Average Energy Consumption

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robert Atkinson 2 on 27/09/2023 19:39:28:

There is more than one type of heat pump. I assume you are referring to the air to water type currently being promoted by the government. […]

.

Sorry Robert … to whom are you referring ?

If it is me, then I pretty clearly stated what I had been looking at … and that is not what you have assumed

MichaelG.

.

Quote from the other thread:

Not straying too far off-topic, I hope

Does anyone have experience of these: **LINK** https://sahp.info

Solar Assisted Heat Pumps for domestic hot water

… I am tempted by the SAHP 130

 

MichaelG.

Ref. further discussion on that post : https://www.model-engineer.co.uk/forums/postings.asp?th=188049&p=3

Edited By Michael Gilligan on 27/09/2023 21:08:55

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bazyle on 27/09/2023 20:39:03:

[…]

MG you could consider building a nice detached workshop, I mean summerhouse outbuilding, the max size permitted first and use it to store the house 'stuff' for a while while making other developments. Then afterwards you have er, a nice workshop.

.

I couldn't consider that for very long … but I haven’t got the will to explain why, here.

MichaelG.

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Michael Gilligan on 27/09/2023 20:49:35:

Posted by Robert Atkinson 2 on 27/09/2023 19:39:28:

There is more than one type of heat pump. I assume you are referring to the air to water type currently being promoted by the government. […]

.

Sorry Robert … to whom are you referring ?

If it is me, then I pretty clearly stated what I had been looking at … and that is not what you have assumed

MichaelG.

.

Quote from the other thread:

Not straying too far off-topic, I hope

Does anyone have experience of these: **LINK** https://sahp.info

Solar Assisted Heat Pumps for domestic hot water

… I am tempted by the SAHP 130

MichaelG.

Ref. further discussion on that post : **LINK**

Edited By Michael Gilligan on 27/09/2023 21:08:55

I was mainly refering to the output side of the pump. Even so the SAHPs are still air-water heatpumps. The key is in the "assisted" in the name. They have a benefit from a degree of solar capture when the sun is shining. How much this affects the air operation is not clear.

Robert

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Joseph Noci 1 on 27/09/2023 16:56:44:

My house/workshop has been off-grid since Dec 2022 reliant on PV solar energy. Monthly usage averaged 1300KW over winter, with 2500KW generated. The excess is exported to the Electricity supplier at 60% consumption value.

I have hot water underfloor heating, which used to run from a solar heated water system, heating a 6000liter insulated water tank, buried in the ground. That heated water ( around 30degC in winter end of day) fed a 3phase 14KW boiler, and then into the pipes in the floors. The boiler was used during many low/no-sun days in winter.

In winter my floor heating energy used was around 50KW/24hour period – I did not run the boiler during day time, since electricity costs are almost double between 10H00 and 18H00. So the floors cooled during the day, and extra energy was needed at night to re-heat.

When I fitted the PV system ( 3phase, 28KW PV capacity) I fitted a Stiebel Eltron heat pump – a 3phase pump, with a variable speed compressor, to heat the floors.. The pump is capable of 12KW output, and is an Air extraction pump.

Since I heat the floor water to 35deg C max, and the floor water return temp is never below 20degC, the delta the heat pump sees is a max of 15deg, at start of heating, with the delta reducing as the floor heats up to 25deg setpoint.

All that gives me a pump COP of 10 (!) and I run day and night, so the floors don't cool in the day. That returns a daily heat output of around 33KW, with a consumption of around 3KW…

My monthly usage for floors in now around 100KW, instead of 1500KW – and THAT ticks all the boxes – energy cost, carbon footprint, comfort….

Lower COP's are to be expected if the water heating temp differential is higher, such as heating water for showers, etc ( 50degC plus..) – but this heat pump delivers a COP of 4 to 5 when doing that…

The heat pump did cost around 8K British Pounds…but is better than sliced bread.

I'm going to be pedantic…

You cannot be "off-grid" if you are exporting power back to the supplier
What is a Kelvin Watt (KW)
Do you mean killowatt kW?
KW is power not energy. Do you mean kWh?
Was the previous consumption, 3500 (assumed kWh) really ALL heating? Did you have a seperate meter on your heater? 3500 kWh in a month is 3 kW 24/7 that's a lot of heating….
It's a bit worrying that the heat pump reporting software also uses Kelvin Watt hours…..

Robert

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robert Atkinson 2 on 28/09/2023 07:55:33:

[…]

I was mainly refering to the output side of the pump. Even so the SAHPs are still air-water heatpumps. The key is in the "assisted" in the name. They have a benefit from a degree of solar capture when the sun is shining. How much this affects the air operation is not clear.

Robert

.

Thanks, Robert

I will say now … just to be clear for everyone who is contributing to this discussion:

I have no interest whatsoever in upgrading circulating water heating system in this property … my ambition is to remove it entirely.

MichaelG.

[Joseph Noci 1Participant @josephnoci1]

Posted by Robert Atkinson 2 on 28/09/2023 08:14:00:

Posted by Joseph Noci 1 on 27/09/2023 16:56:44:

 

 

I'm going to be pedantic…

You are Welcome…

You cannot be "off-grid" if you are exporting power back to the supplier
Fine – Content if I say 'independant of' ?

