[Petrochemicals]

An interesting source indeed.

Onshore and offshore wind provided more than half of the UK’s renewable power in 2020 by generating 24.2% of the UK’s electricity needs (13% from offshore wind and 11.2% from onshore wind).
Low carbon sources (renewables and nuclear) generated 59%.

"Statista" says:

Electricity use in the United Kingdom has seen a significant decrease since the turn of the century. Demand peaked in 2005 at 357.2 TWh but had fallen to just 287.58 TWh by 2020.

That's just electricity, dear boy. Less than 30% of the UK's energy consumption is delivered as electricity. All the rest is fossil- fuelled.

less than 20 more like 15%

[alancalverd (OP)]

www.edfenergy.com has an interesting table that claims EoN supplies 2.6% of UK non-carbon electricity. But EoN  claim to supply 15% of to total demand, so clearly they can't be selling 100% renewable electricity at all.

[wolfekeeper]

Why are you just repeating bullshit over and over again. It's not primary energy that's important, it's exergy:

https://en.wikipedia.org/wiki/Exergy

Which is the useful energy.

The way you're telling it, the fact that about 2/3 the primary energy mined for the UK is wasted is somehow a positive, irreplaceable thing, that must be replicated electrically?

Do you have any recent head injuries to explain this curious preoccupation?

Just to delve a bit deeper into your figures. 24% of electricity came from wind. All other renewables can only provide about 10 - 12%, so around 30% of the non-fossil power came from nuclear stations. Only one new nuke is being built and the old ones are beginning to creak a bit.

LOL, no, nuclear was 17.3% of net generation in the UK in 2020:

https://en.wikipedia.org/wiki/Electricity_sector_in_the_United_Kingdom

[alancalverd (OP)]

No, about half of the "wasted" energy you speak of, is actually used as heat. Even that dreadful internal combustion engine in a car produces around 5 - 8 kW of cabin heat, which is why electric cars don't go as far in the winter. Steel and concrete production is essential if we are to build unnecessary railways at £1,000,000,000 a mile (yes, folks, £568,000 for every step of the way between London and Birmingham) and they require lots of heat.

Must go - some awful process is cooking my lunch. 

[alancalverd (OP)]

LOL, no, nuclear was 17.3% of net generation in the UK in 2020:

17.3 is actually more than 30% of 55. You should read more carefully before laughing.

[Bored chemist]

Even that dreadful internal combustion engine in a car produces around 5 - 8 kW of cabin heat,

And about 70 KW of waste heat that is blown out of the radiator.
Which is what makes them dreadful.

[alancalverd (OP)]

No argument there. It's much the same end-to-end efficiency as burning fossil gas to make electricity, which is what EoN seems to be actually doing under the guise of "renewable".

[wolfekeeper]

No, about half of the "wasted" energy you speak of, is actually used as heat. Even that dreadful internal combustion engine in a car produces around 5 - 8 kW of cabin heat, which is why electric cars don't go as far in the winter.

Pretty sure no normal car gives you 8 kW of cabin heat; and that's a shedload of wasted heat, particularly in summer.

And no, that's not why.

No argument there. It's much the same end-to-end efficiency as burning fossil gas to make electricity, which is what EoN seems to be actually doing under the guise of "renewable".

They're not, that would be fraud.

[alancalverd (OP)]

Quote from: alancalverd on Yesterday at 15:26:01
No argument there. It's much the same end-to-end efficiency as burning fossil gas to make electricity, which is what EoN seems to be actually doing under the guise of "renewable".
They're not, that would be fraud.

My point precisely. It's in all of their TV adverts, and plainly untrue or at least misleading.

[alancalverd (OP)]

Just picked this up from an EV chatroom. A little confused because they (Americans) actually mean BTU/hr, but the numbers are correct and just what I recall from my studies of light aircraft. .

A electric heater is rate at 3412 btus of heat per 1000 watts. If your cab
R-factor is low which could be rated at one R-factor for one single pane of
glass and one layer of 20 gage metal.

