The Death Of Fossil Fuels

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Gfamily
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Re: The Death Of Fossil Fuels

Post by Gfamily » Tue Jul 28, 2020 4:09 pm

AMS wrote:
Tue Jul 28, 2020 3:56 pm
I was reading earlier today about electric combi boilers as replacement for gas. Anyone know if they're any good? It did say that gas is cheaper than leccy for heating per kW, but that this is partially offset by electric boilers being more efficient - close to 100% in fact, as for this application, energy lost as heat is kind of the point.
Presumably gas is much worse for efficiency because of heat carried away in the flue gases.

So when our current elderly boiler dies, are they worth it? (My view of electric water heaters is tarnished by those units you used to get on the hot water tap in places like village halls or pub toilets, which uniformly do nothing to the water temperature.)
Condensing Gas boilers are now about 90% efficient or so we're told.
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dyqik
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Re: The Death Of Fossil Fuels

Post by dyqik » Tue Jul 28, 2020 7:16 pm

Gfamily wrote:
Tue Jul 28, 2020 4:09 pm
AMS wrote:
Tue Jul 28, 2020 3:56 pm
I was reading earlier today about electric combi boilers as replacement for gas. Anyone know if they're any good? It did say that gas is cheaper than leccy for heating per kW, but that this is partially offset by electric boilers being more efficient - close to 100% in fact, as for this application, energy lost as heat is kind of the point.
Presumably gas is much worse for efficiency because of heat carried away in the flue gases.

So when our current elderly boiler dies, are they worth it? (My view of electric water heaters is tarnished by those units you used to get on the hot water tap in places like village halls or pub toilets, which uniformly do nothing to the water temperature.)
Condensing Gas boilers are now about 90% efficient or so we're told.
95% plus.

But the significantly more efficient option is a heat pump system. Those have efficiencies* approaching 300-400% in the UK environment, and thus about the same price to run as gas.

*Coefficient of performance

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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Tue Jul 28, 2020 7:38 pm

AMS wrote:
Tue Jul 28, 2020 3:56 pm
I was reading earlier today about electric combi boilers as replacement for gas. Anyone know if they're any good? It did say that gas is cheaper than leccy for heating per kW, but that this is partially offset by electric boilers being more efficient - close to 100% in fact, as for this application, energy lost as heat is kind of the point.
Presumably gas is much worse for efficiency because of heat carried away in the flue gases.

So when our current elderly boiler dies, are they worth it? (My view of electric water heaters is tarnished by those units you used to get on the hot water tap in places like village halls or pub toilets, which uniformly do nothing to the water temperature.)
Fully charged did an episode on a hot water tank a couple of years ago and say that they’re going to do much more on domestic heat soon.

https://fullycharged.show/episodes/mixe ... ater-tank/
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Martin_B
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Re: The Death Of Fossil Fuels

Post by Martin_B » Wed Jul 29, 2020 11:18 pm

AMS wrote:
Tue Jul 28, 2020 3:56 pm
I was reading earlier today about electric combi boilers as replacement for gas. Anyone know if they're any good? It did say that gas is cheaper than leccy for heating per kW, but that this is partially offset by electric boilers being more efficient - close to 100% in fact, as for this application, energy lost as heat is kind of the point.
Presumably gas is much worse for efficiency because of heat carried away in the flue gases.

So when our current elderly boiler dies, are they worth it? (My view of electric water heaters is tarnished by those units you used to get on the hot water tap in places like village halls or pub toilets, which uniformly do nothing to the water temperature.)
One issue with electric combi boilers (at least when I last looked into them) was their time to reach temperature. Gas combi boilers start hitting the desired water outlet temperature almost immediately; basically once the water that was just about to enter the boiler reaches the outlet it should be at temperature, because flame heat is instantaneous. Electric combi boilers have to heat the element up to temperature before the water outlet temperature hits the target. This leads to more under-heated water flowing through the system and, ultimately, straight down the plughole until the hot water reaches the tap. Electric combi boilers may have improved element reaction time in the last few years, but they cannot compete with gas for reaction time.

