The move to heat pumps

Reed_Richards

JKenH said:

For small properties is it not more efficient to have air to air heat pumps?

Air-to-air is intrinsically better; in cold weather I have to heat the water in my radiators to 50 C in order to heat the rooms to 21 C.  I would have thought that ideally you would have one big heat pump and ducts for the hot air, much as they do in much of North America (the ducts I mean).  If a lot of hardware external to your house is involved then you would probably require planning permission.  An air-to-water ASHP, unless very large, is usually a permitted development.  I imagine there is noise from @JKenH 's units but probably no worse than a fan heater.  I think the main problem here is that it's hard enough to find someone who can install an air-to-water heat pump system, does anyone actually offer to install whole-house air-to-air?  Or must you always DIY?  

ABrass

Baxter100 said:

ABrass said:

Baxter100 said:

Dolor said:

I am not sure what people are worrying about. Octopus is about to release a heat pump for the masses (that said, there is reference to a need for much improved insulation):

https://octopus.energy/blog/heat-pumps/

Seriously, the Government is going to need to think long and hard about how they are going to sell heat pumps (and the associated costs) to the public.

See this is the type of fluffy misinformation that worries me. From the article:

Do heat pumps still run when it is really cold outside? (Yes!)

Thanks to the heat pump’s internal compressor, it will always be able to heat the fluid inside (propane, for example) to the same temperatures, regardless of the temperature outside. When it is extremely cold outside (we’re talking -15°C), the heat pump can’t extract quite as much energy from the atmosphere as usual – but that doesn’t mean your house won’t get as warm as normal. On these incredibly rare, freezing days, the heat pump would just use a little more electricity to create heat, or in other words, work a tiny bit less efficiently, but it will still reach the same temperatures as ever. We see temperatures below -10°C only a few days per year, and even at these temperatures, heat pumps still function more efficiently than gas boilers do.

Paraphrasing:

"Heat pumps work efficiently even in sub-zero outside temperatures. There is a tiny reduction in efficiency, but this only happens on rare -10oC days. Even on these days the heat pump still works more efficiently as a gas boiler."

Flat out lies! The efficiency of a heat pump drops significantly as the outside air temperature decreases, because of course it does. This is how the technology works.

https://aspirationenergy.com/how-low-ambient-temperature-can-affect-your-heat-pump-performance/

And yes, it may still be more efficient than a gas boiler at this COP, but so too is the £20 electric fan heater I have in my conservatory. Can we please not try and mislead people with clever jargon and just give them the actual facts.

That graph is weird. Why would you be heating your house when the Ambient temperature is 43 degrees outside?

The graph just illustrates the fact that the efficiency of the heat pump drops as the outside air temperature drops. It's kind of ridiculous that a company like Octopus Energy would try to claim that it doesn't.

https://www.mibnet.se/house/HeatPumps/NIBE2020HeatPumpCOPCurves.html

Those are less absurd. They have the temperature within a reasonable range.

The lesson to take away is that you can't undersize your heating system or it'll struggle during unusually cold periods, just like an undersized boiler.

Reed_Richards

ABrass said:

The lesson to take away is that you can't undersize your heating system or it'll struggle during unusually cold periods, just like an undersized boiler.

Or undersized radiators.  The heat output capacity of the radiators is every bit as important as the capacity of the heat source.  Fortunately radiators are relatively cheap. 

Baxter100

ABrass said:

Baxter100 said:

ABrass said:

Baxter100 said:

Dolor said:

I am not sure what people are worrying about. Octopus is about to release a heat pump for the masses (that said, there is reference to a need for much improved insulation):

https://octopus.energy/blog/heat-pumps/

Seriously, the Government is going to need to think long and hard about how they are going to sell heat pumps (and the associated costs) to the public.

See this is the type of fluffy misinformation that worries me. From the article:

Do heat pumps still run when it is really cold outside? (Yes!)

Thanks to the heat pump’s internal compressor, it will always be able to heat the fluid inside (propane, for example) to the same temperatures, regardless of the temperature outside. When it is extremely cold outside (we’re talking -15°C), the heat pump can’t extract quite as much energy from the atmosphere as usual – but that doesn’t mean your house won’t get as warm as normal. On these incredibly rare, freezing days, the heat pump would just use a little more electricity to create heat, or in other words, work a tiny bit less efficiently, but it will still reach the same temperatures as ever. We see temperatures below -10°C only a few days per year, and even at these temperatures, heat pumps still function more efficiently than gas boilers do.

