How Does Diesel Electric Propulsion Work?

Multiple diesel engines, each driving an electric generator, create the electric power that energizes the electric motors connected to the propellers, as well as other electrical loads on the ship, in diesel-electric systems. Not all diesel generators must be running at all times, depending on electrical demand.

What is the working principle of a diesel-electric propulsion system?

On ships with unique operational requirements, diesel-electric propulsion systems are used. These systems work by using speed-controlled AC motors to drive the propeller directly or through gearing. The direct drive is the most reliable and low-noise design.

What is the advantage of diesel-electric propulsion?

Diesel-electric propulsion is so common these days, from tugboats to tankers, that it’s easy to forget that most new ships are still powered by traditional engines. However, the keynote speaker at a symposium on electric ships near Washington, D.C. in February reminded architects and engineers that the proportion of diesel-electric vessels built each year varies between 2 and 4.5 percent.

“According to Jukka Kuuskoski, vice president of ABB Marine in Finland, “electric propulsion is a niche industry.”

However, some vessel types are dominated by diesel-electric propulsion. ABB estimates that cruise ships, icebreakers, and drilling boats have a 100 percent market share, whereas LNG carriers have a 45 percent market share. Even orders for large OSVs — those with more than 4 to 6 MW of installed power, according to Kuuskoski — are presently 50% diesel-electric. For example, Tidewater, based in New Orleans, has announced that it will construct 12 new diesel-electric 286-footers in China. Tidewater manages the world’s largest fleet of offshore boats.

In a previous post (PM #110), the benefits of electric — usually diesel-electric — for commercial vessels were outlined, particularly when combined with podded propulsion. They include a more efficient propulsion system, less pollution, improved operating efficiency, particularly at low speeds (essential for applications like dynamic positioning), and greater flexibility in arranging equipment compartments.

The main disadvantage is the significant initial investment. “Commercial shipowners are wary of taking risks in the shipbuilding industry. On the market side, they take enough risks,” Keith Michel, president of the Society of Naval Architects and Marine Engineers, stated (SNAME). The symposium was a collaboration with the American Society of Naval Engineers (ASNE).

Although some U.S. shipyards have extensive experience with diesel-electric propulsion, such as General Dynamics Nassco with its Orca-class ro-ro vessels, BP Alaska-class tankers, and underway replenishment ships for the Military Sealift Command, the cost factor has held back more widespread adoption of the technology. Larry Rigdon was an early convert to diesel-electric among brownwater operators, receiving the first of a series of 210-foot DP-2 OSVs from Bender Shipbuilding in 2004.

Peter G. Noble, chief naval architect for Houston-based ConocoPhillips, presented one of the most broad perspectives at the conference, seeing diesel-electric as the answer for many types of offshore vessels operating in depths of 10,000 to 12,000 feet — seismic vessels, drillships, semisubmersibles, and others.

For Crowley Maritime (PM #118), Seattle-based Glosten Associates has built a 90-foot hybrid tug with 72.5 tonnes of bollard pull. Glosten is also looking into the idea of a battery-powered tug for Southern California that would run on electricity rather than fossil fuels.

Glosten has also finished the design for a 242-foot research vessel for the University of Alaska Fairbanks, demonstrating why diesel-electric propulsion is the best option for ice-capable vessels. The vessel will be propelled by two ice-strengthened azimuth thrusters.

“We can have full torque on the props at zero speed with the diesel-electric podded propulsion,” stated Jeff Hawxhurst, senior electrical engineering technician at Glosten. “We don’t want to become stranded.”

Why do diesel locomotives use electric motors?

Switchers (or shunters), locomotives used for moving trains around in railroad yards and building and disassembling them, were the first to utilise diesel–electric technology in the 1920s. The American Locomotive Company was one of the first companies to offer “Oil-Electric” locomotives (ALCO). In 1931, the ALCO HH series of diesel–electric switchers went into production. The system was modified in the 1930s to accommodate streamliners, the fastest trains of the day. Diesel–electric powerplants were popular because they substantially simplified the transmission of motive power to the wheels, as well as being more efficient and requiring less maintenance. When a locomotive has four or more axles, direct-drive transmissions can become quite complicated. A direct-drive diesel locomotive would also necessitate an excessive number of gears to keep the engine within its powerband; connecting the diesel to a generator solves this problem. In a direct drive system, a torque converter or fluid coupling can be used to replace the gearbox. Hydraulic transmissions are said to be more efficient than diesel-electric transmissions.

