Diesel generators

A diesel generator (DG) (also known as a diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression-ignition engine is usually designed to run on diesel fuel, but some types are adapted for other liquid fuels or natural gas (CNG).

Diesel generating sets are used in places without connection to a power grid or as an emergency power supply if the grid fails, as well as for more complex applications such as peak-lopping, grid support, and export to the power grid.

Diesel generator size is crucial to minimize low load or power shortages. Sizing is complicated by the characteristics of modern electronics, specifically non-linear loads. In size ranges around 50 MW and above, an open cycle gas turbine is more efficient at full load than an array of diesel engines, and far more compact, with comparable capital costs; but for regular part-loading, even at these power levels, diesel arrays are sometimes preferred to open cycle gas turbines, due to their superior efficiencies.

Diesel generator set

Diesel generator on an oil tanker.

The packaged combination of a diesel engine, a generator, and various ancillary devices (such as base, canopy, sound attenuation, control systems, circuit breakers, jacket water heaters, and starting system) is referred to as a “generating set” or a “genset” for short.

Set sizes range from 8 to 30-kW (also 8 to 30-kVA single phase) for homes, small shops, and offices, with the larger industrial generators from 8-kW (11 kVA) up to 2,000-kW (2,500-kVA three phase) used for office complexes, factories, and other industrial facilities. A 2,000-kW set can be housed in a 40 ft (12 m) ISO container with a fuel tank, controls, power distribution equipment and all other equipment needed to operate as a standalone power station or as a standby backup to grid power. These units, referred to as power modules, are gensets on large triple axle trailers weighing 85,000 pounds (38,555 kg) or more. A combination of these modules are used for small power stations and these may use from one to 20 units per power section, these sections can be combined to involve hundreds of power modules. In these larger sizes, the power module (engine and generator) are brought to the site on trailers separately and are connected with large cables and a control cable to form a complete synchronized power plant. A number of options also exist to tailor specific needs, including control panels for AutoStart and mains paralleling, acoustic canopies for fixed or mobile applications, ventilation equipment, fuel supply systems, exhaust systems, etc.

Diesel generators are not only for emergency power but may also have a secondary function of feeding power to utility grids either during peak periods or periods when there is a shortage of large power generators. In the UK, this program is run by the national grid and is called STOR.

Ships often also employ diesel generators, sometimes not only to provide auxiliary power for lights, fans, winches, etc. but also indirectly for main propulsion. With electric propulsion, the generators can be placed in a convenient position, to allow more cargo to be carried. Electric drives for ships were developed before World War I. Electric drives were specified in many warships built during World War II because manufacturing capacity for large reduction gears was in short supply, compared to the capacity for the manufacture of electrical equipment.[1] Such a diesel-electric arrangement is also used in some very large land vehicles, such as railroad locomotives.