Gas combi boilers can struggle with low load, though; if you want hot water at a small but continuous amount, you can end up with the combi boiler cycling on and off and varying the water temperature - electric combi boilers handle this far better (at least if their control system is good enough - I've seen some where the control system was based on the gas version so was the worst of both worlds!)
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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Thu Jul 30, 2020 6:31 am

This may be a silly question, but why don’t we use microwaves to heat water?
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Re: The Death Of Fossil Fuels

Post by shpalman » Thu Jul 30, 2020 6:36 am

Grumble wrote:
Thu Jul 30, 2020 6:31 am
This may be a silly question, but why don’t we use microwaves to heat water?
Some answers from reddit:
https://www.reddit.com/r/askscience/com ... the_water/
molto tricky

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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Thu Jul 30, 2020 6:39 am

At my lab we heat water quickly by having a spiral tube wrapped around an element. Terrible for static water but great for flowing water. You may run the risk of local boiling if there’s a lot of heat in the body when flow turns off, but it should be possible to design something like that. I may resort to drawing a system in Paint.
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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Thu Jul 30, 2020 6:41 am

shpalman wrote:
Thu Jul 30, 2020 6:36 am
Grumble wrote:
Thu Jul 30, 2020 6:31 am
This may be a silly question, but why don’t we use microwaves to heat water?
Some answers from reddit:
https://www.reddit.com/r/askscience/com ... the_water/
Ta, I knew I couldn’t be the first to think of that while having a shower!
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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Tue Aug 04, 2020 11:53 am

I don’t think we’ve had this one, old news now but still awesome, superconducting wind turbine!
https://phys.org/news/2019-11-supercond ... ccess.html
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bjn
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Re: The Death Of Fossil Fuels

Post by bjn » Wed Aug 05, 2020 6:09 pm

BP has read the writing on the wall and has pledged to cut oil production 50% by 2030 as well as the emissions generated to make their stuff. Zero carbon by 2050 (with a minor weasel in that last one).

They also significantly reduced their dividends, partly as a response to the COVID downturn and partly to fund renewables. They plan on increasing investment in “low carbon energy” from $500 million to around $5 billion per year by 2030. Their share price has increased on this news.

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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Wed Aug 05, 2020 6:38 pm

bjn wrote:
Wed Aug 05, 2020 6:09 pm
BP has read the writing on the wall and has pledged to cut oil production 50% by 2030 as well as the emissions generated to make their stuff. Zero carbon by 2050 (with a minor weasel in that last one).

They also significantly reduced their dividends, partly as a response to the COVID downturn and partly to fund renewables. They plan on increasing investment in “low carbon energy” from $500 million to around $5 billion per year by 2030. Their share price has increased on this news.
Good, BP have been reasonably fairly accused of green washing before but this looks more substantive.
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Bird on a Fire
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Re: The Death Of Fossil Fuels

Post by Bird on a Fire » Wed Aug 05, 2020 11:55 pm

Excellent news, thanks bjn!
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Sciolus
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Re: The Death Of Fossil Fuels

Post by Sciolus » Thu Aug 13, 2020 6:40 pm

Latest coal-free run ended after 55 days, because of low winds, and hot weather meaning gas-fired stations generate less.

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Grumble
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Re: The Death Of Fossil Fuels

Post by Grumble » Thu Aug 13, 2020 7:05 pm

Sciolus wrote:
Thu Aug 13, 2020 6:40 pm
Latest coal-free run ended after 55 days, because of low winds, and hot weather meaning gas-fired stations generate less.
Yes, that does highlight the need for large amounts of stored power that we can call on when required. We’ve essentially had a few days of next to no wind production and building more capacity of generation isn’t going to solve that. Orange is gas in these graphs.
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