Are ships diesel-electric?

Your next yacht could be driven by a diesel electric drive, which is a new but old and well-proven power technology. Diesel electric propulsion was first employed on the Volga River and the Caspian Sea in 1903 to move the triple-screw Russian tanker Vandal. It is now utilized in the most contemporary cruise liners and thousands of other commercial boats. Although it may appear that using an indirect, two-step diesel electric energy transfer system to power your boat is overly complicated, its numerous advantages can make it a compellingly attractive alternative to a traditional direct mechanical prop-shaft drive.

The advantages of diesel electric propulsion start with the design freedom that the system provides to the yacht designer. The engine can be placed wherever it is most practical to maximize the amount of room available for lodging. In comparison to a traditional direct engine-to-propeller drive, noise and vibration are easier to control. The use of electric motors to turn the props improves slow-speed maneuverability by allowing for unrestricted minimum prop speeds with 100 percent torque available at all times. Proper synchronization is completely automated and exceedingly accurate. When the vessel is underway, the diesel electric propulsion system can provide all of the vessel’s electrical power, eliminating the requirement for a genset. A diesel electric power system can employ a single engine to power several propellers or numerous engines to power one or more props. When operating within the speed limits enforced in many places, one engine can power both propellers in a twin-engine/twin-prop configuration. Electrical power from the vessel’s genset can be utilized to propel the boat, giving built-in backup, which is especially useful for single-engine boats. The propulsion system, on the other hand, can act as a backup for the yacht’s gensets.

The more than 100-year history of marine diesel electric systems originated as a response to the early direct-to-prop-shaft-coupled diesel engines’ inability to quickly reverse the direction of rotation. The direction of prop rotation could be regulated by a switch using a diesel-powered direct current (DC) generator and a DC motor attached to the prop shaft. The electric motor’s capacity to produce 100 percent torque at zero speed led to the widespread usage of diesel electric locomotives. Submarines and many surface ships have adopted diesel electric drives as a natural fit. Diesel electric power is used on today’s cruise liners, which require 70-80 percent of total onboard electricity for the “hotel” side of the ship. At times, the power needs can be considerable. A simple example: to power half of the 1,500-watt hair dryers on a 1,400-stateroom cruise ship, 1,500,000 watts, or more than 1,400 hp, is required.

What is the concept of electric propulsion?

Electric propulsion (EP) is a type of space propulsion that uses electricity to accelerate a propellant through various electrical and/or magnetic means. When compared to conventional chemical thrusters, the EP thrusters’ propulsive performance is improved by using electrical power. Electric propulsion, unlike chemical systems, requires very little bulk to accelerate a spaceship. The propellant is ejected up to twenty times quicker than in a traditional chemical thruster, resulting in a far more mass efficient overall system.

What are the main components of an electric propulsion system?

2 Technological principles in place and prospective development routes Every electric propulsion system is built on a foundation of critical components that allow the concept to function. The energy storage device (battery system),2 the electric machine, the power electronics, and a proper charging device are the most critical components.

How efficient are diesel-electric trains?

A group of progressive activists and railroad business specialists has proposed that the federal and state governments, in collaboration with the railroad industry, participate in a long-term initiative to electrify US railroads. They detail a plan to update freight and passenger railways with overhead wires to carry high-voltage electricity generated in towns along the lines, and replace diesel locomotives with electric engines in a book published in October 2016, Solutionary Rail, a people-powered campaign to electrify America’s railroads to a clean energy future. These cables would also help supply electricity generated by distributed renewable energy sources by creating a new, nationwide electrical transmission system. The book lists various advantages of an electrified railway system over the current system in the United States, but industry and government analysts are pessimistic that the proposal will be implemented.

