AIR SOURCE & GROUND SOURCE HEAT PUMPS
How weather compensation can work in harmony with heat pumps
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Neil Wooldridge, technical director at Toshiba Carrier UK, Carrier Global Comfort Solutions Europe, explains how weather compensation, working alongside heat pumps, can improve comfort and efficiency
he world is facing a challenge at the intersection of environmental sustainability and the demand for energy – how to satisfy the demand, while reducing greenhouse gas emissions. The pursuit of a sustainable future necessitates a delicate balance between reducing the environmental impact and meeting the rising energy needs of a dynamic and expanding global community.
In this era of heightened environmental awareness, the imperative to transition towards sustainable practices is more pronounced than ever, so it’s crucial to harness innovative solutions that not only combat climate change but also enhance the efficiency of our building energy systems. Weather compensation is a well-established concept in relation to traditional gas-fired heating systems as a means of better regulating output in response to changes in ambient conditions. The ability to avoid heating system lag-time in response to changes in external temperatures can improve comfort for building occupants and significantly reduce energy use. To date, this approach has not been widely applied in relation to DX air conditioning and heat pump-based solutions. Perhaps because of the inherent efficiency advantages of heat pumps, which can deliver Coefficients of Performance (COPs) many times those of even the most efficient gas boilers, the control strategies for the respective technologies have tended to evolve in different directions. For example, inverter controls on heat pumps enable accurate capacity control, enabling output to be precisely matched to load. This ability to modulate heating and cooling output offers a level of sophistication and control simply not possible with conventional gas heating. This, coupled with the ability of heat pumps to harness ‘free’ ambient energy from the environment, gives them a major efficiency advantage. With the challenge of decarbonisation now clearly in view, however, weather compensation may offer the potential to enhance the efficiency of heat pump systems even further, delivering even greater carbon savings, improved comfort and reduced running costs.
What is weather compensation?
The principles behind weather compensation are well established. It involves monitoring both outdoor and indoor temperatures to enable heating system output to be regulated in the most efficient way.1 By using external temperature sensors and advanced algorithms, the approach enables heating
systems to optimise their performance and energy consumption in real-time, as external conditions change. The performance of heat pumps can be influenced by weather conditions. Low ambient temperatures require heat pumps to work harder to extract low grade heat from the environment and sudden changes in ambient conditions require rapid response to maintain comfort within a building. This is where weather compensation technology may help, by enabling heat pumps to react more rapidly to changing ambient conditions. Applied in practice, information from the outdoor temperature sensor is fed to the heat pump’s controller. The controller uses this data in combination with information from building thermostats and adjusts the flow water temperature to the heating system accordingly.2 When the outside temperature changes, this allows the system to anticipate changes in load, effectively ‘compensating’ for changes in external conditions, and adjust output to maintain a stable and comfortable indoor environment. As a result of this dynamic response, people inside the building shouldn’t be aware the temperature outside has changed. With conventional control systems, system
regulation depends on room thermostats, which kick in some time after the exterior of the building has heated up or cooled down due to changes in ambient conditions. This lag time in response allows a thermal gradient to develop between the outside and inside of the building, which the HVAC system has to work hard to overcome. Correctly applied, weather compensation
reduces this lag time and enables the heating or cooling system to ‘get ahead of the curve’ by anticipating temperature changes in the building fabric, effectively smoothing the peaks and troughs in demand. This dynamic response ensures optimal comfort levels, while minimising energy consumption.
In addition to the use of external temperature sensors – either wired or wireless, weather compensation systems can harness real-time data from internet-based local
28 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MARCH 2024
weather tracking, giving further opportunities for refining control.3
What are the benefits of weather compensation?
Weather compensation allows heat pumps to run at the lowest possible temperature in relation to the outside temperature, while maintaining comfortable indoor conditions. This reduces the amount of energy used, saving money on running costs and reducing carbon emissions.4 With more than half of family energy bills accounted for by heating and hot water5, this could lead to significant savings in overall energy bills.
As we have seen, using weather
compensation in conjunction with heat pumps can also improve comfort by maintaining a more consistent, stable temperature inside the building. It also has the added benefit of reducing mechanical shocks on the system by enabling it to operate within a narrower band, rather than constantly switching between extremes of load during on-off cycling. This reduces the amount of wear and tear on the unit and extends its working life.
In essence, weather compensation achieves seamless integration with heat pumps by dynamically adjusting their performance in response to evolving ambient conditions. This not only enhances the already impressive energy efficiency of heat pumps but also improves overall comfort while contributing to a further reduction in carbon emissions.
1.
https://energy-test.co.uk/
boiler-plus-what-do-you-need-to-know- about-the- 2018-legislation/
2.
https://assets.publishing.service.gov.uk/ government/uploads/system/uploads/ attachment_data/file/648337/heating- controls-compensation-tpi-bre.pdf
3. Boiler-additional-guidance-BENCHMARK.pdf 4.
https://energysavingtrust.org.uk/advice/ thermostats-and-heating-controls/
5.
https://energysavingtrust.org.uk/energy- at-home/heating-your-home/
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