Lets say your cabin size has the area of a 5 foot cube, then 5 x 5 x 5 = 125
square foot (SF) of external wall space and the outside temperature is -40
degrees and you want to maintain 70 degree cab temperature which is a 110
degrees temperature difference (TD)

Therefore: Btus = SF x ((1 R factor)/1) x TD
125 x 1 u factor x 110
13,750 Btus

Watts = 13,740 Btus / 3412 btu per 1000 watts
Watts = 4029 watts or 4.029 kw

That's fine for maintaining cabin temperature but you need a bit more for a quick defrost. In an EV you'd do it with another temporary kW or so of wires in the windscreen, but  where the heat is freely available from an ICE, you just increase the size of the heat exchanger to provide 5 kW or more to the circulating air.  The 5 foot cube is pretty small and the calculation only applies to still air, so 8 kW is entirely believable for a medium to large car or SUV.

[Bored chemist]

just what I recall from my studies of light aircraft... .

...Where an outside temperature of minus 40 is plausible.

So what you are staying is that a typical car dumps twice as much heat into the cabin as would be needed if it was forty degrees below outside.

Why would you pick that figure?
And it doesn't really make a difference.
The engine is rated for something of the order of 100KW.
On a good day it's 25% efficient so 75KW is turned into heat.

You can use some to heat the passenger compartment- maybe 4KW on a cold day.
So about 71 KW is wasted.

That's still awful.

[alancalverd (OP)]

I was once challenged in a Civil Service personnel review to respond to the allegation that I did not suffer fools gladly. I said "I didn't expect to meet any" and the subject was never raised again.

Just because your gas cooker is rated at 15 kW doesn't mean you have to use it all. When you design a car for mass production you tend to look at the cost of options. An 8 kW heat exchanger isn't much more expensive to make and install than a 5 kW one, will do the job better and quicker on a frosty morning, and will actually work in places like North America and Central Europe in winter, so why design one specially for gentlemen motorists with heated garages in Henley?   

I don't think anyone here doubts the validity of the Carnot cycle. But some of us appreciate that it applies equally to power stations, which is why we don't like being lied to by or electricity supplier. And of course with an ambient of -40 degrees the engine would be rather more efficient anyway.

[Bored chemist]

I was once challenged in a Civil Service personnel review to respond to the allegation that I did not suffer fools gladly. I said "I didn't expect to meet any" and the subject was never raised again.

Just because your gas cooker is rated at 15 kW doesn't mean you have to use it all. When you design a car for mass production you tend to look at the cost of options. An 8 kW heat exchanger isn't much more expensive to make and install than a 5 kW one, will do the job better and quicker on a frosty morning, and will actually work in places like North America and Central Europe in winter, so why design one specially for gentlemen motorists with heated garages in Henley?   

I don't think anyone here doubts the validity of the Carnot cycle. But some of us appreciate that it applies equally to power stations, which is why we don't like being lied to by or electricity supplier. And of course with an ambient of -40 degrees the engine would be rather more efficient anyway.

And would you like to discuss the piss poor efficiency of the engine?
At best, you are saying that not all of the 70% of wasted energy is wasted; maybe a few KW are used for something.

If you plan to talk about reuse of low grade heat  then that's fine.
Consider a decent CHP station.

[wolfekeeper]

Just because your gas cooker is rated at 15 kW doesn't mean you have to use it all.

Ironically, this only furthers my point, you simply can't. Gas cookers are only about 40% efficient, whereas electric cookers are more like 70%. Gas cookers, are great, if you want a space heater. That produces poisonous fumes. That have to be ventilated. So much win there. That hot air you just made, mostly goes straight out again. And it's mostly hot air. With poisonous carbon monoxide, nitrous oxide and sub PM2.5 particles. Mostly not hot pans.

An 8 kW heat exchanger isn't much more expensive to make and install than a 5 kW one, will do the job better and quicker on a frosty morning, and will actually work in places like North America and Central Europe in winter, so why design one specially for gentlemen motorists with heated garages in Henley?

Electric cars can have 8 kW defrosters too. They're not going to be on for long. Actually, electric cars tend not to need it because you can tell them to defrost themselves at a set time when you plan to drive. So the car is lovely and warm when you get in.

I don't think anyone here doubts the validity of the Carnot cycle. But some of us appreciate that it applies equally to power stations, which is why we don't like being lied to by or electricity supplier. And of course with an ambient of -40 degrees the engine would be rather more efficient anyway.

