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Green Campus Bicycle Generator
There are many ways to convert and use energy. Energy stems from two basic forms; Potential energy, energy that is not yet active and Kinetic energy, energy which comes from the motion of things. This includes energy from our own bodies to do work. Instead of using our own potential energy, our modern day society has switched to using energy harvested from other sources such as fossil fuels. For example instead of using our own energy to walk up a flight of stairs, most Americans chose to use the elevator. However, not every country has this luxury, since most appliances only run off of electricity. One solution that provides electricity by utilizing human energy is a stationary bicycle run on human power.
(Source: Hazeltine & Bull,see below)
Description of Opportunity
Green Campus would like to have a bike powered generator. The human-pedal powered generator will be used as a demo to illustrate the amount of wattage used to light different types of light bulbs; incandescent, CFL, and LCD. The pedals on the bike would use mechanical energy to run the generator which will create electricity and light the bulbs. This demo will illustrate the amount of energy needed to power each type of bulb. It can also inform the public about alternatives to energy sources and perhaps exercising methods as well. It would also help individuals grasp the concept of creating Energy or the capacity of doing work.
In order to design a pedal powered generator fit for Green Campus’ purpose, the amount of power needed to light the bulb which requires the most energy (incandescent) must be known in order to make the right size generator to run it. The power created through the bike which will run the generator is DC power, however LCD's only run off of AC power. This means a transformer will be needed to turn DC electricity into AC electricity. The bike will be used for demonstrations, thus it should be easy to transport and take the stress of several different sized humans using it. This means the device should be light weight, yet stable. A complete bike will not be necessary for this project; instead, emphasis will be placed on a sturdy frame on which the bike will be built.
- Effectiveness; the generator should be able to light all of the light bulbs. This means creating both AC and DC power.
- Reliability; the unit should be able to work when it should. This means a simple design with few on-going repairs.
- Maintainabilty: Few routine maintenance repairs that are easy to identify and to service that are easy and safe.
- Repairability: The parts needed for any repairs should be easy to find and be at a low cost.
- Availability; the unit should be able to be used for several public displays. This includes ease of transportation.
- Safety; the design meets national electrical code guidelines
- Comfortable; the public must want to use the bike. If it is awkward or uncomfortable they will assume all pedal powered generators are.
- Sturdy; it should be able to hold the pressure of an array of body types and velocities.
- Up-cycle; the materials when applicable should be re-used materials.
- initial Cost; should stay with in Green Campus' budget, about $250.
Pedal Power basics
Pedal power is basically using human energy on a bicycle to do work for us. This can range from the most common use of a bike which is transportation, to creating an electrical current for a laptop. There are many ways to apply this technology to several uses. Although the technology of using pulleys and gears has been used for thousands of years, and the use of bikes as transportation has been used for hundreds of years , it was not until Dick Ott created his “Pedal Pusher” in the mid-twentieth century that an attempt was made to harness “power of pedal” (McCullagh 1977). The criteria used to create the Pedal Pusher are still important today; simplicity, easy operation and maintenance, and low cost.
Types of Pedal Power
There are several types of reasons and methods for converting a bicycle into a device other than transportation. According to R.J. Congdon, a human on a bike is the most efficient traveling animal or machine; defining efficiency as the “energy units required per unit weight per unit of distance travelled...[this] based partly on the efficiency of the large diameter of the wheel, the pneumatic tire, and the ball bearings” (Congdon 1977). Please see Figure 6.1. According to James C. McCullagh, “the muscle energy conversion of the bicycle is around 95 percent” (McCullagh 1977).
There are two main types of pedal power that can be crated; Electrical devices and mechanical devices, each having an ability to do the best type of work for certain tasks.
Manual Pedal Power
Like the typical bike, the mechanical pedal power works solely using gears and belts or chains in order for human exertion to become energy for work. Stationary mechanical pedal power devices are usually modified for a specific task. There are two basic methods for creating a stationary manual pedal power device, the modification of a regular bike, or the addition of pedals to any other device that is already hand-driven (Congdon,1977). This means the mechanical device can be used for a number of tasks from pumping water (Example; http://www.usaid.gov/lk/documents/tos/USAEP_solarpedalflo.pdf), grinding wheat or corn, shelling nuts, churning butter, plowing a field, to attaching it to house hold appliances such as a blender or a drill. The mechanical device is more efficient than the electrical one because all of the power created by the pedals is directly used to do its specific task, because the mechanical energy is not converted to electrical energy. Unfortunately, most of these devices are very specific and can only be used for their intended purpose.
