Can we really manage all electric heating ?

[SimonH2]

The thread on 2 x 15kW boilers :
https://www.diynot.com/diy/threads/2-x-15kw-boilers-on-single-phase.533869/#post-4500394
got me thinking ...

TPTB seem keen that we go all electric for heating etc. Combi boilers typically need 30kW or more, yet here's a discussion as to whether two supplies can manage 15kW each.
And yes we are supposed to believe that whole streets can go all electric

 

[flameport]

Without substantial and expensive upgrades, electric combi boilers from the grid supply are fiction.

Hot water will either have to be a stored system where the water is heated over a long period of several hours (as in immersion heater / cylinder), or if 'instant' hot water is desired then significant local battery storage will be required to provide the short duration high current required. Those would likely be charged from solar panels, reducing the reliance on grid power.

 

[SimonH2]

Solar panels are going to work well on blocks of lats aren't they Ditto heat pumps.
I can't help thinking that many of the people who promote these fairy tale policies must live in their own houses, owning their own roofs, with room for their own heat pumps, and probably a drive to park their EV on to recharge.

 

[JohnW2]

Hot water will either have to be a stored system where the water is heated over a long period of several hours (as in immersion heater / cylinder), or if 'instant' hot water is desired then significant local battery storage will be required to provide the short duration high current required.

Given (between-installation) 'diversity', would not the periods of "short duration high current" probably be OK with current infrastructure? The current doesn't have to be all that high, given that a 7.5 kW shower produces hot enough water - so it presumably would not be much worse than every home having such a shower (something which, as far as I am aware, no supplier seeks to prevent, even now)?

Kind Regards, John

 

[flameport]

That assumes that people who currently have proper hot water systems will be happy to have a feeble electric shower instead.

 

[Munroast]

current usage
http://www.ukenergywatch.org/

would suggest the gas supply is 3.7x bigger enery wise than our electric supply
and as nuclear + wind is only producing 35% of our leccy, then our nuclear/wind production would need to be 13x bigger for a full green conversion

(and that don't include if we all had electric cars that would need charging)

 

[SimonH2]

That assumes that people who currently have proper hot water systems will be happy to have a feeble electric shower instead.

Yes indeed.
As it is, even with 30kW, running a bath is "not quick". With only (perhaps) ¼ of the power, it might be difficult to get the bath filled before it's gone cold
And most modern houses don't have room for any storage - by fitting a combi, the developer can save a square yard of floor space

 

[JohnW2]

That assumes that people who currently have proper hot water systems will be happy to have a feeble electric shower instead.

I'm not talking about 'feeble electric showers' - I'm suggesting that hot water comes out of a 7.5 kW shower at an adequately high temp and adequately high flow rate to service 'hot water taps', so I suspect that a 7.5 kW instant heater would probably be adequate for supplying taps. As for showers (in an all-electric house), many people would probably want something meatier than 7.5 kW, but they wouldn't generally be using it for significant periods whilst also drawing 'instantly heated' hot water from a tap - so the maximum 'water heating load' would usually be that of a (10.5 kW or whatever) shower - which is no different from the situation in many a house now (and, as I said, the suppliers currently do nothing to prevent one electric shower being installed in every house in the country).

Taking baths (which is the one thing which might upset the above) should, of course, be banned - since it's hard to think of a better way of easily wasting energy (whatever the fuel)!

Kind Regards, John

 

[SimonH2]

I'm suggesting that hot water comes out of a 7.5 kW shower at an adequately high temp and adequately high flow rate to service 'hot water taps' ...

I respectfully disagree with that suggestion

 

[JohnW2]

I respectfully disagree with that suggestion

Even given ...

... Taking baths (which is the one thing which might upset the above) should, of course, be banned - since it's hard to think of a better way of easily wasting energy (whatever the fuel)!

??

For what purpose other than (perhaps) filling a bath would you need a great flow rate of hot water from a tap than could be provided by a 7.5 kW heater?

Kind Regards, john

 

[flameport]

A flow of 2 litres per minute from a hot tap is woefully inadequate, and while some people might think that's acceptable, most will not.

Likewise anyone who currently has a stored water system delivering 15-20 litres/minute for a shower isn't going to want to change to a pitiful 10.5kW electric effort supplying less than 5 litres/minute.
Even a low end gas combi boiler can do 3x more than most powerful electric shower can provide.

 

[JohnW2]

A flow of 2 litres per minute from a hot tap is woefully inadequate, and while some people might think that's acceptable, most will not.

