Harvesting the energy from friction to create a safer bike

by Dalton Mullinax,  Jonathan Guy, Ryan Koprowski, and Matthew Laczko

Photo credit: static.environmentalgraffiti.com

Today, biker safety is often overlooked because many adults travel by car; however, young people without a driver’s license routinely rely on bicycles to travel short distances. For this reason, we wanted to find a way to increase the safety for bicyclists. Lights, being the predominant method of visibility, are absent on many bikes. For our project, we sought to improve biker safety by being able to power the lights on a bike using the friction that exists between the tires and the road. If we could harvest the energy lost due to friction, we could power the lights on the bike, thus improving biker safety.

We propose constructing bicycle tires with polyester-PDMS fiber interwoven within the fabric of the tire. The recent understanding of PDMS with polyester has opened a new door to the realm of attaining energy from frictional forces between two materials. This polyester-PDMS fabric is capable of generating energy from friction produced between the tire and the surface as the bicycle moves.

Today, many scientists around the world experiment with various methods to find ways to convert mechanical energy from two objects rubbing together to electrical energy. Physicists at the Georgia Institute of Technology in Atlanta, Georgia have found use in the triboelectric effect which is when two plastics rub together to create friction that can be harnessed by a triboelectric generator. These triboelectric generators are composed of smaller generators called nanogenerators that aid in the production of electrical energy (Toon). Although these triboelectric generators are small, the polyester piece rubs against a polydimethysiloxane (PDMS) sheet, thus creating friction that can be converted into electrical energy.

One form of this triboelectric generator is the PENG device, which is shown to the very far left in the picture below (Zyga).  This device has been proven to power the LCD screen, shown in the middle of the picture below, for upwards of one minute. Also, the PENG device has partially charged a lithium-ion battery (the image on the right in the picture) (Zyga).

The triboelectric generator uses the Piezoelectric Effect; “the piezoelectric substance is one that produces an electric charge when a mechanical stress is applied” (“Piezoelectric Effect”). The piezoelectric effect happens when a crystal acquires a charge when it is twisted, compressed, or distorted. One of the most useful characteristics of the piezoelectric effects is that is can be reversed easily (“The Piezoelectric Effect”). The figure below shows the forward and reverse motion of the piezoelectric effect.

When the piezoelectric effect material is stressed in forward motion, positive and negative particles shift which helps create an electrical field that can be harnessed through a nanogenerator. But, when the material is reversed, the electrical field does the exact opposite of the forward motion and uses an electrical field to create the piezoelectric effect material which then can be reused to make the forward motion.

Through our design, we are taking a new step toward nanotechnological use of a polyester-PDMS inner ring: we propose constructing bicycle tires with polyester-PDMS fiber interwoven within the fabric of the tire. This polyester-PDMS fabric will generate energy from friction produced between the tire and the surface as the bicycle moves.  This energy will be harvested and transmitted through a cable attached to the axle of the wheel and terminated at a connection on the handlebars of the bike. This terminal connection will then provide energy to the LED lights on the bicycle.

The picture below demonstrates the use of a PDMS with a rubber surface that can be used to create energy by touch. The inset picture shows that even the touch of a feather could set the sensor off and create energy as well as power the device through a triboelectric generator. This picture illustrates the device we will use in the rubber tires of the bicycle and demonstrates how the triboelectric generator will use friction to produce electricity to power the bicycle’s safety lights.

tribogenerator

Photo Credit: Zhong Lin Wang, Triboelectric generator

Our idea is to put the sheets of PDMS and polyester into the interior of the bike’s tires. One sheet would rotate with the movement of the bike and the other would rub the other way with the use a counter-rotating piece also in the interior of the bike’s tires. As the bike is ridden, friction would be created between the PDMS and polyester sheets rubbing together. The triboelectric generator would capture this energy so it could power the lights on the bike. Assuming technology is developed that shows how the energy consumed into the triboelectric generator could be released, this new technology could immensely increase biker safety.

Lights added onto a bicycle will improve rider safety and also increase the safety of car drivers around the biker. More bikers will be able to travel at night because their visibility will be increased, allowing their confidence in riding at night to be greater. Plus, all the light energy produced by triboelectric generator is environmentally friendly.

References

Fan, Feng-Ru, Zhong-Qun Tian, and Zhong Lin Wang. Flexible Triboelectric Generator! Atlanta, GA: Sciverse Science Direct, 10 Jan. 2012. PDF.

Hum, Phillip W. “Exploration of Large Scale Manufacturing of Polydimethylsiloxane (PDMS) Microfluidic Devices.” Diss. Massachussets Institute of Technology, 2006. Abstract. (2006): 1-56. Print.

“The Piezoelectric Effect.” Nanomotion Piezoelectric Effect. Nanomotion, n.d. Web. 03 Dec. 2012. http://www.nanomotion.com/piezoelectric-effect.html.

“Piezoelectric Effect.” Piezoelectricity. GSU, n.d. Web. 03 Dec. 2012. http://hyperphysics.phy-astr.gsu.edu/hbase/solids/piezo.html.

Quick, Darren. “Triboelectric Generator Could Allow Electricity-generating Touchscreens.” Triboelectric Generator Could Allow Electricity-generating Touchscreens. Gizmag, 9 July 2012. Web. 27 Nov. 2012. http://www.gizmag.com/triboelectric-generator/23248/.

Sihong Wang, Long Lin, Zhong Lin Wang. Nanoscale Triboelectric- Effect-Enabled Energy Conversion for Sustainably Powering Portable Electronics. NanoLetter. Washington, DC: American Chemical Society Publications, 2012.

Toon, John. “Georgia Tech Research News.” Georgia Tech Research News RSS. N.p., 9 July 2012. Web. 27 Nov. 2012. http://gtresearchnews.gatech.edu/triboelectric-generator-produces-electricity-from-friction/.

Toon, John. “Triboelectric Generator Produces Electricity by Harnessing Frictional Forces.” GT. N.p., 10 July 2012. Web. 15 Nov. 2012. http://gatech.edu/newsroom/release.html?nid=139511.

“The TriboElectric Series.” The TriboElectric Series. N.p., 30 Nov. 2012. Web. 30 Nov. 2012. http://www.trifield.com/content/tribo-electric-series/.

Zyga, Lisa. “Pyroelectric Nanogenerator Charges Li-ion Battery with Harvested Energy.” Pyroelectric Nanogenerator Charges Li-ion Battery with Harvested Energy. N.p., 20 Nov. 2012. Web. 29 Nov. 2012. http://phys.org/news/2012-11-pyroelectric-nanogenerator-li-ion-battery-harvested.html.

Featured image photo credit: http://www.tuvie.com/wp-content/uploads/wincycle001-futuristic-bike-by-younes-jmoula1.jpg

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