A diesel–electric transmission, or diesel–electric powertrain is a

transmission system :''See Transmission (mechanics) for a car's transmission system'' In telecommunications, a transmission system is a system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal. Some transmissi ...

for

vehicles A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), ...

road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...

rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

, and marine

transport Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land ( rail and road), water, cable, pipelin ...

. Diesel–electric transmission is based on

petrol–electric transmission Petrol–electric transmission (UK English) or gasoline–electric transmission or gas–electric transmission (US English) is a transmission system for vehicles powered by petrol engines. Petrol–electric transmission was used for a variety of ap ...

, a very similar transmission system used for

petrol engines A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ...

. Diesel–electric transmission is used on railways by diesel–electric locomotives and diesel–electric multiple units, as electric motors are able to supply full

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

at 0

RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...

. Diesel–electric systems are also used in

marine transport Maritime transport (or ocean transport) and hydraulic effluvial transport, or more generally waterborne transport, is the transport of people ( passengers) or goods (cargo) via waterways. Freight transport by sea has been widely used throu ...

, including submarines, and on some land vehicles.

Description

The defining characteristic of diesel–electric transmission is that it avoids the need for a

gearbox Propulsion transmission is the mode of transmitting and controlling propulsion power of a machine. The term ''transmission'' properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differe ...

, by converting the

mechanical force In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, then the mechanical energy is ...

of the diesel engine into electrical energy (through a

dynamo "Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundati ...

), and using the electrical energy to drive

traction motors A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit. Traction motors are used in electrically powered rail vehicles (electric multiple uni ...

, which propel the vehicle mechanically. The traction motors may be powered directly or via

rechargeable batteries A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prima ...

, making the vehicle a type of

hybrid electric vehicle A hybrid electric vehicle (HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system (hybrid vehicle drivetrain). The presence of the electric powertrain is intended ...

. This method of transmission is sometimes termed

electric transmission Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

, as it is identical to petrol-electric transmission, which is used on vehicles powered by petrol engines, and to

turbine-electric transmission A turbine–electric transmission system includes a turboshaft gas turbine connected to an electrical generator, creating electricity that powers electric traction motors. No clutch is required. Turbine–electric transmissions are used to driv ...

, which is used for gas turbines.

Advantages and disadvantages

Diesel Electric transmissions are a type of Continuously variable transmission. The absence of a gearbox offers several advantages, as it removes the need for gear changes, thus eliminating the unevenness of acceleration caused by the disengagement of a clutch.

Ships

The first diesel

motorship A motor ship or motor vessel is a ship propelled by an internal combustion engine, usually a diesel engine. The names of motor ships are often prefixed with MS, M/S, MV or M/V. Engines for motorships were developed during the 1890s, and by th ...

was also the first diesel–electric ship, the Russian tanker ''

Vandal The Vandals were a Germanic people who first inhabited what is now southern Poland. They established Vandal kingdoms on the Iberian Peninsula, Mediterranean islands, and North Africa in the fifth century. The Vandals migrated to the area betw ...

'' from Branobel, which was launched in 1903. Steam turbine–electric propulsion has been in use since the 1920s (s), using diesel–electric powerplants in surface ships has increased lately. The

Finnish Finnish may refer to: * Something or someone from, or related to Finland * Culture of Finland * Finnish people or Finns, the primary ethnic group in Finland * Finnish language, the national language of the Finnish people * Finnish cuisine See also ...

coastal defence ship Coastal defence ships (sometimes called coastal battleships or coast defence ships) were warships built for the purpose of coastal defence, mostly during the period from 1860 to 1920. They were small, often cruiser-sized warships that sacrifi ...

s '' Ilmarinen'' and ''

Väinämöinen Väinämöinen () is a demigod, hero and the central character in Finnish folklore and the main character in the national epic ''Kalevala'' by Elias Lönnrot. Väinämöinen was described as an old and wise man, and he possessed a potent, m ...

