected to take at least 10 years.
For
more information on EADS and CRYOPLANE see: http://www.eads.net/eads/fr/index.htm |
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| Key
data
Funding
provided under the New perspectives in
aeronautics key action is pushing forward the search for alternatives
to fossil fuels. The aircraft industry is likely to gain from
research into liquid hydrogen fuel, helping it keep up with increasing
demand while meeting the need for greater environmental protection.
Project: CRYOPLANE
- Liquid hydrogen fuelled aircraft - system analysis |
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