Comparing the energy efficiency of different transport modes

Iwannahurl

The internal combustion engine is hopelessly inefficient. Even under ideal conditions around 80% of the fuel is wasted.

In the context of commuting and transport, this waste is compounded by the high prevalence of single-occupant car use.

I know that the bicycle is the most energy-efficient mode of mechanical locomotion ever created, but if we want to move large volumes of people and goods around then mass transport must form a major part of the mix.

I'm wondering whether there are any good, easy-to-use and compelling publications (ie documents rather than multi-page websites) that illustrate clearly the comparative energy efficiencies of different modes of travel in the context of mass transit. In other words, something aimed at informing public policy at local, regional or national level rather than at the individual and their transport choices.

It must be a complex topic, especially when transport economics are inevitably brought into it, which is why I'm looking for something relatively Noddy-level, ie not overly detailed or academic.

EDIT: I presume any analysis would have to look at factors such as energy consumed per person per 100 km travelled, or some such.

Iwannahurl

I know I'm talking to myself now, but I just found this interesting graph while searching for information re the above.

It shows the percentage change in transport energy consumption per person 1990-2007 for thirty countries, plus EU-27 average. Ireland is second only to the Czech Republic, with a c. 140% increase.

bk

Iwannahurl wrote: »

I know I'm talking to myself now, but I just found this interesting graph while searching for information re the above.

No, I'd be very interested in such information.

I'd love to know how much fuel is used to carry for instance 50 people by car, bus and train. So less us know anything you find.

CIE

The internal combustion engine is hopelessly inefficient. Even under ideal conditions around 80% of the fuel is wasted

Not true. That's a petrol engine under somewhat less than ideal conditions. Diesels can get over 40% heat efficient, especially in diesel-electric locomotives. Even steam engines at their low thermal efficiency have done work that far outstripped their predecessors and even far outstripping their successors.

I know that the bicycle is the most energy-efficient mode of mechanical locomotion ever created

No it sure is not. Automobile engines are 50 times more efficient than human bodies. Electric motors are even more efficient, especially when the means of locomotion includes steel rather than rubber-tyred wheels. A bicycle will never be able to do what an automobile can do. Putting everyone out of their cars and onto bicycles will help nothing and increase travel times, never mind exponentially increase traffic volumes.

In the context of commuting and transport, this waste is compounded by the high prevalence of single-occupant car use

It's far more than that. It's also the infrastructure that is built to facilitate the movement of such vehicles, whether single-occupant or multiple-occupant. On top of that, you have other factors, such as the requirements of employers with respect to such vehicles, whether in company business or requiring employees to be in possession of autos. Don't exclude government and business policy from this equation.

Generally, city buses are capable of something like 110 passenger miles per litre of diesel fuel, while trains can get much higher. Trolleybuses and electric trains are higher still.

Iwannahurl

bk wrote: »

No, I'd be very interested in such information.

I'd love to know how much fuel is used to carry for instance 50 people by car, bus and train. So less us know anything you find.

Still searching! I found this along the way: an online calculator that allows you to "automatically produce an environmental balance sheet for any selected journey by car or rail". I haven't got around to investigating it yet, but it seems to be mainly focused on CO2 emissions rather than energy efficiency.

mk6705

Iwannahurl wrote: »

The internal combustion engine is hopelessly inefficient. Even under ideal conditions around 80% of the fuel is wasted.

In the context of commuting and transport, this waste is compounded by the high prevalence of single-occupant car use.

I know that the bicycle is the most energy-efficient mode of mechanical locomotion ever created, but if we want to move large volumes of people and goods around then mass transport must form a major part of the mix.

I'm wondering whether there are any good, easy-to-use and compelling publications (ie documents rather than multi-page websites) that illustrate clearly the comparative energy efficiencies of different modes of travel in the context of mass transit. In other words, something aimed at informing public policy at local, regional or national level rather than at the individual and their transport choices.

It must be a complex topic, especially when transport economics are inevitably brought into it, which is why I'm looking for something relatively Noddy-level, ie not overly detailed or academic.

EDIT: I presume any analysis would have to look at factors such as energy consumed per person per 100 km travelled, or some such.