'' laid down in 1928–1929, were among the first surface ships to use diesel–electric transmission. Later, the technology was used in diesel powered

icebreaker An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...

s. In World War II, the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

built diesel–electric surface warships. Due to machinery shortages

destroyer escort Destroyer escort (DE) was the United States Navy mid-20th-century classification for a warship designed with the endurance necessary to escort mid-ocean convoys of merchant marine ships. Development of the destroyer escort was promoted by th ...

s of the and es were diesel–electric, with half their designed horsepower (The and es were full-power steam turbine–electric). The s, on the other hand, were designed for diesel–electric propulsion because of its flexibility and resistance to damage. Some modern diesel–electric ships, including

cruise ships Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, cruise ships typically embark on round-trip voyages to various ports-of-call, where passengers may go on tours known as "sho ...

and icebreakers, use electric motors in pods called

azimuth thruster An azimuth thruster is a configuration of marine propellers placed in pods that can be rotated to any horizontal angle (azimuth), making a rudder unnecessary. These give ships better maneuverability than a fixed propeller and rudder system. Ty ...

s underneath to allow for 360° rotation, making the ships far more maneuverable. An example of this is ''

Symphony of the Seas ''Symphony of the Seas'' is an owned and operated by Royal Caribbean International. She was built in 2018 in the Chantiers de l'Atlantique shipyard in Saint-Nazaire, France, the fourth in Royal Caribbean's ''Oasis'' class of cruise ships. At , ...

'', the largest passenger ship as of 2019.

Gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...

s are also used for electrical power generation and some ships use a combination: ''

Queen Mary 2 RMS ''Queen Mary 2'' (also referred to as the ''QM2'') is a British transatlantic ocean liner. She has served as the flagship of Cunard Line since succeeding ''Queen Elizabeth 2'' in 2004. As of 2022, ''Queen Mary 2'' is the only ocean liner ...

'' has a set of diesel engines in the bottom of the ship plus two gas turbines mounted near the main funnel; all are used for generating electrical power, including those used to drive the propellers. This provides a relatively simple way to use the high-speed, low-torque output of a turbine to drive a low-speed propeller, without the need for excessive reduction gearing.

Submarines

Most early submarines used a direct mechanical connection between the combustion engine and propeller, switching between

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...

s for surface running and

electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate for ...

s for submerged propulsion. This was effectively a "parallel" type of hybrid, since the motor and engine were coupled to the same shaft. On the surface, the motor (driven by the engine) was used as a generator to recharge the batteries and supply other electric loads. The engine would be disconnected for submerged operation, with batteries powering the electric motor and supplying all other power as well. In a true diesel–electric transmission arrangement, by contrast, the propeller or propellers are always driven directly or through reduction gears by one or more

s, while one or more

diesel generator 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-ig ...

s provide electric energy for charging the batteries and driving the motors. While this solution comes with a few disadvantages compared to direct mechanical connection between the diesel engine and the propeller that was initially common, the advantages were eventually found to be more important. One of several significant advantages is that it mechanically isolates the noisy engine compartment from the outer pressure hull and reduces the

acoustic signature The term acoustic signature is used to describe a combination of acoustic emissions of sound emitters, such as those of ships and submarines. In addition, aircraft, machinery, and living animals can be described as having their own characteristic ...

of the submarine when surfaced. Some

nuclear submarine A nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear-armed. Nuclear submarines have considerable performance advantages over "conventional" (typically diesel-electric) submarines. Nuclear propulsion, ...

s also use a similar

turbo-electric A turbo-electric transmission uses electric generators to convert the mechanical energy of a turbine (steam or gas) into electric energy, which then powers electric motors and converts back into mechanical energy that power the driveshafts. Tu ...

propulsion system, with propulsion

turbo generator A turbo generator is an electric generator connected to the shaft of a steam turbine or gas turbine for the generation of electric power. Large steam-powered turbo generators provide the majority of the world's electricity and are also use ...

