As part of the Spring 2013 semester ENGR 305 Class at Cal Poly Humboldt Holly Johnston and Garrett McElroy were assigned to refurbish a bicycle-powered energy generating system for the Campus Center for Appropriate Technologies' (CCAT) Mobile Energy Operations Wagon (MEOW). Four bikes were stored inside the MEOW, three with generators attached, one without. Once upon a time, these bikes were part of the CCAT pedal concert generator. Over time they fell into disrepair. The assignment was to attach at least one, preferably three, bikes to the existing battery system within the MEOW. These batteries were only charged by solar power at the time. After much removal of rust and dust, addition of new wires and plugs for the bikes, two of the bikes were ready to be attached to the MEOW. The MEOW's battery system required a higher voltage than the bikes could produce, so step-up voltage converters were purchased as well as other electrical equipment. After consultation with a local solar engineer who originally helped to set up the MEOW's system, the bikes were able to be attached to the battery system. The MEOW now has two functioning bicycles as part of its mobile energy service.
Background[edit | edit source]
CCAT MEOW (Mobile Energy Operations Wagon) is a mobile system for renewable energies on campus at Cal Poly Humboldt in Arcata, California. The trailer is parked at and run by CCAT: the Campus Center for Appropriate Technologies. The MEOW's intended use is to provide an alternative source of energy for local events and concerts. Currently the MEOW is set up with 6 solar PV panels and houses four exercise bikes. These bikes are to be the pedal power electricity generators of the MEOW. The vision is that when the MEOW goes to an event and the batteries charged by solar are drained, the bikes can be used to recharge the batteries and power the event.
These four exercise bikes were once part of the CCAT pedal concert generator, built in 2002. These bikes were used at such events as the anti-Iraq War protest on the Arcata Plaza in 2002, the Humboldt Renewable Energy Fair in 2003 and were featured on the front page of the Lumberjack - HSU's campus paper.
At the start of the project, three of the bikes were set up with generators. These bikes were in disrepair. There was a fair amount of rust buildup on the exposed metal and well as dirt, dust and old grease that needed to be removed. There existed no mechanism for attaching the bikes to the MEOW battery system nor was there any other battery system that the bikes could attach to.
A small team from Lonny Grafman's Spring 2013 ENGR 305 class worked with CCAT to get these bikes back in action. This team was composed of Garrett McElroy and Holly Johnston, both seniors and environmental science majors at Cal Poly Humboldt.
Problem statement[edit | edit source]
Three bikes were already fitted with generators at the beginning of this project. These three bikes had a fair amount of rust and dust accumulation as well as some worn-out wiring. None of the bikes had a mechanism by which they could attach to each other, nor to any kind of battery system in order to power a stage or event, as was the intended use. There was a battery system in the MEOW, however it was already being fed by the solar panel hookup on the roof of the MEOW. Attaching the bikes to this system would require a higher voltage (Approximately 50V) than could be produced by a single bicycle (approximately 28V), and generators cannot be wired in series.
Construction[edit | edit source]
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The MEOW parked in the driveway at CCAT
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State of the bikes as of January 2013 at the start of the project.
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Disassembling a bike for cleanup
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Holly removing rust with the CCAT pedal grinder
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A bike is fully disassembled for deep cleaning.
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The generator for a bike, with the horrible, horrible electrical tape. The bulge in the wiring is a diode.
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Attaching new wires to the generator by soldering and replacing the disliked electrical tape with wonderful heat-shrink tubing.
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Solar charge controller and battery system of the MEOW before bike hookup.
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Voltage input to battery system. Voltage from the bikes needed to be above 48V to provide charge to the batteries.
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Plugs were attached to the bikes for ease of system hookup.
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Garrett testing the voltage output for a bike generator.
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Connected to MEOW using a 50 amp Fuse.
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Wires running out from the MEOW.
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Garrett attaching the industrial rectifier diode to the junction box, complete with heat-shrink tubing.
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Junction box with Industrial Rectifier
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Step up Converters used to bring voltage from 28 to 52 volts
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Connectors from the bike. Box shown is made from a recycled cutting board.
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Adjusting the voltage from the step-up converters to 52 V.
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Connection to the MEOW.
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Wheels for the two bikes were made from recycled roller blades.
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Hook attached to handlebars keeps bike wires from dragging on the ground.
