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Solar PV production versus heat pump consumption

Air Source Heat Pumps (ASHPs)

Last Post by Derek M 5 years ago

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Mars

(@editor)

Illustrious Member Admin

Joined: 6 years ago

Posts: 4918

Topic starter 13/11/2021 11:02 pm [#162]

For those that have solar PV and heat pumps, let’s compare our heat pump consumption versus solar PV production. I know solar PV can’t fully offset heat pump consumption (unless you’ve got batteries) but it’ll be very interesting to see comparisons.

Please state your heat pump size and solar PV array size and where you are roughly in the UK. I’ll get the ball rolling with our October 2021 numbers:

18kW Caernarfon Global Energy Systems air source heat pump: 523kWh (11.32C average temperature)

6.16kW solar PV array (west midland, Welsh borders): 373kWh

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Derek M

(@derek-m)

Illustrious Member Member

Joined: 6 years ago

Posts: 4425

14/11/2021 12:15 am

Posted by: @editor

For those that have solar PV and heat pumps, let’s compare our heat pump consumption versus solar PV production. I know solar PV can’t fully offset heat pump consumption (unless you’ve got batteries) but it’ll be very interesting to see comparisons.

Please state your heat pump size and solar PV array size and where you are roughly in the UK. I’ll get the ball rolling with our October 2021 numbers:

18kW Caernarfon Global Energy Systems air source heat pump: 523kWh (11.32C average temperature)

6.16kW solar PV array (west midland, Welsh borders): 373kWh

Hi Mars,

Whilst comparison data is always useful to have, I can see a slight problem with comparing just ASHP consumption with just solar PV generation. Some of the solar PV production will have been used within the home, so unless this can be quantified it would be difficult to assess how much solar PV was actually used to power your ASHP. There could be times when your solar PV system is providing more energy than required by your ASHP, so this excess may be used elsewhere. There will also be times when your ASHP is starting and stopping, so using all available excess solar PV energy when running, but then using very little of the excess when it is stopped. You could have a situation where your ASHP uses say 5kWh of energy in a 1 hour period, and your solar PV system generates 5kWh of excess energy over the same 1 hour period. But if your ASHP only ran for 30 minutes during that 1 hour period, then it will only have been able to utilise 2.5kWh of the available solar energy.

The other problem is that ASHP comparison does not work well with average ambient air temperature measurements, since the performance of ASHP's is greatly affected by changes in ambient air temperature, but not in a linear manner.

👍

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Mars

(@editor)

Illustrious Member Admin

Joined: 6 years ago

Posts: 4918

Topic starter 14/11/2021 11:05 am

@derek-m, I know it's far from ideal, but if anyone wants to share their consumption of heat pumps and power generation from solar PV arrays, it'll still act as a metric for consumption and generation if nothing else.

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Derek M

(@derek-m)

Illustrious Member Member

Joined: 6 years ago

Posts: 4425

14/11/2021 2:00 pm

Posted by: @editor

@derek-m, I know it's far from ideal, but if anyone wants to share their consumption of heat pumps and power generation from solar PV arrays, it'll still act as a metric for consumption and generation if nothing else.

Hi Mars,

I fully agree, it would be useful to see lots of data, good and bad, so that members can make a realistic assessment of how their particular system is performing. I'm afraid it is the Engineer in me, that was trained to make the end user aware of the limitations of any measurement taken or data collected.

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