The power consumed overcoming aerodynamic drag goes up with the cube of velocity, so the faster we want to travel the lower the drag coefficient and reference area of our car needs to be.
 

Extensive aerodynamic development was performed on TMM as part of my third-year (bachelors equivalent) dissertation project. The backbone of this development was validating the CFD approach on an aerodynamically similar World Solar Challenge model that the University of Southampton already owned. This was done in the 7’x5’ wind tunnel at Southampton, and proved the CFD approach could capture both the absolute drag values and the relative change in drag when sweeping the tunnel model through different onset angles.

Instead of featuring an internal structure responsible for load bearing, the optimised aerodynamic surfaces described on a previous project page are also used as the template for a composite monocoque. Ideally the chassis mass would be reduced to a minimum whilst still meeting all the safety regulations and structural requirements (plus appropriate safety factors). This is primarily to reduce rolling resistance, which is directly proportional to the total car mass.

Certain aspects of improving Greenpower cars is obvious – reduce drag, reduce mass. However, other aspects are more nuanced – what is the optimal way to deploy your limited battery energy around a lap/race, taking into account hills, headwinds, corners etc. To answer these questions you either need to do extensive and expensive testing, or detailed physics models representing the cars behaviour must be simulated virtually. This is known in racing as lap time simulation (LTS).

In Greenpower, overcoming rolling resistance makes up a significant portion of the energy consumed over a race. The style of cars means unexpected tyres are often used, e.g. those from Brompton bicycles. Given the lack of high-performance Brompton bikes, there has been very little testing on their tyres rolling resistance, and so we took it upon ourselves to build a test rig and determine which tyres were the best.