s driven by reactor plant steam. Among the pioneering users of true diesel–electric transmission was the Swedish Navy with its first submarine, HMS ''Hajen'' (later renamed ''Ub no 1''), launched in 1904 and originally equipped with a semi-diesel engine (a

hot-bulb engine The hot-bulb engine is a type of internal combustion engine in which fuel ignites by coming in contact with a red-hot metal surface inside a bulb, followed by the introduction of air (oxygen) compressed into the hot-bulb chamber by the rising p ...

primarily meant to be fueled by kerosene), later replaced by a true diesel. From 1909 to 1916, the Swedish Navy launched another seven submarines in three different classes ( ''2nd'' class, ''Laxen'' class, and ''Braxen'' class), all using diesel–electric transmission. While Sweden temporarily abandoned diesel–electric transmission as it started to buy submarine designs from abroad in the mid 1910s, the technology was immediately reintroduced when Sweden began to design its own submarines again in the mid 1930s. From that point onwards, diesel–electric transmission has been consistently used for all new classes of Swedish submarines, albeit supplemented by air-independent propulsion (AIP) as provided by

Stirling engine A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas (the ''working fluid'') between different temperatures, resulting in a net conversion of heat energy to mechanical work. More specif ...

s beginning with HMS ''Näcken'' in 1988. Another early adopter of diesel–electric transmission was the

, whose

Bureau of Steam Engineering The Bureau of Steam Engineering was a bureau of the United States Navy, created by the act of 5 July 1862, receiving some of the duties of the former Bureau of Construction, Equipment and Repair. It became, by the Naval Appropriation Act of 4 June ...

proposed its use in 1928. It was subsequently tried in the S-class submarines , , and before being put into production with the ''Porpoise'' class of the 1930s. From that point onwards, it continued to be used on most US conventional submarines. Apart from the British U-class and some submarines of the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrend ...

that used separate diesel generators for low speed running, few navies other than those of Sweden and the US made much use of diesel–electric transmission before 1945. After World War II, by contrast, it gradually became the dominant mode of propulsion for conventional submarines. However, its adoption was not always swift. Notably, the Soviet Navy did not introduce diesel–electric transmission on its conventional submarines until 1980 with its ''Paltus'' class.

Railway locomotives

During

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

, there was a strategic need for rail engines without plumes of smoke above them. Diesel technology was not yet sufficiently developed but a few precursor attempts were made, especially for

s by the French (Crochat-Collardeau, patent dated 1912 also used for tanks and trucks) and British (

Dick, Kerr & Co Dick, Kerr and Company was a locomotive and tramcar manufacturer based in Kilmarnock, Scotland and Preston, Lancashire, Preston, England. Early history W.B. Dick and Company was founded in 1854 in Glasgow by William Bruce Dick. The company wer ...

and British Westinghouse). About 300 of these locomotives, only 96 being standard gauge, were in use at various points in the conflict. In the 1920s, diesel–electric technology first saw limited use in switchers (or ''shunters''), locomotives used for moving trains around in railroad yards and assembling and disassembling them. An early company offering "Oil-Electric" locomotives was the American Locomotive Company (ALCO). The

ALCO HH series The ALCO HH series were an early series of switcher diesel-electric locomotives built by the American Locomotive Company (ALCO) of Schenectady, New York between 1931 and 1940, when they were replaced by the S series; the S-1 and S-2. They ...

of diesel–electric switcher entered series production in 1931. In the 1930s, the system was adapted for streamliners, the fastest trains of their day. Diesel–electric powerplants became popular because they greatly simplified the way motive power was transmitted to the wheels and because they were both more efficient and had greatly reduced maintenance requirements. Direct-drive transmissions can become very complex, considering that a typical locomotive has four or more axles. Additionally, a direct-drive diesel locomotive would require an impractical number of gears to keep the engine within its powerband; coupling the diesel to a generator eliminates this problem. An alternative is to use a

torque converter A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power ...

fluid coupling A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power.

in a direct drive system to replace the gearbox. Hydraulic transmissions are claimed to be somewhat more efficient than diesel–electric technology.

