trivial question:coal train to transmission line efficiencycomparo
trivial question:coal train to transmission line efficiencycomparo
(OP)
This is not a serious question, but something to debate over beer and pizza.
Having recently observed huge unit coal trains in Wyoming State, how does the efficiency of these railroad trains compare to mine-mouth plants using high voltage transmission lines? I am curious what the power lost represents as a percentage of power transported.
Having recently observed huge unit coal trains in Wyoming State, how does the efficiency of these railroad trains compare to mine-mouth plants using high voltage transmission lines? I am curious what the power lost represents as a percentage of power transported.






RE: trivial question:coal train to transmission line efficiencycomparo
Keith Cress
kcress - http://www.flaminsystems.com
RE: trivial question:coal train to transmission line efficiencycomparo
Rafiq Bulsara
http://www.srengineersct.com
RE: trivial question:coal train to transmission line efficiencycomparo
However, a coal train of say 100 cars, at 130 tons per car, not including the car weight, should consume 52 gallons per mile. Also if we consiter that the railroads use more expencive power units for coal trains, that use less fuel (AC traction instead of DC traction) I would presume the 52 gallons per mile is to high.
Also consiter Wyoming where most of the coal comes from dosen't have that many power lines, the savings would have to be reduced by the cost of building transmission lines. Which currently exceeds a $1M a mile.
RE: trivial question:coal train to transmission line efficiencycomparo
Like itsmoked stated, I was initially inclined to assume electricity weighs much less than coal and therefor has the obvious advantage.
However, someone else completely uninformed with either trains or powerlines told me, "power line losses are huge" which prompted me to think a little further.
I'm not familiar with operating transmission lines however, it is not unusual for a distribution line to experience 10% voltage drop from source to final destination, which represents 10% energy loss in a say a 10 mile length. I would expect similar losses over greater distances with higher voltage transmission lines. It would seem unthinkable for a 100 car train to consume 10 carloads of 'equivalent energy' for 5-700 mile journey, Cranky108's approximation would be about 36,400 gallons of diesel fuel.
100 x 130 tons of coal is approx. 260,000,000,000 BTU's of energy delievered in one coal train.
36,400 gallons of diesel is approx. 4,914,000,000 BTU's of energy consumed in delivering one coal train.
That is about 1.9% (if I didn't slip a decimal point). That would seem achievable by a short transmission line but probably lower than typical line losses for a 700mile distance. I would now guess that based on transportation losses, the railroad wins.
(There are other considerations as Rbulsara stated, including the labor to operate either systems)
RE: trivial question:coal train to transmission line efficiencycomparo
Keith Cress
kcress - http://www.flaminsystems.com
RE: trivial question:coal train to transmission line efficiencycomparo
Let's look at the logic.
There's lots of coal in Wyoming and to a somewhat lesser extent, Montanta, Colorado, Utah and New Mexico. Labor is relatively cheap there and the workforce has a good work ethic-farm boys. Plants should be less expensive to build out there where the real estate isn't in high demand.
So why aren't the power plants all located there and instead of two rails stretching to far flung points, aren't there 3 conductors stretched in all directions to the same markets? Even though there are some power plants in Utah and New Mexico that do generate power specifically for the California market.
Must be that it is cheaper to ship coal to where the electricty demand is and generate it when it is needed than to generate the electricity where the coal is and ship the electrons way far away.
And repeat the logic for where the Natural Gas is located on the Gulf coast.
And repeat the logic for locating the nuclear plants all out in the desolate west where it would be in nobody's back yard and...
It tells me that there is a practical limit as to how far you can transmit power. I am a ME, not an EE, so that is the only way I can look at it.
rmw
RE: trivial question:coal train to transmission line efficiencycomparo
I think stability limits would nix your idea.
RE: trivial question:coal train to transmission line efficiencycomparo
So the question is still valid.
RE: trivial question:coal train to transmission line efficiencycomparo
Approximately 30 years ago I was told that invester owned utilities favored mine mouth plants whereas public utilities often desired generators local to their service area. That might have been a trend before licensing requirements became overwhelming.
RE: trivial question:coal train to transmission line efficiencycomparo
And why would I want to pay taxes to a community, or state that my customers don't live in? (Even more of a question if you are a tax exempt utility).
It's sort of like taxation without represation.
