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Post by zbang on Jan 27, 2021 5:25:42 GMT
(splitting this from the Newbury Park Rectifier thread)
"The national grid supplies our electricity, of which 90% is used to power trains in the form of traction current." Total Energy Consumption 1,173 (gigawatt-hours) (or 3.2 GWh/day total or 2.89 GWh/day or 120MWh/hour for the trains over 24 hours) If anyone wanted to figure out how many trains, on average, were operating, one could get a reasonable hourly figure. Energy efficiency 155 Watt-hour / passenger km (1l petrol = ~1KWh, so 6.5km/l if my work is correct)
There must be newer data but this is what I tripped across.
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class411
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Post by class411 on Jan 27, 2021 10:09:35 GMT
These figures enable us to do some very interesting calculations.
Daily usage (traction) 2.89GW
Cost per unit* 15p
Cost per day 433,500
Journeys day 5,000,000
Annual passenger miles ~12e9
Daily passenger miles ~32e6
Thus:
Mean fuel cost per journey: 8.6 pence.
Cost per passenger mile: ~1.3p
Lovely efficient things are trains, at least from a fuel point of view.
* Est
I have to go out but I'll double check these figures later.
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Post by Chris L on Jan 27, 2021 10:35:03 GMT
These figures enable us to do some very interesting calculations. Daily usage (traction) 2.89GW Cost per unit* 15p Cost per day 433,500 Journeys day 5,000,000 Annual passenger miles ~12e9 Daily passenger miles ~32e6 Thus: Mean fuel cost per journey: 8.6 pence. Cost per passenger mile: ~1.3p Lovely efficient things are trains, at least from a fuel point of view. * Est I have to go out but I'll double check these figures later. The power station at Greenwich is being modernised and equipped with additional turbines to enable it to supply most of the power to the Tube. |
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Post by zbang on Jan 27, 2021 16:54:45 GMT
These figures enable us to do some very interesting calculations. ... Journeys day 5,000,000 Annual passenger miles ~12e9 Daily passenger miles ~32e6 I think your numbers may be off, I get about 1384 million underground journeys for 2018/19 = ~3800 k-journeys/day; ridership was maybe 20% lower in 2006. OTOH, I also expect greater efficiencies in the last 15 years. Either way, it's impressive (and a huge rathole  ). The power station at Greenwich is being modernised and equipped with additional turbines to enable it to supply most of the power to the Tube. Do you know if they're going to feed into/pull from the grid or use TfL-owned transmission lines? At those power levels, 22kv, or even 69kv aren't really high enough for distance transmission (e.g. 20-30 miles), although I suppose they could use a lower voltage on their own lines and eat the transmission loss against paying the grid to carry it.
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londoner
thinking on '73 stock
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Post by londoner on Jan 27, 2021 17:20:37 GMT
The correct answer is 1.21 Gigawatts.
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class411
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Post by class411 on Jan 27, 2021 17:34:49 GMT
These figures enable us to do some very interesting calculations. ... Journeys day 5,000,000 Annual passenger miles ~12e9 Daily passenger miles ~32e6 I think your numbers may be off, I get about 1384 million underground journeys for 2018/19
Yes, I can find different figures in different places, but I think the 5 million figure is probably for weekday journeys/day, so the 1384 = 3.791m/day figure you quoted would be the correct one to use for the calculation I did. |
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Post by ducatisti on Jan 28, 2021 10:57:01 GMT
so the irony is, from a fuel consumption point of view, it should be cheaper to travel on-peak
(I reckon one should see tenths, if not fifths of a penny off one's oystercard...)
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class411
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Post by class411 on Jan 28, 2021 11:10:37 GMT
so the irony is, from a fuel consumption point of view, it should be cheaper to travel on-peak (I reckon one should see tenths, if not fifths of a penny off one's oystercard...) Well, yes. With any* kind of conveyance, it will be more fuel efficient the more fully loaded it is. Even with a horse and cart! * Except in some cases of a dual fuel vehicle where increasing the load beyond a certain point will cause it to start using a less efficient fuel**. ** Between the start and end of typing the above sentence I realised that that includes hybrid electric/hydrocarbon based vehicles. |
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Post by ducatisti on Jan 28, 2021 11:24:09 GMT
with a horse and cart, your limit is more the output of the horse than anything else. To maximise your equine output, the best thing to do is fashion some kind of low-friction route for the wheels (such as metal girders) with a crushed stone path down the middle. But tat will never catch on...
