A positive experience
Although they are still in the minority, the proportion of electric passenger cars on the road continues to rise as consumers realize the benefits. The switch to lithium-ion battery packs has enabled more range for vehicles, while the charging technology has been improved to the point of the process of “refueling” from empty taking minutes as opposed to hours.
There are plenty of examples that illustrate the industry is not standing still despite these advances. One such company that is continuing to push boundaries is NAWA Technologies, based in southern France.
Before he founded NAWA, Pascal Boulanger was a researcher at the Atomic Energy Commission (AEC) in France and has spent most of his career involved in nuclear energy, solar energy, batteries, and nanotechnology.
“At AEC I worked on many different materials and, in early 2000, I discovered that one of the laboratories was working on a new material based on nanocarbon,” he recalled. “I followed the development of this material in the lab—as head of the institute as opposed to a researcher—and saw how it was pioneered in Europe.”
Meanwhile, another nanocarbon that is composed of trillions of small nanotubes was also under development at NAWA. These tubes are aligned like a paintbrush and packed very densely—in a 1 cm2 (0.16 in²) area, there are more than three trillion nanotubes.
“The topology and nature of the material—specifically the tubes—make it very good for storing electricity,” said Boulanger. “So, in 2009, I decided to go back to the lab and once again became a researcher with the intention of developing a process to fabricate the material. At the time it had a lot of potential, but no one was talking about the possibilities of commercialization.”
Fast forward a decade and the company now offers a new-generation ultracapacitor using the aforementioned nanotubes, which offer power, energy, and charging benefits over the products that are currently on the market and, therefore, huge potential for the electric vehicle industry. The key is a combination of lithium-ion battery and an ultracapacitor that offers five times the power/energy of existing ultracapacitors. The powerplant can also be charged in a matter of seconds, for more than one million cycles. As well as ultra-fast charging, the energy is also capable of being discharged very quickly, enabling rapid acceleration.
“Everything starts with the material, and we have been able to design and develop the fastest—in terms of the charging time—electrode in the world,” said Boulanger. “The electrode has the highest electrical connectivity of any batteries or ultracapacitors on the market; it is one thousand times higher than any other electrodes, and we have lower internal resistance, so it is easier to get the electricity out of our battery.”
One other advantage of the NAWA solution is the mechanical strength of the nanotubes. Boulanger explained it is impossible to break them: “One of the main problems of today’s lithium-ion batteries and ultracapacitors is that when you charge and discharge them, there is volumetric expansion, so cracks can appear, damaging the stack. This cracking does not occur with our electrodes.”
There are also strong environmental benefits of the ultracapacitors. “The ultracapacitors have a low raw material content—no lithium, carbon, or rare earth metals—which means very little mining is required,” said Boulanger. “The manufacturing process is more simplistic, and they are easier to recycle because we can give the ultracapacitors multiple lives. In fact, over the course of its entire life, an ultracapacitor can store 100 times more energy than a lithium battery.”
There are, however, three main obstacles where ultracapacitors are concerned: their energy density, which is low compared to batteries; high costs to the point of them being pretty prohibitive on their own for the current EV market; and the fact that their use with a battery often requires a DC-DC converter, which adds complexity to the design as well as further cost. But Ulrich Grape, NAWA’s CEO, believes the company can solve these three problems.
“Our ultracapacitor will have high energy density because the carbon nanotubes provide a greater specific surface on which to store the energy,” he explained. “In terms of cost, thanks to our manufacturing process, we expect to be able to reduce the cost per watt hour of the ultracapacitors. They will have a longer life, so a lower relative cost over the lifetime of the product.” Grape added that, due to the design of the ultracapacitor/lithium-ion battery pack combo, the DC-DC converter can be eliminated.
Real world work
Testing and evaluation of its Formula E battery by the NAWA team led to some interesting results. Replacing the Formula E battery in cars that run in the all-electric race series with their own power pack saved 100 kg (220 lb)—going from 300 to 200 kg (660 to 440 lb)—of the weight of the whole race car, maintaining the same power and range. The NAWA hybrid battery managed to recover 90% of the energy lost as heat when braking, whereas a regular lithium-ion battery would recover only around 20%.
“The company we were doing the simulation with said it could take another 100 kg out of the vehicle,” said Grape. “You reduce the weight of the overall system by over 30% and, instead of changing the battery halfway through the race, you could go the full race on one battery because the ultracapacitor would allow for regenerative braking.”
Away from the track, NAWA revealed its first official in-house appellation at CES 2020 when the covers came off the NAWA Racer—a zero-emission motorbike that is powered by the same ultracapacitor and lithium-ion “hybrid” battery pack (see this issue’s Vehicles & Concepts article). The Racer is the first illustration of what NAWA hopes to achieve across a range of markets, including transportation (from automotive to maritime to personal mobility) and smart energy grids. Grape says the company is also developing NAWA Shell, a structural energy storage for composite materials that allows cars and aircraft to have batteries directly embedded in their body or wings.