# Are Diesel-Electric locomotives effectively Hybrids? **URL:** \ **Category:** Factual Questions\ **Created:** [June 20, 2011, 4:05pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165 "2011-06-20T16:05:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![robert\_columbia](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)\ **Post date:** [June 20, 2011, 4:05pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/1 "2011-06-20T16:05:41Z")
Reading about Diesel-Electric rail locomotives, it seems that they are effectively Hybrid vehicles. Are they actually Hybrids in the sames sense that a Toyota Prius is a Gasoline-Electric vehicle? [http://boards.straightdope.com/sdmb/archive/index.php/t-63293.html](http://boards.straightdope.com/sdmb/archive/index.php/t-63293.html) ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [June 20, 2011, 4:10pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/2 "2011-06-20T16:10:12Z")
Not exactly the same thing. A Prius has an electric motor and a gas engine; it can run on either one, depending on circumstances. A diesel locomotive uses diesel engines to run electric motors on the wheels. It can’t directly use the diesel engines to move the wheels. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 20, 2011, 4:10pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/3 "2011-06-20T16:10:59Z")
More like a serial hybrid like a Chevy Volt. The diesel engines don’t provide motive power. They just run generators to provide electricity for the electric motors which drive the wheels. ---
**Author:** ![SanDiegoTim](https://avatars.discourse-cdn.com/v4/letter/s/85e7bf/32.png) [@SanDiegoTim](https://boards.straightdope.com/u/SanDiegoTim)\ **Post date:** [June 20, 2011, 4:13pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/4 "2011-06-20T16:13:07Z")
Further, and in opposition to a hybrid vehicle, the diesel engine is always running. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [June 20, 2011, 4:16pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/5 "2011-06-20T16:16:42Z")
> [@SanDiegoTim](#): > > Further, and in opposition to a hybrid vehicle, the diesel engine is always running. Right. A better analogy for a diesel locomotive would be a gas-powered electric generator, hooked up to the “motor” of an electric car. The diesel locomotive isn’t using the diesel engine to charge an electric battery, which then is “drawn down” when the engineer needs the locomotive to move (unlike a hybrid automobile); the diesel engine is an “always-on” power source for the electric motors on the axles. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 20, 2011, 4:19pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/6 "2011-06-20T16:19:00Z")
> [@SanDiegoTim](#): > > Further, and in opposition to a hybrid vehicle, the diesel engine is always running. Which is a difference with a serial hybrid car like the Volt, which can manage short trips on its batteries. The Volt’s ICE runs to charge the batteries. Personally, I wouldn’t make “the ICE doesn’t run all the time” as a condition for defining something as a “hybrid” vehicle. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [June 20, 2011, 4:21pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/7 "2011-06-20T16:21:18Z")
There apparently are (and have been) true “hybrid” diesel locomotives, though most are fairly recent prototypes or experimental designs: > **[Hybrid train](https://en.wikipedia.org/wiki/Hybrid_locomotive)** > > A hybrid train is a locomotive, railcar or train that uses an onboard rechargeable energy storage system (RESS), placed between the power source (often a diesel engine prime mover) and the traction transmission system connected to the wheels. Since most diesel locomotives are diesel-electric, they have all the components of a series hybrid transmission except the storage battery, making this a relatively simple prospect. > Surplus energy from the power source, or energy derived from regenerative b... ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [June 20, 2011, 4:30pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/8 "2011-06-20T16:30:30Z")
It’s a hybrid drive system, but not for efficiency, more for practicality. Locomotives dump extra energy (such as from braking), into resistors to generate heat, none of it is stored or even dumped into a 3rd rail AFAIK. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 20, 2011, 4:32pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/9 "2011-06-20T16:32:55Z")
OTOH, in the general article about “hybrid vehicles”, says the following: > [@](#): > > Hybrid power trains use diesel-electric or turbo-electric to power railway locomotives, buses, heavy goods vehicles, mobile hydraulic machinery, and ships. Typically some form of heat engine (usually diesel) drives an electric generator or hydraulic pump which powers one or more electric or hydraulic motors. There are advantages in distributing power through wires or pipes rather than mechanical elements especially when multiple drives—e.g. driven wheels or propellers—are required. There is power lost in the double conversion from typically diesel fuel to electricity to power an electric or hydraulic motor. With large vehicles the advantages often outweigh the disadvantages especially as the conversion losses typically decrease with size. With the exception of non nuclear