Question: How can we design, operate, and power aircraft to reduce the climate impacts of aviation?
Submit proposals: https://www.climatecolab.org/contests/2016/aviation
Deadline: Monday, May 23, 2016 at 19:00:00 PM Eastern Time
Judging Criteria & Prizes: See below.
Aviation emissions contribute to changing the energy balance between incoming and outgoing radiation in the atmosphere, or the so called radiative forcing (RF) of climate. The emissions that are of most importance from a climate mitigation perspective are carbon dioxide (CO2), nitrogen oxides (NOx) and the increased cloudiness in the form of persistent linear contrails and induced cloudiness. Background on each is provided below. There are additional emission species that contribute to radiative forcing such soot, water, and sulfates into the atmosphere, as shown in the figure below, however CO2, NOx and contrail impacts are the key players to tackle.
CO2 - Aircraft use a significant amount of fuel on a typical journey and CO2 emissions due to fuel burn are the most significant and well-understood out of all the environmental impacts. Interestingly, aviation emissions per passenger-km are of a similar order to those from cars at ~50 g C per passenger-km. However, given the predicted growth rate of the aviation industry compared to the automotive industry, reducing aviation’s CO2 emissions is critical to reducing its long term environmental impact. Given that CO2 remains in the atmosphere for around 100 years, it is important to reduce emissions now to reduce the accumulation of CO2 over a long period of time
NOx - The production of NOx is particularly prevalent at the high temperatures and pressures in the combustor of aircraft engines. However, the efficiency of gas turbines increases with combustor temperatures. There is thus a trade-off between increasing NOx emissions and decreasing CO2 emissions. Aircraft are estimated to have emitted 2.7 Tg of NOx in 2005, almost double of that emitted in 1992. Despite improvements in NOx reduction technologies, the expected growth rate of the industry means that NOx emissions are expected to increase to 13 Tg/year by 2050. Overall aircraft NOx has been found to have a net warming impact on the environment. In addition to the climate impacts, NOx emissions are responsible for the majority of aviation’s air pollution (air quality) impacts.
Contrails - Contrails are line-shaped ice clouds produced by the aircraft engine exhaust when ambient temperatures are below a critical level. They can persist, and therefore have a potentially large warming effect, if they remain within ice supersaturated (ISS) regions of air. While CO2 emissions will always remain the dominant long-term climate forcer, the presence of contrails and contrail cirrus also plays a critical role, despite having a comparatively short-term effect (hours compared with decades to centuries). Studies have shown that aviation CO2 emissions contributed around 36% of aviation induced radiative forcing in 2005, while contrails contributed ~30%. Therefore, mitigating or controlling contrail impact on the environment is potentially as important as reducing aircraft CO2 emissions.
Aviation: the challenges and opportunities
Like other uses of fossil fuels, aircraft emit CO2, NOx, soot, water, and sulfates into the atmosphere, all of which can impact the earth’s energy balance. Moreover, because of the altitude at which the emissions are deposited, the effects on the climate can be accentuated, especially through the formation of contrails and high altitude cirrus clouds. Aviation emissions currently account for up to 5% of direct anthropogenic radiative forcing (energy imbalance), and this percentage is expected to increase to up to 15% by 2050.
The aviation industry itself is constrained by the inherent long timelines of design, production and fleet penetration of an aircraft. For example, the design of the Boeing 747 began in the 60s, it entered service in the 70s, and some versions of it are not only still flying today, but still getting produced. The long aircraft life implies that the turnaround time for introducing new, green technologies is slow. Significant effort is thus invested in altering the operations of the aircraft, which has a direct, albeit small, impact. Additionally, design of conventional aircraft is nowadays mostly optimized, with any additional significant effort only reducing aviation’s climate footprint by a few decimals of a percent.The use of alternative fuels, such as biofuels, is one option, although this has indirect implications for the climate in terms of land use change and of energy needed to process the fuel.
All in all, this is difficult problem without an obvious solution. A breakthrough is needed in the way we envision aviation, and we are welcoming ideas that will contribute to that.
The US Federal Aviation Administration (FAA) has set an industry goal for carbon neutral growth from 2020 onwards. Given the rate of increase of the industry and the number of flights, technological advances are not expected to ensure the neutral growth. Given the long timescales involved with introducing major changes to the aviation industry, there are two ways to approach this. First, we look for short-term mitigation options to reduce environmental impact today or in the near future, and second, for long-term options to revolutionize the industry.
Short term concepts - these are ideas that may be adopted and have an impact within the next 5-10 years. Potential concepts may include, but are not limited to:
- Contrail mitigation strategies
- Improved aircraft ground and in-flight operations to minimize environmental impact
Long term concepts - these are ideas that would involve revolutionary changes to the industry. They are significantly more difficult to implement, however could have a considerable improvement in reducing aviation’s environmental impact. Potential concepts may include, but are not limited to:
- Solar Aircraft
- Electric Aircraft with wireless power transfers
- Alternative Designs such as the Double-Bubble concept
- Hybrid Engine Technology
- Regenerative Braking
This contest seeks the following:
- Novel concepts or breakthrough technologies for reducing aviation’s climate footprint (the contest is designed to be open-ended so as to allow any creative, yet realistic, idea)
- Ideally, a mix of ideas that can tackle long-term, short-term or even both impacts.
- Proposals that are accompanied with an estimate of the climate impacts benefit (in terms of emissions (or equivalent) ‘avoided’ or fuel saved)
- Innovative, out-of-the-box concepts that may positively impact the industry
Contest entries can be in the form of the following:
- Technical solutions
- Operational and regulatory/monetary-based solutions
Proposals can be at any stage of development:
- Well thought-out ideas that require additional research or planning
- Comprehensive strategies that are ready for prototyping or implementation
- Initiatives that have already achieved success and are ready to be scaled
Top proposals in each contest will be awarded...
Judges’ Choice Winner – Strongest overall
Popular Choice Winner – Received the most votes during the voting period
Impact Award – Largest impact and highly feasible
Novelty Award – Most innovative
The Judges’ and Popular Choice Winners will be invited to MIT to present their proposal, enter the Climate CoLab Winners Program and be eligible for the $10,000 Grand Prize. All award winners will receive wide recognition and visibility by the MIT Climate CoLab.
All Finalists are asked to submit a 3-minute video outlining their proposal. Videos will be featured on the MIT Climate CoLab website and Winners will show their videos at the conference.
If your proposal is included in a top global climate action plan, you will receive CoLab Points, which are redeemable for cash prizes.
Resources for Proposal Authors
Aviation IPCC special report https://www.ipcc.ch/pdf/special-reports/spm/av-en.pdf.