The UK has made little progress in reducing the carbon intensity of heat, which accounts for around one third of CO2 emissions. Contrast this with the power sector, where emissions have fallen sharply and renewables provide around 40% of supply.
As rapid decarbonisation of the power grid continues, switching to electric heat pumps provides a lower carbon alternative to conventional fossil-fuelled heating systems.
Relative to a boiler burning natural gas, a heat pump can reduce overall greenhouse gas emissions by as much as 80%. Heat pumps are classified as a form of renewable heat by the Government via the Renewable Heat Incentive (RHI), which provides a pence per kWh support payment for 20 years.
The RHI has been extended until 31 March 2022 for certain schemes with a Tariff Guarantee, but new applications must be submitted by 31 March 2021. The Industrial Energy Transformation Fund is another funding opportunity, and applications to phase one close on 28 October 2020.
If powered by renewable electricity, heat pump emissions are zero. There are substantial cost and carbon emission savings from combining heat pumps with solar or combined heat and power.
How do heat pumps work?
Heat pumps extract natural warmth from the ground, air, water, or other source (even in winter) and use it for both space heating and hot water. This operates similar to an air conditioning unit running in reverse. This process will typically deliver between three and five units of heat for every one unit of electricity it uses. When configured to provide chilled water to supplement cooling, they can operate at a ratio of 5-9 units of heat /cooling per one unit of electricity.
The soon to be published UK Government heat white paper will provide urgent clarity on policy direction, but it is likely that electrified heat pumps will play a major role in the transition to net zero.
One of the key drivers is new build planning regulation. The proposed update to SAP (SAP10.1), which is scheduled for late 2020, will reduce the carbon factor of electricity by 75%.
Despite being a proven and mature technology, heat pumps currently only satisfy around 5% of global heat demand from buildings, but the market is growing rapidly. The International Energy Agency forecasts that, in the absence of a large build out of hydrogen infrastructure, over 50% of heating in Europe could be supplied by heat pumps in 2050.
Types of heat pump
Heat pumps can use a range of heat sources and operate through a wide range of temperatures from 40°C up to 130°C. They can be used in many applications and make use of any suitable heat sources that is available. Heat pumps can be categorised into four key types: air source; ground source; water source; and high temperature – for use in industry.
1. High Temperature heat pump High temperature heat pumps can be used in industry for high grade, high carbon intensity heat processes, such as drying, pre-heating and distillation. A waste heat interface recovers heat from site processes or CHP plant and supplies it to the heat pump, which then upgrades the heat to a higher temperature. This can be used in processes, to generate low pressure steam, or provide high temperature hot water.
2. Air Source heat pump Air Source heat pumps can supply temperatures up to 70°C and are the lowest cost technology from a CapEx and O&M perspective. The relatively simple and scalable solution can supply hot water to the site under most conditions. It is possible to use waste heat from chillers or waste water, where available, to increase system efficiency and improve payback.
3. Ground Source heat pump Ground source heat pumps can supply temperatures up to 70°C. Thermal boreholes provide the heat source, supplying a year-round reliable and predictable source of stable temperature heat. A waste heat interface can be used to recover heat from chillers or waste water, where available. The thermal boreholes can provide ‘free cooling’, which reduces chiller electricity demand.
4. Water Source heat pump There are many potential water sources, such as: a river; a lake or reservoir; waste water outlet, such as sewer offtake; or aquifer. The water source can be used to provide low cost ‘free’ cooling. CapEx costs are typically lower than for ground source and less physical land space is usually required.