ISSUE 011 Autumn 2021 Candela C-7 hydrofoil speedboat dossier l In conversation: Robert Hoevers l Battery recycling focus l Vehicle dynamics insight l ZeroAvia hydrogen-electric aircraft digest l Motor materials

that the car was rather expensive – it’s a large and advanced passenger EV – so this great platform for sustainable mobility wouldn’t be accessible to everybody,” Hoevers explains. “It’s especially striking to me because solar is priced so incredibly low now. A kilowatt of solar cells – which is what the Lightyear One has on its roof – costs only €200. A €150,000 car shouldn’t be necessary to get the clean energy benefits of €200 worth of solar cells, especially when PV reduces the quantity of batteries your car needs.” Seeing an opportunity to provide a highly affordable clean energy vehicle, Hoevers and Klok founded Squad Mobility in May 2019, with much of their initial r&d focused on determining which vehicle design made the most sense for their goals of affordability and widespread access. Hoevers and Klok soon identified huge room for growth in the personal, shared urban mobility market, where numerous single-person scooters and bikes exist but where there are practically no robust solutions for transporting two people (or one person with luggage). The first prototype was completed earlier this year, although Hoevers notes that the automotive world often quibbles over what actually constitutes a prototype. “The first tangible, life-size recreation of a new car design is often actually a side-view print of the car, which is placed on the ground or attached to a wall so that the company can judge early on how the driver or riders actually fit into it. The public will never see these ‘prototypes’ of course, because to the uninitiated they look quite strange,” he says. “Producing a mock-up is very important though, not necessarily for showcasing the design at auto events but more for judging the driver’s ergonomics – their field of view, leg room, the height of the roof, the space between them and their passengers. All these and more have to be suitable or people won’t want to drive the car.” Charged by the sun The core aspect of the Squad is, of course, its solar array. To successfully engineer a solar-recharged EV, two figures must first be optimised. The first is the yield of the solar cells, as in how much energy they will typically generate. The second is the energy consumption of the EV – and naturally, this figure must be minimised while the former is maximised. “That’s from an engineering perspective, but again, we want the benefits of solar to be widely accessible to people seeking convenient personal mobility, so we need to consider the consumer perspective too, so the component prices are also very important to us,” Hoevers says. A wide range of solar cell materials and designs are now available as mass- produced commodities, with prices often running proportionally to yield. To strike a balance between cost, yield and availability, Hoevers and his team have installed panels of monocrystalline silicon in the Squad’s roof. “Mass-produced commodities give you the best per-unit price, but we also wanted a decent yield – why, and how racing or commercial regulations for them can be formed,” he explains. “For example, it always struck me as strange that Formula E initially stuck to a central e-motor with a mechanical differential, when using separate motors in the rear with electronic differentials or potentially four-wheel drive would make so much more sense.” Hoevers’ move into solar technology came gradually. During his fourth and fifth years heading EPowerGP, he also worked at BonGo Innovations, a retailer for home photovoltaic (PV) systems, and in 2018 he started working at solar EV maker Lightyear. That company was spun out from Solar Team Eindhoven, which has won the World Solar Challenge numerous times and has gained a lot of attention for its Lightyear One EV. This is a large hatchback that is due to start serial production this year, and it features solar cells across its roof that charge at an average rate of 0.996 kW – enough for 12 km per hour. “The Lightyear One incorporates a number of great EV technologies, such as in-wheel motors that are independently controlled using advanced torque vectoring, but Chris and I felt it was something of a shame Robert Hoevers previously worked at Lightyear, known for its solar- Wowered 3iNOtyear 6ne Äve door hatchback (Courtesy of Lightyear) Autumn 2021 | E-Mobility Engineering 17 InConversation | Robert Hoevers