Turning Road Speed Into Charge

Electric vehicles and plug-in hybrids are no longer unusual on American roads. They deliver nearly all the benefits and functionality of conventional fossil-fuel vehicles while cutting air pollution, running quieter, staying easier to maintain, and matching or exceeding gas-powered vehicles on power. On almost every axis the comparison has closed.

Almost. The exception is refueling. Recharging an electric vehicle takes hours where a conventional vehicle takes several minutes at a pump, and that single difference severely limits continuous operating range on electric power alone. It is why manufacturers stay on constant lookout for anything that improves efficiency and lets a vehicle operate for longer times over longer distances. Inventor Michael A. Davis built the Wind Car to address exactly that need.

The Wind Car, as the name implies, is an apparatus that produces electrical power for an electric or hybrid vehicle as it moves. The design uses a series of wind turbines located inside a series of tubes routed from the front to the rear of the vehicle. Those turbines drive alternators, which generate electricity once the vehicle begins moving down the road. Under starting, uphill, or low-speed conditions, conventional rechargeable batteries drive motors located at each wheel through a conventional voltage regulator circuit. Once a suitable speed is reached, the turbine array is intended to contribute power back toward driving the motors and recharging the batteries.

• Front-to-rear tube routing. Tubes carry airflow through the vehicle body rather than mounting hardware into the slipstream as an external add-on.
• Turbine and alternator pairing. Each turbine drives an alternator; output rises in ratio to vehicle speed.
• Scalable array. Additional tubes with turbines and alternators are added according to the power needs of the host vehicle.
• Standard components. Batteries, turbines, charge controllers, drive motors, and interconnects are readily available industrial parts from existing wholesalers.
• Straightforward assembly. Relatively simple construction with low material and labor cost, suited to manufacturing workers of average skill.

On the manufacturing side the picture is unusually clean. Every material required to produce the Wind Car is well known to manufacturers working in this category. The work an engineering design team would take on is coordination — matching turbine output to the charging requirements of the battery pack and to the operating characteristics of the drive motors. The discrete components are best procured from wholesalers and manufacturers that already deal in goods of that nature, then assembled in final location. Low material and labor costs follow from the simplicity of the design.

Why an Alternator Pushes Back

Anyone who has turned a generator by hand notices it gets harder to spin once it is connected to something that uses power. That resistance is not magnetic attraction between the copper coils and the permanent magnets — copper is not magnetic, so the coils themselves are not pulled toward the magnet. The resistance comes from electromagnetic induction working in both directions.

As the turbine spins the alternator, the magnets sweep past the copper coils and induce a voltage in them. Adding more turns of wire raises that induced voltage. When the alternator is connected to a load — the battery charger or the drive motors — that voltage pushes a current through the coils, and current flowing in a coil creates its own magnetic field. By Lenz’s law, that field always opposes the motion that created it, so the turbine feels a braking force, called counter-torque. The more current the load draws, the stronger that braking force becomes.

This is simply energy conservation at work: every watt of electricity the alternator delivers has to be supplied as mechanical work by the turbine, and every watt the turbine supplies has to come out of the airflow passing through the tubes. That is why the engineering team’s job is one of balance — matching coil count, alternator size, and electrical load so the system captures useful energy without demanding more from the airflow than the vehicle’s speed can provide.

Key Terms

Electromagnetic induction

A changing magnetic field passing through a coil of wire creates a voltage in that coil. This is how every alternator and generator makes electricity.

Faraday’s law

The induced voltage grows with the number of turns in the coil and with how fast the magnetic field changes — more coils or faster spinning means more voltage.

Lenz’s law

The current produced by induction always creates a magnetic field that opposes the motion causing it. This is the source of the “push back” felt when an alternator is under load.

Counter-torque (electromagnetic braking)

The resisting force on the spinning shaft caused by Lenz’s law. It rises with the current drawn: no load means almost no braking; a heavy load means strong braking.

Back-EMF

The voltage generated inside a spinning motor or alternator that opposes the applied voltage. Drive motors produce it too, which is part of why a motor can also act as a generator.

Electrical load

Whatever draws current from the alternator — here, the battery charging circuit and the wheel motors. The load, not the coils alone, determines how much current flows.

Coil resistance (copper loss)

More turns mean a longer wire and higher resistance. Resistance does not cause the braking force — it actually limits current — but it wastes some of the generated energy as heat, so coil design is a trade-off between voltage and efficiency.

Permanent magnet

The magnet in the alternator’s rotor that supplies the moving magnetic field. Copper coils are not attracted to it; only iron or steel parts in the alternator are.

Cogging

A slight notchy resistance felt when turning an unloaded alternator by hand, caused by the permanent magnets being attracted to the iron core the coils are wound on — not to the copper itself.

The Wind Car is patent pending, a prototype has been built, and a complete product specification is on file. Inventor Michael A. Davis is seeking manufacturing, retail, wholesale, distribution, and licensing partners, and the full technical package is available to qualified parties under appropriate agreement. Contact us now to start that conversation.