The mobility transition continues to present us with challenges. How can we reduce the massive carbon footprint of our transport and travel without sacrificing comfort? Electric powertrains are often seen as the solution, were it not for the problems of generating and storing our energy.
If we use electric cars, electric lorries and electric ferries powered by electricity derived even partly from fossil fuels, we do indeed reduce our CO2 emissions and improve air quality in our city centres. However, a complete green transformation will not take place until we are ‘fuelling up’ with 100 percent green electricity.
The findings of a new study by the Fraunhofer Institute (in German) are therefore all the more exciting. The researchers have discovered that if we were to install modern, high-efficiency solar cells directly onto our vehicles, they could meet between 55 and 70 percent of their annual energy requirements themselves.
The potential of vehicle-integrated photovoltaics
Solar cells offer a number of advantages as a source of electricity. Firstly, the sun is an infinite source of energy – at least for the next five billion years. Apart from panel manufacturing and energy storage, solar energy is also completely carbon-neutral and can be generated locally. This means that, unlike fossil fuels such as coal-fired or gas-fired power stations, solar cells do not rely on a centralised infrastructure for fuel supply.
They can supply electricity locally and easily wherever there is sufficient sunlight. More and more private households are recognising this advantage and installing solar power systems on their balconies or rooftops. There, they quietly and continuously help to reduce electricity bills by the end of the year. This raises the question: if solar cells operate so independently, why don’t we use them in our vehicles?
The SolarMoves research project run by the Fraunhofer Institute in Freiburg has now carried out a detailed investigation into the potential of vehicle-integrated photovoltaics (VIPV for short). The basic idea is surprisingly simple: why not fit vehicles – whether electric cars or those with internal combustion engines – with solar cells? After all, according to figures from the Federal Environment Agency, private cars are parked for an average of 23 hours a day anyway. As long as they are not in garages, multi-storey car parks or under carports, they could simply recharge their own energy storage systems during this time.
The SolarMoves study examines how effectively this could be achieved in Central and Southern Europe. The results are surprisingly positive.
VIPV could meet 55 to 80 percent of vehicles’ annual energy requirements
The differences between northern and southern Europe stem primarily from the fact that southern Europe enjoys more hours of sunshine. In countries such as France or Italy, electric vehicles could therefore meet up to 80 per cent of their annual energy requirements through solar panels. For Germany, Poland and the Netherlands, the figure is still as high as 55 percent.
In their study, the researchers examined 23 different vehicle types. The selection covered a range of vehicles, from compact cars with low power consumption and a small surface area for solar cells to lorries with a large surface area and high energy requirements. The researchers combined the vehicle data with vehicle and journey profiles obtained from satellite data. This was supplemented by weather data from Amsterdam and Madrid. As Christian Braun from the SolarMoves project explains in a press release, the vehicles were also fitted with sensors. Taken together, the analyses were thus based on a total of 1.3 million kilometres driven.
The result: VIPV can offer significant benefits to individual users, which in turn could have an impact on Europe’s overall energy consumption. If, for example, all new vehicles were fitted with VIPV between 2024 and 2030, this could reduce the load on the European energy grid by 15.6 terawatt-hours by 2030. That would be equivalent to 2,200 wind turbines, each with a capacity of 3 megawatts.
Potential in logistics, too
Solar cells offer benefits on vehicles even when they are not powered by an electric drive. The study showed that diesel-powered lorries consume less fuel when systems such as air conditioning, heating or other electronics are powered by solar cells. The investment in the solar cells would pay for itself within two years. Thanks to VIPV, purely electric lorries would also have a range up to 15 per cent greater.
Reducing emissions from our transport systems can, however, only be achieved through a multimodal approach. This is also made clear in our feature on the mobility transition. We should therefore, despite the rise of electric vehicles and vehicle-integrated photovoltaics, move away from private passenger transport and design the vehicles we use to be as climate-neutral and focused on the common good as possible.
Fitting existing vehicles with solar cells could offer a number of benefits. Parked at the roadside, they would help accelerate a green transformation of road transport. They could also be used as decentralised electricity storage units. An electric vehicle that has collected solar energy throughout the day could, for example, help meet the electricity needs of a detached house in the evening or even serve as an additional solar panel during the day.
However, previous attempts to bring electric cars fitted with solar panels to market have met with limited success. Whilst there have been concept studies such as the Mercedes-Benz Vision EQXX and market-ready models such as the Lightyear 0, the technology has failed to gain a foothold. More modern solar cells with higher efficiency and lower weight could, however, change this in the future. In the best-case scenario, the new study by SolarMoves will create the necessary incentives.
