The wheelchair that would charge its own lights

What it was

The concept had a long name, Roll.Charge.Light.Protect, and a simple aim. Designers Mingoo Kim, Yunjin Chang and Sueun Park wanted wheelchair users to be seen on the street after dark, without batteries to buy or a charger to remember.

The power came from the wheels. In the published description, a magnet geared to each wheel spins as the chair moves, and a coil carries the current to a set of LEDs under the wheel cover. Electricity gathered during the day would be stored for the evening. A small LCD in the center of each wheel showed how much charge was left and how long the lights would last.

It was shown as renderings only. A reader at the design site Tuvie raised the practical questions: how much weight the system would add, what it would cost, and whether the lights could be switched off, since not everyone wants to glow all the time.

A wheel that is already turning is a power source nobody has to remember to charge.

Where the idea went

We found no prototype, no maker and no sale, and no later trace of the project from its three designers.

The physics was never the problem. Reelight, founded in Denmark in 2003, makes bicycle lights that work the same way: magnets on the spokes pass a coil in the lamp, and each pass produces a flash. A BikeRadar review in December 2007 named the catch, which is that the lights stop when the wheel stops, and noted that a version with battery backup was available.

A small version did reach wheelchairs. A US patent granted in 2011 to An-Min Hu describes a caster wheel with a coil, a permanent magnet and LEDs set in a translucent tire, lit by rotation alone. Wheelchair parts dealers now list casters that light up as they roll. One 3-inch Rolko model has a clear wheel with LEDs that flash when rolling, and it needs no batteries.

What it means now

The concept asked a good question. Why should being visible at night depend on remembering to charge something? The wheels are moving anyway. Bicycle makers had already answered it, and the answer transfers.

What it underestimated is the trade-off its reader spotted. A manual wheelchair is pushed by hand, so any weight or drag added at the wheel is paid for by the person pushing. A generator, storage and a display in each main wheel is a lot to carry for a light. The version that reached the market is a tiny generator in a caster.

The switch matters as well. A light should be something a wheelchair user chooses for a dark road, not a permanent feature of the chair. That is one reason a small clip-on light is still the simpler answer.