Paraphrasing:

"Heat pumps work efficiently even in sub-zero outside temperatures. There is a tiny reduction in efficiency, but this only happens on rare -10oC days. Even on these days the heat pump still works more efficiently as a gas boiler."

Flat out lies! The efficiency of a heat pump drops significantly as the outside air temperature decreases, because of course it does. This is how the technology works.

https://aspirationenergy.com/how-low-ambient-temperature-can-affect-your-heat-pump-performance/

And yes, it may still be more efficient than a gas boiler at this COP, but so too is the £20 electric fan heater I have in my conservatory. Can we please not try and mislead people with clever jargon and just give them the actual facts.

That graph is weird. Why would you be heating your house when the Ambient temperature is 43 degrees outside?

The graph just illustrates the fact that the efficiency of the heat pump drops as the outside air temperature drops. It's kind of ridiculous that a company like Octopus Energy would try to claim that it doesn't.

https://www.mibnet.se/house/HeatPumps/NIBE2020HeatPumpCOPCurves.html

Those are less absurd. They have the temperature within a reasonable range.

The lesson to take away is that you can't undersize your heating system or it'll struggle during unusually cold periods, just like an undersized boiler.

ABrass said:

Baxter100 said:

ABrass said:

Baxter100 said:

Dolor said:

I am not sure what people are worrying about. Octopus is about to release a heat pump for the masses (that said, there is reference to a need for much improved insulation):

https://octopus.energy/blog/heat-pumps/

Seriously, the Government is going to need to think long and hard about how they are going to sell heat pumps (and the associated costs) to the public.

See this is the type of fluffy misinformation that worries me. From the article:

Do heat pumps still run when it is really cold outside? (Yes!)

Thanks to the heat pump’s internal compressor, it will always be able to heat the fluid inside (propane, for example) to the same temperatures, regardless of the temperature outside. When it is extremely cold outside (we’re talking -15°C), the heat pump can’t extract quite as much energy from the atmosphere as usual – but that doesn’t mean your house won’t get as warm as normal. On these incredibly rare, freezing days, the heat pump would just use a little more electricity to create heat, or in other words, work a tiny bit less efficiently, but it will still reach the same temperatures as ever. We see temperatures below -10°C only a few days per year, and even at these temperatures, heat pumps still function more efficiently than gas boilers do.

Paraphrasing:

"Heat pumps work efficiently even in sub-zero outside temperatures. There is a tiny reduction in efficiency, but this only happens on rare -10oC days. Even on these days the heat pump still works more efficiently as a gas boiler."

Flat out lies! The efficiency of a heat pump drops significantly as the outside air temperature decreases, because of course it does. This is how the technology works.

https://aspirationenergy.com/how-low-ambient-temperature-can-affect-your-heat-pump-performance/

And yes, it may still be more efficient than a gas boiler at this COP, but so too is the £20 electric fan heater I have in my conservatory. Can we please not try and mislead people with clever jargon and just give them the actual facts.

That graph is weird. Why would you be heating your house when the Ambient temperature is 43 degrees outside?

The graph just illustrates the fact that the efficiency of the heat pump drops as the outside air temperature drops. It's kind of ridiculous that a company like Octopus Energy would try to claim that it doesn't.

https://www.mibnet.se/house/HeatPumps/NIBE2020HeatPumpCOPCurves.html

Those are less absurd. They have the temperature within a reasonable range.

The lesson to take away is that you can't undersize your heating system or it'll struggle during unusually cold periods, just like an undersized boiler.

The graph wasn't absurd by any means, but whatever.

But with regards the bolded statement, the two aren't even remotely comparable! Yes an undersized boiler may struggle to provide the overall level of heating required but the boiler efficiency remains relatively stable regardless, so you are paying no more money for each kWh of heating.

For a heat pump however, the efficiency of system drops proportional to the ambient/output temperature difference, typically about 70% for each 10 degrees C of temperature change.

As an example at an ambient air temperature of 10 degrees C and a flow temperature of 55 degrees C (45 degree differential), a heat pump may operate at an efficiency of say 260%.