A problem you may run into here is that electrically powered modes of transport can give the illusion of being very efficient while they are in fact not. The conversion from electrical to kinetic energy may be great, but then you have to ask where the electricity came from. You must consider how much is lost in transmission also. Nuclear or renewable stands a chance, but the fact of the matter is no country is 100% dependant on either nowadays and fossil fuels won't deliver enormous efficiency.

Iwannahurl

CIE wrote: »

Not true. That's a petrol engine under somewhat less than ideal conditions. Diesels can get over 40% heat efficient, especially in diesel-electric locomotives. Even steam engines at their low thermal efficiency have done work that far outstripped their predecessors and even far outstripping their successors.

No it sure is not. Automobile engines are 50 times more efficient than human bodies. Electric motors are even more efficient, especially when the means of locomotion includes steel rather than rubber-tyred wheels. A bicycle will never be able to do what an automobile can do. Putting everyone out of their cars and onto bicycles will help nothing and increase travel times, never mind exponentially increase traffic volumes.

It's far more than that. It's also the infrastructure that is built to facilitate the movement of such vehicles, whether single-occupant or multiple-occupant. On top of that, you have other factors, such as the requirements of employers with respect to such vehicles, whether in company business or requiring employees to be in possession of autos. Don't exclude government and business policy from this equation.

Generally, city buses are capable of something like 110 passenger miles per litre of diesel fuel, while trains can get much higher. Trolleybuses and electric trains are higher still.

I'd need to see some sources for the above points re energy efficiency.

However, I wouldn't argue with you about the energy efficiency of public transport. As I made clear in my original post, mass transit has to be the main focus of any attempt to address issues of energy efficiency (and hence emissions) in the transport sector. My main point is that travel modes such as public transport and cycling beat the single-occupant private car hands down.

Even if diesel and diesel-electric locomotives waste ~60% of their fuel, as you appear to suggest, that's still much better than the performance of a private car in terms of energy used to transport a given number of people over a given distance. I'm still looking for a publication that illustrates that equation in an accessible fashion.

Since I'm a big fan of cycling, I can't accept your assertion that bicycle are not hugely energy efficient. Can you point to any reputable sources that indicate otherwise?

AFAIK, it has been shown repeatedly that bicycles are highly energy efficient. Of course all direct and indirect energy inputs have to be factored in, and there's even the possibility that regular cyclists will live longer and therefore consume more energy over a lifetime!

Perhaps it all depends on how you look at it, and what assumptions you make:

The fossil fuel energy required to travel on a typical bicycle is compared to that of a typical automobile. Based on the mechanical energy used (by calculating the forces needed for steady motion) the bicycle is roughly 10 times more efficient. But since the auto must brake from a higher velocity it uses relatively more braking energy than a bicycle so the ratio of 10 becomes about 13.5. But while an auto engine is rated about 50% higher in thermal efficiency than the "human engine", in actual urban use the auto engine is about 40% lower in thermal efficiency and about 10% of fuel is burned during idling. Result: The bicycle is about 25 times more efficient than the auto. But when one considers that for every Calorie of food eaten, it takes perhaps 15 Calories of fuel to grow, transport, and cook that food, then the bicycle is only about 1.7 time more energy efficient than the auto. Due to low annual miles bicycles are ridden, the energy cost of making bicycles per mile of use is quite high and estimating this is still a "to-do" item. In addition if one counts the energy cost of the extra time it takes to travel by bicycle, it's not clear that the bicycle is any more energy-efficient than the auto. But if one counts the energy expended by bicycling as the energy cost of healthy exercise and doesn't count it as an input to transportation, then the bicycle would be extremely energy-efficient.

I wonder whether the above takes into account that both the cyclist and the car driver have to eat...

Here are a few articles pointing to the energy efficiency of the bicycle:

Bicycle performance (Wikipedia page)

Energy cost and mechanical efficiency of riding a human-powered recumbent bicycle.

Lab Tests Find that a Two-Wheeler's Chain Drive is up to 98.6 Percent Efficient.

monument

CIE wrote: »

No it sure is not. Automobile engines are 50 times more efficient than human bodies. Electric motors are even more efficient, especially when the means of locomotion includes steel rather than rubber-tyred wheels.

Sorry, but you're wrong!

