Becky Kazansky @ ITP

re-cyclelight: Energy Harvesting With Your Bike

re-cyclelight is a regenerative brake-light system by Alexander Kozovski and Becky Kazansky.

visit recyclelight.me
Featured in Best Student Green Designs on Inhabitat

Bikes are a part of our daily lives. Sustainability is a concept we hear about so much that its meaning has become diluted. Alex and I set out to make a small intervention in our daily lives — which involve bicycles — in order to see what that big concept could mean for us.

We decided to create a bike lighting system powered by the kinetic energy from braking the bike. Regenerative breaking isn’t a new thing: Scandinavian train systems have generated a surplus for local electrical grids for a hundred years with a system that utilizes the friction produced from breaking.

Dynamo systems for bikes often require an installation into the hub, generate power with each pedaling cycle, and cause an additional amount resistance for the rider. We wanted to make a system as non-invasive as possible; something you could ideally clip into the pre-existing setup on your bike.

Initial concept:

To use the brake calipers to drive generators to produce power.
Discreet unit of 2 geared motors per caliper, connected to an array of LEDs.

Activating the brake(pressing on the lever) puts the motor shaft to the wheel(tire). The friction turns the motors, thereby generating power to light the LEDs.
*The motors are placed on the caliper in front of the brake pads.
This is done for safety as engineering redundancy: If motors fail for any reason, the bike reverts to the default mechanism of the brake caliper.

Final Design Implementation:

Once installed, we found that each motor outputs at its highest revolutions approx 12V at 1 : 24 gear ratio; more than enough to power our circuit positioned under the seat.

We like that our device is only actuated when needed. It requires very little effort from the user, as it takes advantage of lost energy that would normally be converted to heat by friction.A standard dynamo design would affect the user during the entirety of the ride, requiring extra effort to generate power.

This design, allows both the control/actuation and the power generation to happen at the same moment, thereby not requiring a separate control mechanism (i.e switch) to power the circuit. This makes for both robust/efficient minimum constraint design.

Issues:
The mini gear head motors we used were well sized for the application (1.26″ x 0.63″ x 0.63), but the output shaft was very delicate 0.275″-long, 3 mm-diameter . The assembly process required us to remove the output gear from the shaft of the motor enough times that the pin holding it in place wore down, causing it to wobble. In the end, we used just one motor to generate power to our “STOP” LEDs.

Future:

We wish to use both motors as a pair to generate more power for other applications. Adding capacitance can expand the function of the lights beyond moments that the breaks are actuated.

One idea is to utilize an LED projector (paired to a smart phone) to visually provide directions in the form of projected directional arrows and serve as a headlight to light the way at night.