I thought that as transportation is impacted by rising oil prices, tanker ships would be the least affected as they are so efficient compared to plane, truck and rail. But I was surprised to read Krugman touting Slow Steaming. Slow Steaming (cargo ships reducing their speed to save fuel) apparently started in 2007 as a response to higher fuel prices. Are trucks and freight trains driving slower or planes flying slower as a response to the higher fuel prices?
It would be nice if tanker shipping costs started "job import" to the USA and other OECD countries after decades of "job export", but in the USA at least, the elite would call for more "worker import" at the same time to perform the returned jobs, ultimately negating the job import or even making things worse by "over importing workers" and making our energy problems worse with an even faster population growth.
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Slow Steaming
Slow Steaming
by dashster » Mon 17 Nov 2014, 21:55:44
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Re: Slow Steaming
by tom_s2 » Mon 17 Nov 2014, 22:37:50
Hi dashster,
The fuel economy of a ship is largely determined by its size and speed. Larger and slower ships use far less energy per ton-mile. For example, a ship which is 4x the size uses 1/2 the fuel per ton-mile, and a ship which is travelling at half the speed uses 1/4th the fuel per ton-mile. As a result, a ship which is 4x the size and half the speed uses 12.5% as much fuel per ton-mile.
Shipping companies select a level of fuel efficiency they want, within limits. More fuel efficient ships are more expensive, so it's only worth it when fuel prices are higher. There's an "ideal" size and speed of a ship to minimize monetary costs depending on a given fuel price. This is a basic calculus optimization problem, which shipping companies carry out routinely. When the price of fuel goes up, the fuel consumption of ships goes down (and vice-versa) as older ships are replaced with more (or less) fuel efficient ones. Of course it takes about 30 years for the entire fleet of ships to turn over, so the average fuel consumption of ships changes fairly gradually.
Very large, slow ships, such as iron ore carriers, which are 400,000 dwt and travel at 8 knots, use an absurdly small amount of fuel. They use less than 5% as much fuel as a tractor-trailer truck per ton-mile.
I wrote something about this on my blog, if you're interested:
http://bountifulenergy.blogspot.com/201 ... nding.html
-Tom S
The fuel economy of a ship is largely determined by its size and speed. Larger and slower ships use far less energy per ton-mile. For example, a ship which is 4x the size uses 1/2 the fuel per ton-mile, and a ship which is travelling at half the speed uses 1/4th the fuel per ton-mile. As a result, a ship which is 4x the size and half the speed uses 12.5% as much fuel per ton-mile.
Shipping companies select a level of fuel efficiency they want, within limits. More fuel efficient ships are more expensive, so it's only worth it when fuel prices are higher. There's an "ideal" size and speed of a ship to minimize monetary costs depending on a given fuel price. This is a basic calculus optimization problem, which shipping companies carry out routinely. When the price of fuel goes up, the fuel consumption of ships goes down (and vice-versa) as older ships are replaced with more (or less) fuel efficient ones. Of course it takes about 30 years for the entire fleet of ships to turn over, so the average fuel consumption of ships changes fairly gradually.
Very large, slow ships, such as iron ore carriers, which are 400,000 dwt and travel at 8 knots, use an absurdly small amount of fuel. They use less than 5% as much fuel as a tractor-trailer truck per ton-mile.
I wrote something about this on my blog, if you're interested:
http://bountifulenergy.blogspot.com/201 ... nding.html
-Tom S
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Re: Slow Steaming
by tom_s2 » Mon 17 Nov 2014, 22:50:25
$this->bbcode_second_pass_quote('', 'A')re trucks and freight trains driving slower or planes flying slower as a response to the higher fuel prices?
Trucks and other motorized vehicles will only save fuel by slowing down if they were traveling at freeway speeds. If you're only going 25 mph then the big problem is rolling resistance. The only way to solve rolling resistance is to use trains instead. I realize there are low-resistance tires but they don't help that much.
It would help a lot at freeway speeds to have longer trucks, like 4 or 5 trailers. At freeway speeds, that makes a big difference because the tractor is pushing air out of the way for the entire train and subsequent trailers have lower wind resistance. Of course there's a safety issue.
IIRC, trucks have far less scope for improvement in fuel economy, because of basic physics. I think it would be hard to more than double the fuel economy of trucks by any combination of strategies (slowing down, regenerative braking, etc).
One possible response to peak oil, is a migration to dense "port cities" such as San Francisco, Shanghai, London, Hong Kong, etc, and a migration away from inland suburbs. Almost everyone in dense port cities lives within 10 miles of a railroad or port. Railroads in very dense cities (such as those of Japan) are often electrified using overhead wires anyway.
-Tom S
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Re: Slow Steaming
by KaiserJeep » Mon 17 Nov 2014, 22:53:01
The short answer is YES, slowing down generally saves energy. This is because the drag on a moving object (air drag for an airplane, vehicle, or train, water drag for a ship) goes up as the square of the speed (i.e. a car going 80 miles an hour experiences four times the air drag of a car going 40 miles an hour). Therefore you save a disproportionate amount of the drag resistance by slowing down. However the friction losses in the engine, powertrain, and wheels (or propellor) remain the same, and slowing down makes the trip longer in duration which increases labor costs.
The exception to the above is a turbofan jet engine, which is designed to operate at a specific altitude (air density) and speed (air velocity). When operated faster, slower, higher, or lower than the designed operating speed and altitude, efficiency is lost and fuel consumption goes up. So slowing down airplanes doesn't work, you need to switch to a different engine type such as a turboprop or piston engine and propellor when you want slower or lower operation.