submarines, presently there is no or relatively little secondary energy storage capacity on most heavy vehicles, e.g. auxiliary batteries and hydraulic accumulators—this is changing. It then goes on to link to the “hybrid train” provided above. I would suggest there’s a lot of wiggle room in what one means by “hybrid vehicle”. The one sentence definition that starts the article is pretty broad: > [@](#): > > A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. > **[Hybrid vehicle](https://en.wikipedia.org/wiki/Hybrid_vehicle)** > > A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids. > Hybrid powertrains are designed to switch from one power source to another to maximize both fuel efficiency and energy efficiency. In hybrid electric vehicles, for instance, the electric motor is more efficient at producing torque, or turning power, while the combustion eng... ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 20, 2011, 4:37pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/10 "2011-06-20T16:37:10Z")
I would argue that a diesel-electric locomotive is NOT a hybrid, because it only has one source of energy (the diesel engine). A gas-electric hybrid car has two sources of energy: a battery and a gasoline engine. The two are used in a way that maximizes energy efficiency. Namely, when the engine is run, it is run at a RPM and power output that offers good energy efficiency. When more power is needed, the electric motor kicks in, instead of revving up the engine. A diesel-electric locomotive can’t do that; you need to rev up the engine when accelerating, and run the engine at a lower PRM when cruising at a low speed. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [June 20, 2011, 4:53pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/11 "2011-06-20T16:53:19Z")
The real question is what definition of hybrid do we accept. I think as applied to cars, it came into common usage to describe the Prius and Insight. Diesel locomotives are different. I am not sure who is in a position to say whether they fit the difination or not. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [June 20, 2011, 5:03pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/12 "2011-06-20T17:03:58Z")
I think the main advantage of diesel-electric isn’t ease of power transmission, but rather that they can run that diesel in a much more efficient manner than if it was directly powering the wheels. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [June 20, 2011, 5:13pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/13 "2011-06-20T17:13:00Z")
> [@scr4](#): > > I would argue that a diesel-electric locomotive is NOT a hybrid, because it only has one source of energy (the diesel engine). > > A gas-electric hybrid car has two sources of energy: a battery and a gasoline engine. I see your point, but a hybrid car (like a Prius) has one source of energy: the gasoline. The battery is charged only by energy from the generator (powered by the gas engine) and reclaimed from braking. All the energy in the battery comes from energy that the gas engine created to start with. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [June 20, 2011, 6:05pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/14 "2011-06-20T18:05:51Z")
Years ago, I read that the diesel electric locomotive was a solution to an engineering problem related to the inability to build the strong, efficient transmission necessary to power the multiple drive wheels. Getting power to all the drive wheels was simplified by the use of the multiple electrical motors. ---
**Author:** ![Hbns](https://avatars.discourse-cdn.com/v4/letter/h/8edcca/32.png) [@Hbns](https://boards.straightdope.com/u/Hbns)\ **Post date:** [June 20, 2011, 6:08pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/15 "2011-06-20T18:08:45Z")
[Looking back](http://www.google.com/search?tbo=p&tbm=pts&hl=en&q=%22hybrid+drive+system%22&tbs=,cdr:1,cd_min:Jan%201_2%201970,cd_max:Oct%2031_2%201990&num=10) through some old patents the term Hybrid Drive System has been in use for many decades. Just browsing quickly it seems the term is generally applied in cases where there is more than one way to deliver a driving force to the drive wheels. Looking through these was a bit of an eye opener. I found [this patent](http://www.google.com/patents?id=oU4sAAAAEBAJ&pg=PA4&dq=%22hybrid+drive+system%22&hl=en&ei=-Yf_TdFnhI-zBtmqsPEN&sa=X&oi=book_result&ct=result&resnum=6&ved=0CDQQ6AEwBQ#v=onepage&q=%22hybrid%20drive%20system%22&f=false) from the early seventies that is earily close to modern hybrids. So from that, I would say that locomotives and large off highway vehicles are not hybrids. Just vehicles with a diesel-electric powertrain instead of a mechanical one. ---