Fuel consumption maximisation is in opposition to service frequency (acceleration costs energy),so it goes to part of the complex balancing act. the optimal service from a power consumption point of view would be packed trains, with a low frequency to allow minimal stop/start.
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class411
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Post by class411 on Jan 28, 2021 12:12:32 GMT
so the irony is, from a fuel consumption point of view, it should be cheaper to travel on-peak (I reckon one should see tenths, if not fifths of a penny off one's oystercard...) I'd also point out that from the point of view of the fuel efficiency of LU as a whole, switching trains achieves nothing. They still have to accelerate and decelerate your x kilos y times. with a horse and cart, your limit is more the output of the horse than anything else. Just the same, mutatis mutandis, with a train.  |
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Post by zbang on Jan 28, 2021 17:10:50 GMT
I'd also point out that from the point of view of the fuel efficiency of LU as a whole, switching trains achieves nothing. They still have to accelerate and decelerate your x kilos y times. Certainly, transportation is transportation, as it were.
One thing that plays in is mass of the train vs total mass of the passengers- If the entire train is ~167t and tops out at ~700 passengers, that's a train mass of 238kg/passenger at best (figures from TfL).
Assuming the average passenger is 90kg (just a WAG), the total mass of passengers can not exceed maybe 38% of the total train weight, so a lot of the energy goes into moving the train itself.
(For comparison, a Ford Focus might be 1300kg, so two passengers is 15% of the total mass; those are fuzzy figures.)
Feel free to poke holes in my reasoning.
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class411
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Post by class411 on Jan 28, 2021 18:26:26 GMT
I'd also point out that from the point of view of the fuel efficiency of LU as a whole, switching trains achieves nothing. They still have to accelerate and decelerate your x kilos y times. Assuming the average passenger is 90kg (just a WAG), the total mass of passengers can not exceed maybe 38% of the total train weight, so a lot of the energy goes into moving the train itself. Yes, I think that was what ducatisti was getting at. If you join a peak period train, then the journey will be more efficient calculated for that train (because, as you say, there is a lot of train to get moving but your 'share' will be smaller). However there will be a complementary reduction in efficiency for the off-peak train you are not using. |
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slugabed
Zu lang am schnuller.
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Post by slugabed on Jan 28, 2021 19:27:58 GMT
This reminds me of a post made by a well-connected member of either this board or Another Place who told of a conversation he'd had with (I think) Treasury economists who put forward the idea that the first passenger on any bus should be charged,say,£20,with subsequent passengers being charged only the marginal extra cost that carrying them incurs....until it was pointed out to them that the buses would then run around empty all day...
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Post by stapler on Jan 29, 2021 8:23:54 GMT
1.Should an obese person be charged more to travel than a beanpole?
2. Cost per unit 15p? Really that's what I pay at home. Surely LU get a discount for quantity?
3. What about feedback from regenerative braking?
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class411
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Post by class411 on Jan 29, 2021 8:53:13 GMT
1.Should an obese person be charged more to travel than a beanpole? Theoretically, yes, but as the cost of electricity is a marginal part of the ticket price it wouldn't be worth the admin. And it would almost certainly be considered unacceptable. That's why there was an * Est. It's not easy finding out what the tariff is for people buying by the gigabyte. Does anyone have a clue? That's already accounted for in the GW used figure. |
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Chris M
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Post by Chris M on Jan 29, 2021 12:41:22 GMT
That's why there was an * Est. It's not easy finding out what the tariff is for people buying by the gigabyte. Buying electricity by the giga byte is an unusual way of doing things! |
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Post by humbug on Jan 29, 2021 13:11:40 GMT
The correct answer is 1.21 Gigawatts. Which is the equivalent of sending 969 and a half DeLoreans back in time every year! |
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class411
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Post by class411 on Jan 29, 2021 13:27:34 GMT
That's why there was an * Est. It's not easy finding out what the tariff is for people buying by the gigabyte. Buying electricity by the giga byte is an unusual way of doing things! ROFLMAO! I've bought and used many, many, gigabytes over the years, but I've never bought or used a gigawatt in one go. |
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Post by zbang on Jan 29, 2021 16:28:28 GMT
The correct answer is 1.21 Gigawatts. I missed that, sigh, but it's gigawatt-HOURS to get consumption.
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