When we go at high speeds in our vehicle, we experience wind resistance which tends to slow down your vehicle. When you want that particular speed at which you were driving from the beginning, then you need to supply more fuel. I thought of an idea based on thermodynamics 1st law: energy can be neither created nor destroyed but it can be transformed from one form to another. When we place a turbine at the back of the vehicle,.the wind which passes us tends to flow through the turbine and in turn rotates the turbine producing electricity which can be used to power batteries and any secondary functions can be done. Now the main role comes in studying the velocity distribution of turbine and bike when it moves at high velocity. It has to be done by CFD (which is to be done yet) which is essential for installation of turbine to produce the maximum power.
To calculate the amount of power a turbine can actually generate from the wind, you need to know the wind speed at the turbine site and the turbine power rating. Most large turbines produce their maximum power at wind speeds around 15 meters per second (33 mph).