Now a days we have the problem of energy wastage alot.
That is why it is needed to increase the efficiency of energy.

In cars we have, especially electric or solar car, it runs with the electricity. It has some particular range to have kms. Then after we need to drive it, we need to charge it again.

If introduce d.c. generator at all 4 tires we can have energy to recharge the battery in running condition of car. By this energy regeneration some frictional losses will be there. But efficiency will be increased, compared to what was gotten before.

There is an option to set it with the gear ratio. If any problem of size of dc generator. Weight will be considered as of load calculation by battery capacity.

4 pole generator will have lesser weight, so that can be used

As an option we can use the wind force while driving. As we can make energy by making wind mill type energy by rotation. For this aerodynamic law will be in picture, for less frictional losses.