However at an ambient air temperature of 0 Degrees C and a flow temperature of 60 degrees C (60 degree differential) that same installation will work at an efficiency of 155%. This would equate to a 68% increase in the kWh unit price of electricity.

So the takeaway isn't about correct sizing of the system (althouth of course important) it is that minimising the temperature difference between ambient and output is pretty much everything for ensuring that the heat pump roll out works effectively.

QrizB

Regarding this table:

Baxter100 said:

Reed_Richards said:

My heat pump does not heat water above 55 C and only then for the purposes of heating the hot water tank.  It could go hotter but then the efficiency is dreadful and so would be my RHI payments.  80 C "final temperature"?!?  No wonder that comes from a site called "aspirationenergy" because it's only some fantastic aspiration, not real.     

This is exactly the point. Simply retrofitting heat pumps in place of existing boilers will not work effectively for the vast majority of houses in the UK, as the operating efficiencies of the systems would be as you say, dreadful. It would be a disaster.

Aspiration Energy is an Indian company marketing itself to the chemical process industry where process water at 80 deg. C might reasonably be required. This is why they are quoting COPs at 43 deg. C.

Here's the product spec for a modren domestic ASHP:
https://www.daikin.ie/content/dam/internet-ireland/ECODesign_Data/DAIKIN EPGA14DV3&EAVH(Z)16S18-23D6V ECODESIGN data.pdf

If I'm reading that correctly (and there's a good chance I'm not) the COP for 55C heating varies from 2.17 at -7C ambient to 5.94 at +12C ambient. For 35C heating the equivalent COP values are 2.85 and 8.12.

JKenH

Reed_Richards said:

JKenH said:

For small properties is it not more efficient to have air to air heat pumps?

Air-to-air is intrinsically better; in cold weather I have to heat the water in my radiators to 50 C in order to heat the rooms to 21 C.  I would have thought that ideally you would have one big heat pump and ducts for the hot air, much as they do in much of North America (the ducts I mean).  If a lot of hardware external to your house is involved then you would probably require planning permission.  An air-to-water ASHP, unless very large, is usually a permitted development.  I imagine there is noise from @JKenH 's units but probably no worse than a fan heater.  I think the main problem here is that it's hard enough to find someone who can install an air-to-water heat pump system, does anyone actually offer to install whole-house air-to-air?  Or must you always DIY?  

Actually mine are incredibly quiet and we just aren’t aware of them (unless you put it on a boost setting to warm a room up quickly from cold when it does sound like a fan heater). One of the reasons I chose the ones I have was the noise levels quoted. The installer runs an air conditioning company and has the same units in his house. I was lucky, just contacting a commercial aircon installation company who came out gave me a price and did the job. From talking to them I couldn’t see any reason why they couldn’t duct for a whole house. 

Exiled_Tyke

Reed_Richards said:

JKenH said:

For small properties is it not more efficient to have air to air heat pumps?

Air-to-air is intrinsically better; in cold weather I have to heat the water in my radiators to 50 C in order to heat the rooms to 21 C.  I would have thought that ideally you would have one big heat pump and ducts for the hot air, much as they do in much of North America (the ducts I mean).  If a lot of hardware external to your house is involved then you would probably require planning permission.  An air-to-water ASHP, unless very large, is usually a permitted development.  I imagine there is noise from @JKenH 's units but probably no worse than a fan heater.  I think the main problem here is that it's hard enough to find someone who can install an air-to-water heat pump system, does anyone actually offer to install whole-house air-to-air?  Or must you always DIY?  

When I was looking to getting a small ASHP for a couple of rooms I found that the installers were only interested in selling me whole house air to air at ridiculous costs.  I gave up trying in the end.  I may still look to follow the trend here and get a small set up for a couple of rooms.

JKenH

Exiled_Tyke said:

Reed_Richards said:

JKenH said:

For small properties is it not more efficient to have air to air heat pumps?

Air-to-air is intrinsically better; in cold weather I have to heat the water in my radiators to 50 C in order to heat the rooms to 21 C.  I would have thought that ideally you would have one big heat pump and ducts for the hot air, much as they do in much of North America (the ducts I mean).  If a lot of hardware external to your house is involved then you would probably require planning permission.  An air-to-water ASHP, unless very large, is usually a permitted development.  I imagine there is noise from @JKenH 's units but probably no worse than a fan heater.  I think the main problem here is that it's hard enough to find someone who can install an air-to-water heat pump system, does anyone actually offer to install whole-house air-to-air?  Or must you always DIY?  