Road and other land vehicles

Buses

Diesel electric based buses have also been produced, including hybrid systems able to run on and store electrical power in batteries. The two main providers of hybrid systems for diesel–electric transit buses include Allison Transmission and BAE Systems.

New Flyer Industries New Flyer is a Canadian multinational bus manufacturer, specializing in the production of transit buses. New Flyer is owned by the NFI Group, a holding company for several bus manufacturers. New Flyer has several manufacturing facilities in Can ...

, Gillig Corporation, and

North American Bus Industries NABI Bus, LLC (NABI) is a former manufacturer of heavy-duty transit buses with its headquarters, bus manufacturing and assembly operations, located in Anniston, Alabama. Its products ranged from 31-feet to 60-feet in length, and were sold to ...

are major customers for the Allison EP hybrid systems, while

Orion Bus Industries Orion Bus Industries, also known as Bus Industries of America in the United States, was a private bus manufacturer based in Mississauga, Ontario, Canada. The company had its main manufacturing plant in Mississauga and sent bus body shells to ...

and

Nova Bus Nova Bus (stylized as NOVABUS) is a Canadian bus manufacturer headquartered in Saint-Eustache, Quebec, Canada. Nova is owned by the Volvo Group. The company has roots in the General Motors Diesel Division, which opened in 1979. Nova Bus was es ...

are major customer for the BAE HybriDrive system.

Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...

makes their own diesel–electric drive system, which is used in their Citaro. The only bus that runs on single diesel-electric transmission is the Mercedes Benz Cito low floor concept bus which was introduced in 1998.

Trucks

Examples include: * Large mining machines, such as the

Liebherr T 282B The Liebherr T 282 series are off-highway, ultra class, rigid frame, two axle, diesel-electric, AC powertrain haul trucks designed and manufactured in the United States by Liebherr Mining Equipment Co. The Liebherr T 282 series is no longer ...

dump truck or

LeTourneau L-2350 The P&H L-2350 Wheel Loader (formerly the L-2350 loader) is a loader used for surface mining. It is manufactured by Komatsu Limited. It holds the Guinness World Record for Biggest Earth Mover. Designed to center-load haul truck Haul trucks are o ...

wheel loader A loader is a heavy equipment machine used in construction to move or load materials such as soil, rock, sand, demolition debris, etc. into or onto another type of machinery (such as a dump truck, conveyor belt, feed-hopper, or railroad car) ...

. *

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

's Crawler-Transporters. * Mitsubishi Fuso Canter Eco Hybrid commercial truck. * International DuraStar Hybrid diesel–electric truck. * Dodge is conducting fleet tests of a diesel–electric version of the

Dodge Sprinter The Mercedes-Benz Sprinter is a light commercial vehicle ( van) built by Mercedes-Benz Group AG of Stuttgart, Germany as a large van, chassis cab, minibus, and pickup truck. In the past, the Sprinter had been sold under the Mercedes-Benz, Do ...

Concepts

In the automobile industry, diesel engines in combination with electric transmissions and battery power are being developed for future vehicle drive systems.

Partnership for a New Generation of Vehicles The Partnership for a New Generation of Vehicles was a co-operative research program between the US government and the three major domestic auto corporations that was aimed at bringing extremely fuel-efficient (up to vehicles to market by 2003. ...

was a cooperative research program between the U.S. government and "The Big Three" automobile manufacturers (

DaimlerChrysler The Mercedes-Benz Group AG (previously named Daimler-Benz, DaimlerChrysler and Daimler) is a German multinational automotive corporation headquartered in Stuttgart, Baden-Württemberg, Germany. It is one of the world's leading car manufacture ...

Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...

and General Motors) that developed diesel hybrid cars. *"Third-Millennium Cruiser", an attempt to commercialize a diesel–electric automobile in the early 1980s. *

General Motors Precept The General Motors Precept was a 2000 low emission vehicle concept car aimed at meeting the fuel economy goal of the Partnership for a New Generation of Vehicles between the US Government and GM, Ford, and Chrysler. GM was able to meet the ...

