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What Are Diesel Generators? How Are They Different?

What are Diesel Generators?

Generators are electro-mechanical devices that convert a source of rotational kinetic energy into electrical energy in accordance with the laws of electromagnetic induction discovered by Michael Faraday in 1831. Diesel generators provide this rotational kinetic energy by burning fuel in an internal combustion engine, releasing the chemical energy stored in the fuel. The rotational energy is used to rotate an armature made up of copper coils wound around a metal core in a magnetic field produced by a series of permanent (or electro) magnets. Diesel generators are the most commonly encountered gensets in larger-capacity units but petrol, natural gas, or even steam may be used to provide the rotational kinetic energy required.

A generator is also referred to as a genset because it is made up of two primary components – the engine and the alternator. They typically produce alternating current (AC) voltage in three-phase or single-phase sine waves. The waves produce AC voltage in each single revolution, producing continuous, stable output provided that the engine runs at stable revolutions per minute (RPM). Diesel generators can also be configured to produce direct current (DC) output by using a dynamo instead of an alternator, but this is rare as most modern appliances and electric motors run on AC power.

Gensets were initially mostly powered by steam engines but the invention of the first compressed charge, compression ignition engine by the German engineer, Rudolf Diesel, in 1892 saw the introduction of more and more diesel generators. The death knell for steam-powered units was sounded when even early prototypes demonstrated an efficiency of over 26% compared with the steam engines of the day which ran at an efficiency of about 10%.

Three-phase gensets usually produce a voltage output of 480 volts and are considered superior to single-phase machines. Three-phase gensets are more efficient, weigh less, have better energy density, cost less, and take up less space than a similar-capacity single-phase machine. The characteristics of three-phase gensets are particularly desirable at sites with high load and constant demand.

Leading-Edge Engines

Modern diesel generators are extremely versatile and adaptable sources of electrical power. They have developed into powerful, efficient, and easily portable miniature power stations that come in a range of sizes from units that two men can pick up to units weighing in at over 2300 tonnes. Some improvements to these engines came from individual inventors, such as the invention of the turbo charger by Alfred Büchi in 1905 but leading manufacturers of engines for gensets such as Perkins, Volvo, Cummins, Scania, Deutz, John Deere, and FAW have invested in research and development for decades and engines for gensets have improved and are improving continuously.

Three-phase gensets are also electrically flexible, being capable of two different three-phase configurations which provide different output. The Delta connection does not utilise a neutral wire and provides better output for electric motors with their high starting current requirement than the “Y” or “star” connection, which uses a neutral in addition to the three-phase wires.

One of the phases from a three-phase genset may be used to supply single-phase loads as long as the output rating of the individual phase being used is not exceeded. It is even possible to derate many gensets and convert them from three-phase to single-phase units. Multiple three-phase units can be wired in parallel and synchronised to provide increased system capacity or very high, utility-scale output.

Parallelable multiple units are often installed where the need for additional load arises, and the units installed initially are inadequate to handle the additional demand. It is more desirable, and simpler, to join identical generators than units of different capacities or units made by different manufacturers.

Diesel Generators or Renewables?

Diesel generators have a number of advantages over most forms of renewable energy, but the most significant is the fact that they offer reliable continuity of supply. Properly maintained gensets will deliver power continuously 24/7, in sunshine or bad weather, as long as they are constantly provided with fuel.

Solar- and wind-powered systems do not have the ability to provide power as reliably. If it rains, is overcast, or even if the sun goes behind a cloud, the output of a solar plant will drop rapidly and dramatically, and even very windy locations have wind-still days. Continuity of supply is essential for many businesses and absolutely critical for facilities such as hospitals and server farms. Inconsistency in supply from solar plants and wind farms is known as intermittency.

Diesel generators and renewable energy systems should not be viewed as mutually exclusive. To overcome intermittency, some form of storage or cogeneration is required. While batteries are currently used for storage, battery storage is still capital intensive and batteries have a finite lifespan. Even though the price of battery storage has come down in the last decade, large-scale battery storage is still relatively expensive. This creates an important role for diesel generators as cogeneration units to mitigate renewable energy intermittency. Diesel generators allow engineers to create backup systems for commercial and industrial entities using a blend of renewables and diesel generators without incurring the high capital cost of batteries or other forms of energy storage.

Microgrids using diesel generators, solar photovoltaic panels, and wind turbines can be created by using the gensets as spinning reserves to smooth out dips in solar and wind production. Batteries may be added to such systems at a later stage when improvements in battery technology and cost justify their addition. While it’s possible to create a system that does not use diesel generators, this tends to be prohibitively costly. The renewable energy component of these systems is typically sized to provide the entire 24-hour energy requirement, including system losses. Even where battery storage is employed, diesel generators are still an essential component in a blended renewable power system.

Looking for Large Diesel Generators?

Whether utility or commercial and industrial scale, it is crucial to engage with a company that has an established reputation for being an industry leader in respect of anything to do with gensets and power generation. Look for a company that provides leading engine brands and alternators with their equipment. This is particularly true for commercial and industrial-size diesel generators where the consequences of choosing badly, financially and operationally, are severe.

Go with a company like PacB. We do not only stock the leading brand products, offer top-tier technical competence, and have an unimpeachable track record, but we also have a cutting-edge Renewable Energy Solutions division that makes us experts in the integration of diesel generators and renewable energy sources. Explore our website today and get the peace of mind that goes with engaging with an industry leader.