What is a Kelvin Watt (KW)
No Idea- What is a Kelvin Watt?

Do you mean killowatt kW?
For you, and most others, yes, although the Germans do use KW, as they do MW (mega) as opposed to mW (milli..)..

KW is power not energy. Do you mean kWh?
Don't understand the question – I qualified each consumption figure with a relevant period, 24hours, or monthly, etc, and watts over that period is energy.. – some mental arithmetic will reduce that to kWh if that's your fancy.

Was the previous consumption, 3500 (assumed kWh) really ALL heating? Did you have a seperate meter on your heater? 3500 kWh in a month is 3 kW 24/7 that's a lot of heating….
Again, don't understand the question…

I did not find a mention of '3500' anythings in my text. I did say "My monthly usage for floors in now around 100KW, instead of 1500KW"… so the period is clearly 1 month. Using your '3500' things per month is 4.8kWh or so ,not your stated 3kW 24/7 ( did you mean 3kWh ?).

And if we use the figure I stated, 1500 'KW' per month, that's 2kWh 24/7, not a huge amount of heating – one bar of a two bar foot warmer heater…
Yes I have a seperate energy meter on the heat pump (and on the house and on the workshop feed).

It's a bit worrying that the heat pump reporting software also uses Kelvin Watt hours…..
Wouldn't worry too much – it seems to know what it's doing.

Robert

Joe

 

(Apologies MichaelG)

 

Edited By Joseph Noci 1 on 28/09/2023 10:01:51

[Robert Atkinson 2Participant @robertatkinson2]

Sorry mis-read 2500 as 3500. 2kW 24/7 is still a lot of heat.

Robert.

[Martin Johnson 1Participant @martinjohnson1]

We have run ASHP for 7years now. Through a program of window replacement, upgrading lofT insulation and the heat pump, we eliminated a £1000 annual LPG bill without increasing the leccy bill. The house has never been warmer. We live near Inverness about 240m ASL.

Yes, get as much radiator surface as possible, this lets you run the HP more efficiently at lower temperature. Run it 24/7 for the same reason. You will need a larger pressurised hot water cylinder and possibly a buffer tank. Run it on economy 7 if you can get that tariff – we were told opposite, but have proved eco 7 is best.

Ours works fine down to -20. Ignore the BS about not working below freezing. There is a region around zero where the defrost load increases and COP drops, but it all works fine.

Why would you want water hot enough to scald yourself? Especially when you pay handsomely for the privilege. Derrrr!

Martin

[modeng2000Participant @modeng2000]

Water hot enough, above 55 degrees Centigrade to stop bugs breeding in the heated stored water.

John

[Joseph Noci 1Participant @josephnoci1]

Posted by Robert Atkinson 2 on 28/09/2023 12:22:54:

Sorry mis-read 2500 as 3500. 2kW 24/7 is still a lot of heat.

Robert.

you mean 1500 instead of 3500….

2kW 24/7 for heating only is only in the winter -June-Sept – so 4 months typically. Zero for heating for the other 8, while Geyser is heated from Solar PV all year.

[Neil WyattModerator @neilwyatt]

If you have good insulation, it's worth considering the contributions other devices make to heating.

Even though my office doesn't have a cavity wall (it's in a 125-year-old house) the ~300 watts from my computer makes a useful contribution to keeping the room warm (and can be a pain in summer!)

Similarly, in my previous home a condensing tumble drier in the kitchen made a significant contribution to heating, so effectively you got to use the energy twice.

[Robert Atkinson 2Participant @robertatkinson2]

Even better than a condensing tumble dryer is one with a heatpump. Uses latent heat of evaporation to dry the clothes. No heater involved.

Robert.

[duncan webster 1Participant @duncanwebster1]

Posted by Robert Atkinson 2 on 28/09/2023 17:23:41:

Even better than a condensing tumble dryer is one with a heatpump. Uses latent heat of evaporation to dry the clothes. No heater involved.

Robert.

You're going to have to explain that one to me. Starting with water absorbed in clothing and finishing with water in a bucket. This description might be called a heat pump, but it is just like a condensing drier that recycles the air. We did think of getting a condensing drier, but as it spews out 100% humidity air at slightly above room temperature there must be some residual water to condense in the house as the air cools from above ambient. We do most clothes drying in an enclosed space with a dehumidifier. Came as a great surprise to SWMBO just how much water it collects. I'd been telling her for years that drying clothes on radiators causes condensation, now she believes me.

[Mark RandParticipant @markrand96270]

The condensing driers normally recirculate the internal air. They do have the disadvantage that they don't work at all well at low ambient temperatures, such as an external garage or utility room. But they are a bloody sight more efficient than any other varieties which don't rely on string, wind and sunshine

Edited By Mark Rand on 28/09/2023 19:48:51

[Robert Atkinson 2Participant @robertatkinson2]

That is not a good description. It misses out the important fact that the heat extracted from condensing the water vapour (latent heat of evaporation 2250kJ/kg) is used to heat the air circulated back into the drum.
It only uses about 20% of the energy of a conventional dryer. They release virtually no moisture to the house and little heat. According to SWBO it is also much more gentle on the clothes as the temperature is lower.

