Heat pumps - COP

waqasahmed

So I've seen from numerous places that the COP of ASHPs has got continually better ie: from a max COP of 2 or 2.5 a decade ago, to about 5 now. There's obviously seasonal variations

I've not however seen the same said about a GSHP. 

Is it because that ASHPs are merely catching up to GSHPs in terms of COP? Or is it that the COP of GSHPs has equally gone up? I mean the heat pump itself is surely more or less a very similar product 

Meatballs

From my very rough understanding:

The main improvement was changing to inverter based compressors which can modulate a lot better and don't require preheating (old ones had direct electric heating coils to get compressor up to temp).

Other improvements are due to the refrigerants, some of which have only recently entered the market. Newer ones have been developed which are better suited for the temperatures we want to achieve (but also have a lower GWP if released into the atmosphere).

I suspect GSHP have benefited similarly but it's a lot smaller market (and they already did a good job) and there's going to be much more focus on ASHP improvements as one of the main viable net zero routes for a lot of our housing stock.

Reed_Richards

The key thing about a Seasonal COP of a something-to-water heat pump is that it depends critically on what temperature you are heating your water to.  Throwing numbers around without the context of a target water temperature and a locale for the seasonal variation in outside temperature is meaningless.  Typically there will be one temperature used for heating your hot water and another temperature for your central heating (although this can be reduced in warmer weather) so a different SCOP for each.  I very much doubt that if you were comparing like target temperature with like temperature in the same locale the improvement in performance has been anywhere as large as your numbers suggest.      

Screwdriva

waqasahmed said:

Is it because that ASHPs are merely catching up to GSHPs in terms of COP? Or is it that the COP of GSHPs has equally gone up? I mean the heat pump itself is surely more or less a very similar product 

 The latest GSHP's deliver an incremental real world SCOP of upto 1 over the newest ASHPs. More importantly perhaps, this performance is more consistent in sub zero temperatures, when an ASHP's SCOP will drop. 

The cost difference is substantial, often 3X the cost of an ASHP.

Reed_Richards

Screwdriva said:
The latest GSHP's deliver an incremental real world SCOP of upto 1 over the newest ASHPs. More importantly perhaps, this performance is more consistent in sub zero temperatures, when an ASHP's SCOP will drop. 

The cost difference is substantial, often 3X the cost of an ASHP.

I think you are confusing COP with SCOP.  The latter, Seasonal Coefficient of Performance, is an average over the year whereas the COP is the instantaneous value.  So your reference to sub zero temperatures makes more sense in the context of the COP, unless you are talking about a place where the seasonal average temperatures are sub zero.

Contrariwise, an ASHP should achieve a better COP than a GSHP when the outside air temperature is higher than the ground temperature.  So for ultimate performance you would want a hybrid ASHP/GSHP that could take account of this.     

shinytop

waqasahmed said:

So I've seen from numerous places that the COP of ASHPs has got continually better ie: from a max COP of 2 or 2.5 a decade ago, to about 5 now. There's obviously seasonal variations

I've not however seen the same said about a GSHP. 

Is it because that ASHPs are merely catching up to GSHPs in terms of COP? Or is it that the COP of GSHPs has equally gone up? I mean the heat pump itself is surely more or less a very similar product 

An ASHP heating system will only achieve a COP of 5 in very favourable conditions and, for the majority of homes, not when heating is really needed.

The inherent COPs of ASHPs may have improved slightly over the years but it's nothing like the 2:1 or more you are suggesting.  The overall heating system design and the way it is run has a much greater effect.

GSHPs are irrelevant for most people due to their cost and space requirement.    

waqasahmed

shinytop said:

waqasahmed said:

So I've seen from numerous places that the COP of ASHPs has got continually better ie: from a max COP of 2 or 2.5 a decade ago, to about 5 now. There's obviously seasonal variations

I've not however seen the same said about a GSHP. 

Is it because that ASHPs are merely catching up to GSHPs in terms of COP? Or is it that the COP of GSHPs has equally gone up? I mean the heat pump itself is surely more or less a very similar product 

An ASHP heating system will only achieve a COP of 5 in very favourable conditions and, for the majority of homes, not when heating is really needed.

The inherent COPs of ASHPs may have improved slightly over the years but it's nothing like the 2:1 or more you are suggesting.  The overall heating system design and the way it is run has a much greater effect.

GSHPs are irrelevant for most people due to their cost and space requirement.    

Oh for sure that is absolutely in favourable conditions. I'm not suggesting otherwise 

I was also talking more in general terms vs in terms of whether something is feasible to put in. I'm sure why people don't discuss GSHPs that much in terms of how they might have improved, is probably for the reasons you've said but I did wonder if ASHPs have improved "alone" or whether GSHPs have improved at the same time 

Grandad2b

That's a great question and one I'd like to know the answer to.

UncleK

Just looking at our GSHP and for heating, for the year to date, it shows an SPF of 4.2.
Energy in of 5.5 MWh, heating out of 23.3 MWh. If that helps any?
Fairly new pump - installed in 2021.

waqasahmed

UncleK said:

Just looking at our GSHP and for heating, for the year to date, it shows an SPF of 4.2.
Energy in of 5.5 MWh, heating out of 23.3 MWh. If that helps any?
Fairly new pump - installed in 2021.

Apologies SPF? Also how come you got a GSHP instead of an ASHP? 

UncleK

Dunno - that's what I read from the panel on the pump. I assume it's something like Seasonal Power Factor. The manual isn't that clear (EcoForest/Nuenta) but on one screen has COP and PF both at the same value.