One of the larger contributors to UK emissions is domestic power use for heating, hot water, etc taking 15% of UK emissions. The main fuel source for heating in the UK is gas with 63% of the total. The primary option for zero carbon emission heating (based on used zero carbon electricity) is an air source heat pump. Hydrogen may be an option in due course, but it will require a significant investment in renewable power as currently over 90% of hydrogen is produced using carbon sources.
So, Air Source heat pumps or Ground Source heat pumps are the main option for carbon free residential heating and hot water (if they use non carbon electricity). This is simple technology, outdoor ambient heat is transferred to a coolant using a heat exchanger coil, this coolant is compressed and the temperature increased, this heated coolant transfers heat to the hot water store through a heat exchanger coil. A “standard” domestic air source heat pump can extract useful heat down to about −15 °C (5 °F).
I had an air source heat pump installed earlier this year. The main difference from conventional central heating is that it operates at a lower background temperature throughout 24 hours a day. Its sophistication is that based on sensors outdoors that will adjust the temperature of the water in the system.
The controls of the Unit .
My calculations are that it is competitive with gas and four times as efficient as an electric boiler. The investment cost is higher than a gas boiler, but the maintenance costs lower. The costs are further reduced if electricity generated from residential solar is used.
The issue for the UK is that a conventional plumber’s training is not sufficient for installing and maintaining air source heat pumps. As a result, there may be logistical issues in installing the over 20 million systems that would be needed in the UK. Only 207,000 systems had been installed in the UK by 2018 so the rate of installation would have to increase dramatically. There are UK producers of air source heat pumps, but most pumps fitted in the UK are imported.
My experience of the air source heat pump is favourable. It is known technology capable of mass rollout. The take up to date is disappointing despite the Renewable Heat Incentive support. While new homes will have to fit non carbon heating from from 2025, the question is will consumers switch to this heating? Zero carbon is our choice as consumers – will we make that choice?
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