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Wires easily hang on hook
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Bikes cleaned up and ready for action.
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Garrett demonstrating proper form for pedaling a MEOW bike.
Addressing the Problems[edit | edit source]
Clean-up[edit | edit source]
Cleaning up the bikes took many hours of work. Over time there had been an accumulation of rust, dust and old grease as well as old wiring on the bikes. Each bike was meticulously disassembled and rust was removed with a combination of wire brushes, steel wool, electric sanders and the CCAT pedal grinder. Dusty parts were wiped clean and fresh grease was applied where needed. Once free of rust, the bikes were reassembled with some extraneous parts removed. New wires and connectors were attached, mostly by soldering, and these connectors and the diodes that also went with the bikes were covered with heat-shrink tubing.
Transportability[edit | edit source]
Transportation for the bikes over a long distance was easy to address, as the bikes are already stored in the portable MEOW trailer. The primary concern with transport for these bikes was for shorter distances. Each bike is fitted with a heavy motor and the front wheels also add significant weight. Several different wheel types were considered and discarded either because they were too large or not strong enough to support the weight of the bicycle and a person. Eventually rollerblades were bought from a local thrift store. Wheels and the wheel frames were removed from the rollerblades and the frames were cut in half to fit on the front of the two bikes. Originally, two wheels were attached on each frame, however the weight of the bike made it impossible to spin the wheels directly underneath the bike frame. These malfunctioning wheels were removed, leaving only one wheel per frame as can be observed in the above photo gallery. These wheels allow for ease of transport and are strong enough to withstand the weight of the bike and the person riding it. There were concerns that the bikes would be tilted back more than was comfortable or safe for the user, however this proved to not be the case, and the bikes are both secure and comfortable to ride with the wheels attached. As can be seen in the above video, the wheels make the bikes highly mobile over short distances.
Energy Production[edit | edit source]
Before the bikes could be hooked up to the MEOW, the generators had to be tested. This was done with a multimeter and each bike was found to produce approximately 28 volts when pedaled at a constant and maintainable rate. The battery system of the MEOW required at least 48 volts to charge the batteries, and as the bike generators would have to be wired in parallel, somehow the bikes had to be made to produce more voltage. A solution was found in the form of voltage step-up converters, two of which were ordered from E-bay. These step-up converters converted current from the bikes into voltage, making the bikes capable of producing well over 50 volts each. The converters are also capable of regulating the voltage into the battery system, currently they are set at 52.5 volts and should not be set above 54 volts with the existing battery system. Each bike has a positive and negative wire extending from the generator and attaching to a plug for ease of hookup. The step-up converters are fitted with boxes (one designed from a recycled cutting board) and with plugs of their own at either end which can then be attached to the wires coming off the battery system. These converters take a maximum of 600 Watts, so only two bikes can be attached to each converter.
Attaching to the MEOW[edit | edit source]
Once the bikes were capable of producing ample voltage the next question was how to attach them to the MEOW. The team questioned whether a charge controller would be needed for the bikes, and it was unknown how complicated the battery hookup would have to be. "Solar" Roger, a local solar technician who had originally helped to set up the MEOW solar system, was contacted and was able to provide extremely helpful information. A charge controller would not be needed for the bikes as there was already one in place for transferring the energy from the battery system. A 50 amp fuse was needed in order to ensure that the current flow from the bikes would not overheat the batteries or the wires. The wires were attached to the batteries directly through the shunt on the positive side and the negative wire was attached to the negative wire coming off the battery. To ensure that excess energy would not come off the battery into the bikes, wires were passed through a 20 amp industrial rectifier diode before going into the fuse.
Interpretive Materials[edit | edit source]
An informational poster on the setup and history of the bikes will be presented to CCAT along with the completion of the project.
How it Works[edit | edit source]
When a person pedals one of the completed MEOW bikes, they produce mechanical energy, which spins the front wheel of the bicycle. This energy is transferred to a generator by means of a V-belt that goes around both the wheel of the bicycle and around the wheel of the generator. When the generator wheel is spun, magnets react with copper coils inside converting the mechanical energy to electrical energy which can then be transferred through wires. This energy goes into 10-gauge wires attached to the generator and subsequently through a diode, which keeps excess energy from flowing backwards into the bikes which would make the generator act as a motor and spin the bike wheels against the person pedaling. At this point the two bikes come together, wired in parallel and the energy from both bikes flows into the step-up voltage converter. The step-up converter takes input voltage of 28 from the bikes and boosts it to 52.5 volts. The energy then flows through another diode, though the 50 amp fuse and into the battery system where it is stored for future use.
