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A new type of eco-friendly car tyre may be able to convert the static electricity between the tyre and the ground into useful energy that could be used to recharge the car’s battery.

Previous research has shown that rolling resistance of a standard car tyre on the road accounts for 5 to 30 per cent of a car’s fuel consumption. Now, Ning Wang at the University of Science and Technology Beijing and his colleagues have designed a new type of eco-friendly tyre that can recycle that wasted energy.

Normal tyres are made from rubber and reinforced by a material called carbon black. Wang’s tyres swap the latter for silica fillers that let the tyres grip wet roadways better and can last longer, but they also generate much more static electricity as they roll against the street, which can be bad for the car’s electrical systems.

That static electricity can be a boon instead of a problem, the researchers say. By incorporating triboelectric nanogenerators (TENGs) made of layers of rubber and copper into the tyres, they could capture the electrons causing the static charge and funnel them into the car’s battery. Eventually, Wang says, the researchers hope tyres like this could save 800 kilojoules of energy per year while also reducing energy waste.

The energy generating tyres could also help make driverless cars smarter, says Wang, by measuring road conditions. The current from the TENGs decreases with decreasing tyre pressure and changes based on whether the ground is smooth or bumpy, so it could also be used to monitor both the tyres and roads.