Flying cars and efficiency

Those who spent several hours of the Easter weekend in traffic jams on one of the highways would be sure buyers for a flying car. Then there is no such problem when one sees congested cars, just pulls the height lever and in a few moments it is already waving to the car line from above. But how green is it to fly instead of driving?

The VTOL (vertical takeoff and landing aircraft) combines a helicopter capable of taking off from a small aircraft with favorable aerodynamic properties, while the taxiing ground unit allows comfortable driving. Such vehicles could be brought to market quickly after the regulations are expected to be finalized in 2020, as several serious companies are already developing them.

From an environmental point of view, however, it does not matter how we will use VTOLs. Researchers at the University of Michigan, together with Ford engineers, have calculated the energy consumption, emissions and time savings we can expect over different distances compared to conventional cars. This is the first research in the world to examine the sustainability of VTOLs. The results were published in the April 2019 issue of the journal Nature Communications.

Although the electric motor VTOL does not emit harmful substances into the air, its batteries need to be charged regularly, and it does not matter what the source of that electrical energy comes from. The researchers found that an approx. Over a 100-kilometer run, a full-load four-seater VTOL carrying a pilot and three passengers means less environmental impact than a normal car with an average passenger (in America) of 1.54. Emissions associated with flying cars were 52 percent less than those of a gasoline-powered car and 6 percent less than those of an electric car.

The results of the research could help regulate the sustainability of VTOLs developed at a rapid pace before the market breakthrough, said Akshat Kasliwal, lead author of the research. “The use of flying cars means minimal environmental impact, as well as economical operation, if their utilization is as high as possible.” Prospective passengers can also be encouraged to share seats by saving time on flights instead of driving.

In the coming decades, the global freight and passenger industry will have to figure out how to meet the expectations of passengers who want comfortable transportation while reducing traffic congestion, increasing safety, and mitigating the negative factors that accelerate climate change. Electric and self-driving cars meet the criteria of green and comfort – all the way to the first traffic jam. VTOLs may go beyond such restrictions, as they allow taxi-type or regional air passenger transport.

Many aircraft manufacturers (Airbus, Boeing, Joby Aviation, Lilium, etc.) are working on prototypes, as is the U.S. space agency, NASA. The researchers made their efficiency calculations by analyzing the plans published so far, taking into account the weight of the planned vehicles, the development of the buoyancy-to-resistance ratio, and the energy storage capacity of future batteries.

Energy use and emissions were analyzed in all five VTOL phases: during take-off hover, take-off, flight, landing, landing hover. VTOL vehicles require an enormous amount of energy to take off and land, but flying is already a relatively energy-efficient process at speeds of roughly 240 kilometers per hour.

Because of this, the use of flying cars over longer distances will make sense when the flight phase dominates the other phases. On the other hand, in a period shorter than 35 kilometers, a car powered by an internal combustion engine consumes less energy and emits less pollutants, especially if there is only one person in each vehicle (VTOL and car). This is an important calculation because an average highway is roughly 17 kilometers. That is, at present, only a fraction of annual car use should be replaced by aviation – that is, in terms of pollution and sustainability.

The main advantage of VTOLs will be time savings, as they will deliver their passengers to their destination in 80 percent less time. Small electric-powered aircraft are assumed to fundamentally change aviation. However, according to the researchers, a number of questions remain to be answered, and price is not the most important of these, but the noise pollution caused by VTOLs and their social and consumer acceptance, i.e. whether their everyday usefulness is proven.

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