Real-world data confirms potential of vehicle-integrated solar panels…

09 Sep 2025

…and PEARL consortium achieves roll-to-roll production of flexible perovskite solar cells.

A consortium comprising the Netherlands Organization for Applied Scientific Research (TNO), the Fraunhofer Institute for Solar Energy Systems (ISE), and the three solar technology system suppliers for vehicles Lightyear, IM Efficiency, and Sono Motors, have measured the potential of solar cars on European roads over a nine month period.

The group has this week announced that the results of the measurements “confirm that solar panels on vehicles can be a valuable, mobile source of renewable energy for the transport sector.” However, the findings also highlight significant challenges such as the effects of shading (over roads) and user behavior.

Since March 2024, 18 vehicles, ranging from trucks and buses to delivery vans and passenger cars, equipped with rooftop and side-mounted solar panels and sensors, have traveled more than one million kilometers on European roads.

“The measurements carried out during drive cycles in the Netherlands and North Germany confirm that side-mounted panels receive approximately 50% less irradiance than rooftop panels, validating earlier modelling assumptions, namely on average 2.8 kWh/m² per day for the top and 1.3 kWh/m² per day for the sides”, said Dr. Lenneke Slooff- Hoek, senior researcher at TNO.

Shading a critical factor

The study confirms that satellite and meteorological data help to fine-tune the shading factor that is used in modelling and takes into account shading from buildings, trees, and other vehicles.

“We recommend refining shading models and incorporating route-location-specific data as well as usage-specific behaviour to improve the accuracy of VIPV [vehicle-integrated photovoltaics] performance predictions,” commented Christian Braun, senior engineer at ISE. “This is essential for realistic energy yield assessments and effective system design.”

The SolarMoves campaign also validates predictive models developed in the first phase of the project, both on irradiance prediction and energy consumption of the vehicles.

For the energy validation the Lightyear 0 from Lightyear, a Ford E-transit van tested by Sono Motors and a eVolvo truck tested by IM Efficiency have been used as research tools in several case studies.

Initial results on the van show strong alignment between simulated and measured data, for solar yield and vehicle energy consumption and confirm that VIPV can contribute up to 50% of the annual energy consumption for passenger cars in Southern Europe and 35% in Central Europe. However, further seasonal data - especially from spring and summer - is needed to confirm long-term trends for the three types of vehicles.

Roll-to-roll production of flexible perovskite solar cells

A Horizon Europe project called PEARL has reported “decisive progress toward its target of 25% efficient, low-cost flexible perovskite solar cells with carbon electrodes.” The PEARL consortium, including Dutch group TNO, Finnish agency VTT Research, and Fraunhofer Institute for Electron Beam and Plasma Technology (FEP).

By combining cutting-edge materials research, pilot-scale roll-to-roll manufacturing and comprehensive sustainability measures, partners across Europe have delivered a series of significant achievements. The researchers have developed solar cells with an efficiency of over 21% on flexible PET substrates. The most important achievements of the project partners include:

• Power conversion efficiency of 21.6% through special surface treatments (molecular surface passivation with fullerene and silane self-assembled materials) was achieved by the Spanish research institute ICIQ.
• University of Rome Tor Vergata achieved 17.03% using greener perovskite solvents and optimized blade-coating protocols.
• Finnish research organization VTT demonstrated a lab-scale champion cell power conversion efficiency of 14.8% with a new printing process (gravure printed perovskite with DMSO-based ink).
• 9.1% power conversion efficiency with a fully roll-to-roll slot-die coated perovskite stack was achieved by the Dutch research institute TNO.

In parallel, VTT and TNO have scaled up R2R coating and patterning to larger formats and developed flexible minimodules with an area of 36 cm² and a power conversion efficiency of 4.5%. The consortium has also developed protective encapsulation that keeps the solar cells stable for over 2,000 hours under damp-heat conditions (85°C temperature and 85% humidity) – proving their durability for real-world applications.

“Our flexible perovskite cells have already surpassed 21% efficiency on bendable substrates, and we’ve demonstrated scalable roll-to-roll processes,” said Dr. Riikka Suhonen, PEARL Project Coordinator at VTT. “These achievements bring us firmly within reach of our 25 % target – paving the way to low-cost, high-performance solar modules for applications from building-integrated photovoltaics to the Internet of Things.”

PEARL will be exhibiting at the joint stand F6 at the European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC), in Bilbao, Spain, between September 22 and 24, 2025. PEARL will be represented as a panelist in the Perovskite Innovation Roundtable: Driving EU Leadership in Perovskite Innovation, on Monday, September 25 at 17:00.