RE: trivial question:coal train to transmission line efficiencycomparo
old field guy
RE: trivial question:coal train to transmission line efficiencycomparo
Bottom line depends on the HV AC voltage itself, but seems to come out that you loose 20% of your power if you "ship it" 750 miles. Ship it 1200 miles, and you've lost just under 50% of the power you have created.
But - remember, that distance would be thinking like a piping engineer (fluid in must equal fluid out). With the grid, it's more like each regional power plant supplies it's own (nearby 50 - 200 mile) local area, and outside plants are connected to the grid and sharing voltage, but the current (energy) is used locally. So in each grid region (large area) losses are NOT equal to that 750 or 1200 mile percent.
Each plant assumes it's local distribution losses are around 3 - 6%. (That included the big plant transformers, the local small transformers, and the small telephone pole transformers, the total copper line losses, and the AC reactive current "resistance" that comes into play at high voltage.
Very high volt DC connections are normally used to cross-connect grid regions, Complicated pro's and con's there, but very high volt DC can be economic over long distances as well under some circumstances. (For example, HV DC can get by with smaller vertical and horizontal clearances for wires than HV AC, so the right-of-way purchases can be much lower. Over 800 miles, that difference in land cost alone can add up to a lot of money.)
Anyway, if you build wind farms in deep west Texas, or solar panels in AZ or NM, or coal plants in upstate ND or SD or Montana almost all of your power will get lost as heat loads and resistance before it crosses the Mississippi River. Much less get all the way to NYC or upstate Michigan. Triple the size of your power plant in AZ, triple the size and number of your copper "pipelines" across country, and you "might" end up with a single power plant's worth of unreliable (lightening storms en route!) electricity at the end of your very, very expensive HV AC extension cord.
(By the way, remember the difference between just getting "voltage" across country, or restarting a grid from long distance power plants (when you really, really, really don't care about about efficiency at all!), and getting "POWER" delivered cross country.)
I can run a 1/2" garden hose for 50 feet, and get reasonable flow at 20 psi. Run a 3/4" garden hose for 120 or 150 feet, and I start seeing significant flow loss and only pressure at 10 - 12 psi. Try to run that 3/4" hose for 500 feet, and I see almost no flow and no pressure when the valve is open. But pressure (at zero flow) will still be 20 psi. Pressure (voltage) at long distances is not energy transmitted long distances.
RE: trivial question:coal train to transmission line efficiencycomparo
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So, energy generated in the middle of the US and shipped to either coast (~2000km) would have a guestimated loss of around 9%
RE: trivial question:coal train to transmission line efficiencycomparo
We require our plants to produce vars during voltage excursions, if we ever have any.
How many lines would be required to avert regional storms from killing all power to the East and West cosasts? Or cascading events from a single line outage (does the new york blackout ring a bell?)?
Have you ever tried to buy right of way? The land owners don't think like it's thinner so it should cost less. They think more like you are intruding on my land, so you must pay what I want.
So a 30 FT or 50 FT right of way costs about the same.
RE: trivial question:coal train to transmission line efficiencycomparo
RE: trivial question:coal train to transmission line efficiencycomparo
That much Gas was enough to run a 6 or 700 MW power plant.
It was spposed to be cheaper to gasify the coal in North Dakota put it in a pipe and generate power in detroit than it was to generate power with int in North Dakota and put it on the wire an deliver it to Detroit.
The coal was not worth hauling anywhere. It was 37% water and about 12,000 BTus /lb.
It might be more efficient to run a fuel cell in Detroit than put the gas in a turbine.
I don't have the paper any longer.
I expect to see more gasificatio plants in The Dakotas and eastern Montana. The reason would be the gas which would be the CO2 produced is in demand to recover oil from the Bakken oil field. There is supposedly enough coal in the area to power the US for 400 years or so. The Bakken oil field has 3 or 4 billion barrels of oil.
In addition to all that the wind fields that run from Alberta down the Dakotas/Montana boarder into Nebraska have the potential to power ALL the US. We could wind up with lots of power in a small area. How do you get it out??
http://www.dakotagas.com/
http:/
RE: trivial question:coal train to transmission line efficiencycomparo
The bottom has dropped out of the pricing on REAL out-of-the-ground natural gas here in the USA. Huge reserves have been discovered to be economically feasible in north Texas, north Louisiana, the northeast US (Pennsylvania - upstate New York) and if I remember correctly, the northwestern plains states. I've heard numbers in the 60-250 year range for reserves.
