Cutting carbon without compromise
Heat pump technology has significant potential to meet the heating, cooling and hot water needs of occupants while achieving carbon reduction targets. Here, Matteo Dall’Ombra, Commercial Marketing Manager at Daikin, outlines the key considerations to ensure the correct system specification, taking into account refrigerant selection in line with the ongoing F Gas phase down.
To achieve decarbonisation of heating, cooling and hot water generation we need a change in mindset to embrace the low carbon technologies that are already widely available. One of the strongest solutions is heat pumps, which offer low carbon heating and cooling, which will only become lower carbon as the electricity grid is decarbonised.
There are a wide range of options on the market and like with any such system, ensuring the right system specification and design will ensure it meets the needs of occupants.
Type of heat pump
There are broadly three types of heat pump; air source (ASHP), water source (WSHP) and ground source heat pumps (GSHP), which all have different applications. For the vast majority of projects in the UK, ASHPs will be the most suitable. They are highly effective and can be installed on almost any type of building.
Importantly, they do not rely on the presence of a suitable water source or the correct geology close to the building as WSHPs and GSHPs do.
Heating and cooling demands
When specifying a heat pump system, it is essential to ensure that it can reliably meet the requirements of the building. Heat pumps can generally achieve the space heating requirements of most buildings provided the system is sized correctly. Similarly, on projects that have comfort cooling requirements, the refrigerant cycle on the heat pumps can be reversed to deliver cooling.
This is one of the key benefits of heat pumps over conventional heating systems. Achieving the higher temperatures of above 70ºC for domestic hot water (DHW) generation has traditionally been more challenging for heat pump systems. However, significant breakthroughs in heat pump technology have been made in recent years that enable this requirement to be met easily. Units such as the Daikin CZ-HT have been specifically engineered to directly achieve domestic hot water of 70ºC across the UK ambient temperature range. Previously, complex solutions were sometimes required to achieve the performance and energy efficiency required. With the innovations and technology now available, it is far simpler to design a system that perfectly fits the requirements of the project. This has been a focus of Daikin’s new product development process over recent years and is at the core of many of the solutions in our range.
For buildings with more complex heating and cooling requirements, there are ‘four pipe’ multi-purpose heat pumps that can deliver heating, cooling or a combination of the two by taking advantage of heat recovery. These multi-purpose heat pumps provide an advantage in the intermediate seasons to treat the fresh air load, traditionally covered by gas burners in the central air handling units.
Accounting for defrost derate
The outdoor coils on ASHPs operate at low temperatures to maximise the differential between ambient and refrigerant temperatures to deliver the heating required. This means that water vapour in the air may freeze on the coils, and this ice must be removed to maintain efficiency. This is achieved by periodically reversing the heat pump’s refrigerant cycle to deliver heat to the coil. This automated process generally reduces the heating capacity by around 15% and as a result will impact the water temperatures within the system. Therefore, it is important to ensure that the system is specified based on the ‘integrated capacity’ – the capacity during defrost – rather than the instantaneous capacity to deliver the required performance.
Solutions from leading suppliers include intelligent software andm processes to effectively manage this requirement with minimal impact. Additionally, if the system has multiple connected units, the defrost cycles can be sequenced so that only one circuit or unit is in defrost mode at a time to minimise the impact on the heating capacity.
Choosing the right refrigerant
Over the last decade, the industry has moved to lower Global Warming Potential (GWP)
refrigerants such as R-32 (GWP 675) to improve sustainability and comply with tightening standards and quotas introduced through the F Gas regulations. These will continue to tighten and require further shifts to even more sustainable options in the future.
For example, from January 2027 air-to-water systems between 12kW and 50kW must use a refrigerant with a GWP below 150 and smaller air-to-air split systems will have to comply with this limit from 2029. However, no such restrictions have yet been announced for larger systems, and it is unlikely that anything will be introduced before the 2030 review date. This means R-32 remains a suitable refrigerant for commercial systems for the foreseeable future. It is also worth noting that even if restrictions are introduced after the 2030 review, existing R-32 systems can still be maintained and repaired as normal.
However, for clients that are looking for greater sustainability now, there is a growing range of heat pump systems, such as Daikin’s CZ-HT, that use R-454C, which has a GWP of just 145.5 and is in the same A2L (mildly flammable) category as R-32.
Heat pumps are one of the leading technologies for decarbonisation of commercial heating, cooling and hot water generation, but the systems must be specified correctly to ensure they meet the needs of occupants.
Partnering with a leading supplier will help ensure the right solution applied to each project.
