Application of Coulomb's friction law to define energy consumption of new drive-trains

Abstract

A key argument in the transport field is about improving the energy consumption of cars. Should we go electric, ban combustion, move to fuel cells or change to renewable fuels [1-5]? This is an important research question because the number of cars worldwide is predicted to grow from 0.7bn in 2010 to 2bn in 2050, leading to a huge penalty in fossil fuel depletion, climate change and energy security in the near future [6]. But these discussions of electric cars, new battery materials and renewable fuels have missed a key point:that the main difficulty with cars is their evolution in terms of increasing weight. Evidence shows that cars increase in weight by about 2% per annum. This paper demonstrates that car weight dominates the energy question by showing that Coulomb's law of friction surprisingly applies to a complex system like a car, such that the energy usage, in other words overall friction force, depends mainly on weight. A new theory shows that dissipation in complex systems resolves into Coulomb's Law. Experiments demonstrate that the results fit this theory reasonably well. We have tested a hydrogen fuel cell battery hybrid composite car of 7kN weight and present results better than all existing hydrogen cars in terms of low energy use. The conclusion is that Coulomb's Law can be used to quantify precisely the energy consumption of cars and that lightweight designs are as important as hydrogen electric drive-trains in cutting fuel consumption.