Page 135 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 5 Mechanical and Electrical Power, Work, and Energy 115

Solar Energy
Solar cells convert light energy to electric energy. The amount of energy you get
depends on the area of the cell, so you need a pretty big cell to power the motors
we’ll talk about in this book. SparkFun’s huge solar cell (TOL-09241) can provide 5.2
watts of power (8V at 650mA current) in direct sunlight, and that’s enough to drive
most of the smaller motors we’ll talk about in the next chapter. They call it huge, but
at about 7 × 8.5 in, it’s smaller than a sheet of notebook paper. The solar cells used
in SADbot in Project 10-3 are 13.5 × 18 in and they are from Silicon Solar (www
.siliconsolar.com/).

Wind, Water, and Other Fluids
A fluid is anything that flows. It could be air, water, or maple syrup. Historically, wind
and water power were used directly by using the circular motion from a water wheel
or a windmill to grind flour or cut wood. Nowadays, fluid power is mostly used to
generate electricity as a cleaner alternative to fossil fuels.
You can try harnessing the power of the wind to make your own wind turbine to
create small amounts of electricity. For example, try connecting a small wind turbine
to a small electric motor like in the Wind Lantern project in Chapter 10 (Project 10-2).
When we give electricity to electric motors, they give us motion (as discussed in
Chapter 6). However, if we give an electric motor motion by spinning the shaft, we
get electricity. One company, Duggal Energy Solutions, created a streetlight powered
by a small vertical-axis wind turbine and solar cell called the LUMI-SOLAIR
(www.lumisolair.com). This is a commercial product, but there are also quite a few
hobbyist sites devoted to making your own power using wind (for example, see
www.gotwind.org and www.windstuffnow.com).

Compressed gases are another way you can use fluids like air and carbon dioxide to
do work for you. Potato guns and bottle rockets are good examples of movement
created by harnessing compressed air. Pneumatics is the name of the field concerned
with using pressurized gas to create mechanical motion, but these devices are usually
driven by an air compressor that works on electricity to begin with (more on this in
Chapter 6).
Unless you have a large dam nearby or a river running through your backyard,
hydropower will not be very useful for you in terms of powering projects in this book.
I have seen a concept for a showerhead that uses a mini-hydroelectric generator to
power an electronic display that shows users how much water they are consuming,
but it has not been tested (see www.epmid.com).