Setup[edit | edit source]
The bikes are set up so that they can be pedaled outside the MEOW. The two wires coming out of the connector box near the battery system can be passed through a small flapped hole on the same side of the trailer and outside. The bikes will be set up just outside the trailer and the wires from the bikes are plugged in to the step-up converter which is in turn plugged in to wires coming out of the MEOW. A small stool, bucket or stand should be used to hold the step-up converter so that it doesn't hang free and risk damage. For ease of hookup, the plugs are color and size coded. Red is for positive wires, black is for negative wires.
Maintenance[edit | edit source]
A "How-to" manual for the bikes will be presented to CCAT along with the completion of the project. The bikes must be stored inside the MEOW or otherwise indoors to avoid rust in the moist Arcata climate. Bike chains will require periodic lubrication in order to ensure maximum efficiency and functionality for the bikes. The wire connector must periodically be checked for corrosion to make sure there are solid connections made.
Timeline[edit | edit source]
| Task | Description | Proposed Date | Actual Date |
|---|---|---|---|
| Meet with Dustin | Talk to him about bike getting hooked up to MEOW | 2-22-13 | 2-22-13 |
| Get other bikes to be able to get hooked up | Rewire and get back bikes into operating order | 3-3-13 | 3-17-13 |
| Possible meeting with solar Roger. | to talk about attaching the bikes to the meow | 3-11-13 | 3-11-13 |
| Make bikes transportable | Make sure bikes are easy to transport (add wheels) | 3-11-13 | 5-10-13 |
| Test bikes for full capacity | Test voltage output | 3-29-13 | 3-29-13 |
| Get 1-3 bikes completely operational | Make sure they all work and connect and charge the meow | 4-2-13 | 5-10-13 |
| Educational Pamphlet | Make educational pamphlet and poster to go with system | 4-5-13 | 5-15-13 |
| Solar Roger Talk | Attaching the bikes to the meow after figuring out source | 4-28-13 | 5-05-13 |
Costs[edit | edit source]
Following are the costs incurred over the course of the project.
| Quantity | Material | Source | Unit Cost (US $) | Total ($) |
|---|---|---|---|---|
| 4 | Wheels for bikes | Angels of Hope Thrift Store | 4.00 | 4.00 |
| 5 | 20A Industrial Rectifier (Diode) | Redwood Electronics Corporation | 4.00 | 21.64 |
| 2 | 12-80V, 600W Step-up Converter | Ebay | 19.94 | 39.88 |
| 20 ft | 10 Gauge Wire (10 ft red, 10 ft black) | Ken's Auto Parts | 0.54 | 10.84 |
| 1 | 50A Fuse | Ken's Auto Parts | 4.49 | 4.49 |
| 1 | Fuse Holder | Ken's Auto Parts | 6.05 | 6.05 |
| 1 | Cutting Board | thrift store | 0.50 | 0.50 |
| 2 | Peco boxes 4x4x2 | Industrial electric | 11.00 | 22.00 |
| Misc | Nuts, bolts, screws | Ace Hardware | 10.00 | 10.00 |
| Total Cost | 119.40 | |||
Future Project Needs and Suggestions[edit | edit source]
The Spring 2013 team was only able to finish and hook up two bikes to the MEOW system. Two bikes remain to be hooked up, and in order to generate enough electricity for an event, more bikes will be needed. Of the two remaining bikes, one is nearly ready to be hooked up to the system, however there has been an issue with the generator on that bike: it is either running backwards or the diode attached to that bike is not of a high enough amperage (it is approximately 8A, while the bikes require at least 10A-20A diodes) or both. This bike's wheel may also need some repair as it is not spinning correctly. This likely has to do with the ball bearings inside the wheel, as during the cleaning process they may not have been replaced properly. The other bike lacks a generator and any infrastructure for electricity generation.
There currently exist two step-up converters to hook up the bikes. As it is set up now, the two working bikes can attach to one converter and the other is available for use by the next two bikes. Each step up converter has a maximum capacity of 600 Watts, so one converter can take a maximum of two bikes. The industrial rectifier diode inside the connector box has a maximum amperage of 20A, so adding more bikes to the system will likely require either more diodes or a diode with a higher amperage rating.
