Interview: Evolito chief technology officer Marc Holme

Evolito has already marked itself as an innovator in electric aviation with the development of its axial-flux electric motors, power electronics, and battery solutions. The Bicester-based company has been working on sustainable solutions for aerospace applications since 2021, when it was hived off from automotive company YASA.

Founded in 2006, YASA was a spin-out from Oxford University following the PhD of founder Dr Tim Woolmer, who believed that small, powerful and efficient electric motors were the future of automotive. Since then, YASA has developed an alternative – known as axial flux technology - to the legacy radial motors that the majority of EVs use today.

The company now supplies world-leading sports car manufacturers with ‘innovative powertrain solutions based around its axial flux electric motors,’ including Ferrari, which was its first OEM customer in volume production, and Mercedes-Benz, who acquired YASA as a wholly owned subsidiary in 2021.

Evolito has adopted both YASA’s technology and its passion for a sustainable future, and the company’s newly appointed CTO, Marc Holme, hopes to continue its advancement to all-electric aviation.

“Having grown over the last two years from a handful of folks to over 200 employees, Evolito is more than a start-up now,” Holme told The Engineer.

“I think my role since coming in as CTO just before Christmas last year has been to help the company on that journey, in terms of developing a product strategy, evolving this really cool technology that we’ve inherited from YASA, and adding in electronics, control technologies and a wider system understanding to help Evolito develop further.”

Holme has a solid foundation of 24 years in the sector, having worked for both Lucas automative and aerospace at the beginning of his career, and as senior director and general manager for the electric propulsion side of Collins Aerospace’s electric power systems business, prior to his new role.

When asked what attracted him to Evolito, Holme said: “It was really the technology. I’ve always been interested in the axial flux technology coming out of YASA but never had a chance to get really ingrained in it, so this was an opportunity to look at that technology in detail and bring my own experience from an aerospace electronics development perspective to add to that.

“I was also interested in the battery technology, and how these technologies can be brought together as either an all-electric system or in a hybrid aircraft architecture type system.”

YASA’s axial flux design is said to be 50 per cent lighter and smaller than the radial flux motor equivalent that many EVs still use. The company said that its compact technology doesn’t compromise on power, though, as the axial flux motor can provide up to four times more torque and double the power densities compared to alternative EV technologies.

Holme said Evolito is pushing the technology to a power density of 16 – 20 kWh/kg compared to the radial 10 kWh/kg equivalent, adding that he can see a route even beyond that in the future.

“As we’re developing and applying YASA’s technology into the aerospace sector, we’re finding ways to optimise the design – and this is a two-way street,” he said. 

“We’re feeding our findings back to the YASA team, and they’re feeding their years of learning and know-how back into Evolito. We’re both working to optimise a shared design tool in the tool suite. It’s a very collaborative relationship, which is great.”

The adoption of this automotive technology into the aerospace sector isn’t without its challenges, said Holme, particularly with the change in size and weight from automobile to aircraft, as well as a change in the vibrations and temperatures the technology has to withstand.

“We also have to consider the adoption of battery technology,” said Holme. “The current range of an all-electric aircraft is very short, probably only suited to certain applications like vertical take-off and landing (VTOL) aircraft and air taxis.

“As you start to think about larger aircraft platforms with more passengers or cargo, it becomes a much harder equation to solve – the battery technology just isn’t there for aerospace yet.”

The potential answer to these problems, said Holme, may be hybrid technologies, with Evolito beginning to look at using a thermal-engine driven motor as a generator, which can provide power and offer electric propulsion to propel the aircraft.

Holme imagines that batteries will still play a part in this solution as energy storage initially, but that the future may lie with sustainable aviation fuels, or even hydrogen, to achieve a net zero requirement whilst still reaping the benefits of a hybrid and electric powertrain.

In July 2022, Evolito acquired and later integrated Electroflight batteries into the business to offer complete propulsion solutions that are fully optimised for future aircraft applications, which Holme said was an exciting step for the company and electrification as a whole.

“There are lots of challenges we have to tackle,” he said. “But ultimately, there’s a great opportunity in the coming years to make air travel both more efficient and more sustainable.”

Evolito is already working with a number of OEM partners, developing motors and propulsion systems for a variety of electric vertical take-off and landing (eVTOL) aircraft, urban air mobility and fixed-wing applications. According to Holme, 2024 should see a series of customer test flights later in the year.

And as for the industry as a whole: “It’s really evolving at the moment, but I think the direction in the next ten years or so will be driven by large OEMs like Airbus and Boeing and the directions their platforms are heading in” he said. “There’s a lot of interest and funded studies going on, but we’re waiting for those platforms to emerge to drive us towards greater levels of electrification.

“In the interim, I think we’re going to see a lot of the urban air mobility start-ups evolving, looking to certify their products, and Evolito’s plan is to be at the forefront of the propulsion technology to support this market space.

“It’s amazing to see how far the industry has come in the last 20 years. We’re definitely on an upward curve in terms of accelerating development, and I think its a fantastic opportunity and space to be in.”