Could the non-drivers not take a train?

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kwackers
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Re: Could the non-drivers not take a train?

Postby kwackers » 4 Dec 2020, 2:13pm

Phileas wrote:I’m sorry but this isn’t correct as has been pointed out several times upthread.
Power can be measured in Watts which is Joules per second, i.e. energy divided by time.
Therefore a quantity of energy is given by power multiplied by time e.g. Watt x hours or Wh, GWh etc.
TW is not a quantity of energy, is a rate of energy usage.

Fair point, I've amended my post since the basics are still correct and I'd rather it was used as I intended than get into a discussion about 'units'.

Carlton green
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Re: Could the non-drivers not take a train?

Postby Carlton green » 4 Dec 2020, 4:24pm

MikeF wrote:
Jdsk wrote:But the National Grid is in an excellent position to talk about current (!) and future demand and capacity of supply as well as of distribution.

Here's a recent accessible piece on EVs:
"6 myths about electric vehicles busted"
https://www.nationalgrid.com/stories/journey-to-net-zero/5-myths-about-electric-vehicles-busted

And here's the long version: "Future Energy Scenarios"
https://www.nationalgrideso.com/future-energy/future-energy-scenarios/fes-2020-documents

Jonathan
Yes indeed, and I stated that about National Grid in my post.
As stated on their website this is what National Grid does "We move electricity through the system" .
However what the National Grid doesn't do is generate any power and that is the fundamental point. To make a similar analogy with water although it's not quite the same as water isn't generated. In times of drought it's not the pipework in the roads and elsewhere that causes problems for users, but the lack of water to put through them.

You need to look at the link I gave previously https://gridwatch.co.uk or similar ones to understand what the issues are.

It's simply is how do we generate enough electrical energy. That's the question. It won't magically happen at the flick of a switch or laying a cable. It's also worth noting that nuclear power is about 30% efficient so a lot of thermal energy is used in heating the sea around us :wink:


I’m wondering what the point about nuclear energy efficiency really is?

Fossil fuel power stations are similarly energy inefficient. IC Engines are thermally inefficient and so are Gas Turbines. Whatever energy converter you use has losses and Nuclear isn’t particularly worse than any other. It would be a valid point to say that both fossil fuel and nuclear generation contribute to global warming through their steam cycle waste heat, but as far as I know the significant pollution is via burnt fossil fuel emissions - the gas is probably hot as well - and the waste heat effects (heat ‘given’ to rivers and the sea) are of no environmental concern to anyone.

I’d quite like to see a few data sources to back up the claimed inefficiency. Modern Nuclear is a solution rather than a problem.

Bmblbzzz
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Re: Could the non-drivers not take a train?

Postby Bmblbzzz » 4 Dec 2020, 8:17pm

Carlton green wrote:Freedom of movement is, I think, a reasonable human right.

It's more than just 'reasonable'.
https://www.un.org/en/universal-declara ... an-rights/
Article 13.

MikeF
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Re: Could the non-drivers not take a train?

Postby MikeF » 4 Dec 2020, 9:56pm

Jdsk wrote:
MikeF wrote:That is a similar figure to what I would estimate for 10million cars, but the number of UK cars is 3 times that. Power is MW but energy is MW/h so the energy needed in your example is 55GW/h or if you count the total number of cars it's 150GW/h. Assuming an average power generation of 30GW per day the energy is 720GW/h per day. The energy production needed if all cars are electric is significant. At the moment extra demand is met by CCGT which uses natural gas so electric cars are not as green as they might be.
Hence my original question how is this energy being produced?
Obviously how electricity is produced doesn't seem to concern most people.

Energy can't be measured in MW/h or GW/h, the dimensions are wrong. It can be measured in GWh etc.

For what date would you like the estimate of sources?

And what fraction of vehicles do you expect to be powered by electricity by that date?

Jonathan
You're right. I don't know why on earth I typed that. I've edited my post to correct it the error.
I'm not sure the date has much relevance does it?
Last edited by MikeF on 4 Dec 2020, 10:01pm, edited 1 time in total.
"It takes a genius to spot the obvious" - my old physics master

Jdsk
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Re: Could the non-drivers not take a train?

Postby Jdsk » 4 Dec 2020, 9:58pm

I was going to look up the projected sources of electricity on that date...

Jonathan

Carlton green
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Re: Could the non-drivers not take a train?

Postby Carlton green » 4 Dec 2020, 10:07pm

Bmblbzzz wrote:
Carlton green wrote:Freedom of movement is, I think, a reasonable human right.

It's more than just 'reasonable'.
https://www.un.org/en/universal-declara ... an-rights/
Article 13.


I wonder if China signed up to this ...?

MikeF
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Re: Could the non-drivers not take a train?