One thing that all analysts agree on is that long-haul transportation by train is more efficient than by truck. Steel rolling on steel is far more efficient in terms of energy transfer than rubber rolling on concrete, creating just approximately one-fifth of the friction. Trains are also more aerodynamically efficient than lorries. Overall, railways transport freight 1.9 to 5.5 times more effectively than trucks, with substantially lower overall labor costs and far less pollution. Truckers could also benefit from a change to rail for long-haul freight because they could focus on the last miles of the voyage and work more normal hours. A cleaner, more robust railroad system may replace a significant percentage of truck traffic, while also improving the reliability and competitiveness of intercity passenger service compared to highways and airlines.

Electric Trains vs. Diesel Trains

Trains are more efficient than trucks, but not all trains are created equal. Diesel trains send roughly 30% to 35% of the energy generated by combustion to the wheels, whereas delivering electricity straight from an overhead powerline delivers about 95% of the energy to the wheels. According to the authors of Solutionary Rail: Electric Trains, there are several further advantages of using electricity rather than diesel to power trains.

  • While diesel fuel prices are now low, many analysts believe that the long-term trend will be for them to rise. Electricity prices, on the other hand, are lowering as the usage of renewable energy sources expands. Even at present pricing, using the energy conversion rates mentioned above, it is predicted that running a train on electricity is 50% less expensive than running one on fuel.
  • On the global market, electric locomotive engines cost around 20% less than diesel locomotive engines, and maintenance expenses are 25-35 percent lower than diesel engines.
  • Diesel locomotives would be phased out, reducing air pollution such as soot, volatile organic compounds, nitrogen oxides, and sulfur oxides, all of which are harmful to human health and the environment. This is particularly essential because many railroads run through cities. It would help minimize city noise levels and highway fatalities caused by trucks (rail freight causes only about one-eighth as many fatalities as truck freight per ton-mile).
  • Switching from diesel to electricity would also help with the problem of replacing petroleum-based liquid transportation fuels with greener alternatives as part of our efforts to reduce greenhouse gas emissions.

Solutionary Rail not only asks for the electrification of railroads, but also for the use of renewable energy sources to power the new electric railroad system. Renewable energy sources might be connected across the country if transmission lines are installed with enough capacity, producing a nationwide electric power grid that also supplies all of our railway energy demands. Railway electrification would not only provide a new market for renewable energy, but it would also offer it access to a variety of other sectors. The variable production of electricity by wind turbines and photovoltaic solar panels would be offset by the large range of sources (the country isn’t always gloomy or windless).

Why Didn’t U.S. Railroads Go Electric?

Why aren’t electric locomotives more widely used in the United States since they have so many advantages over diesel locomotives? During much of the twentieth century, railroads in the United States were the world leaders in innovation and the use of cutting-edge technology. They have now fallen behind many other sophisticated nations, which have been investing in electric-powered trains for many years. Steam locomotives were replaced by more efficient electric locomotives and diesel-electric (often referred to as just diesel) locomotives in the early to mid-twentieth century. During that shift, railroad firms in the United States preferred diesel locomotives over electric locomotives because diesel has lower upfront costs, even though electric systems are less expensive to operate and maintain. Electric locomotives were chosen by railroad operators in many other developed countries, partially because the railroads were owned by the governments of those countries, who could better finance the necessary transmission infrastructure. Because railroads in the United States have historically been a regulated private sector industry, financing electrification upgrades is far more difficult than building diesel-fueled systems. As a result, electrified rail is currently used on less than 1% of railroad tracks in the United States, despite the fact that electricity provides more than one-third of the energy used to power trains worldwide.

In the United States, a few passenger rail lines (Amtrak’s Northeast corridor and the Harrisburg, PA, line) have been converted to electric power, while the rest of passenger rail and all freight train is diesel-powered. CalTrain, California’s commuter train system, is being upgraded to very high speed rail (VHSR) service, which will run on electricity. The system is expected to be operational by 2022 at a cost of $5 billion at the outset. Other electric VHSR systems (which would be powered by electricity) are being studied around the country, although money has not yet been secured.

Is Rail Electrification a Feasible Undertaking in the United States?

Transitioning from the current railway infrastructure in the United States to a nationally electrified rail system is a major endeavor, and the Solutionary Rail proposal does not include a cost estimate. It does, however, note that many other countries (Switzerland, Sweden, the Netherlands, Italy, France, Germany, Russia, China, India, Japan, and so on) have made substantial attempts to electrify their railway networks, and that many more are currently doing so. However, because their railway services are government-owned and run, whereas U.S. railways are privately held, it is easier for other countries to acquire finance for big infrastructure expenditures like this than it is for their American equivalents (except for Amtrak, which is partially government-funded).

