ASHP vs GSHP for Non-Domestic Building

Mona · 2021-12-16T11:33:43Z

Hi all Currently, I am working with a team that looks for decarbonization of a community centre in London. We need information about the real experience of installing heat pumps for a non-domestic building like the community centre and a comparison between ASHP and GSHP. As for the community centre, GSHP has been suggested but for the high capital cost of GSHP, ASHP as an alternative is under consideration. Our main concern is that ASHP would not be efficient in cold seasons and doesn’t meet the site requirement. We need to know about the real COP of ASHP in different temperatures especially in the range of -7 to 7 C degrees. Are provided COPs for ASHP by the manufacturer reliable especially in low temperatures? If not what percentage of that should be considered? I appreciate it if you share your thoughts and experiences which would be very helpful. Thanks

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Air Source Heat Pumps (ASHPs)

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Derek M

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18/12/2021 1:10 am

@mona

Hi Mona,

A further item to consider, that Rusty pointed out, is usage of the building. The reason I mention this is because heat pumps, in particular ASHP's, are much more efficient when operating at lower water flow temperatures, so are more of a 24/7 device rather than a fan heater. An alternative to GSHP's or Air to Water ASHP's is Air to Air ASHP's, which are basically air conditioners that can reverse and heat as well as cool. If A2A heat pumps are used in conjunction with a solar PV system, they can provide cooling on hot Summer days for negligible cost.

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Rusty

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18/12/2021 3:22 pm

Posted by: @derek-m

@mona

Hi Mona,

A further item to consider, that Rusty pointed out, is usage of the building. The reason I mention this is because heat pumps, in particular ASHP's, are much more efficient when operating at lower water flow temperatures, so are more of a 24/7 device rather than a fan heater. An alternative to GSHP's or Air to Water ASHP's is Air to Air ASHP's, which are basically air conditioners that can reverse and heat as well as cool. If A2A heat pumps are used in conjunction with a solar PV system, they can provide cooling on hot Summer days for negligible cost.

@derek-m

Thats one of the things that I was thinking about, the amount of time the building is in use, presumably careful HP scheduling would help, or a bivalent (is that right, a supplementary heater for cold conditions?) system. I was also thinking of the accuracy of any heat loss calculations, particularly with regard to the amount of air exchanges, which could be higher in a more public building. I’m trying to do a heat loss calculation, and without good knowledge of the building fabric and other factors, it’s likely to be not that accurate using default values. Even then, what was intended to be built might not be what was actually built, with things like cold bridging and other poor building practices. Undersizing would obviously be bad, but considerable oversizing would also not be a good thing. I found a government report from a few years ago that looked at HP performance in regard to the initial MCS heat loss estimates, that indicated large differences positive and negative, though based on earlier MCS standards which have probably been improved. This is probably a discussion for another thread though.

I also found this, which may help @mona:

CSE.ORG.UK "https://www.cse.org.uk/downloads/reports-and-publications/renewables/building-performance/symes-ave-study.pdf"

Quite old, but some useful information. Might be worth @mona investigating this organisation also. There is a wealth of information out there on the Internet, you just need to dig around (with care).

Apologies, Woolfardisworthy is also known as Woolsery, which I should have got right.

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Mona

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Topic starter 25/01/2022 6:35 pm

Hi all

I would like to thank you all for the helpful information provided above.

The feasibility study has been completed for the building, and the choice has to be between ASHP and GSHP. Apart from capital cost and SCOPs, I am also interested in knowing about the lifespan of the two options.

In an interview with Graham Hendra, he stated that HP ( which I believe is ASHP) will last reasonably for 10-15 years. Also, in GSHP Association, it has been mentioned that the ground heat exchanger, the more expensive part of a GSHP installation, should have a life of over 100 years.