09. April 2021, 08:49 Uhr | Irina Hübner
WORK L test vehicle on the road in the Weserbergland region.
An electric vehicle without dependence on charging stations - the first steps toward this have been taken: the prototype of a light commercial vehicle is equipped with vehicle-integrated photovoltaics. The energy converted from sunlight can be fed into the high-voltage vehicle electrical system.
The Street research project consortium, in close cooperation with Continental Engineering Services, has put a prototype light commercial vehicle on the road that is equipped with highly efficient vehicle integrated photovoltaics (VIPV). What makes it special is that the energy converted from sunlight can be fed into the high-voltage vehicle electrical system and thus used directly to extend the vehicle's range. The project is being coordinated by the Institute for Solar Energy Research Hameln (ISFH). The companies Vitesco Technologies, a2-solar and Meyer Burger as well as the Forschungszentrum Jülich, the Helmholtz-Zentrum Berlin and the MBE Institute of the Leibniz Universität Hannover are project partners.
Modern battery electric vehicles always have two power storage units on board: a small 12 V battery that can supply electrical consumers, lights and power steering, and a large traction battery that operates at a higher voltage of 400 V and supplies energy to the electric drive. In order for the energy generated by VIPV to be fed into the large traction battery and thus contribute to range extension, it is necessary to couple the PV modules to the high-voltage vehicle electrical system.
This is technically very demanding, as it requires a conversion from 12 V to 400 V and is associated with many safety aspects. It is precisely this challenge that the Street consortium has now successfully tackled. The basis for this was the combination of different competences: The conversion of solar energy into electrical energy takes place in PV modules from a2-solar developed for automotive use. These are based on highly efficient silicon heterojunction solar cells from Meyer Burger, which were interconnected at ISFH using Smartwire interconnection technology. This interconnection technology, designed in Europe, not only enables very high cell and module efficiencies, but also very high module yields due to a lower temperature coefficient.
Control to the point with maximum power is provided by electronics from Vitesco Technologies. The company also developed the DC/DC converter from 12 V to 400 V as a central innovation. Continental Engineering Services handled the integration of all components and their integration into the vehicle electrical system.
The WORK L light commercial vehicle from StreetScooter used as a demonstrator offers ideal conditions for VIPV: A total area of 15 m2 is available for the 10 PV modules. In contrast to integration on passenger cars, the modules did not have to be curved or colored. Their nominal total output is 2180 Wp. At the same time, the energy requirement for driving, at circa 19 kWh / 100 km, is similarly low to that of passenger cars.
»We expect an annual range extension of circa 5200 km for driving in Lower Saxony, and significantly more in more southern regions. This would save more than one in four grid-based charging stops,« says Prof. Robby Peibst, coordinator of the Street project. »Our results will demonstrate the attractiveness of vehicle-integrated photovoltaics first for such light-duty vehicles. But beyond that, they will also provide important insights for transferring VIPV to other vehicle classes.«
The demonstrator vehicle has road approval in accordance with StVZO and has already completed initial tests. It is equipped with numerous sensors to precisely track energy flows. By the end of the project, all components will have been put through their paces in test drives at different times of day and year and under different weather conditions. The vehicle will therefore be seen frequently in the near future on the roads of the Weserbergland region, the Hannover region and in the capital of Lower Saxony itself.
The Street research project is funded by the German Federal Ministry for Economic Affairs and Energy. The results of the project are also being incorporated into the international working group »Task 17 - PV for Transport« in the Photovoltaic Power Systems Program of the International Energy Agency (IEA). There, experts from around the world exchange ideas on how photovoltaics can be used to reduce CO2 emissions in the transportation sector.