|Aviation and the Global Atmosphere|
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22.214.171.124. FESG Technology Projections
Calculations of fuel burned and NOx emissions produced by the 2050 scheduled fleet were made by applying projections of overall improvement in fleet fuel efficiency and emission characteristics to regional traffic flows and summing the results. These projections were created from technology-level estimates for new aircraft over time made by a working group of the International Coordinating Council of Aerospace Industries Associations (ICCAIA) (Sutkus, 1997); they are discussed in Section 7.5.5. A "fleet rollover" model was used to project a fleet average fuel efficiency trend, using characteristics of the present-day fleet and traffic demand from the FESG scenarios (Greene and Meisenheimer, 1997). The ICCAIA projections were made for two technology scenarios. The first scenario assumes that fuel efficiency and NOx reduction will be considered in the design of future aircraft in a manner similar to the current design philosophy. The second technology scenario assumes a more aggressive NOx reduction design strategy that will result in smaller improvements in fuel efficiency. The assumptions associated with the two technology scenarios are given in Table 9-11. The basis for projections of aircraft emissions made by FESG for the year 2050 was the 3-D NASA emissions scenarios for the year 2015 discussed in Section 9.3.2. The NASA 2015 emissions inventory was factored on the basis of the product of the ratios of regional traffic (as departures), fleet fuel efficiency, and fleet EI(NOx) as calculated for 2050 over the same values in 2015. For all flights in a given region:
Figure 9-18 shows the trend for average new production and fleet average fuel efficiency as a function of time, derived from ICCAIA inputs and the fleet rollover model for the FESG high-demand traffic growth scenario. The average NOx emission index for the scheduled fleet over the same time period is shown in Figure 9-19. The 2050 fleet average values used in the calculation of emissions from scheduled traffic as well as the baseline 2015 value are given in Table 9-12 (Sutkus, 1997). Fleet fuel efficiency is predicted to improve by about 30% between 2015 and 2050. Traffic in the FSU and the People's Republic of China has not historically been reported in airline schedule databases such as the OAG. Fuel burned and emissions from aviation in these regions were estimated individually and projected to 2015 (Mortlock and Van Alystyne, 1998), then extended to 2050 (CAEP/4-FESG, 1998).
Results of calculations of fuel burned and NOx emissions for the year 2050 based on the long-term scenarios described above are given in Table 9-13. The FESG complete scenarios are identified below and in the remainder of this chapter by combining the demand scenario (e.g., Fa) with the technology scenario number (e.g., Fa1, Fe2).
The DTI projection for air traffic and emissions for 2050 (Newton and Falk, 1997) has been developed from the DTI traffic and fleet forecast demand model, in conjunction with data from the ANCAT/EC2 inventory. The forecast model was developed from DTI's global and regional traffic forecast models for passenger and freight traffic. Fuel consumption trends were estimated with a fleet fuel efficiency model, and fleet emissions performance were estimated on the basis of assumed regulatory change. Finally, appropriate fuel and emissions factors were calculated to estimate 2050 figures from the base year; these factors were then applied to the 1992 ANCAT/EC2 emissions inventory to produce gridded results for the 2050 scenario.
The DTI model relates air traffic demand in RPKs with regional and global economic performance as reflected in GDP trends, as was the case with the ANCAT/EC2 2015 forecast. Generally, a load factor of 70% is assumed to estimate ASKs (capacity) from traffic demand. Long-term traffic demand is also assumed to be modified by the same assumptions on fares pricing, market maturity, and so forth that the ANCAT/EC2 2015 forecast used. Capacity estimates are converted to fuel consumption estimates by using the concept of traffic efficiency as described in Section 9.3.2 and a fuel efficiency trend for the scenario period. Model coverage includes all global aviation markets, but separate fuel consumption estimates are made for freight and for the FSU on the basis of aligning growth with global civil passenger market trends.
The scenario modeled for 2050 assumes that sufficient aviation infrastructure would be available to accommodate the forecast increase in traffic. No new city pairs are introduced during the scenario period, and aircraft flight profiles remain unaltered from the present day; altitude, speed, and method of operation are assumed to be the same as present-day values, even for larger aircraft types (600+ seats) that are assumed to enter service beginning in about 2005. All traffic is assumed to be carried by a subsonic aircraft fleet (i.e., no HSCT would be operating by 2050). The model forecasts traffic growth to be positive throughout the scenario, but growth rate declines during the period. Decadal capacity growth rates-actual and forecast-are given in Table 9-14. The traffic forecast includes civil and freight operations as well as civil charter and business jet traffic but excludes military aviation activity and possible future supersonic operations.
Fuel usage was determined for the base year fleet from the capacity offered in that year (ASKs) and the fleet's traffic efficiency (ASK per kg fuel). A fuel efficiency trend suggested by Greene (1992) and modified by DTI was included as a scenario parameter, as given in Table 9-15.
The traffic efficiency of the fleet over the scenario period was estimated to range from 30 ASK kg-1 in the base year 1992 to 48 ASK kg-1 in 2050 (a 60% improvement). This estimate was based on the performance of existing aircraft types and forecasts of the type and number of aircraft (categorized by seat band and technology level) that might be flying in 2050. Future aircraft types included size developments to 799 seats.
A major scenario element was the NOx reduction technology assumption. Current technology will allow engines to achieve reductions of around 30% below the current certification level (CAEP/2 standards). The basis of the technology scenario was that NOx regulations would be made considerably more stringent than today and that the manufacturing industry would develop appropriate technology solutions. This development was modeled by assuming that from 1992:
With a fleet development trend determined by the capacity forecast, the rate of introduction of the scenario above implies a global fleet emissions index trend that is as compatible with the relatively modest fuel efficiency assumption given in Table 9-16. The fleet EI(NOx) of 7.0 implies widespread use of ultra-low NOx technology (Section 7.5). The total calculated fuel burned and emissions for 2050 under the DTI/ANCAT scenario are given in Table 9-17.
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