Large Scale installation of 742 Heat Pumps in UK Homes

Baxter100

I don't know if there has been a thread on this, but the government has subsidised the installation of 742 heat pumps in three separate regions in the UK - https://es.catapult.org.uk/news/electrification-of-heat-trial-finds-heat-pumps-suitable-for-all-housing-types/

As someone who is doubtful about large scale heat pump retrofit, I'll be keeping a very close eye on the monitoring results as and when they publish them to see how efficiently these installations actually. I'm expecting average COPs somewhere in the 1.8-2.2 region.

Somewhat bizarrely the project has already claimed that the mere installation of these heat pumps shows that they are suitable for all UK homes. It's a strange claim for sure, but given the investment that the government has in heat pumps we must expect a lot of spin! Like this for example from one of the case studies:

michaels

What scop is needed to use less gas overall if the electricity comes from ccgt gas power station? 

Baxter100

Based on a gas station being 35% efficient (and compared to a 90% efficient) gas boiler it would be somewhere around 3.

QrizB

Baxter100 said:

I don't know if there has been a thread on this, ...

There hasn't been a thread but it did get a mention and brief discussion.

See https://forums.moneysavingexpert.com/discussion/comment/78844243/#Comment_78844243

Baxter100 said:

I'm expecting average COPs somewhere in the 1.8-2.2 region.

Considering the equipment that was fitted and the level of manufacturer support, I would be very surprised if the average COP is below 2.5. We'll have to see what the results are.

michaels said:

What scop is needed to use less gas overall if the electricity comes from ccgt gas power station? 

According to this document the carbon intensity of a CCGT is around 400g/kWh. Direct burning of natural gas per this spreadsheet is around 204g/kWh, so when burned in a boiler at 90% efficient that becomes 227g/kWh. You would need a COP of 1.76 in order for a heat pump to match it.

However, the UK generates power from a range of sources. If https://electricinsights.co.uk is to be believed, over the past 12 months the average carbon intensity of the UK electricity grid has been 181g/kWh. Electric heating with a COP of ~0.8 would have resulted in fewer carbon emissions than a 90% gas boiler.

Even looking at the gloomiest bit of December, when wind and solar were poor and we were burning a comparatively large amount of coal, carbon emissions were only 300g/kWh. Under those circumstances you would need a COP of ~1.3 for electric heating to be greener than gas.

Martyn1981

Baxter100 said:

Based on a gas station being 35% efficient (and compared to a 90% efficient) gas boiler it would be somewhere around 3.

Hiya, I thought CCGT's (combined cycle gas turbines) were about 50% efficient, with 60% possible? The UK fleet is around 25-28GW in capacity.

Are you thinking of OCGT's (open cycle gas turbines) which can be little more than a jet engine with a driveshaft and are typically used as peakers to meet short term demand, and are around 35% (to 40%) efficient? I'm not sure what the UK fleet size is, as these are much smaller units, often deployed in just 50-100MW scale, and operated very little during the year. In fact batteries are now starting to displace some of the UK's peaker fleet for FFR (firm frequency response) and peaking roles.

So at 50% efficiency of gas generation, and ~10% losses, that gives 0.45kWh of leccy from 1kWh of gas, v's approx 0.9kWh(t) from a GCH boiler, so that would require a COP of approx 2, though it's far more complicated as QrizB explains better.