Karen Knewtson
Hydrogen as an Alternative Fuel
Due to the rising cost and depleting supply of fossil fuels the Department of Energy has implemented
the Hydrogen Posture Plan to explore a cost effective and environmentally friendly fuel source. In 2004
President Bush proposed a 1.2 billion dollar hydrogen fuel initiative for research and development in order to
accelerate technology and development in alternative fuels. The hydrogen program supports a parallel
advancement in hydrogen fuel cell technology along with hydrogen production delivery system. The program
describes plans for developing solar and wind- based hydrogen production technologies. The goal is to
incorporate hydrogen as a sustainable primary fuel source for major transportation by 2040.
While hydrogen is renewable and the most abundant element on earth it must be produced. Currently
there are three ways being explored to produce hydrogen sustainably without carbon emissions. Electrolysis is a
process of placing two electrodes in a liquid and running direct current across them, thus separating the oxygen
and hydrogen. There are two different forms of solar conversion, thermolysis and photolysis. Neither one
emitting carbon based molecules. The most promising and economically beneficial solution is biomass
gasification. This is when biomass is subjected to high temperature and pressure in order to reduce the organic
materials to hydrogen and subsequent carbon monoxide and dioxide gases. This process is affordable and
feasible in the short-term.
Because hydrogen takes four times more volume than kerosene for the same energy value, large tanks
must be installed on the aircraft. Because of the cryogenic state of liquid hydrogen the tanks cannot be in the
wings due to the large surface area to insulate. Installing the tanks in the top portion of the fuselage is the most
practical even with the 9-14% energy loss because the fact that liquid hydrogen is lighter than kerosene means
that there is no substantial loss in payload.
Research shows that hydrogen is just as safe as kerosene so no huge regulatory actions need to be taken
due to the new fuel. Because the tanks are installed above the passengers any leaking gas will automatically rise
due to the atomic weight of hydrogen being so light. Transportation of hydrogen to airports as well as storage
and refueling system are going to require a new infrastructure to include new insulated electric fueling trucks
and insulated tanks. Transportation of hydrogen can be done in both gaseous and liquid state. Europe already
has a working hydrogen infrastructure of more than 880 km of active pipelines. Germany has an active hydrogen
pipeline 50 kilometers long that has been transporting hydrogen at 2Mpa for 50 years without incident. So while
it will take time and money, it is feasible and safe for the long run.
Due to the necessity of design modifications to the gas turbine engine, there are several companies now
racing to modify the turbine to use hydrogen as an alternative fuel source. General Electric is working on a
combustion housing designed to withstand the higher firing temperatures and higher moisture content that are
needed to reach the efficiency level desired for the transition to hydrogen. Along with the change in the design
of the can the fuel nozzles have new configurations to compensate for the pressure changes. They are
developing special alloys specifically tailored to withstand the temperature and pressure differences that come
with using hydrogen as a primary fuel source.
Because of the variations of volume flow rate, the use of hydrogen affects the original design match
between the compressor and expander originally designed for natural gas. Hydrogen has a higher heating value
but a lower molecular mass therefor making it impossible to be operated in the same parameters and running
point as natural gas. Compressor design changes include using variable geometric guide vanes in several starter
rows of the axial type compressors, adding more rows and tighter tip clearances for the high pressure ratio
compressor.
Along with the higher temperatures and pressures come issues with cooling and sealing. In order to
maximize efficiency a very aggressive cooling airflow must be created. The shape of the airfoil will need to be
changed as well as the size. These needed changes are still in a state of collaboration and design, many with
major universities. Likewise to compensate for the increase in temperature and pressure in the hot section,
feasibility studies and collaborative programs are in place to address the problems with leaking before
development and testing actually take place.
Due to the specific characteristics of liquid hydrogen the fuel system needs a complete redesign from
the conventional kerosene system. Similar to conventional aircraft a feed tank will be installed in the wing for
each engine. All fuselage mounted liquid hydrogen tanks will keep the wing mounted feed tanks full. From the
feed tanks the hydrogen will pass through high pressure pumps and before heading to the injector nozzles must
pass through a heat exchanger. The heat exchanger is needed to raise the temperature of liquid hydrogen at 20K
to gaseous hydrogen at 150K after which it can be injected into the combustion chamber. Research has shown a
need for a return line to the feed tank to avoid high pressure fluctuations and cavitations in the engine fuel lines.
The development of hydrogen powered commercial aircraft has a long way to go before it will evolve
into the primary fuel source, if it even will. This is only a very brief overview of what might be the norm in the
world of aviation by 2040. I am looking forward to one day working on hydrogen powered aircraft and I am
excited to see this major push away from fossil fuels and pollutants and hope we can make this happen.
General Electric Project Plans
Airbus Proposed Hydrogen Cryoplane
Works Cited
1.Bancalari, Ed, Pedy Chan, and Ihor S. Diakunchak. "siemens.com." ADVANCED HYDROGEN TURBINE
DEVELOPMENT. Siemens Power Generation Inc.,, n.d. Web. 23 Sept. 2012.
<www.energy.siemens.com/co/pool/hq/energy-topics/pdfs/en/igcc/6_Avanced_Hydrogen.pdf>.
2."energy.gov." Hydrogen Posture Plan. United States Department of Energy, 1 Dec. 2006. Web. 23 Sept. 2012.
<www.hydrogen.energy.gov/pdfs/hydrogen_posture_plan_dec06.pdf>.
3.van Zon, Nout. "noutvanzon.nl." Liquid Hydrogen Powered Commercial Aircraft. N.p., n.d. Web. 23 Sept. 2012.
<www.noutvanzon.nl/files/documents/spaceforinnovation.pdf>.
4.Bradley, Tim, and Joseph Fadok. "ADVANCED HYDROGEN TURBINE DEVELOPMENT UPDATE." seimons.com.
Siemens Energy, 12 June 2009. Web. 25 Sept. 2012. <www.energy.siemens.com/us/pool/hq/powergeneration/power-plants/integrated-gasification-combined-cycle/Advanced-h2-turbine-developmentupdate.pdf>.
5.Chiesa, Paolo, Giovanni Lozza, and Liugi Mazzicchi. "Using Hydrogen as a Gas Turbine Fuel." doe.gov. Journal of
Engineering for Gas Turbines and Power, n.d. Web. 25 Sept. 2012.
<www.netl.doe.gov/technologies/coalpower/turbines/refshelf/igcc-h2sygas/Using%20H2%20as%20a%20GT%20Fuel.pdf>.
6."Recovery Act: Advanced Hydrogen Turbine Development." doe.gov. General Electric, n.d. Web. 1 Oct. 2012.
<www.netl.doe.gov/publications/factsheets/project/NT42643.pdf>.