Turbines and Generators
Turbines are made up of a set of blades or cups (impellers) and an axle which are caused to rotate rapidly by the action of a physical or mechanical force such as wind, water or steam. The turbine axle is connected to a generator and the inner section of the generator is also caused to rotate. This inner section contains a magnet with a strong magnetic force. Around this magnet is a large coil of wire which is connected at each end to an electrical system (solenoid).
A very important natural effect is brought into action when the magnet rapidly spins near the wire coil: an electrical current is induced (this is somewhat like static electricity from a balloon causing hair to rise, even though the balloon is not touching the hair). The induced current will be AC voltage due to the spinning causing the voltage to rise and fall with each rotation. If the magnet is rotated at 50 revolutions per second (i.e. 3000 rpm) the frequency will be the same as that of mains electricity, 50 Hertz. In practice, the production of electricity by generators is more complicated, but the principles are the same.
This electricity is generated at power stations, most commonly through the heat of uranium break-down or burning fuel (e.g. coal). The heat is used to boil water, producing steam under pressure which spins the turbines. More simply, wind energy, the flow of water in a river or from a dam (i.e. hydro electricity) can be harnessed to spin the turbines.
Windmills and small-scale hydro systems are self-contained systems which trap natural mechanical energy and convert it to electrical energy. These can be operated independently of the mains electricity supply or as a supplement. Portable petrol or diesel generators may be hired or purchased to be used in similar way. They are useful in isolated situations or during power strikes.
As we have already discussed batteries (chemical reaction) can range from small torch batteries to large vehicle or industrial batteries. One advantage is that they can be used in remote situations or when a mains supply is unavailable. Batteries generate electricity by a chemical reaction which slowly occurs between layers of different chemicals encased in the battery. As the reaction takes place, electrons are released allowing them to move and create an electrical flow or current. Unlike turbine generated electricity which is AC voltage, battery power is DC voltage. That is because it is produced by a continuous, even source.
Primary batteries are non-rechargeable. When the chemical reaction is completed, the battery is finished. However, secondary batteries can be discharged and recharged again. The recharging occurs when electrical energy is fed back into the battery and reverses the chemical reaction.
The two main types of rechargeable are Lead-Acid batteries which are cheap and used in cars; and Nickel-Cadmium batteries which are expensive and long-lasting.
One of the advantages of wind power is that the wind may still blow even if the sun is covered by clouds. Developing a two-energy source system by using both these resources is an excellent method for alternative energy self sustainability, however initial costs may be daunting.
Assuring the wind has the strength for the turbines is essential. Just because a site looks windy, it may not produce the necessary wind velocity to produce sufficient energy. Turbulent wind can negate benefits of a rotating propeller. Turbulence can be developed from nearby trees, buildings, etc. It is therefore important to ensure the proposed turbine site is above any "external" influence.
To ensure an even air flow in the area under scrutiny, place a ribbon on the end of a long pole and position this in the wind stream. If the ribbon flows strong and evenly, then this is a good indication of a good site. Air speed is best measured by an anemometer. Note that air speed increases with height due to no ground surface friction. At a height of 26 metres, the wind speed reportedly is about 50% more than at ground level, which can equate to about 300% increase in power at this height.
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