When I was looking to getting a small ASHP for a couple of rooms I found that the installers were only interested in selling me whole house air to air at ridiculous costs.  I gave up trying in the end.  I may still look to follow the trend here and get a small set up for a couple of rooms.

My installer was Lincold Refrigeration in Scunthorpe. They do commercial work all over the country but I imagine the issue would be getting them to come out to W. Yorkshire to give you a quote. Maybe you could get in touch and see if they could quote on the basis of photos. Obviously there would be additional travel costs for a couple of blokes to do the job - might add £200 or so to the price. (Edit: the boss of the firm lived in a village near me and popped in on the way home so it was pretty convenient for him to do a quote for me.)

shinytop

QrizB said:

Regarding this table:

Baxter100 said:

Reed_Richards said:

My heat pump does not heat water above 55 C and only then for the purposes of heating the hot water tank.  It could go hotter but then the efficiency is dreadful and so would be my RHI payments.  80 C "final temperature"?!?  No wonder that comes from a site called "aspirationenergy" because it's only some fantastic aspiration, not real.     

This is exactly the point. Simply retrofitting heat pumps in place of existing boilers will not work effectively for the vast majority of houses in the UK, as the operating efficiencies of the systems would be as you say, dreadful. It would be a disaster.

Aspiration Energy is an Indian company marketing itself to the chemical process industry where process water at 80 deg. C might reasonably be required. This is why they are quoting COPs at 43 deg. C.

Here's the product spec for a modren domestic ASHP:
https://www.daikin.ie/content/dam/internet-ireland/ECODesign_Data/DAIKIN EPGA14DV3&EAVH(Z)16S18-23D6V ECODESIGN data.pdf

If I'm reading that correctly (and there's a good chance I'm not) the COP for 55C heating varies from 2.17 at -7C ambient to 5.94 at +12C ambient. For 35C heating the equivalent COP values are 2.85 and 8.12.

The Octopus article is a blog rather than an advert, which means it doesn't have to be true.  And it isn't; at best it's full of half truths and misleading statistics that do not stand up to any sort of scrutiny.  

Spec sheets from ASHP makers are also slightly miseleading in the same way that mpg (ICE) or range (EV) figures are but they are are a starting point.  In the real world, sensibly set up ASHPs in UK homes seem to achieve a SCOP of 2.5-3.  And yes, it's more expensive to heat your house when it's cold (who would have thought it?). 

ASHPs will be significantly more expensive than mains gas to run and install, especially if we want tropical levels of heat in our homes and treat showers and baths as a leisure activity.  I think it's something we're going to have to get used to because one way or another, we're all going to be paying for it.         

Martyn1981

I think this idea / article ticks a lot of boxes regarding this discussion, it even mentions the idea of changing the green levy on leccy to help address the cost comparison v's gas. Obviously mentions insulation and housing standards, and the hope that costs will fall, if installs rise.

Poorer households in UK should get free heat pumps, say experts

Households on low incomes should be supplied with free heat pumps in order to kickstart the market for low-carbon heating equipment and meet the UK’s climate targets, experts have told the government.

Heat pumps can currently cost thousands of pounds to install, but the more that are installed, the faster that cost is likely to come down. They are widely regarded as the best way to replace the UK’s gas boilers and reduce carbon dioxide emissions from homes.

More than 20 organisations representing builders and construction businesses, energy companies and civil society groups have signed an open letter calling for a “fair heat deal” that would ensure people on low incomes can gain access to heat pumps.

About 14% of the UK’s greenhouse gas emissions come from heating the UK’s poor housing stock, most of which is also draughty and energy inefficient. The group also called for insulation to be made available to people on low incomes.

The letter also called on ministers to remove environmental levies from energy bills, to ensure it is always cheaper to run a heat pump than a boiler, and for grants to all households not on low incomes, to ensure that the cost of a new heat pump is competitive with the cost of installing a new gas boiler.

The signatories also called for the removal of VAT on green home products and servicers, and for changes to stamp duty to reduce the cost of homes that have been fitted with low-carbon technology.