Graphene could lead to greener more fuel-efficient cars in the future by converting heat into electricity, according to researchers at the University of Manchester.
Harvesting heat produced by a car’s engine which would otherwise be wasted and using it to recharge the car’s batteries or powering the air-conditioning system could be a significant feature in the next generation of hybrid cars.
Thermoelectric materials convert heat to electricity (or vice-versa). The challenge with these devices is to use a material that is a good conductor of electricity but also dissipates heat well, so that the 70% of energy generated through fuel consumption that is currently lost as heat can be used to generate an electrical current.
Currently, materials which exhibit these properties are often toxic and operate at temperatures higher than those produced by car engines. By adding graphene, a new generation of composite materials could reduce carbon emissions from car use.
Scientists from The University of Manchester, working with European Thermodynamics Ltd, have increased the potential for low cost thermoelectric materials to be used more widely in the automotive industry.
The team, led by professor Ian Kinloch, professor Robert Freer and Yue Lin, added a small amount of graphene to strontium titanium oxide. The resulting composite was able to convert heat which would otherwise be lost as waste into an electric current over a broad temperature range, going down to room temperature.
“Current oxide thermoelectric materials are limited by their operating temperatures, which can be around 700 degrees Celsius. This has been a problem which has hampered efforts to improve efficiency by utilising heat energy waste for some time.
“Introducing a small amount of graphene to the base material can reduce the thermal operating window to room temperature, which offers a huge range of potential for applications.
“The new material will convert 3%-5% of the heat into electricity. That is not much but, given that the average vehicle loses roughly 70% of the energy supplied to it by its fuel to waste heat and friction, recovering even a small percentage of this with thermoelectric technology would be worthwhile.”
The findings were published in the journal ACS Applied Materials and Interfaces.
Graphene’s range of superlative properties and small size causes the transfer of heat through the material to slow, leading to the desired lower operating temperatures.
Source: Alun Williams, Electronics Weekly