Innovating Solar Cars: Thermal Conductive Polycarbonates

A weight-efficient design is of fundamental importance for solar-cells powered cars in order to enable high speeds and ranges. Every component counts. In the automotive industry the heat sinks for headlights are usually made of aluminum, as it has a very high thermal conductivity. An innovative lightweight material solution is sought.

Even though the high thermal conductivity of aluminum enables a very good cooling system performance, it also has numerous disadvantages, such as severe limitations in terms of design and processing, a high CO₂ footprint and a high weight. Although plastics promise benefits, standard plastics have a thermally insulating effect. Can a new type of thermally conductive advanced materials  lead to new solutions?

Although aluminum is an excellent heat conductor, with around 100 W/(m∙K) it is clearly overengineered for the majority of heat sink applications in the lighting sector. The 10-20 W/(m∙K) usually required can now be achieved by plastics in combination with high levels of conductive additives. Compared to other plastics, polycarbonates offer the advantage of high dimensional and temperature stability.

Due to the sometimes very high thermal requirements - for example at the World Solar Challenge 2023 in Australia - Covestro recommended the new Makrolon® TC629 RE. This advanced material is a highly conductive polycarbonate and  as a mass-balanced RE product , it has a very low CO₂ footprint too. Covestro provided Team Sonnenwagen with several blocks of the material, from which the students were able to mill their individual heat sink solution. Very short production times and even more complex designs would be possible in an industrial injection molding process.