It put a severe crimp on the people who were spending a lot of money to build plants to receive LNG from overseas.
I would also figure they can develop the gas deposits and lay pipelines cheaper than coal can be gasified. I just haven't seen the numbers on that equation.
old field guy
RE: trivial question:coal train to transmission line efficiencycomparo
If it had droped out, they would have switched our coal plants to run on gas (dual burners are nice).
Also I haven't seen real low numbers in my gas bill.
The thing I don't see is if the power plants were located close to the customers, then district heating might be more usable. Although it isen't.
Some power plants are located close to the customers so they can supply electricty, steam, cooling water, and sometimes recieve fuel.
And since many power companies started as city power companies, or as ice companies, they would be located close to there customers.
Another thought is that many power plants, while not located close to there fuel source, they are located close to water.
Now that I think of it, most of the coal fields are not close to water.
Would transporting water cost less than transporting coal?
RE: trivial question:coal train to transmission line efficiencycomparo
Wyoming coal fields are at higher elevations than Midwest power plants. The coal coasts downhill and the empty train cars come back up. Electricty can't coast downhill.
Our power plant developer clients tell us that it is a lot easier and cheaper to bring the fuel to the plant than the power to the load. For example, they could place the power plant near the country border where the gas entered the country and build trasnmission lines to the major loads or build closer to the loads and run pipelines. The latter design alwasy won.
RE: trivial question:coal train to transmission line efficiencycomparo
http://
October 2005: $10+ per thousand cubic feet
September 2009: $3.43
Maybe NOT the bottom, but certainly a significant change.
Swapping over fueling for existing plants is a pretty big deal, I'd guess. I don't know about up north, but I know my employer is spending a lot of bucks to move gas volume to Florida where natural gas is the preferred fuel for new power generation. I've been enjoying the idea of several 22,000 horsepower electric drive compressors on that project.
Much of the new shale sources lie to the north of my chunk of the pipeline, but we've got enough of the old stuff to keep us busy for a long time, at least until they bring the rainbows and unicorn fa*ts on line.
old field guy
RE: trivial question:coal train to transmission line efficiencycomparo
Another factor in gas prices is the mild Winters, and reduced electricty demand. With the lower demand, the least cost efficent unit are shut down first (simple cycle gas turbans).
There was an article in a recent Forbes magazine about the LNG inports from ExxonMoble. It seems the gas fields in Qutar have sigficent liquids, that it would make more money giving away the LNG, and selling the liquids. More money in fact than from the oil fields.
(sounded odd to me, but I don't know the prices for the liquids). What is the price of Butane, Propane anyway?
The water issue is probally more of an issue than what we think. In fact a local plant here is using recycled water, to reduce water costs.
RE: trivial question:coal train to transmission line efficiencycomparo
RE: trivial question:coal train to transmission line efficiencycomparo
RE: trivial question:coal train to transmission line efficiencycomparo
RE: trivial question:coal train to transmission line efficiencycomparo
One local LNG plant just built a unit specifically to deal with the heavy components in LNG. They figure they can make money selling the LNG, make MORE money selling the heavy fractions like ethane and propane, AND my pipeline doesn't have to deal with the liquids from this one client.
electic--
Back in the late Fifties or early sixties I remember reading an article about a little transistor radio that was to be distributed as assistance in Third-World aid programs. It was powered by a thermopile. As shipped, a candle heated the thermopile. After the candle was gone, any other small flame source could be substituted. the article specifically noted this could be dried cow dung. I'm thinking that I already get enough cr*p off the radio...
old field guy
RE: trivial question:coal train to transmission line efficiencycomparo
Why not just use solar.
Or an article recent article in popular science using crystals in your shoes to power an ipod.
A few years ago I looked into gas air conditioners, at the time the cost was about the same as an electric model. The problem was no one worked on them.
So now they have windup radios. But there isen't much to lisen to (sort of like watching TV).
RE: trivial question:coal train to transmission line efficiencycomparo
But you are in the power plant business, aren't you, based on your comments. Don't you want everyone using elec A/C? For job security, etc.?
rmw
RE: trivial question:coal train to transmission line efficiencycomparo