Update October 2013[edit | edit source]
The MEOW was stolen in 2010 and later found in Hoopa stripped of the solar panels and other expensive equipment. After receiving donations, the repairs to the MEOW were completed in Spring 2013. Presently the MEOW has not been used at any events or functions. It is currently utilizing the new solar panels to keep the new batteries charged and there are plans to attach the MEOW to the CCAT main building in order to supplement the buildings energy independence. However, at this time HSU is requiring CCAT to work with PG&E before this can be implemented. This requirement is to insure safety of CCAT workers as well as the surrounding community as when it was first attempted to connect there were some breakers that were tripped.
New Equipment Images[edit | edit source]
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New Battery Array
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Bike Unit
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Generator Unit
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Bike Input Cables
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Charge Control Unit & Meter Unit
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Solar Input Digital Display
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MEOW Front Access
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Inside MEOW
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Inverter
Literature Review[edit | edit source]
Following is a review of relevant literature with respect to pedal power systems both from an educational and mechanical perspective, bike repair and working with batteries for the pedal power hookups at CCAT.
Pedal Power Basics[edit | edit source]
For many years, human machinery was based upon human power from hand cranks and mechanical systems that mostly used the upper body. Pedal power challenges this concept, using the most powerful muscles in the human body, the legs, to power our mechanics instead.[1]
Education & History[edit | edit source]
Of humanity's many mechanical achievements, the bicycle is one of the most efficient machines ever devised. Effectively, the bicycle has changed little since the first modern bicycle prototype was built in 1885 (with different styles of bicycle preceding this). Many mechanical advances owe their beginnings to the bicycle, including ball bearings, pneumatic (air-filled) tires, and even the first flying machine.[2]
For many years, the primary methods of machine power were either hand crank or foot levers. As bicycles became more popular in the 1890s these methods were largely replaced with pedal power. Advertisements for machines from this time show saws and lathes on tables run by pedal power.[3]
From well pumps and corn shellers; to sewing machines and televisions, pedal power can apply. Stationary pedal power systems can be developed with existing bicycles or exercise bikes, adapting hand powered machines or designing a pedal powered system from the ground up.[4]
For many years, the primary methods of machine power were either hand crank or foot levers. As bicycles became more popular in the 1890s these methods were largely replaced with pedal power. Advertisements for machines from this time show saws and lathes on tables run by pedal power.[5]
Spreading education about appropriate technology is a very important part in the continuing growth in the success in harnessing alternative energy.[6]
Setting up Pedal Power Systems[edit | edit source]
Setting up a pedal power system that produces electricity requires converting the mechanical energy from the pedaling to the electrical energy used in many appliances and electrical equipment. In the case of the MEOW's exercise bikes, this can be done by looping a V-belt around the wheel and a generator. The generator is hooked up to a battery system to store the energy flow. This can then be attached to an inverter to operate higher voltage appliances, although some have recommended powering low-voltage DC appliances instead, not requiring an inverter.[7]
Hooking up more than one bike, each with its own generator requires the use of diodes to ensure that the energy produced does not go back into the generator, making it act as a motor, working against the person pedaling.[8]
Bike Repair[edit | edit source]
In their current state, the bicycles where not fit to be used as generators due to rough operation that was from the lack of maintenance and care. Bikes where stripped down and grease from base to bars and no put back together brining them back to working order.
Chains[edit | edit source]
A dirty or rusty chain on a bicycle can impair the efficiency. Cleaning and lubricant can help to assuage these concerns, as can proper storage of the bicycles to ensure that they are not exposed to undue moisture. If one of the chains is in poor enough condition, it may be necessary to replace the chain. If this is needed the size of the chain will have to be determined. Bike chains come in either 1/8 inch width or 3/32 inch width. This can be determined by measuring the thickness of one of the bike's gear teeth. Given that the bikes are one-speed exercise bikes it is likely that the chains are 1/8 inch. Cleaning a chain can be done by submerging it in a solvent. This source suggests either a cleaning/degreasing fluid or kerosene. After cleaning, the chain should be thoroughly dried and lubricated once dry.[9]
http://www.parktool.com/blog/repair-help
Batteries*[edit | edit source]
Batteries are extremely useful for alternative energy sources, but they must be dealt with carefully.