Still no. An electric car is still more efficient even at -40℉. And the electric motors themselves are more efficient at low temperatures anyway.

[alancalverd (OP)]

And would you like to discuss the piss poor efficiency of the engine?

As I said, Sadi Carnot put that one to bed 200 years ago. But those unacquainted with thermodynamics might just refer to Wikipedia :

Modern passenger car diesel engines may have an effective efficiency of up to 43%, whilst engines in large diesel trucks, and buses can achieve peak efficiencies around 45%.

The energy efficiency of a conventional thermal power station is defined as saleable energy produced as a percent of the heating value of the fuel consumed. A simple cycle gas turbine achieves energy conversion efficiencies from 20 to 35%.

A bit sad, really, because I'd love to have an electric car, but for the foreseeable future it seems that it's going to burn more fossil fuel than the old diesel I already have, and I care about the planet. But that's the subject of another thread.

[Petrochemicals]

And would you like to discuss the piss poor efficiency of the engine?

As I said, Sadi Carnot put that one to bed 200 years ago. But those unacquainted with thermodynamics might just refer to Wikipedia :

Given that adding cars to the electric requirement, I would like to discuss the piss poor efficiency of the electric car. Petrol 30 percent efficient.

[alancalverd (OP)]

An electric car is still more efficient even at -40℉.

Sadly not. You use some of the battery energy to raise the battery temperature and reduce its internal impedance so it can deliver full rated power to the motors. It's a neat trick that we use to start aircraft on a cold day with a tiny battery (because battery weight is much more important in a plane) and is adopted in all current production electric cars. Difference is, of course, that the plane quickly recharges the battery and doesn't rely on it staying warm once the engine is turning.

[alancalverd (OP)]

It's way off the subject, but out of interest I wondered how much power you need from a car heater to prevent ice building on a windscreen in a snow shower. Assuming you are driving at a sensible speed of about 10 m/s (22 mph) and the snow is falling at a "light shower" rate of 10 gram/second per square meter of ground, you actually need about 30 kW to keep a square meter of windscreen above freezing point. Once the inside drops below 10°C it will mist up, and of course a layer of ice will form inside if it drops below zero. The trick is that "defrost " mode doesn't deliver the warm air evenly over the screen but principally in the driver's immediate line of sight.

You can get away with less in a car because you can slow down and use windscreen wipers, but the deeply curved windshield of a small plane won't accommodate a wiper and you have to travel at around 50 m/s to stay airborne and make progress over the ground, which is why icing is such a problem in light aviation. 

[alancalverd (OP)]

Gas cookers are only about 40% efficient, whereas electric cookers are more like 70%.

Depends on how competently you use the heat. A gas cooker converts about 95% of the gas energy to heat. A resistive electrical element converts 100% of the electrical energy to heat, and an induction cooker transfers over 85% of the input power to a properly-designed pan.     

What I have never understood is the rarity of electric kettles in American kitchens. All my US and Canadian friends and business associates boil water by putting a tin kettle on a radiant electric or gas ring. Can anyone explain? Could we save the planet by making 110 volt kettles compulsory? 

[wolfekeeper]

And would you like to discuss the piss poor efficiency of the engine?

As I said, Sadi Carnot put that one to bed 200 years ago. But those unacquainted with thermodynamics might just refer to Wikipedia :

Modern passenger car diesel engines may have an effective efficiency of up to 43%, whilst engines in large diesel trucks, and buses can achieve peak efficiencies around 45%.

The energy efficiency of a conventional thermal power station is defined as saleable energy produced as a percent of the heating value of the fuel consumed. A simple cycle gas turbine achieves energy conversion efficiencies from 20 to 35%.

A bit sad, really, because I'd love to have an electric car, but for the foreseeable future it seems that it's going to burn more fossil fuel than the old diesel I already have, and I care about the planet. But that's the subject of another thread.

The UK doesn't use single turbine cycles for gas generators, it uses CCGT, the output from the gas turbines goes through a steam engine, running on the waste heat. They can achieve about 55% efficiency which makes them cheap to run while being less polluting as well. That together with nuclear and the ever growing amount of renewable generation means that the electricity is much more efficiently generated and electric cars make enormous sense in the UK.