A Pedal Powered generator provides a method of generating electricity by means of a modified exercise bike for use in energy storage and running household appliances. Human/mechanical energy is converted into electrical current by means of a Direct Current (DC) generator that is connected by a fanbelt to an exercise bike flywheel. The energy created by the DC generator can be stored in various types of lead-acid batteries. Energy stored in battery form can act as a supplemental energy source for battery banks that may already be used for wind, hydro and photovoltaic systems. Also, energy that is stored within the lead-acid battery can be utilized as DC current for use in DC appliances such as those found in automotive mobile homes. If Alternating Current (AC) appliances are in place then a inverter must be used to transfer the 12 volts of DC current into the standard 110 volts of AC current for usage by these appliances.
As discussed in Pedal Power: In work, leisure, and transportation by James McCullagh (1977), tests at Oxford by Stuart Wilson on a bicycle showed that 75 watts of power is possible to be generated by an average rider at road speed in a one hour time frame. Wilson also found that at 18 mph it is possible to achieve 200 watts for short periods, while 750 watts is possible only for a second or so, under extreme load. These calculations show that human/mechanical energy, if harnessed could add to existing battery banks, or could be set up alone to run appliances. Appliances that could be powered include radios, televisions, lights, power tools and other appliances that pull relatively low amounts of energy for their usage.
Now that the potential power output for an average cyclist has been defined it is possible to design a human powered energy generator. The information that is contained within this web page is intended to allow the reader to examine potential uses for this design. This example is based upon calculations done by myself, and can be used as a template for design of different energy demand systems. This system would be most appropriate for a household with more than four people that do not have high energy demands, and are in average physical condition.
The following contents of this information include a list of the components necessary for assembly of this system, followed by an example of potential usage for this design.
Components needed to build a 12 volt pedal powered generator
1. Exercise bike:
Preferably a front mounted flywheel with a channel to accommodate a fan belt. The bike gearing that has proved effective is with a 52-tooth chainring on the exercise bike connected by the chain to the flywheel, which has a 16 tooth freewheel. The flywheel diameter that has proven effective is with a solid metal flywheel that is 15.5" in diameter. The generator pulley is recommended at 2.5" in diameter. The pulley diameter can be altered to make the effort required to spin the pulley easier by putting on a larger pulley diameter.
2. Fan belt:
Must be large enough to cover circumference of flywheel, generator wheel, and distance between each wheel.
3. Generator:
24 volt DC. Generators that have proved effective are permanent magnet generators that are rated at 1800 rotations per minute (rpm), and a potential of 1/3 horsepower of output. The voltage output is directly proportional to the rpm's and the capability of this system is to rotate the generator at 900 rpm's. This will lead to an output of 12 volts.
4. Wiring:
10 gauge copper solid copper wire, Electrical resistance value of R=.1 ohm’s / 1000 feet
5. Voltage regulator:
20 amp flat automotive fuse that is to be placed in line with the positive electric wire. The voltage regulator limits amount of current flow when battery reaches full charge to prevent damage to battery.
6. Diode:
A one way electricity valve placed on either the positive or negative wiring. Must be rated at 25 amps,
and at least 35 volts.
7. Lead-Acid Battery:
12 volt marine/trolling battery, 55 lbs., 100 amp hour @ 20 hour cycle, with cycles life 300 discharges.
8. Inverter:
Changes 12 volt DC into 110 AC. Inverters must be able to handle potential peak electrical loads. To determine the loads, look at the watt requirement on the back of the appliances. This calculation should be used to insure that the inverter can handle the electrical loads. Most inverters vary in there efficiency under electrical loads allowing for 60%-90% of original 12 volt DC current to be transferred into 110 volt AC.
9. Ampere, Voltage, and RPM meter:
Attached to exercise bike.
10. Wooden Platform with wheels:
Example of potential use for 12 volt pedal powered generator with listed components
This section provides an example of the electrical output that is possible with this system and the power input that is demanded from a person peddling to make up for the energy consumption. To equate these values we must first examine what the daily Kilowatt hour (Kwh) usage is going to be, so that time of peddling can be determined.
For the purpose of this example, this systems daily energy demand are to be as followed:
Radio/clock: 50 watts x 2 hours/day = 100watts/day
Lights: 50 watts x 5 hours/day =250 watts/day
Total watts/ day = 350 watts, .350 kw, or 29 amps/day
Total watts/hr = 14.6 watts/hr, .0146 kw/h, or 1.2 amps/hr
Now that the daily and hourly energy demand has been calculated it is possible to calculate the rate of recharge that is needed to replenish the battery. Again remember that we are examining a system with a 12 volt, 100 amp/hr battery with a 20hr cycle. So, if daily there is a demand of 29 amps per day, then there needs to be a recharge rate equal to the daily usage. Earlier in this text it was explained that an average rider could generate approximately 75 watts of power for an hour. Using the equation of Amps(I)=Watts(W)/Volts(V), we come up with a potential of 6.25 amps/hr. Using this example would mean that it would take 4.64 hours of peddling to recharge the electricity used by the appliances in 7 hours (4.64 hrs x 6.25 amps =29 amp). These equations do not include the loss of efficiency that is created when electricity is converted from DC to AC.
In this example there would be an increase in the amount of energy needed to be stored for conversion. Though the time needed to generate electricity seems too high for one person to put out, it would probably be most appropriate for households with multiple people.
^^ Might be useful one day!