#future of

This artist’s concept of NASA’s experimental electric plane design shows 14 motors along the wings. NASA

From electric trucks to flying vehicles

We based our research on a very accurate description of the energy required to move the vehicle along with details of the underlying chemical processes involved in Li-ion batteries. We found that an electric semi-truck similar to today’s diesel-powered ones could be designed to travel up to 500 miles on a single charge while being able to carry the cargo of about 93 percent of all freight trips.

Batteries will need to get cheaper before it makes economic sense to begin the process of converting the U.S. trucking fleet to electric power. That seems likely to happen by the early 2020s.

Flying vehicles are a bit further away, because they have different power needs, especially during taking off and landing.

What is an e-VTOL?

Unlike passenger planes, small battery-powered drones that carry personal packages over short distances, while flying below 400 feet, are already coming into use. But carrying people and luggage requires 10 times as much energy – or more.

We looked at how much energy a small battery-powered aircraft capable of vertical takeoff and landing would need. These are typically designed to launch straight up like helicopters, shift to a more efficient airplane mode by rotating their propellers or entire wings during flight, then transition back to helicopter mode for landing. They could be an efficient and economic way to navigate busy urban areas, avoiding clogged roads.

Energy requirements of e-VTOL aircraft

Our research group has built a computer model that calculates the power needed for a single-passenger e-VTOL along the lines of designs that are already under development. One such example is an e-VTOL that weighs 1,000 kilograms, including the passenger.

The longest part of the trip, cruising in airplane mode, needs the least energy per mile. Our sample e-VTOL would need about 400 to 500 watt-hours per mile, around the same amount of energy an electric pickup truck would need – and about twice the energy consumption of an electric passenger sedan.

However, takeoff and landing require much more power. Regardless of how far an e-VTOL travels, our analysis predicts takeoff and landing combined will require between 8,000 and 10,000 watt-hours per trip. This is about half the energy available in most compact electric cars, like a Nissan Leaf.

For an entire flight, with the best batteries available today, we calculated that a single-passenger e-VTOL designed to carry a person 20 miles or less would require about 800 to 900 watt-hours per mile. That’s about half the amount of energy as a semi-truck, which is not very efficient: If you needed to make a quick visit to shop in a nearby town, you wouldn’t hop into the cab of a fully loaded tractor-trailer to get there.

As batteries improve over the next few years, they may be able to pack in about 50 percent more energy for the same battery weight. That would help make e-VTOLS more viable for short- and medium-range trips. But, there are a few more things needed before people can really start using e-VTOLS regularly.

Slide the ‘specific energy’ slider side to side to see how making batteries better can change vehicles’ energy needs. Venkat Viswanathan

It’s not just energy

For ground vehicles, determining the useful range of travel is enough – but not for planes and helicopters. Aircraft designers also need to closely examine the power – or how quickly the stored energy is available. This is important because ramping up to take off in a jet or pushing down against gravity in a helicopter takes much more power than turning the wheels of a car or truck.

Therefore, e-VTOL batteries must be able to discharge at rates roughly 10 times faster than the batteries in electric road vehicles. When batteries discharge more quickly, they get a lot hotter. Just as your laptop fan spins up to full speed when you try to stream a TV show while playing a game and downloading a large file, a vehicle battery pack needs to be cooled down even faster whenever it is asked to produce more power.

Road vehicles’ batteries don’t heat up nearly as much while driving, so they can be cooled by the air passing by or with simple coolants. An e-VTOL taxi, however, would generate an enormous amount of heat on takeoff that would take a long time to cool – and on short trips might not even fully cool down before heating up again on landing. Relative to the battery pack size, for the same distance traveled, the amount of heat generated by an e-VTOL battery during takeoff and landing is far more than electric cars and semi-trucks.

That extra heat will shorten e-VTOL batteries’ useful lives, and possibly make them more susceptible to catching fire. To preserve both reliability and safety, electric aircraft will need specialized cooling systems – which would require more energy and weight.

This is a crucial difference between electric road vehicles and electric aircraft: Designers of trucks and cars don’t have any need to radically improve either their power output or their cooling systems, because that would add cost without helping performance. Only specialized research will find these vital advances for electric aircraft.

Our next research topic will continue to explore ways to improve e-VTOL battery and cooling system requirements to provide enough energy for useful range and enough power for takeoff and landing – all without overheating.