How Batteries Work[edit | edit source]
The rechargeable batteries that the pedal power group will be working with are likely deep-cycle lead acid batteries. Such batteries are composed of lead plates immersed in a solution of sulfuric acid. As the battery loses charge, sulfur molecules bond with the lead plates, releasing electrons which then flow from the negative side of the battery to the positive side. When the voltage of a power generator is higher than the voltage within the battery, electrons will flow into the battery, breaking the bonds between the sulfur and lead and charging the battery. Deep-cycle batteries can withstand full drainage of energy and still be functional, although constantly draining the battery is a situation better avoided as the battery will have a shorter lifespan. It is recommended that batteries be discharged to a maximum of 50% on a more regular basis.[10]
Connecting Generators to Batteries[edit | edit source]
To connect a generator to a battery system feed wires must be run from the generator to the battery. Given the consistent voltage given by the step-up converters we are able to use those as the controller units themselves setting them to a output voltage just below the full charge cut-off. There are NEC/CEC requirement that over-current protection and disconnection devices be installed so we are installing a inline fuse along with Industrial rectifiers and disconnects. This can be done with either switches, circuit breakers or plugs[11]
Regulating DC Voltage[edit | edit source]
In our setup we are using DC~DC step-ups which allow us to set the output voltage to the one needed, this can also be achieved using a charge controller which can help to regulate the voltage from a generator before attachment to a battery system.[12]
*Please note that this is a work in progress and not a complete description of how to set up a battery operating system!
Criteria[edit | edit source]
Following is a consideration of the project criteria. It is essential that the bikes be functional, safe and educational to the public. Criteria are weighted by importance on a scale of 0-10, 10 being the most important to the project.
| Criteria | Constraints | Weight (1-10) |
|---|---|---|
| Functionality | Bikes need to be able to generate electricity | 10 |
| Transportability | Need to be able to move around with relative ease | 6 |
| Education | Bikes should have educational information on or around them | 8 |
| System Integration | Bikes need to be hooked up to the MEOW energy/battery system | 10 |
| Operability of System | System must be relatively easy to operate | 8 |
| Safety | All potentially hazardous equipment must be covered | 10 |
| Appropriate Tech | Use of recycled/upcycled or alternative materials | 7 |
| Budget | Must not exceed CCAT budget | 9 |
| Aesthetics | Bikes need to be presentable to public, removal of rust, chipped paint, etc. | 8 |
| Aesthetics | "Prettiness" - painting, making bikes aesthetically pleasing | 5 |
Special Thanks[edit | edit source]
We had help on this project and would like to extend our thanks to Lonny Grafman, "Solar" Roger and his Band of Merry Solar Installers, Industrial Electric of Arcata, David Katz, Emmanuel, Jacob and Cassandra the three wonderful CCAT Co-Directors. Thanks also to Roger Tuan who has been our CCAT liaison and Dustin who also works at CCAT and provided us with very helpful information on the MEOW.
References[edit | edit source]
- ↑ Pedal power for occupational activities: Effect of power output and pedaling rate on physiological responses Tiwari, P S; Gite, L P; Pandey, M M; Shrivastava, A K. International Journal of Industrial Ergonomics41. 3 (May 2011): 261-267.
- ↑ Congdon, R.J. Introduction to Appropriate Technology Toward a Simpler Lifestyle. Chapter 6. Rodale Press, Emmaus PA. 1977.
- ↑ McCullagh, James C. Pedal Power in Work Leisure and Transportation. Chapter 1. David G. Wilson. Rodale Press. 1977.
- ↑ ibid.
- ↑ McCullagh, James C. Pedal Power in Work Leisure and Transportation. Chapter 1. David G. Wilson. Rodale Press. 1977.
- ↑ Gates, John-Paul. 2012. "pedal power!." Children's Technology & Engineering 16, no. 3: 17. Academic Search Elite, EBSCOhost (accessed February 14, 2013).
- ↑ needed
- ↑ https://www.appropedia.org/Pedal_power_howto
- ↑ Bicycling Magazine's Complete Guide to Bicycle Maintenance and Repair. Chapter 7. Rockdale Press. 1986.
- ↑ Kemp, William H. The Renewable Energy Handbook. Chapters 9, 10, 13. Aztext Press. 2009.
- ↑ ibid.
- ↑ ibid.