An electric car is only as green as the electricity that powers it. And given that most power generators burn environmentally suspect fossil or nuclear fuels, it is noteworthy when someone develops an EV that can self-charge from the sun.
That’s true even if the European Union’s P-MOB micro EV concept can manage only 20 km (12 mi) on a full day’s solar power charge, and then only in sunnier regions such as southern Europe. But that should be enough range for many city travelers in Italy and elsewhere, said Pietro Perlo, a former Centro Ricerche Fiat (CRF) director and now principal at Interactive Fully Electric Vehicles, which is dedicated to urban e-vehicle development and local production.
The three-seat, solar runabout, which has a mass less than 600 kg (1325 lb) without a battery, has a top speed of 100 km/h (62 mph) and a fully charged range of more than 100 km (75 mi).
P-MOB is the product of a three-year, $6-million joint industry-university research program, partly EU-funded and partly industry-financed, that aimed to develop "Integrated Enabling Technologies for Efficient Electrical Personal Mobility." CFR-coordinated the research consortium, which included Germany’s Siemens, Spain’s Mazel Group, and the UK’s University of Sheffield and Magnomatics.
P-MOB was accompanied by a parallel, $5.3-million (partially EC-supported) program that addressed the design and development of the basic building blocks of EVs and attempted to solve some specific technical shortcomings. WIDE-MOB, also coordinated by CRF, involved not only the P-MOB partners, but Warsaw University of Technology, France’s IFP Energies, Swiss DuPont, and the French-Italian STM Microelectronics.
Safe as a tank
“Our goal was ‘small and clean, but safe as a tank,’” said Perlo, who helped guide the project. “The P-MOB has met the highest safety ranking, a low footprint, and extremely low energy consumption, making the vehicle ideal for most people’s needs in cities as well as on suburban roads.” During track-testing this summer at Fiat in Turin, “the vehicle's performance met our expectations for the design,” he said. “It showed very high stability on small radius curves and had an average energy consumption of around 80 W·h/km.”
The design meets new European regulations on micro EVs, he noted, adding, “The idea of having a vehicle that with minor additions could meet both the homologation of micro electric vehicles and the classical M1 world is new.” (M1 is a vehicle category, a car with eight passenger seats or fewer.)
Although reducing system complexity while focusing on the essentials was key to lightweight design, “we’re Italian, so of course we wanted to build an electric microsupercar,’” Perlo said. The little car thus has a good deal of style as well as four-wheel drive, precise handling, swift acceleration, and low-drag aerodynamics. The design may even presage some trends in this expanding and changing car segment.
The problem with current fuel-burning microcars, Perlo said, is that they are “unsafe, inefficient, and very polluting.” In Europe, quadricycles or ‘q-cars’ are defined as weighing 700 kg maximum, though the category also extends to Japan and China. In the city car market, he observed, top speed is less important to drivers; a focus on the essential functions is what is required.
And it’s only a matter of time until this market goes increasingly electric. Today micro EVs such as Renault’s Twizy, make up only a tiny fraction of the European car fleet, but exponential sales growth is expected in the next few years. Micro EVs are expected to be the fastest growing e-vehicle market segment. “By 2020, all Smart cars and most Japanese ‘kei’ cars will be electric-powered,” he said. The Colibri EV micro-car, which was unveiled this spring, has already netted 700 pre-orders for German firm Innovative Mobility Automobile, for example.
EV building blocks
The WIDE-MOB effort focused on design elements to boost the efficiency of the solely solar-powered city car and on developing more efficient solar cells, improved electric motor and magnetic torque control, better batteries, and adaptive technologies to enable e-vehicles to inject power back into the grid and home (V2G, V2H) when they have no need for it. Aerodynamics advancement was another goal; according to EU contract documentation, the team was to implement “embedded synthetic micro-jets that radically reduce the drag at any speeds.”
All the technologies were developed during the course of the project by the partners, Perlo said. The concepts have been patented. “Only the battery cells were produced outside Europe, though the design came from within the project.”
The vehicle sits on a low-cost tubular frame stiffened with formed sheet-metal parts that was developed by the WIDE-MOB team for acceptable crash resistance. The bench seats serve as structural supports, a part of a full safety cage that has a single aperture on the side.
“We have two doors on one side only, which helps ensure a high degree of safety, better ergonomics, and reduced complexity with extremely low aerodynamic drag, around 30% lower than similar size vehicles,” Perlo explained. The facing double doors enable “easy entry for 90% of people.”
Perlo said that this project has had several funding stops and starts until it was completed last spring, but even in its initial stages in 2008, the P-MOB vehicle was always to have “two electric motors on two axles, a high stability, and fail-safe configuration…that has since been adopted by Tesla and others.”
The integrated ICT-based control systems allow two motors and two differentials to operate simultaneously, providing independent axle actuation and therefore 4WD capability and the ability to alter torque ratio as driving conditions change. “The split-power provides for control, makes it easier to recover energy, and a fully independent fail-safe propulsion system,” he said. The system enhances control on tight turns, supplies more grip on wet and icy roads, and delivers quicker acceleration without drawing more power.
The plug-in supercompact EV features just under 2 m² (21.6 ft²) of crystalline silicon solar cell panels on the roof and on solar windshield and window sunshades that slide out on the inside to soak up sun while parked. The car’s photovoltaic arrays operate using smart diodes and self-adapting electronics to minimize energy loss during reduced-light conditions or malfunction.
Part of the P-MOB concept is that distributed battery packs separately power the motors. The photovoltaics feed into the front axle motor/battery whereas some of the rear battery modules—at 8 kg (18 lb) each—can be easily can be swapped out by hand in seconds.
“Who needs a fast-charging battery if you can just change out the batteries?” asked Perlo, an experienced practitioner who shares Leonardo da Vinci’s view that “simplicity is the ultimate sophistication.”