| Don't just stand there watching -- read on and learn about some of the great activities you can do with an Energy Bike! |
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Light Bulb or Heat Bulb?
A 50-watt incandescent bulb is much harder to pedal and draws four times more current than a 13-watt compact fluorescent bulb, but is no brighter. Where is all that pedaling energy going? Don't touch the bulbs to find out! The cyclist's legs feel what the current meter shows - that four fluorescent bulbs can be lit with the same amount of power that it takes to light a single incandescent bulb.
Mighty Motors
Watching the current meter as they pedal, students see that when the fan is switched on, there is a brief
surge as the motor starts. The current then settles to a lower, steady run value, which is pretty easy to
pedal, and cyclists enjoy the cooling breeze. Switch off the fan and switch on the hair dryer. Whoa! Why is
it so hard to pedal when it doesn't blow nearly as much air as the fan? Students are amazed at the effort
needed for such a small amount of heat.
Capacitors ... They've got Potential !
Some younger students are not strong enough to power even one compact fluorescent bulb, but they can charge the capacitor bank with short bursts of pedaling. During each burst, the capacitors "trap" additional energy, which is seen as voltage build-up. This potential energy can then be converted back into kinetic energy, powering a radio for
about 2 minutes, a tape player for 30 seconds, and a fluorescent bulb for 8 seconds. How long would an incandescent bulb last?
Getting into Hot Water
A British Thermal Unit (Btu) is the amount of heat required to raise the
temperature of one pound of water one degree Fahrenheit, but this doesn't
have much meaning until you find yourself on the pedal-powering end of a
beverage heater immersed in a pint of water. Even teenagers are good for
only about 10 BTU, becoming too tired to maintain steady voltage after
just a minute or two of pedaling. For a powerful calculation, how many
energy bikes would it take to heat their bath or shower?
Resistance over Distance
The resistance of an electrical wire or transmission cable is inversely proportional to the
thickness of the conductor and directly proportional to its length. Electrons lose a
significant amount of potential energy (voltage drop) as they travel along a high-resistance
wire. Using the panel's knife switch to toggle from a short piece of thick wire to a long loop
of thin wire, students see that the decreased voltage results in a dimmer bulb and
slower-spinning fan. The "lost" potential energy is actually converted
to molecular vibration (heat) within the conductor.
Fuse it or Lose it!
Switching a large electric load through a short piece of thin wire heats it to the point of
burning when the energy bike is pedaled. To prevent such fires in buildings, the National
Electric Code specifies the maximum safe load for a given wire thickness. As a precaution
in case this load is exceeded, a fuse should be placed in the circuit. This activity uses a
second piece of thin wire and a correctly sized fuse to show that when it blows, the fuse
conducting element melts, causing an open circuit that stops the current before the wire
heats up. Blown fuses must be replaced, but not by a penny!
Growing and Growing and Growing ...
The students imagine that they are directors of a utility and that each incandescent bulb
represents a new housing development. They have a new biomass-fired power plant (a
fresh cyclist), and people move into the area, attracted by this renewable energy source.
At first all is well, but as more new developments are added to the grid (more bulbs
switched on), the plant has trouble maintaining steady voltage. What to do? They could
expand the plant - get a bigger cyclist - but then they'd have a bigger grocery bill! They
could buy a second energy bike, but they'd have to borrow money to place the order,
paying interest and not earning any cash until the bike is delivered. For real-world utilities,
new power plant construction can take years! Is there a more economical way to meet
growing demand with the same cyclist?
Rock Around the Clock
This activity simulates a utility's daily load profile and is all about handling a "peak experience." At
midnight, the only loads are building ventilation and street/security lighting. At six in the evening,
add residential lighting, resistive heating/cooking, and entertainment loads. Then when two
students blow dry their hair at exactly the same instant, they cause a blackout. How can they both
dry their hair and still have the light to see in the mirror by?
Your Nickel ...
... or dime can buy a kilowatt-hour (kWh) of electricity in most parts of the US depending on whether you are a residential or business user. Students can appreciate what a real bargain this is when they have to keep two 50-watt incandescent bulbs lit for six minutes, generating 1/100 of a kWh. This will easily exhaust half a dozen teenagers.
Horsepower to Go!
Students calculate the horsepower of an energy bike traveling at 20 miles per hour and compare it to that
of their family cars, which average much the same speed for errands in town. To be sure, a bicycle is not
weatherproof, cannot carry passengers, cannot travel highway speeds, and is not very crashworthy.
Nevertheless, a suitable hybrid or electric vehicle shouldn't have to be several hundred times more powerful
than a cyclist to do the same job as today's cars.