The Etive kinetic energy charger gives power walking a whole new meaning
By Jude Garvey
May 20, 2009
May 20, 2009 Hiking has its share of highs and lows. One of the less pleasing aspects is ensuring you have an adequate source of energy to power your personal electronic equipment. There are a number of renewable energy options available that you may consider when planning your next hiking trip. You could harness the sun’s energy and use a solar-powered charger or solar-wrapped batteries. Perhaps you might choose to use wind power to keep you in touch with the world? But wouldn’t it be great if you could harness power using your own kinetic energy? It makes sense. You’re using your legs all day, surely all that sweat, pain and muscle fatigue is good for something? Enter Kyle Toole, an industrial designer who has figured out a way to use our own energy to act as a power source for recharging batteries.
Faraday’s Law of Induction
The device is called Etive and it uses the naturally occurring, vibrating, shock forces that are concentrated at the knee, after the heel has struck the ground, during walking. Toole used the theory behind Faraday’s law of induction to create his device. Faraday’s law states that when magnetic forces are changed an electric current can be created.
Also, the amount of current that can be created is also directly related to the change in the magnetic field and the size of the field. As the magnetic field increases so does the amount of voltage created. This is called magnetic flux and is equal to the surface area of the magnetic field multiplied by the strength of the field.
How much energy do we create?
Initially, Toole did some calculations of a person’s power dissipation using data from the heel and knee (the two areas subjected to the most vibration during walking) and the ankle and wrist (the two points that are subjected to the largest rotational motion) as well as the calorific expenditure from hiking at 3.5 mph. He then determined that a person could expend an estimated 407 watts of power during hiking.
The development of the device
Toole then set about creating a device that uses repelling magnets and a high grade neodymium magnet (NdFeB) suspended within a magnetic field to generate voltage. As the generator module is exposed to shock (the heel strike) the NdFeB magnet "bounces" within a tube and induces a current within a copper wire coil, which is wound around the tube. A single generator module can produce 3.8V (peak AC) and significantly more power can be produced by stacking four generator modules.
With further development, the Etive should be capable of recharging a 2000mAh lithium-Ion battery in about five hours. It is expected that it will also come with multiple connector heads to fit the multitude of personal electronic devices on the market.
Smart idea. We hope this clever hiker-friendly design follows the similarly conceived nPower PEG in finding it's way to market.
Images via Coroflot