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I'm a air-to-air heat pump owner and I love it and think they will be a key part of climate mitigation. However, from a climate change policy perspective, it i
by RobinL 4y ago
I'm a air-to-air heat pump owner and I love it and think they will be a key part of climate mitigation.
However, from a climate change policy perspective, it is important to _emphasise_ that heat pumps are less efficient at lower temperatures (lower COP) and not try and pass this off as a myth. (I recognise this article is presenting the 'myth' as operating at a COP of < 1, but many people will misinterpret that)
To put this in perspective in the UK, in mild weather demand is something like:
- about 40GW total electricity demand
- about 100GW of gas
In mild weather, my heat pump gets a COP between about 3 and 4. Which means that, if we want to replace gas usage with heat pumps, we need a further 25-33GW of electricity to power the heat pumps.
This is eminently achievable. See here https://twitter.com/heatpolicyrich/status/1612385243251572738 https://twitter.com/heatpolicyrich/status/161238524325157273... and the latest edition of the economist quotes there being 260GW of wind projects in the pipeline for the North Sea (amongst 9 countries): https://www.economist.com/leaders/2023/01/05/why-the-gusty-north-sea-could-give-europe-an-industrial-edge https://www.economist.com/leaders/2023/01/05/why-the-gusty-n...
In extreme cold snaps, total gas demand doubles to about 200GW, and electricity goes up to maybe 60GW.
The problem is that now the heat pumps are getting a COP of maybe 2, if you're lucky.
So now in the UK we need 100GW of electricity to replace gas, which is a big ask even when the wind's blowing. At the moment, wind output peaks at about 21GW, though records are being broken all the time.
None of this is to say we shouldn't switch to heat pumps where possible. Mine was cheap to install (£1,895+vat) and has halved my gas usage. Must be one of the most cost effective way of mitigating the current gas crisis (after reducing usage!). I think it's just worth understanding some of the important numbers.
- nickspicer1993 4y agoAlso worth adding that in the UK new homes will not allowed to be built with boilers by 2025 and they will need to be slowly phased out in next decades so definitely invest in home insulation and a heat pump if your boiler is on the way out!
- RobinL 4y agoYes - good point. That touches on another myth I've heard frequently - that heat pumps are only suitable on well insulated homes. I think this may be true in relation to some air-to-water systems (?), but it ignores the possibility of just installing a cheap air-to-air system on top of existing heating (either gas or air-to-water). Air to air systems are really well suited to homes with a combined kitchen/living room which is the main room in use most of the day. We only heat the kitchen/living room during the day (our main living space), and the heat pump is more than adequate for this. It typically uses around 10kwh a day for quite a big, not very well insulated room.
- HPsquared 4y agoThe trouble is that the electricity demand is always topped-up by gas-fired generators. It's always there at the margin. Things like nuclear and renewables usually run at 100% of their ability, their generation is not affected by demand. Therefore any increase in electrical demand is made up by turning up the gas-fired generators an equal amount. So if a heat pump has a COP of 3, and the additional electricity consumed is generated from gas with, say, 33% efficiency (from the gas burner to the house electrical meter), there would be zero net change in overall gas consumption by converting from a gas boiler. This is especially the case in winter, which is when most heating demand is, and the gas generators are definitely going to be running and making up that marginal generation.
- iso1631 4y agoMy understanding from the Technology Connections youtube channel is a heatpump has a typical COP of about 3.5 and a gas power plant about 45% from plant to home, making it more efficient to use the gas to generate electricity to run the heat pump than to burn the gas directly for heat.
- mnw21cam 4y agoPlus you can also use the waste heat from the power plant to heat some more homes.
- nayuki 4y agoHe made several excellent videos explaining residential heat pumps: [2021-02-28] https://www.youtube.com/watch?v=7J52mDjZzto https://www.youtube.com/watch?v=7J52mDjZzto "Heat Pumps: the Future of Home Heating" (35m14s) [2021-04-01] https://www.youtube.com/watch?v=7zrx-b2sLUs https://www.youtube.com/watch?v=7zrx-b2sLUs "Ground Source / Geothermal Heat Pumps and Other Info" (28m03s) [2022-03-26] https://www.youtube.com/watch?v=MFEHFsO-XSI https://www.youtube.com/watch?v=MFEHFsO-XSI "Why Heat Pumps are Immensely Important Right Now" (21m02s) [2022-04-13] https://www.youtube.com/watch?v=43XKfuptnik https://www.youtube.com/watch?v=43XKfuptnik "Heat Pumps are Not Hard: Here's what it will take to start pumping" (46m32s)
- nickspicer1993 4y ago
- ClumsyPilot 4y ago> - about 40GW total electricity demand > - about 100GW of gas That gas demand should be 70% less, UK has the worst insulation in Europe. https://theenergyst.com/europes-leakiest-homes-new-study-fingers-britain-fails-to-plug-gaps/ https://theenergyst.com/europes-leakiest-homes-new-study-fin... There are countries where bombs fell, then communism fell, then bombs fell again, then their currency collapsed, and the houses are still better insulated.