If there was ever a political reason, the US government could mandate that all railways be electrified by a specified date. The massive investment required is an apparent roadblock, and there is little appetite in Congress to reduce the nation’s carbon impact by converting to electric rail. Our would be more difficult in this country than in Europe or Asia, where urban populations are denser. While several other technologically advanced countries (e.g., Japan, Germany, France, Mexico, and Australia) have seen steady decreases in their consumption of petroleum (from which diesel is derived) in recent years, the United States’ consumption of petroleum has increased, owing in large part to transportation demand. I Despite the fact that the transportation sector emits 27% of all greenhouse gases in the United States, there is no national discussion about limiting the usage of combustion engines. ii

Public-Private Partnerships, Industry and Labor Groups Could Make the Difference

Some suggest employing a combination of federal, state, private sector, and possibly regional money to construct an electrified rail network through public-private partnerships (PPPs). In recent years, PPPs have been successful in a number of railroad projects, including the Norfolk Southern Heartland Corridor, which connected the Ohio-West Virginia-Virginia lines (and commenced service in 2010), and the Alameda Corridor, which connects Long Beach and Los Angeles, CA (which began operation in 2002). Electrification of freight train might begin with a demonstration project along the Northern Corridor, which connects various cities and villages from Seattle to Chicago. Several funding models to involve public and private actors in the investment process have been presented.

A push to electrify might garner the help of a variety of industrial and labor groups. Railway electrification would create new opportunities for rail employees (as well as many other industrial trades), making it appealing to labor unions, which might assist win public support for electrifying and modernizing railroads. Several railroad unions are likewise in favor of a more sustainable economy and would certainly support railway electrification. Railroad Workers United, for example, has approved a resolution to move the railroad industry away from fossil fuel shipping and toward more sustainable business prospects. Railroad Workers United represents rail workers from a number of unions involved in North American rail transport. The agriculture sector may be interested in railway electrification as a cost-effective means of moving produce. Agricultural items make up a far smaller percentage of freight rail shipments than fossil fuel shipments, and hence take a back seat in rail traffic. Rail shipments might become considerably more punctual and frequent than they are now, thanks to the greater capacity that electrified railways could give. Electric utilities may also play a role in assisting railway electrification. Utilities are one of freight rail’s most important customers, especially for delivering coal to power plants and carrying coal ash away. The revenues of freight train will decline as utilities become less reliant on coal, unless the railways establish a new business model, such as one that includes energy transfer. Finally, Native American tribes may gain from the project if their right-of-ways are properly negotiated and compensated, as well as if they are allowed to use the new transmission routes to distribute the electricity they create.

The fact that no federal, state, or municipal government action has been taken since the publication of Solutionary Rail in 2016 does not bode well. One critic challenged the idea to electrify railroads shortly after it was published, citing a number of economic issues. The critic, on the other hand, overlooked the environmental benefits of converting to electric-powered rail. Prioritizing the reduction of fossil fuel consumption, including the transition away from diesel fuel, is vital to avert the worst effects of climate change. Although such a transformation will be costly and time demanding, it is nonetheless necessary.

According to the US Energy Information Administration, petroleum consumption in the United States increased by 3.06 percent from 2013 to 2015.

ii. Environmental Protection Agency, Sources of Greenhouse Gas Emissions, September 26, 2017,

How does a diesel hydraulic locomotive work?

One or more torque converters are used in tandem with fixed ratio gears in diesel–hydraulic locomotives. The final drive is made up of drive shafts and gears that transmit power from the torque converters to the wheels and allow for reverse. The location where the speed and torque are controlled is the distinction between hydraulic and mechanical systems. If there is a hydraulic component in a mechanical transmission system with numerous ratios, such as in a gearbox, it is merely to allow the engine to continue when the train is too slow or halted. Hydraulics are the principal system for adapting engine speed and torque to the train’s position in the hydraulic system, with gear selection being used primarily in limited circumstances, such as reverse gear.