Electrical Pedal Power
The electrical pedal power stationary bike is used to create an electrical current for electrical devices, this makes it possible for different appliances to run off the same pedal power generator. Here is a very brief introduction of how electricity is created taken from Appropriate Technology; Tools, Choices, and Implications (Hazeltine 1999). First and foremost, energy is the capacity to do work. In essence work is the transfer of energy in one form to the next. Different types of energy include potential, kinetic, mechanical, electrical and chemical energy. When we convert energy from one form to the next, there is always energy loss. The loss of energy in the conversion process is calculated through its efficiency. Efficiency= energy out/energy in.
Thus in the case of the electrical pedal power device, mechanical energy is converted into electrical energy. The efficiency of this electrical device is not as high as the manual device but it is more adaptable to several situations, usually not just one specific task. The efficiency of the device is further lowered if the Direct Current (DC) created must be converted into Alternating Current (AC) in order to run an appliance. This raises the initial cost of the device because added parts such as diodes and inverters are needed to convert the currents (Russavage, 4).
Pedal Power concerns
The first aspect of pedal power is identifying the most efficient design that will be appropriate for the task at hand. The design must be safe for the peddler; thus it must be secured to the stationary stand and all parts should be secured. When dealing with the electrical pedal powered device, more concerns are raised. There should not be more volts entering the appliance than it can handle, otherwise it could short circuit and damage the pedal power device and or the appliance.
Designing interpretive materials
According to Yvette Garcia from the “Powering a laptop computer at CCAT” (Garcia5) materials needed to create an electrical pedal powered device include:
Bike: the bike should be stationary.
Flywheel: a heavy rotating disk used to store momentum.
Battery: It is important to match the voltage of the appliance you are trying to power.
Diode: allows energy to be transferred from the generator to the battery
Fuses: needed to protect your wiring should your system short circuit.
Generator: The generator actually transforms human energy into electrical energy.
Inverter: converts DC current into AC current for powering common household appliances.
1. McCullagh, James C. (1977) Pedal Power: in work, leisure, and transportation.. Rodale Press, Emmaus, PA.
2. Congdon, R.J. (1977) Introduction to Appropriate Technology; toward a simpler life-style. Rodale Press, Emmaus, PA.
3. Hazeltine, Barrett & Bull, Christopher. (1999) Appropriate Technology; Tools, Choices, and Implications. Academic Press,.
4. CCAT Website; Russavage, Joseph; Pedal Power: How to do it yourself;http://www.humboldt.edu/~ccat/pedalpower/josephSP2004/index.html
5. CCAT Website; Garcia, Yvette; Powering a Laptop Computer at CCAT. http://www.humboldt.edu/~ccat/pedalpower/computer/index.html
Budget for Pedal powered generator modeled from www.scienceshareware.com
- no battery in design & bike not in budget
|1||bicycle||anyone, not permanent||$0||$0|
|1||skateboard wheel||Transitions skate shop||$0||$0|
|1||800 watt Inverter|
|1||Flat washers||Hardware store/ had||$0||$0|
TOTAL = $235
|hack saw||need (CCAT/friends)|
|wire striper||need (CCAT/friends)|
|heat gun||need (CCAT/friends)|
|Solder iron||need (CCAT/friends)|
|Wire Crimper||need (CCAT/friends)|
Proposed time line
|Week 1||Decide on concrete design||Have budget completed|
|Week 2||Have all parts located||As many purchased/ ordered|
|Week 3||Start on assembly||detail once design is chosen|
|Week 4||Work on Assembly||detail once design is chosen|
|Week 1||Work on Assembly|
|Week 2||Have a working Pedal Powered generator|
|Week 3||Work on Poster|
|Week 4||Work on Poster|