Energy use by air taxis and drones for parcel delivery, is it practical? Is it sustainable?
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Commentary Energy use by air taxis and drones for parcel delivery, is it practical? Is it sustainable?
Peter Rez, Department of Physics, Arizona State University, Tempe, Arizona 85287-1704, USA Address all correspondence to Peter Rez at [email protected] (Received 28 November 2017; accepted 22 February 2018)
ABSTRACT Aircraft that take off and land vertically with rotors or horizontal propellers like drones use more energy than conventional aircraft whose lift is provided by wings. Drones with propellers are less efficient than helicopters with large rotors. The poor energy density of batteries compared to hydrocarbon fuels limits the range and endurance of the electrically powered aircraft. Although the ratio of the mass of payload and fuel (or battery) to the total aircraft mass for the proposed Amazon drone is not that different from the same ratio for a Boeing 747, the range and time in the air is very much less. In principle, a conventional aircraft powered by photovoltaic panels covering a wing with a span of 6 m could match the performance of the proposed Amazon drone. Amazon has proposed delivering packages by an electrically powered drone capable of vertical take off and landing. By comparison with helicopters, the energy needed to move a 2.5 kg package is estimated to be more than 130 times the energy used in delivering the same package in a small delivery truck. By comparison, a conventional airplane with the same mass could, in principle, be powered by photovoltaic panels, covering the wings, and it would use an energy equivalent to about 3 times the energy used by a small delivery truck. Based on the performance of existing small helicopters, the analysis shows that an electrically powered air taxi would only be able to make journeys of 10 min or less. Vertical take-off and landing add to energy requirements, and drones using a large number of propellers are less efficient than helicopters. The major limitation, not surprisingly, is the poor energy density of batteries compared to liquid hydrocarbon fuels. Keywords: energy storage; photovoltaic; transportation
DISCUSSION POINTS • How much energy is used in delivering small packages by a drone? • H ow does the energy used to move a given mass compare for an electrically powered drone, a helicopter, an airplane, and a delivery truck? • D oes a drone that has vertical take-off and landing capabilities use more energy than a conventional airplane? • Could the package delivery drone be solar powered? • Is such a drone less efficient than a helicopter? • C ould a passenger-carrying air taxi, capable of vertical take-off and landing, be powered by batteries?
There has been much excitement recently on the possibility of using drones instead of trucks for parcel delivery. As a consequence of the widespread growth of online retailing as pioneered by Amazon, many people would find it appealing to have
something that they ordered dropped directly to their backyard, rather than wait for a truck to show up sometime late in the day. Given the congestion
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