What is a generator?
A generator is a machine that converts one form of energy into electrical energy. There are many types of generators, which can be broken down into three different groups: AC generators, DC generators, and transducers. These groups include AC synchronous and induction generators, DC machines such as shunt and series machines, and transducers such as the Faraday generator and magnetohydrodynamic generator. Types of commonly-used generators include diesel generators, gasoline-powered portable generators, auto engines connected to carriages with electric drive trains (called Genset vehicles), Uninterruptible Power Supply (UPS) systems, Tesla coils (just for fun—not functional), and rotating cylinder steam generators (popular in the early 1900s).
Generators are frequently used to supply electricity for buildings, homes, offices, and communities. When used to power devices that require low power (less than 1 kW), they are commonly called “small generators.” Large generators which feed commercial buildings or communities can be tens of megawatts (e.g., a large coal-fired plant supplies more than 200 MW), so you’ll likely want to skip the “large” category if you’re learning about this stuff! The figure below identifies many of the components inside a generator.
Professor C. J. Smith invented the rotating cylinder steam generator at University College London in 1866. Walter Hancock and Co Ltd Engineers built it, who also made the steam engines for Brunel’s world-famous steamship “SS Great Eastern.” In 1867, a more significant 3.75 MW unit was installed to power arc lamps at Holborn Viaduct in London.
This machine still exists in working order and is kept in running order by enthusiasts who have restored it to complete working order. This generator supplied 800 watts of electricity through an underground system (wireless energy transfer), providing 8,000 lamps on Holborn Viaduct and Fleet Street-based upon similar wireless transmission towers designed by Professor Oliver Lodge.
Generators are used to convert mechanical energy into electrical energy for applications such as lighting or starting motors. The source of mechanical energy can be from various sources, the most common being an internal combustion engine running on either diesel fuel, gasoline, or natural gas. Other generators are powered by steam turbines that use steam heated in a boiler or nuclear power plants using nuclear reactors to produce heat to turn water into pressurized steam, which is then passed through the blades of a turbine connected to an electrical generator.
Electricity cannot be stored in large quantities for very long because it must be constantly moved along wires by electrical devices called “motors” – anything that uses electricity. This means that any power plant doesn’t create electricity for long-term storage, no matter what type. The stored energy must be used almost immediately after it is made, or the generators will have to be shut down until demand for electricity increases again.
Another way of storing large quantities of electrical energy is to store chemical energy in batteries and connect them to the generator with a motor-generator set connected to the battery. A battery can store enough chemical energy during times of low demand to then run the generator when demand for electricity increases at a later time point – essentially acting as an “energy storage system.”