Let me preface this by agreeing with you that an all-electric (give or take whatever fuel is used to generate the electricity!) UK is pure science fiction, at least for the next many decades, if not more. I have just been responding to the specifics of what you said.

As I've been implying, it seems to me that this is all about filling baths. Unless you're thinking of something I haven't considered, I can't think of anything else (other than filling baths) for which 2-3 litres/minute (or whatever) out of a hot tap wouldn't be adequate. As for baths, as I've said, no matter what form of fuel one uses, I can't help but wonder whether they aren't an energy-hogging 'luxury', the wisdom of which we perhaps should be seriously thinking about.

Likewise anyone who currently has a stored water system delivering 15-20 litres/minute for a shower isn't going to want to change to a pitiful 10.5kW electric effort supplying less than 5 litres/minute.

Maybe not, but if one went with your other suggestion ["a stored system where the water is heated over a long period of several hours (as in immersion heater / cylinder)" ] they wouldn't need to. That's precisely what I've been doing successfully for the past 30+ years - a 3kW immersion heating water in an extremely well-lagged cylinder for 7 hours every day(night)** - but, again, the 140 litre cylinder (and hence the amount of 'slow heating') would be inadequate if we wanted baths.

[ ** I would add that, in terms of energy (rather than power or current), although 'powered' for 7 hours per night, my immersion consumes an average of only about 5.5 kWh per day ]

P.S. I do have a second 140 L cyclinder and immersion, but that it virtually never used - other than usually for a day or three if/when we have 'a full house' at Christmas!

Kind Regards, John

 

[Notch7]

Im just pondering a scenario:

I come home from work in my EV, plug it in to recharge.....mmm house a bit chilly I shall put on my 30kw electric boiler.

If the green party have a solution, Im all ears.

 

[SimonH2]

For what purpose other than (perhaps) filling a bath would you need a great flow rate of hot water from a tap than could be provided by a 7.5 kW heater?

Washing up. Showering. Cleaning (filling the mop bucket). Washing the car (filling the bucket).
As it is, SWMBO is prone to putting the hot tap on and getting on with other kitchen cleaning activities while the bowl fills. We have a 30kW (or there abouts) combi and our flow is primarily limited by the supply (old galve pipe, probably a bit furred up internally, shared with neighbours). It's "not unknown" for her to get sidetracked and let the bowl overflow
Cut the flow rate down further and that sort of thing will happen more.

If the green party have a solution, Im all ears.

But (waving hands to dismiss awkward questions), "Smart" meters and more windmills Your car won't charge (so tough if you are going out again before the morning commute), and the heating will only work at a fraction of it's capacity.
As John suggests, certain things we take for granted will be banned. Like an occasional bath to relax - you're a heretic. Want to use the car for a "social" (i.e. not absolutely essential) purpose - you're a heretic. Want to live in a "comfortable" house - you're a heretic (especially in weather like this weekend when the windmills won't have been doing much)
"Green" mantra would seem to end up as "burn the heretics" - as long as we capture the heat created
A quick look at Gridwatch and I see that we've been running a lot of CCGT, some coal, and a bit of pumped storage. Wind output has been quite low - around 10 to 15%

 

[JohnW2]

Washing up. Showering. Cleaning (filling the mop bucket). Washing the car (filling the bucket).

Electric showers don't draw water from hot taps As I've said, if one wants an electric shower, one can have one 'as large as one wants', to use when required. If one wants something better than an electric shower, then one would presumably (like I do **) take the other approach and slowly heat water in a cylinder with a ('low powered') immersion. As for washing up and filling buckets (for mopping or car washing) I was expressing my opinion that I could live with that happening at "7.5 kw shower speed" - but opinions clearly vary!

** As I've said, for me our hot water requirements (with very few baths) are satisfactorily served with about 5.5 kWh electricity usage per day, hence an average power draw/ current of around 0.23 kW/1A. If things could be arranged so that was reasonably evened out (time-wise) between properties, it would not be a massive load on the system.

As it is, SWMBO is prone to putting the hot tap on and getting on with other kitchen cleaning activities while the bowl fills. We have a 30kW (or there abouts) combi and our flow is primarily limited by the supply (old galve pipe, probably a bit furred up internally, shared with neighbours). It's "not unknown" for her to get sidetracked and let the bowl overflow Cut the flow rate down further and that sort of thing will happen more.

That may well be true to some extent (I suspect that few of us have never been guilty!) but, in terms of the big picture, I would suggest that it is only a pretty minor factor working against instantaneous water heating!

Kind Regards, John