Solar panels on vehicles can be a valuable, mobile source of renewable energy for the transport sector. However, there are several challenges in generating energy using this approach, such as shading and user behaviour.
This is according to the SolarMoves study by TNO, the Fraunhofer Institute for Solar Energy Systems ISE and vehicle solar energy system suppliers Lightyear, IM Efficiency and Sono Motor. The study focuses on the technical and practical potential of solar energy in mobility. The study was set up in response to a request from the European Commission (DG MOVE) to explore the role of solar vehicles and identify the impact on both future regulation and charging infrastructure.
From trucks to passenger cars
Eighteen vehicles ranging from trucks and buses to vans and passenger cars were examined. They were fitted with sensors on the roof and sides. The vehicles covered one million kilometres on European roads since March 2024.
This shows, among other things, that solar panels on vehicle roofs have the highest yields. "The measurements done in the Netherlands and northern Germany show that side panels receive about 50% less solar radiation than roof panels. This is similar to previous model assumptions: an average of 2.8 kWh/m² per day for the roof and 1.3 kWh/m² per day for the side panels," explains Lenneke Slooff, senior consultant at TNO.
Shading makes yield prediction complex
Not surprisingly, shading is found to have a major impact on the yield of solar panels. This makes yield prediction complex and challenging. For instance, shadows from buildings, trees and other vehicles have to be taken into account. As vehicles move across the road, shadowing varies continuously.
Satellite and meteorological data can help predict returns more accurately. "We recommend further refining shading models, including route and location data, and usage-related behaviour for a more realistic picture of energy yield and more effective system design," says Christian Braun, senior engineer at Fraunhofer ISE.
Geographical location is of great influence
The study also shows that the yield of solar panels is highly dependent on the geographical location of a vehicle. For example, a Lightyear 0, a Ford E-Transit (via Sono Motors) and an eVolvo truck (via IM Efficiency) fitted with solar panels were scrutinised during the study. It shows that in southern Europe, vehicles with integrated solar panels can cover up to 50% of the annual energy consumption of passenger cars. In central Europe, the figure is 35%.
The researchers stress that more seasonal data - especially from spring and summer - is needed to confirm these long-term trends for all vehicle types. To improve geographical and seasonal coverage, stakeholders are extending the study to southern and eastern Europe.
The final report is expected next year. This report will contain updated findings and recommendations for optimal deployment of integrated solar cells by vehicle type and region. More information on the SolarMoves study is available here.
Image: PublicDomainPictures via Pixabay