Robert.

Edited By Robert Atkinson 2 on 28/09/2023 19:56:37

[BazyleParticipant @bazyle]

I use WEADS. Wind Energy Assisted drying with Solar. aka washing line.

Aside from Passivehaus I recall a target a few years ago was 10KWh per day. So start with 500W and insulate until you can heat that room then additional rooms. We need to get away from the recent habit of overheating the entire house propagated by gas adverts in the sixties.

I'm a bit surprised by this. 10KWh would be say £4 so only £400 for 100 days of winter – way short of the thousands being touted as current bills.

[duncan webster 1Participant @duncanwebster1]

Posted by Robert Atkinson 2 on 28/09/2023 19:56:08:

That is not a good description. It misses out the important fact that the heat extracted from condensing the water vapour (latent heat of evaporation 2250kJ/kg) is used to heat the air circulated back into the drum.
It only uses about 20% of the energy of a conventional dryer. They release virtually no moisture to the house and little heat. According to SWBO it is also much more gentle on the clothes as the temperature is lower.

Robert.

Edited By Robert Atkinson 2 on 28/09/2023 19:56:37

Ah, that makes sense

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Martin Johnson 1 on 28/09/2023 13:00:03:

We have run ASHP for 7years now. Through a program of window replacement, upgrading lofT insulation and the heat pump, we eliminated a £1000 annual LPG bill without increasing the leccy bill. The house has never been warmer. We live near Inverness about 240m ASL.

<snip>

Martin

Yes, I had an air to air heat pump, otherwise known as reversible air conditioning, installed seven years ago. It is a dual split unit with a maximum heating output of 5.4 kW. Living considerably south of Inverness the cooling is essential in summer. COP for heating is about 5 at outside temperature above +7 C but drops to about 3 below -7 C as a result of the defrost cycle. With the prevailing wind coming off a mountain range over 2000 m elevation I expected to have to use our wood burner for supplementary heat but it hasn't been used for years.

I would expect more recent models to be yet more efficient.

Russell

[Michael GilliganParticipant @michaelgilligan61133]

Turning to the other side of the coin … I now have a reasonable ‘feel’ for what my modest electricity requirements might be, and it looks like an adequate solar array would fit on the new roof … so I had a look at this [which is what has replaced the Feed In Tariff] : **LINK**

https://www.shellenergy.co.uk/info/terms/smart-export-guarantee/tariff-guide

at 3.5 pence per kWh, paid annually; it seems that there might be better ways to dispose of any surplus electricity produced … perhaps a nice little electro-forming tank for making stuff ?

Does the team have any better ideas ?

MichaelG.

[David JuppParticipant @davidjupp51506]

Michael,

All the people that I spoke to about solar PV were agreed on one thing – that I should switch to Octopus once the system is installed as they pay a lot more per kWh for export (and can offer a low overnight price to top up the storage battery in Winter). I haven't done so yet as there are a couple of things to resolve with current supplier.

You do get best value by using the PV generated energy yourself, as it is then backing out full price imports.

The SEG is something the suppliers are forced to do, so is generally at a minimal per unit price.

A further complication that you may not be aware of – even if you have a smart meter which can measure the exports, you won't get paid for any until a new MPAN is assigned, your existing reference number it seems is just for consuming, not for supply! I've now been providing free electricity into the system for several weeks.

With any potential change of supplier – check unit costs and standing charges in relation to your own circumstance.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for that, David

MichaelG.

.

Ref. https://octopus.energy/smart/outgoing/

Edited By Michael Gilligan on 30/09/2023 08:45:04

[Maurice TaylorParticipant @mauricetaylor82093]

Hi, How much does all this electricity saving kit (panels,batteries,etc) cost and how much is saved per year ?

Maurice

[Grindstone CowboyParticipant @grindstonecowboy]

Just a small point – Michael references Shell Energy, David recommends swapping to Octopus. Apparently Octopus are going to take over Shell Energy in the not too distant future, so I don't know if that will have any effect on their respective feed-in rates.

Rob

[Michael GilliganParticipant @michaelgilligan61133]

Very interesting, and encouraging, Rob … provided the rates move in the right direction.

MichaelG.

.

Ref. https://octopus.energy/shell/

Edited By Michael Gilligan on 30/09/2023 12:38:29

[David JuppParticipant @davidjupp51506]

Posted by Maurice Taylor on 30/09/2023 10:04:16:

Hi, How much does all this electricity saving kit (panels, batteries, etc.) cost and how much is saved per year ?

Maurice

Cost very much depends upon, size of array, size of battery (if any) – conventional inverter or multiple micro inverters and any additional equipment. Also how much the installer wants the job.

Savings will depend on array size, geographic location, direction it points, angle of roof, any shading issues, then how much of the generated energy you use yourself, and what tariff you are on.

MCS registered installers all use the same set of assumptions and formula to give 'projected savings' as part of their quotations.

In short – it is fairly complicated.

[Author]

Posts