An experimental electric aircraft for two passengers. AP Photo/Remy de la Mauviniere

About The Authors:

Venkat Viswanathan, Assistant Professor of Mechanical Engineering, Carnegie Mellon University; Shashank Sripad, Ph.D. Candidate in Mechanical Engineering, Carnegie Mellon University, and William Leif Fredericks, Research Assistant in Mechanical Engineering, Carnegie Mellon University

Tracing food items

An early trial of a blockchain system to track food from farm to consumer was in 2016, when Walmart collected information about pork being raised in China, where consumers are rightly skeptical about sellers’ claims of what their food is and where it’s from. Employees at a pork farm scanned images of farm inspection reports and livestock health certificates, storing them in a secure online database where the records could not be deleted or modified – only added to.

Government inspectors review processing plants for safe handling practices. U.S. Department of Agriculture

As the animals moved from farm to slaughter to processing, packaging and then to stores, the drivers of the freight trucks played a key role. At each step, they would collect documents detailing the shipment, storage temperature and other inspections and safety reports, and official stamps as authorities reviewed them – just as they did normally. In Walmart’s test, however, the drivers would photograph those documents and upload them to the blockchain-based database. The company controlled the computers running the database, but government agencies’ systems could also be involved, to further ensure data integrity.

As the pork was packaged for sale, a sticker was put on each container, displaying a smartphone-readable code that would link to that meat’s record on the blockchain. Consumers could scan the code right in the store and assure themselves that they were buying exactly what they thought they were. More recent advances in the technology of the stickers themselves have made them more secure and counterfeit-resistant.

Walmart did similar tests on mangoes imported to the U.S. from Latin America. The company found that it took only 2.2 seconds for consumers to find out an individual fruit’s weight, variety, growing location, time it was harvested, date it passed through U.S. customs, when and where it was sliced, which cold-storage facility the sliced mango was held in and for how long it waited before being delivered to a store.

Preventing counterfeiting

Beyond tracking products’ origins, blockchain systems are helping ensure cheap plonk isn’t sold in bottles promising expensive wines. Some counterfeiters get their hands on empty wine bottles with top-quality labels, refill them with cheaper wine and reap fraudulent profits.

A secure database could help buyers identify if any of these wines are counterfeit. Matt Pourney/Wikimedia Commons

In December 2016, wine expert Maureen Downey debuted a blockchain system that gives each bottle a unique digital identity combining more than 90 pieces of data about its production, ownership and storage history – including high-resolution photographs and data from the glass and cork. As the bottle moves from winery to distributors and resellers, the data are updated, and can easily be checked by warehouses, retailers and even auction houses.

More recently, Downey’s system has been updated to fight even more sophisticated wine counterfeiters, who have reverse-engineered a wine-preservation system to extract wine without opening the bottle. The upgraded protection embeds a small microchip above the top of a wine’s cork, so if someone removes the capsule wrapper or pierces the chip, it will be unreadable.

Ensuring living wages

Consumers are worried not only about contaminated or counterfeit food products. Many consumers say they prefer products that are environmentally friendly and contribute to improved living and working conditions of small farmers and workers. Middlemen siphon off a lot of the money. In the US$200 billion global coffee industry, for instance, only 10 percent stays in producing countries.

Global sales of products approved by Fairtrade, a major certifier of products that respect environmental and human-rights concerns, reached $9.6 billion in 2017. But Fairtrade and other programs like it have not substantially improved poor people’s lives. A study of small farms growing flowers, coffee and tea in Ethiopia and Uganda indicated that areas dominated by Fairtrade producers paid lower wages compared to farms that were larger, commercial and not Fairtrade-certified.

Each of these coffee cherries is unique, ready for a 3D scan to help determine quality. P-fotography/Shutterstock.com

Colorado-based Coda Coffee seeks to ensure fair payments by using a blockchain system to track its coffee from African farms to U.S. coffee shops. The system includes a camera that takes a three-dimensional scan of each bean’s outer fruit, called a cherry, paying farmers more if they supply bigger and riper cherries and recording the amount paid in a blockchain database for consumers to inspect later.

The bean’s record is updated as it is processed, packed, blended with other beans, roasted and ground, letting consumers know who did what to the bean and how much they got paid. Wholesalers and roasters can learn about where it came from and how it was handled, and evaluate the resulting taste, informing future purchasing decisions.

These are far from the only examples – countless others around the world are underway.

Ensuring data integrity

Blockchain systems are secure, but their data – like other databases – are only as accurate as what is entered. Fraudsters may try to counterfeit certifications of organic processes or farm inspections.

In addition, most of the food products in developing economies like Africa and China are produced on very small farms that don’t have access to technology or internet connectivity. Blockchain systems can also be expensive, which is part of why early trials have involved high-end beef, wine and coffee.

The research already happening holds the promise of developing cheaper systems that are easier to use and trust – for farmers, food processing plants and customers alike.

About The Author:

Nir Kshetri is Professor of Management at the University of North Carolina – Greensboro