Postby MikeF » 4 Dec 2020, 10:22pm

Carlton green wrote:
I’d quite like to see a few data sources to back up the claimed inefficiency.
https://www.nuclear-power.net/nuclear-engineering/thermodynamics/laws-of-thermodynamics/thermal-efficiency/thermal-efficiency-of-nuclear-power-plants/
"It takes a genius to spot the obvious" - my old physics master

Bmblbzzz
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Re: Could the non-drivers not take a train?

Postby Bmblbzzz » 4 Dec 2020, 11:44pm

Carlton green wrote:
Bmblbzzz wrote:
Carlton green wrote:Freedom of movement is, I think, a reasonable human right.

It's more than just 'reasonable'.
https://www.un.org/en/universal-declara ... an-rights/
Article 13.


I wonder if China signed up to this ...?

Yes, but they haven't ratified the International Covenant on Civil and Political Rights. Interestingly, those countries which abstained from voting for the UDHR have ratified the ICCPR.

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[XAP]Bob
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Re: Could the non-drivers not take a train?

Postby [XAP]Bob » 6 Dec 2020, 4:14pm

Carlton green wrote:It would be a valid point to say that both fossil fuel and nuclear generation contribute to global warming through their steam cycle waste heat, but as far as I know the significant pollution is via burnt fossil fuel emissions - the gas is probably hot as well - and the waste heat effects (heat ‘given’ to rivers and the sea) are of no environmental concern to anyone.


The waste heat output has next to no effect on global temperatures. The pollutants do - because they trap more of the incident solar radiation.

The earth has a diameter of about 6400km, which means it has an area (as seen from the sun) of pi r^2.
That’s 4e13 m^2
Solar incident radiation is ~1.4kW/m^2 at the top of the atmosphere, and about 400W is absorbed/reflected before it hits the ground

That’s 40 Peta watts.

It’s changing the balance of that 40PW radiation balance that has an effect on global temperatures. Because almost energy that passes through a power station ends up as heat in relatively short order anyway. We produce/use somewhere less than 20TW on average, so 5% of 1% of the solar radiation.

A tiny change in that balance will more than dwarf anything else we could possibly do.


However thermal pollution from power plants has long been a significant local issue. Water is less gas soluble as its temperature increases, so local river populations end up starved of oxygen...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

Carlton green
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Re: Could the non-drivers not take a train?

Postby Carlton green » 6 Dec 2020, 5:18pm

MikeF wrote:
Carlton green wrote:
I’d quite like to see a few data sources to back up the claimed inefficiency.
https://www.nuclear-power.net/nuclear-engineering/thermodynamics/laws-of-thermodynamics/thermal-efficiency/thermal-efficiency-of-nuclear-power-plants/


H’mm it’s many years since I attended Thermodynamics lectures but if I’m not mistaken we’re talking about two different types of efficiency here. Certainly steam cycle power stations do not release thermal energy at the level implied, it’s no longer within my competency and I don’t won’t to spend a week relearning things that once I knew well enough to pass exams in.

[XAP]Bob’s post is perfect, well I couldn’t have put it better myself. Good job done.

Jdsk
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Re: Could the non-drivers not take a train?

Postby Jdsk » 6 Dec 2020, 5:22pm

If there is any confusion AIUI it's only between thermodynamic efficiency and some other meaning which hasn't been defined.

Jonathan

Pete Owens
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Re: Could the non-drivers not take a train?

Postby Pete Owens » 8 Dec 2020, 2:03am

To answer the question that is the title of this thread (not that I think the OP is actually interested). Having been following the news over the past year I can think of a very good reason why people might wish to avoid using trains at the present.

More seriously, as a test for self driving cars using a fleet of only six vehicles the choice of route is entirely sensible. Anyone using one for their outward journey, needs an alternative means of making the return trip when it is likely that all the cars will be busy at the time.

Have any Oxford cyclists spotted one of these in action?

Carlton green
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Re: Could the non-drivers not take a train?

Postby Carlton green » 8 Dec 2020, 6:14pm

Jdsk wrote:If there is any confusion AIUI it's only between thermodynamic efficiency and some other meaning which hasn't been defined.

Jonathan


MikeF’s post of 3rd December might help you out there.
Edit. page 6 “It's also worth noting that nuclear power is about 30% efficient so a lot of thermal energy is used in heating the sea around us“.
Last edited by Carlton green on 8 Dec 2020, 6:17pm, edited 1 time in total.

Jdsk
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Re: Could the non-drivers not take a train?

Postby Jdsk » 8 Dec 2020, 6:16pm

Carlton green wrote:
Jdsk wrote:If there is any confusion AIUI it's only between thermodynamic efficiency and some other meaning which hasn't been defined.

MikeF’s post of 3rd December might help you out there.

I wasn't suggesting that I was confused...

;- )

Jonathan