Air transport is responsible for two to three percent of global carbon dioxide emissions, and has also contributed to the steady increase in other air pollutants such as nitrogen oxides and sulfur dioxide. In the United States, aircrafts emission has increased 17 percent since 1990, and without further advancements in environmental friendly aviation technology, researchers estimate a 43 percent rise in NO emissions by 2035. And, of course, these statistics reflect devastating consequences. Ten thousand people die every year due to airplane exhaust, which cause cardiovascular and respiratory diseases and infections. With growing concern over the effects of air travel pollutants, research upon improving aviation technology has increased significantly in recent years.
An emerging technology is the Hybrid Electric Propulsion System (HEPS), which combines conventional combustion engines with an electrically-fueled method. In order to effectively integrate and reduce the possibility of failure, many studies have developed energy management strategies, such as various configurations and system designs. In addition, newly discovered advancements have been included as Harmon et al. from the University of California-Davis did by applying the concept of neural network control to the system to optimize energy efficiency. For small-scale, mid-scale, and large-scale aircrafts, researchers developed distinct strategies, each having certain advantages and disadvantages, and their respective maximum payload, seats, and flight time varied. Despite the fact that they had made an arduous effort, it seems very challenging for them to create feasible designs.
Figure 1: MIT’s new hybrid-electric plane design with the emissions control system.
Source Credit: MIT(LINK)
MIT, however, revealed that their hybrid-electric plane design has no significant fundamental physics limitations compared to previous studies, and that its system is quite viable with the addition of another concept called the emissions control systems, a setup that filters the exhaust. While researching the Volkswagen emissions cheating scandal—an incident in 2015 of car manufacturers turning on the emissions control systems only during lab testing to merely pass the NO emission standard—they became interested in the emission control systems and how they are used in diesel trucks to eliminate nitrogen oxide emissions. Combining the idea with hybrid electric propulsion seemed to provide two environmental advantages: reduction in use of fossil fuels and less harmful chemical released from exhaust.
However, in current aircrafts, jet engines are beneath each wing with a gas turbine that is directly connected with the propeller. Due to the fact that their exhaust is pushed out to the back of the aircraft, MIT engineers could not attach the emissions control systems for they would significantly block the thrust produced. As a solution to this problem, the team suggested placing the gas turbines in the plane cargo hold. Then, instead of them directly powering the propellers, would drive a generator, which would also be repositioned in the cargo hold. Now, applying hybrid propulsion, specifically in the form of series configurations, the electricity produced from the generators would power the propellers or the fans. The emissions control system will also be located in the cargo hold, and the exhaust from the turbine would be filtered without issues. MIT revealed that this newly developed system can reduce the amount of NO emissions by 95 percent and possibly contribute to the decrease in associated diseases and early deaths by 92 percent.
Not only does HEPS help reduce pollution, but it can help sustain natural resources with its use of electricity. Indeed, a total electric system is more favorable in terms of being eco friendly, but there is a reason for this semi-electrified plan: battery weight. Compared to a volume of fuel that can provide the same amount of energy, the electric motors require batteries that are 30 times heavier. For small planes flying a short distance, this implementation might be possible, but for large planes that need to carry passengers as well as the batteries, they might have problems taking off due to its weight. However, with ongoing developments in battery technology, it will not be long until this system will be finalized, allowing us to fly green.
Q&A:
Jiwon: You briefly mentioned the Volkswagen’s emissions cheating scandal. For what reason did the scientists only turn on the emissions control system during lab testing, and what exact environmental impacts did this action have?
- They only turned on the system to meet the NO emission standard, and after testing, the cars emitted 40 times more NO than it did during testing.
Xavier: The only downside seems to be a constraint regarding the weight hybrid-electric planes can carry. Are there no other obstacles preventing the possibility of flying green?
- The design is finalized, but the plane is not actually produced, so there might be other challenges, but for now, the only problem explained is the weight.
Works Cited:
“How Hybrid Electric and Fuel Aircraft Could Green Air Travel.” Horizon, horizon-magazine.eu/article/how-hybrid-electric-and-fuel-aircraft-could-green-air-travel.html.
“Hybrid Electric Aircraft: State of the Art and Key Electrical System Challenges.” IEEE Transportation Electrification Community, tec.ieee.org/newsletter/september-2016/hybrid-electric-aircraft-state-of-the-art-and-key-electrical-system-challenges.
Jennifer Chu | MIT News Office. “Concept for a Hybrid-Electric Plane May Reduce Aviation's Air Pollution Problem.” MIT News | Massachusetts Institute of Technology, news.mit.edu/2021/hybrid-electric-plane-pollution-0114.
Zart, Nicolas. “This Hybrid Airplane Could Become the Tesla of the Skies in the Next Two Years.” Robb Report, Robb Report, 7 May 2020, robbreport.com/motors/aviation/hybrid-electric-airplane-rewrite-aviation-two-years-2919373/.
flydragon/Depositphotos, and Mit. “MIT's Hybrid Electric Plane Concept Captures Its Own Harmful Pollutants.” New Atlas, 19 Jan. 2021, newatlas.com/aircraft/mits-hybrid-electric-plane-concept-pollutants/.
Comentarios