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LAZAR's GUIDE TO ELECTRIC GENERATORS
AND OTHER BACKUP POWER SYSTEMS

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Electrical generator is a device that produces electrical energy from mechanical energy. Electric energy is often casually called electricity. Technically speaking, it is the energy associated with electromagnetic fields or interacting electrical charges. Electricity is a secondary energy source because for practical use it is derived from other sources, which are called primary. The mechanical energy for electric generators in turn is produced from other forms of energy by using various methods. Currently, the dominating method of electricity generation employed in power plants is the method that uses steam turbines. The turbines burn fossil fuels (coal, petroleum, and natural gas) or split atoms of nuclear fuel (usually enriched uranium) to heat water and make highly pressurized steam whose pressure turns the blades on a turbine shaft.



The spinning shafts turn the generator's electromagnets inside electric coils. This creates an alternating magnetic field in the coils, which induces AC voltage. This voltage is then stepped up in power transformers and is applied to the network of cables of the power transmission grids. The reason electricity is transmitted at high voltages (230-765 kV in US) is that at a higher voltage you need a lower current to deliver the same power. Lower currents result in higher efficiency due to reduced copper losses in transmission lines. The AC form of voltage is used because it is easy to change from one level to another with the electrical transformers. The transmission lines carry the electricity across long distances to substations. Substations use step down transformers that reduce the AC voltage to medium-high level (typically 2.2 - 34.5 kV). From the substation, distribution lines go to the transformers on utility poles or on the ground. These transformers reduce the voltage to the level suitable for conventional household devices.

In the US, all power stations are interconnected in the systems called grids. In the continental US, there are three main grids (interconnected systems): Eastern, Western and Texas. Within each grid, all electric generators are synchronized and share the load in order to provide redundant power to all users. As a result, any changes in electricity generation or consumption at any point in the grid will change the loads on generators and transmission lines at every other point. Power outages can be caused by many things such as storms, earthquakes, falling trees, lightning, various accidents, high demand, or equipment failure. If for whatever reason one plant fails or disconnects from the grid, the remaining plants have to pick up an extra load. If they are all operating near their maximum capacity and cannot handle the extra load, they may automatically disconnect from the grid as well. This may cause a cascading effect resulting in a wide-spread blackout.

Due to our dependence on electricity and because of frequent blackouts, power backup has become a necessity. Emergency backup systems can supply electricity to critical circuits or the whole house during power outages. These systems typically include either an AC generator or a battery-based energy storage system with DC-AC inverters.

Backup generators for a home or a business are normally driven by small engines that produce the mechanical energy from burning fuel. The electric generator and the engine are mounted together to form a single device, which is called an engine-generator set or a genset. This combined device is casually simply referred to as a generator.

This site is a consumer's guide to electric generators and other backup power systems for home use. Here you will find an overview of various types of backup power systems, principles of operation, selection guides, comparisons, reviews and ratings of portable and permanently connected (standby) gensets, as well as information on producing electricity from renewable sources such as the sun's radiated energy.



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