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

monocrystalline silicon cells give us a yield of 22%, which is pretty decent for our purposes,” Hoevers says. “Our roof area is about 1.2-1.3 m 2 , and about 1 m wide, which corresponds size-wise to the types of solar panels supplied wholesale for houses. That’s a major reason why we’ve been able to get a very good price on our solar components.” While solar materials of much higher yield are available, such as gallium arsenide or even multi-junction cells that combine semiconductors to achieve upwards of 30% efficiency, a panel of such PV cells could cost 10 times the price of a single Squad. Even going to cells with slightly higher yield (with 23-25% efficiency, for example) would bring exponential increases in price, Hoevers notes. He has no doubt however that higher-yield solar panels will be mass-produced in the future, and is closely watching developments in solar supply chains to see where production costs are likely to fall. “An efficiency of 22% was considered lofty and exotic 10 years ago, and things are only moving faster in solar tech and manufacturing,” he observes. “And if we want to get as much range as possible from our passive solar recharging without sacrificing weight, we need the highest energy density commercially available, so NMC lithium-ion batteries were a must- have to guarantee the lowest weight relative to kilowatt-hours that the Squad can store.” The battery pack is made from four modules, each storing up to 1.5 kWh of energy, while the solar cells can charge at a rate of up to 250 W. The solar panel is expected to enable up to 20 km of driving per day during summer across most of the EU, while the batteries store enough energy for 100 km (and can also be charged using a 220 V input). “Depending on customisations here and there, each Squad should cost between €5000 and €10,000, positioning them between electric scooters which are €2500-5000, and conventional city cars that cost around €12,000-13,000,” Hoevers says. “That price works for mass production, and in EU certification terms it works for classing them as L6e – legally speaking, they’re effectively four-wheeled mopeds.” Light, safe and aerodynamic As mentioned, the energy consumption of the car has been a critical factor in making it viable for reliable and cost- effective urban mobility. To improve energy efficiency, Hoevers and his team spent a lot of time and resources on optimising weight and aerodynamics. As such, its frame is a major part of its design. “As with solar cells, if you try to go exotic with body and chassis materials to reduce weight, for example by making it all out of carbon fibre, you might find yourself burning through a lot of money very quickly,” he notes. “During my years in racing, I saw brilliant uses of carbon fibre, but I also saw that it’s not coming down in price particularly quickly. It’s also not the easiest material to mass-produce, despite there being many variants for different price and performance requirements. “You do see some marvels with carbon though. BMW for example have done a great job with the i3 to implement it with carbon fibre, but those are far more the exception than the rule in the automotive world.” The major weight-saving move for the Squad has been to make the entire frame and chassis as extruded aluminium profiles. Customer feedback was a key motivator for going down this route – much of the research and trialling of the car has taken place in areas by the sea, and in city districts with hotel resorts and marinas. “The air in those places is thick with saltwater humidity, so a request we kept getting was, ‘Please, make an aluminium version, or it will corrode really badly.’ Durability is necessary for commercial fleet and ride-sharing operators to get plenty of years of return on their investments,” Hoevers says. He adds that aluminium is one of the most widely and efficiently recycled materials in the world, being a very pure element rather than a composite, with 60-90% of newly produced aluminium expected to be re-used later in its life (depending on where it is made and exported). Making a lot of the car from it therefore chimed with his and Klok’s earlier goal of widely accessible and highly sustainable mobility. “Aerodynamics are a little less important than weight or sustainability, because we’re making a low-speed vehicle; it’s really only at higher speeds that drag becomes a serious issue,” Hoevers notes. Robert Hoevers Robert Hoevers is the CEO and co-founder of Squad Mobility, which is based in Breda, Netherlands. He was educated at Rijnlands Lyceum Wassenaar before studying at the Technical University of Delft from 1989 to 1996 and achieving an MSc in Industrial Design Engineering. Between 1996 and 2009 he held numerous positions across a variety of industries, primarily in IC engine- based racing but also across web development, food processing and home heating systems. In 2009, he founded EPowerGP (which helped lead to the founding of Formula E), and he would go on to work as the commercial manager for Chinese e-mobility irm NIO and its Formula E team. In 2018 he then started working for solar EV maker Lightyear. After about a year there he chose to form Squad Mobility as a new company to produce a solar EV that would be inexpensive and widely accessible compared with the Lightyear One. 18 Autumn 2021 | E-Mobility Engineering