Drone deliveries up to ten times less energy efficient than vans

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Scientists have identified a number of factors that make deliveries by drone considerably less energy efficient than those made by vans.

Firms such as Amazon are hopeful that once regulatory hurdles are cleared, they will eventually be able to deliver items by drone, which could allow for exceptionally short delivery times and could help to ease congestion on the roads. 

However, a team from the Martin Luther University of Halle-Wittenberg (MLU) in Germany has found that in densely populated areas, drones consume comparatively high amounts of energy and their range is strongly influenced by wind conditions.

The study also shows that this disparity is less relevant in rural areas, where vans may need to drive considerable distances between each drop off.

“Google, DHL and Amazon have been experimenting with this concept for several years and launched the first commercial pilot projects in the USA and Australia in 2019,” said Dr Thomas Kirschstein from MLU’s department of Production and Logistics.

“When evaluating the hypothetical use of delivery drones, attention has frequently only been on whether drones could deliver parcels faster and cheaper. Sustainability aspects, on the other hand, played less of a role.”

The energy consumption of drones was compared with diesel-powered delivery vans and electric transport vehicles currently used by parcel carriers in the greater Berlin area.

“Among other things, we investigated how the number of parcels per stop and the traffic situation impacted energy consumption,” Kirschstein said.

He expanded his calculations to include the emissions produced through the generation of electricity or the consumption of diesel. One clear trend was that electric vans were significantly more economical than diesel vans, consuming up to 50 per cent less energy.

“This is not surprising for an urban setting. In cities, vans have to drive slowly and stop and start a lot. Here, electric vehicles consume significantly less energy,” Kirschstein explained.

Drones were found to be heavily impacted by wind conditions, which play a crucial role in how they perform. If there is a crosswind, for example, more energy must be expended to keep the drone on course. On the other hand, headwinds or tailwinds can even have a slightly positive effect on energy consumption.

“Drones consume a relatively large amount of energy when they have to hover in one place in the air; for example, when they want to deliver a parcel and have to wait outside the door of the recipient’s home,” he said.

On average, the drones in the simulation consumed up to ten times more energy than electric delivery vans in a densely populated city like Berlin.

“Parcel carriers, for example, can stop and deliver several parcels on foot if multiple customers are receiving deliveries in one street. This is not possible for drones, as they can only deliver one package at a time. This increases their energy consumption, sometimes drastically,” Kirschstein said.

Drones were found to be more energy-efficient than delivery vans in sparsely populated rural areas.

Higher energy consumption also does not necessarily have a worse impact on the environmental.

“Even if drones require more energy, they could represent an alternative to diesel vehicles, provided the electricity they need is generated by environmentally friendly means,” Kirschstein said.

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