A private car sits parked and unused for about 23 hours a day, on average. What if it used that time to power itself? That is precisely the question the European research project SolarMoves set out to answer – and its findings hold out a surprisingly large extra source of energy for electric mobility.
Led by the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, the team analysed vehicle-integrated photovoltaics (VIPV): solar cells built directly into a vehicle's roof, hood and side panels. The conclusion: in Central Europe, passenger cars could generate up to 55 percent of their annual electricity demand this way, and in the sunnier countries of Southern Europe up to 80 percent. The estimates rest on real driving data from 23 vehicle types – from compact city cars to heavy trucks – combined with satellite and weather data and 1.3 million kilometres of recorded travel.
Relief for the grid, a win for logistics
The benefits reach beyond the individual vehicle. If every new vehicle sold between 2024 and 2030 were fitted with solar cells, electricity drawn from the European grid could fall by 15.6 terawatt-hours by 2030 – roughly the annual output of 2,200 onshore wind turbines. Because solar cars top up part of their own charge while out on the road, charging costs and the need for public charging infrastructure drop at the same time.
The freight sector stands to gain the most, the study found. Vans, trucks and trailers combine large roof areas with heavy electricity demand for cooling, heating and auxiliary systems. Solar panels on the roof of a semi-trailer can deliver up to 55 kilowatt-hours a day in summer; add modules to the side walls and the yield rises to between 90 and 110 kilowatt-hours – enough to fully run refrigeration units or hydraulics. The daily range of electric trucks could grow by up to 15 percent.
“Electrification alone is not enough. We need innovations that structurally reduce energy demand,” says Lenneke Slooff-Hoek, project manager at the research partner TNO. Even in diesel vehicles the cells could power air conditioning and auxiliary loads and so save fuel – in which case, the project says, the technology pays for itself in less than two years. Alongside Fraunhofer ISE, the partners included TNO, Sono Motors, IM Efficiency and Lightyear.