The bicycle is the most energy-efficient mode of transport, at least for transporting people. Other modes such as Dart come close, but only when close to 100% occupied -- which doesn't even happen all the time at peak times!

CIE wrote: »

A bicycle will never be able to do what an automobile can do. Putting everyone out of their cars and onto bicycles will help nothing and increase travel times, never mind exponentially increase traffic volumes.

Bull**** of the highest order!

The bicycle is today already able to beat travel times of cars for most commuter and other trips in our cities and towns. Getting more people who currently have 10km or lower to travel onto bicycles, also means roads and public transport are freer for those travelling longer distances or those who need to drive.

As for "exponentially increase traffic volumes", that's a good thing if you're increasing volumes of bicycles on the road as bicycles need far less space than cars:

CIE wrote: »

On top of that, you have other factors, such as the requirements of employers with respect to such vehicles, whether in company business or requiring employees to be in possession of autos. Don't exclude government and business policy from this equation.

People who need to drive benefit if the people who don't get on bicycles.

CIE wrote: »

Generally, city buses are capable of something like 110 passenger miles per litre of diesel fuel, while trains can get much higher. Trolleybuses and electric trains are higher still.

They may be capable of this, but over all the public transport system is far less efficient as in order to make it attractive buses etc have to be run at all times not just when there is demand which leads to them reaching their full potential.

Bicycles on the other hand have pretty much the same efficient the vast majority of the time.

Aidan1

For those of you interested in determining accurately the actual energy efficiency of cars used on Irish roads, this article is very useful (it's primarily about the efficiency of PHEVs, but it uses the New European Drive Cycle (NEDC), adapted to Ireland, as a baseline). Outstanding article.

W. J. Smith, “Plug-in hybrid electric vehicles–A low-carbon solution for Ireland?,” Energy Policy, vol. 38, pp. 1485-1499, 2010.

The author reckons that the real world primary energy requirement (PER - which is the proper basis for calculation) of the Irish private car fleet is roughly 750Wh km, so you can adapt that by passenger number to see the effect.

Interestingly (and going back to the previous discussion about the grid) he also reckons that (on the basis of 2006 numbers for electricity supply efficiency) that an EV running off electricity sourced from the Irish grid will reduce the PER by 55%, rising to more than 66% by 2020 if the targets for renewables are met. Similarly, GHG emissions fall by 50% per km on the 2006 figures, and by 70% by 2020 if the targets for renewables are met (and yes, that takes account of improvements in conventional vehicles over that period. This is down to the fact that the supply efficiency of the Irish grid was 41.6% in 06.


If anyone is really interested, these reports are a goldmine of figures;
http://www.seai.ie/Publications/Statistics_Publications/EPSSU_Publications/Energy_in_Transport/Energy_In_Transport_2009_Report.pdf


http://www.seai.ie/Publications/Statistics_Publications/Energy_in_Ireland/Energy_in_Ireland_1990-2009.pdf

Iwannahurl

Just found these webpages while looking for something else.

Haven't had time to look at them, so make of them what you will.

http://www.straightdope.com/columns/read/2917/is-mass-transit-a-waste-of-energy

http://www.lafn.org/~dave/trans/energy/does_mt_saveE.html

Stonewolf

My motorbike uses about as much fuel as a small car or a larger diesel one (fuelly link) but it does take up much less roadspace (for reference it's the motorbike equivalent of a hot hatch). I've no idea about emissions as I don't think motorbike mfrs care (it's not a big selling point and here at least it has no effect on cost) so long as they meet current euro regs (my model was replaced for this reason). There are plenty of good smaller motorbikes and scooters out there that beat cars hands down on efficiency and running costs though bikes aren't well supported in terms of parking and in common with pedal bikes are not well suited to our climate.

foggy_lad

Iwannahurl wrote: »

I know I'm talking to myself now, but I just found this interesting graph while searching for information re the above.

It shows the percentage change in transport energy consumption per person 1990-2007 for thirty countries, plus EU-27 average. Ireland is second only to the Czech Republic, with a c. 140% increase.

Would it not be reasonable to assume that the increased motor vehicle use by Irish people in purely social and leisure capacity during the years covered by the graph indicate the massive increase may be due to the rise in disposable incomes during the celtic tiger boom years? People earned more so bought a second car and drove a lot more.