In this method, natural gas is used as the feedstock. Waste or natural gas that cannot be marketed is partially oxidized into CO and H2 gases. This synthesis gas is then supplied to a synthesis unit to similarly produce a liquid fuel. The development of synthetic jet fuels to augment petroleum fuels is becoming reenergized with the U.S. Government's Total Energy Development (TED) program. The technical hurdles for a pure synthetic jet fuel are not insurmountable, but manufacturers and regulatory agencies will still need to evaluate and test these fuels before approving them for unlimited use. (Daggett, Hendricks, Walther and Corporan, 2008)
The work of Altman (2007) entitled: "Alternative Fuels in Commercial Aviation: The Need, the Approach, Progress" states that the commercial need drivers for alternative fuels are those of: (1) price; (2) availability; (3) energy independence; and (4) environmental issues and (5) the need to meet safety specifications. (Altman, 2007)
Stated as well is a need for the commercial aviation alternative fuels initiative to work together with DoD/DOE to pursue alternative fuels for the purpose of: (1) securing a stable fuel supply; (2) furthering research and analysis; (3) quantifying the ability to reduce environmental impacts; and (4) improving aircraft operations. (Altman, 2007)
Altman (2007) states that alternative aviation fuel options identified for consideration are the following: (1) Near-Term (0-5 years) -- Fischer-Tropsch fuel from coal; (2) Mid Term (5-15 years) - oil shale and other HC:LNG, ethanol blends, and biodiesel; hydrogen for fuel cells in APUs; and (3) Far Term (15+ years) -- Biomass: black liquor fuels; and hydrogen fuel for turbine engines. (Altman, 2007)
Stated as the need for alternative fuels in aviation is the supply of stability for operators. Stated as the approach for alternative fuels in commercial aviation is the United Aviation Supply Chain via CAAFI process. Progress for commercial aviation use of alternative fuels is near-term FT qualification, long-term renewables, and always environmental gains. (Altman, 2007) the following three charts, labeled Figure 1 and Figure 2 in this study list the development and qualification status of Fischer Tropsch Derived Aviation Fuels and Sason Fully Synthetic Aviation Fuels respectively.
Figure 1
Fischer Tropsch Derived Aviation Fuels: Development and Qualification Status
Source: Altman (2007)
Figure
Sason Fully Synthetic Fuel: Development and Qualification Status
Source: Altman (2007)
The following illustration has been adapted from the work of Altman (2007) in his factsheet concerning the environment of alternative aviation fuels.
Figure 3
Aviation Fuel Alternatives/Environment
Source: Altman (2007)
Altman states in his alternative fuels environment analysis a specified full life cycle assessment process which is related in the following adapted illustration of Altman (2007) labeled Figure 4 in this study.
Figure 4
Source: Altman (2007)
The Alternative Fuels Roadmap as cited in the work of Altman lists the following goals for alternative fuel use in aviation.
Figure 5
Alternative Fuels Roadmap
Source: Altman (2007)
It is reported by the NASA Glenn Research Center in the work entitled: "Early Demonstration Opportunities for Electric Propulsion & Power" that current gas turbine APUs operate at ~15% load cycle efficiency, contribute up to 20% of the aircraft ground-based emissions, and APU/secondary power systems account for 50% of the maintenance...
(Liang, nd)
Major challenges cited by NASA for implementation of alterative fuels in aviation include those of: (1) ultra high energy density power source; (2) fuel cell stack configuration; (3) fuel processing & reforming; (4) thermal management; (5) nano, light material systems; (6) high voltage power & control; and (7) multidisciplinary CFD. (Liang, nd)
Current NASA activities are stated to include those as follows: (1) Develop compact, lightweight, and efficient jet-fuel processing technology to enable near-term application of SOFCs to aircraft power systems with collaboration from DOE: (a) obtain a fundamental understanding of SOFC reforming process and to access SOFC and system integrators for technology advancement, performance system optimization; and (b) identify and characterize promising candidate hydrocarbon fuels by developing a fundamental data base of chemical kinetic reaction rates and high temperature characteristics; (2) Improve SOFC material capabilities to meet aircraft performance, size, weight and life requirements: (a) improve power density through a combination of reducing anode thickness by a factor of 10-15 and reducing electrochemical losses by developing new and improved cathode material; and (b) improved, durable high temperature seal. (Liang, nd) the following illustration labeled Figure 5 in this study shows NASA's vision for fuel cell powered aircraft.
Figure 5
NASA's Vision for Fuel Cell Powered Aircraft
Source: Liang (nd)
Summary & Conclusion
Presently the alternative fuel initiatives are pressing forward in hopes of use of these fuels in the near- mid- and long-term and in various phases of implementation and geared toward sustainability and profitability of commercial aviation. Driving these initiatives are factors of price, availability, energy dependence, environmental issues and the need to meet safety standards.
Bibliography
Altman, Richard L. (2007) Alternative Fuels in Commercial Aviation the Need, the Approach, Progress. 32 ndAnnual FAA Forecasting Conference Commercial Aviation Alternative Fuels Initiative Friday, March 16, 2007. Online available at: http://www.faa.gov/news/conferences_events/aviation_forecast_2007/agenda_presentation/media/9-%20Rich%20Altman.pdf
Daggett, David L., Hendricks, Robert C., Walther, Rainer, and Corporan, Edwin (2008) Alternate Fuels for Use in Commercial Aircraft. NASA STI Program. Online available at: http://gltrs.grc.nasa.gov/reports/2008/TM-2008-214833.pdf
Kemp, Rene (nd) Technology and the Transition to Environmental Sustainability: The Problem of Technological Regime Shifts. Futures Journal. Online available at: http://kemp.unu-merit.nl/docs/FUTURES2.pdf
Liang, Anita (nd) Emerging Fuel Cell Developments at NASA for Aircraft Applications. Aeropropulsion Projects Office NASA Glenn Research Center. Online available at: http://www.netl.doe.gov/publications/proceedings/03/seca/Anita%20Liang.pdf
