Uncle Bobs Tips: Generator Guide


Believe it or not, nearly everyone can build a generator.

Believe it or not, nearly everyone can build a generator. Using parts that can be found at home, as well as store bought parts, many types of generators can be built: you can build electric generators, solar generators, wind generators, etc.

For example, to build a generator, within every home in America there are motors that can be converted to operate as generators. They may not be labeled as generators, but they will function just the same. These motors are often called "squirrel cage motors" and are in washing machines, dryers, water pumps and other devices. Besides being numerous and cheap, these motors will generate AC voltage of the purest sine wave. They use no brushes and do not produce any RFI (Radio Frequency Interference). A motor converted to an induction generator will power florescent and incandescent lights, televisions, VCR's, stereo sets, electric drills, small power saws and other items.

To build your own generator, you must add capacitors to the motor in parallel with the motor power leads, driving it a little above the nameplate RPM, and the motor will generate AC voltage! The capacitance helps to induce currents into the rotor conductors and causes it to produce AC current. The power is taken off of the motor power leads, or the capacitor leads, since they are all in parallel. The capacitors used must be the type designated as "running" capacitors and NOT "starting" capacitors. Starting capacitors are used for a very short time, usually less than a second or two, and would be destroyed by being connected across the AC line continuously. Running capacitors are connected while the motor is powered.

To build a small solar power generator, use parts easily available from your local stores for $250 to $300. Built solar generators are great for power failures and life outside the power grid. Power your computer, VCR, TV, cameras, lights, or DC appliances anywhere you go. Use in cabins, boats, tents, archaeological digs, or while traveling. Build a solar generator for the office storeroom in case of power failures.

To build a solar generator, begin by buying a small solar panel. For about $100 you should be able to get one rated at 12 volts or better (look for 16 volts) at an RV or marine supplies store. Buy a battery: Get any size deep cycle 12-volt lead/acid or gel battery. You need the deep cycle battery for continuous use. The kind in your car is a cranking battery--just for starting an engine. With a bargain, it should cost about $50-60. Get a battery box to put it in for $10. (This is good for covering up the exposed terminals in case there are children about. If you are going to install the system in a pump shed, cabin, or boat, skip this.) Buy a 12-volt DC meter. Radio Shack has them for about $25. Buy a DC input. This can be found at a car parts store in the cigarette lighter parts section for about $10. This is enough to power DC appliances, and there are many commercially available, like fans, one-pint water boilers, lights, hair dryers, baby bottle warmers, and vacuum cleaners. Many cassette players, answering machines, and other electrical appliances are DC already and with the right cable will run straight off the box.

However, if you want to run AC appliances, you will have to invest in an inverter. This will convert the stored DC power in the battery into AC power for most of your household appliances. Use a drill to attach the meter and DC input to the top of the box. Use insulated wire to attach the meter to the wingnut terminals on the battery. Connect the negative (-) pole first. Only handle one wire at a time. Connect the DC inlet to the battery in the same way. Connect the solar panel to the battery in the same way.

If you think you might be interested in building a wind generator, you should first check the libraries for wind-related articles and books to learn about estimating the local wind speed, site selection, types of towers and appropriate height and descriptions of successful wind generators. The key to simplicity comes from building a direct-drive machine with the propeller mounted directly to the generator. This means there are no gearboxes or belts to deal with, but it will take some time to locate the ideal generator.

The ideal generator to build a wind generator will be a large four-pole one that weighs at least 40 pounds. A few semi type trucks and old city buses used such generators. Even though these generators will be 20-30 years old, they are generally quite serviceable after replacing or repacking the bearings and replacing worn brushes. Some generators even have their rated output at a specific rpm on the generator tag. The most desirable generators are the ones with the lowest rated rpm since it will lower the wind speed at which the generator starts to put out usable power. For best results the generator should have a rated output no greater than 650 rpm when using a seven-foot prop and no greater than 750 rpm with a higher speed six-foot-diameter prop.

For high winds you need a governor. A governor can change the pitch of the blades at a certain speed or it can act as a drag brake. Another type of over-speed protection is to have the tail fold parallel with the prop in high winds. Folding the tail manually is also a very good way to shut down the wind plant during periods of high winds.

A home-built wind generator has many advantages: very low cost, a little over a kilowatt-hour a day of electricity on the average for a machine with a 6-foot prop where winds average 12 mph, tremendous job satisfaction and a joy to watch--especially on stormy windy days or nights when solar panels aren't doing anything. However, low-cost wind-generated electricity does not figure in your labor. This labor will be many times the amount needed for installing a PV system. If you are going to build your own wind plant, keep it relatively small and simple.

The Internet is replete with educational sites on how to build your own generator. In fact, building a generator is one of science teachers' favorite projects. Most sites not only provide instructions on how to build a generator, but include technical explanations about how the generator works, strengths and weaknesses, discussion questions, etc.

The following websites are only a small sampling of the multitude of websites on how to build a generator: Building a simple electric generator: Science Project. Use an empty soda can, a nail, a rubber band and other household and store items to build a simple homemade Van de Graaff generator: SciToys.

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