**Author:** ![cochrane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cochrane/32/10441_2.png) [@cochrane](https://boards.straightdope.com/u/cochrane)\ **Post date:** [June 20, 2011, 6:37pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/16 "2011-06-20T18:37:06Z")
> [@yabob](#): > > More like a serial hybrid like a Chevy Volt. The diesel engines don’t provide motive power. They just run generators to provide electricity for the electric motors which drive the wheels. A Volt’s engine can propel the car directly when the batteries are depleted, however, in addition to providing charge to the batteries. [Chevrolet Volt - Drivetrain](http://en.wikipedia.org/wiki/Chevy_volt#Drivetrain) > [@](#): > > After the Volt battery has dropped to a predetermined threshold from full charge, a small naturally aspirated 1.4-liter 4-cylinder internal combustion engine (Opel’s Family 0) with approximately 80 horsepower, burns premium gasoline to power a 55 kW (74 hp) generator to extend the Volt’s range **or when performance needs to be improved, the gas engine engages mechanically to assist propulsion directly.** ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [June 20, 2011, 7:27pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/17 "2011-06-20T19:27:15Z")
> [@bump](#): > > I think the main advantage of diesel-electric isn’t ease of power transmission, but rather that they can run that diesel in a much more efficient manner than if it was directly powering the wheels. Do you know where you learned that? I’m not a vehicle engineer, but my understanding is that diesel-electric locomotives came about mainly because it’s a lot easier to run electrical wire from the engine to drive wheels than it is to run mechanical driveshafts with enough power to move a freight train. Secondarily, the electric motors (unlike diesels) are efficient at low-speed high-torque conditions, so you don’t need the huge gear ranges you would need to start a train with direct-diesel. The less extensive gearing probably helps efficiency a little, but is probably more valuable for simplicity and low-cost. I believe the real efficiency gains from internal combustion–electric drive come when there’s enough battery storage to smooth the loading on the IC engine; this lets the engine stay in its sweet spot for power output, and be smaller overall, both of which give you a big efficiency gain. (Regenerative braking adds another big dollop of efficiency as well). Since most traditional diesel-electric locomotives don’t store power in batteries, they don’t get these efficiency gains. But the OP seems to understand how locomotives work, so anything further is just arguing about what ‘hybrid’ means. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [June 20, 2011, 8:01pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/18 "2011-06-20T20:01:24Z")
What about the dual-mode buses that are in Seattle as well as in at least one town in Switzerland (Fribourg). Also, they are about to introduce dual-mode locomotives for a new commuter line in Montreal. The line will run partly in a tunnel where only electric locomotion is permitted and partly on some non-electrified freight lines. So they will run on diesel (or, it seems more likely, diesel-electric) over the freight line and on pure electricity (with catenaries and pantographs) in the tunnel. These locomotives were developed in conjunction with NJ Transit, which then canceled after the carhead governor canceled the proposed new tunnel under the Hudson. ---
**Author:** ![Cabin\_Fever\_1](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cabin_fever_1/32/2908_2.png) [@Cabin\_Fever\_1](https://boards.straightdope.com/u/Cabin_Fever_1)\ **Post date:** [June 20, 2011, 8:35pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/19 "2011-06-20T20:35:31Z")
> [@Quercus](#): > > Do you know where you learned that? > I’m not a vehicle engineer, but my understanding is that diesel-electric locomotives came about mainly because it’s a lot easier to run electrical wire from the engine to drive wheels than it is to run mechanical driveshafts with enough power to move a freight train. > Secondarily, the electric motors (unlike diesels) are efficient at low-speed high-torque conditions, so you don’t need the huge gear ranges you would need to start a train with direct-diesel. It’s quite impressive when you see it in action from an engineer/mechanical standpoint. > **[GE Companies: Next Generation and Future | General Electric](https://www.ge.com)** > > The future of GE's companies begins now with the planned spinoff of GE Aerospace and GE Vernova. See how the GE companies are empowering the next generation. Then again, I’ve always been a fan of their jet engines for some reason. [http://www.ge.com/products\_services/aviation.html](http://www.ge.com/products_services/aviation.html) How this could translate into more efficient cars, I dunno. But would love to find out. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [June 20, 2011, 9:33pm UTC](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165/20 "2011-06-20T21:33:19Z")
A critical reason for using a diesel electric is that the electric motors generate maximum torque at stall. Which is pretty much the opposite of an internal combustion engine. What this means is that you can run the diesel engine at maximum power when the train is stopped and dump all the power into moving the train. You can’t do that easily with a mechanical transmission, and certainly not at the large powers the bigger freight locos provide. Efficiency gains from regenerative braking and the availability of a useful power boost for dragging a train up steep grades are advantages with a hybrid, when you add batteries. One useful thing about a locomotive, you are not worried about adding mass. In order to get traction they are built heavy in the first place. [Next page](https://boards.straightdope.com/t/are-diesel-electric-locomotives-effectively-hybrids/586165.md?page=2)