Ford Prodigy The Ford Prodigy was a low emission vehicle 72 mpg-US (3.3 L/100 km; 86 mpg-imp) diesel-hybrid concept car built in 2000 by Ford and aimed at establishing U.S. leadership in the development of extremely fuel-efficient (up to ) vehicles while ...

Dodge Intrepid ESX The Dodge Intrepid ESX prototype cars are the result of the 1993 response by the Chrysler Corporation to a challenge by U.S. President Bill Clinton to produce a vehicle which was capable of meeting the demands of the modern consumer, while still ...

Ford Reflex The Ford Reflex (or ''REFL3X'', as spelled on the vehicle nameplate) is a concept car introduced at the 2006 North American International Auto Show that, according to Ford, "proves small cars can be bold and American". It is a technological showc ...

is a diesel hybrid concept car. *

Zytek Gibson Technology is an automotive and motorsport company based at Repton, Derbyshire, England. It was founded by Bill Gibson as "Zytek Engineering" in 1981. In 1981 Gibson founded the "Zytech Group" with two main divisions: Zytek Automotive, ...

develops a diesel hybrid powertrain * Peugeot 307 Hybrid HDi *

Citroën C-Cactus Citroën () is a French automobile brand. The "Automobiles Citroën" manufacturing company was founded in March 1919 by André Citroën. Citroën is owned by Stellantis since 2021 and previously was part of the PSA Group after Peugeot acquired ...

* Opel Flextreme *

Top Gear Top Gear may refer to: * "Top gear", the highest gear available in a vehicle's manual transmission Television * ''Top Gear'' (1977 TV series), a British motoring magazine programme * ''Top Gear'' (2002 TV series), a relaunched version of the or ...

Hammerhead-i Eagle Thrust * Rivian Automotive is developing a diesel–electric engine that should achieve an estimated 90 miles per U.S. gallon (2.61 L/100 km) in the city and over 100 miles per U.S. gallon (2.35 L/100 km) on the highway

Military vehicles

Diesel–electric propulsion has been tried on some military vehicles, such as

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and good battlefield mobility provided by tracks and a powerful engi ...

s. The prototype

TOG1 The Tank, Heavy, TOG 1 was a prototype British heavy tank produced in the early part of the Second World War in the expectation that battlefields might end up like those of the First World War. It was designed so it could cross churned-up count ...

and

TOG2 The Tank, Heavy, TOG II was a British super-heavy tank design produced in the early part of World War II in case the battlefields of northern France devolved into a morass of mud, trenches and craters as had happened during World War I. When t ...

super heavy tanks of the Second World War used twin generators driven by V12 diesel engines. More recent prototypes include the SEP modular armoured vehicle and T95e. Future tanks may use diesel–electric drives to improve fuel efficiency while reducing the size, weight and noise of the power plant."Electric/Hybrid Electric Drive Vehicles for Military Applications", Military Technology (Moench Verlagsgesellschaft mbH) (9/2007): 132–144, September 2007, pp. 132–144 Attempts with diesel–electric drives on wheeled military vehicles include the unsuccessful

ACEC Cobra The ACEC Cobra is a tracked armored personnel carrier with amphibious capabilities, similar in concept to the BTR-50. It was developed by Ateliers de Constructions Electriques de Charleroi (ACEC) along with the Belgian Army. The Cobra was the fi ...

, MGV, and

XM1219 Armed Robotic Vehicle The XM1219 Armed Robotic Vehicle was an unmanned ground combat vehicle based on the MULE Platform. The ARV-A-L MULE Vehicle (XM1219) would feature integrated anti-tank and anti-personnel and reconnaissance, surveillance, and target acquisition (R ...

References

External links

*
EERE Clean Fleet Guide by vehicle typeHybrid-Vehicle.org: Information on hybrid vehicle history, technology and practical application in a broad spectrum of vehicles

Diesel Hybrid News
{{DEFAULTSORT:Diesel-electric Transmission Diesel engine technology Marine propulsion Diesel engines Swedish inventions Diesel-electric vehicles Automotive transmission technologies