A team of researchers from The University of Manchester have worked together with experts at European Thermodynamics to enhance the chances for economical thermoelectric materials to be more widely applied in the automotive sector.
Heat from a car’s engine is wasted, but if this could be harvested and used to recharge the batteries of the car and also for operating the air-conditioning units, that could pave the way for advanced hybrid cars. About 70% of energy generated through fuel consumption is lost in the form of heat by the average car. Using that lost energy would require a thermoelectric material capable of producing electrical current from heat.
Thermoelectric materials possess the ability to transform heat to electricity and electricity to heat similar to refrigerators. The key is finding a material which is not only a good electricity conductor but also a good heat dissipater.
At the moment, materials with these characteristics are mostly toxic and operate at temperatures higher than that generated by car engines. Using graphene in the material could create a range of advanced composite materials capable of decreasing global carbon emissions from car use.
The University of Manchester team was headed by Prof Ian Kinloch, Prof Robert Freer and Yue Lin. They added a small quantity of graphene to strontium titanium oxide. The composite created from that combination had the capacity to convert heat into an electric current over a wide range of temperatures, beginning from room temperature.
Current oxide thermoelectric materials are limited by their operating temperatures which can be around 700°C. This has been a problem which has hampered efforts to improve efficiency by utilising heat energy waste for some time.
Our findings show that by 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 exceptional properties of graphene and its miniature size allow heat to be transferred slowly through the material, thereby causing the preferred lower operating temperatures to be achieved.
Car manufacturers have always been keen on finding ways to improve fuel efficiency and at the same time, maintaining good performance. Graphene as a composite material can be applied in the bodywork or chassis of the car so as to reduce fuel consumption by decreasing the weight in comparison to conventional materials.
Graphene was discovered by Sir Andre Geim and Sir Kostya Novoselov in 2004. It was isolated at The University of Manchester. This feat earned them the Nobel Prize for Physics in 2010. Since then, the £61m National Graphene Institute at The University of Manchester has been the research center for graphene and associated with more than 40 industrial partners working on graphene-related projects.
The team’s findings can be found in the journal ACS Applied Materials and Interfaces.