The untold part of the "slow steaming" is that as ocean trips lengthen, the number of crew members is reduced to save labor expenses. This results in such abuses as the illegal and dangerous practice of a huge container ship or tanker steaming on autopilot with NOBODY AT THE WHEEL. This is why for example a tanker like the Exxon Valdez ends up on one of the few rocks in a huge body of water - because the drunken captain allowed the ship's only watchstander to make his rounds and glance at the radar screen only every 30 minutes or so. Which is also why many wooden or fiberglass sailing craft go missing when they get run over by a giant ship driven by an autopilot.
The exception to the above is a turbofan jet engine, which is designed to operate at a specific altitude (air density) and speed (air velocity). When operated faster, slower, higher, or lower than the designed operating speed and altitude, efficiency is lost and fuel consumption goes up. So slowing down airplanes doesn't work, you need to switch to a different engine type such as a turboprop or piston engine and propellor when you want slower or lower operation.
The untold part of the "slow steaming" is that as ocean trips lengthen, the number of crew members is reduced to save labor expenses. This results in such abuses as the illegal and dangerous practice of a huge container ship or tanker steaming on autopilot with NOBODY AT THE WHEEL. This is why for example a tanker like the Exxon Valdez ends up on one of the few rocks in a huge body of water - because the drunken captain allowed the ship's only watchstander to make his rounds and glance at the radar screen only every 30 minutes or so. Which is also why many wooden or fiberglass sailing craft go missing when they get run over by a giant ship driven by an autopilot.
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Re: Slow Steaming
by dashster » Mon 17 Nov 2014, 23:21:20
Ships are the most efficient, and going slower saves fuel . But, while I see the most efficient transportation has made an effort to slow down due to the fuel costs, I haven't heard about the others. It seems odd for the most efficient to be the one making the adjustment. I was wondering if trains were doing "slow chugging" or trucks were doing "slow rolling". But from Kaiser Jeep's comment, jet planes can't do "slow flying" as a response to fuel prices.
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Re: Slow Steaming
by dashster » Mon 17 Nov 2014, 23:42:21
$this->bbcode_second_pass_quote('tom_s2', '
')Trucks and other motorized vehicles will only save fuel by slowing down if they were traveling at freeway speeds.
')Trucks and other motorized vehicles will only save fuel by slowing down if they were traveling at freeway speeds.
That's what I was referring to. Big rigs traveling on freeways.
$this->bbcode_second_pass_quote('', 'I')f you're only going 25 mph then the big problem is rolling resistance.
I wonder what the average speed of a freight train is? I guess those long trains with a big load don't go that fast normally, so they can't gain by slowing down.
$this->bbcode_second_pass_quote('', '
')It would help a lot at freeway speeds to have longer trucks, like 4 or 5 trailers. At freeway speeds, that makes a big difference because the tractor is pushing air out of the way for the entire train and subsequent trailers have lower wind resistance. Of course there's a safety issue.
I would advocate 4 or 5 trailers on those long flat stretches in the heartland if trains didn't exist. It would be nice if trains became the standard way to move freight cross-country and trucks were only used locally. But I believe that the truck lobby pumps more money into politicians pockets so they get the more preferential treatment from Congress at the moment.
$this->bbcode_second_pass_quote('', '
')IIRC, trucks have far less scope for improvement in fuel economy, because of basic physics. I think it would be hard to more than double the fuel economy of trucks by any combination of strategies (slowing down, regenerative braking, etc).
It wouldn't have to double. Just improve significantly. Although I believe there is a minimum speed limit on freeways. There would have to be laws passed to allow trucks to go 35 or 45 on one.
$this->bbcode_second_pass_quote('', '
')One possible response to peak oil, is a migration to dense "port cities" such as San Francisco, Shanghai, London, Hong Kong, etc, and a migration away from inland suburbs. Almost everyone in dense port cities lives within 10 miles of a railroad or port. Railroads in very dense cities (such as those of Japan) are often electrified using overhead wires anyway.
Another possible response is the exact opposite. A migration out of the mega-cities that produce no food or fuel or raw materials (although they could go big on recycling) and must have it all transported in, and also have low per-capita manufacturing, to mini-cities in location that can be much more self-sufficient. I was dismayed to learn that the sewage treatment plant in my area puts its solid waste in the local landfill. It is deemed to expensive to transport it to farms which could use it as fertilizer. You can't have any onshore windfarms in the mega-cities, and there are probably too many people to be supported via off-shore wind. Their big hope with regard to renewables would be roof-top solar, but that can't take advantage of the trick where they heat up water and use it to turn a turbine 24 hours. But maybe they would end up tearing down the big sports stadiums and amusement parks and other entertainment options in the mega-cities and replacing them with thermal solar installations. Or instead of "infill", where the cities councils authorize re-zoning so warehouses and other one or two story buildings are torn down to build high density housing and office space, they could tear down and build solar arrays. It is sad that the USA still sees population growth as part of the solution so that when buildings go down the replacement is always a bigger building. A farm would be out of the question.
You have that right. We will have to wait until gas gets north of $7.00 a gallon and stays there a while before they park the F-250s or start driving 55 again. But that will happen soon enough. The country is still served pretty well with its rail and canal/river transport system and they will gain market share as fuel prices rise. Locations close to active rail lines will rise in value and suburbs not served by rail will decline. Watch the government get in the way of the market driven transition and create trillions in unnecessary hardship.
