Due to our complete dependence on electricity and because of frequent blackouts,
power backup has become a necessity. Before discussing various types of generators for home use, let’s briefly review how electricity is produced and what causes power outages. Technically speaking, electric energy is the energy associated with electromagnetic fields or interacting electrical charges. It is often casually called
electricity. It is a secondary energy source because for practical use it is derived from other sources (called primary), such as coal, natural gas, or nuclear fuel. An
electrical generator by definition is a device that produces electricity from mechanical energy. The
mechanical energy for electric generators in turn is produced from primary 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's shaft. The spinning shafts turn the generator's
electromagnets inside electromagnetic coils. This creates an alternating magnetic field in
the coils, which induces AC voltage. This voltage is then stepped up in
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 amount of power.
Lower currents result in higher efficiency due to reduced
copper losses in transmission lines. The AC form of voltage is preferred
because it is easy to change from one level to another with the
transformers. Nevertheless, there are some high-voltage DC transmission
lines too. The transmission lines carry the currents 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 generator 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 power 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.
Emergency backup systems can supply electricity to critical circuits or the whole house during blackouts. These systems typically include either an AC genset or a battery-based energy storage system with
DC-AC inverters.
Electric generators for home use or commercial applications are normally driven by small engines that produce the mechanical energy from burning fuel. The alternator 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 practical consumer buying guide to backup generators and other power systems for home or business use. You may want to start with the
choosing generators for the home page, which includes a review of the basic types and detailed selection recommendations. You will also find in this site an overview of various types of back up systems, principles of their operation, selection guides, comparisons,
reviews and ratings of portable and permanently connected (standby) gensets. We also provide basic facts and information on electricity generation from renewable
solar energy.
