HEAT PUMPS
Heat pumps >50kW for commercial climate control
Here, Cliff Jones, head of applied at Daikin, looks at how heat pump technology can be used to meet the climate control needs of commercial buildings and outlines some of the key considerations.
For buildings with more complex heating
and cooling requirements, there are ‘four pipe’ multipurpose heat pump units that can achieve heating, cooling or a mixture of both taking advantage of heat recovery.
I
t is clear that to decarbonise the heating and cooling of buildings will require a change in the systems and technologies used, with heat pumps off ering major opportunities to lower the environmental impact, especially as the electrical grid itself is decarbonised. There are broadly two types of heat pump. Air-based systems, also known as air-source heat pumps (ASHP), draw heat directly from ambient air via a heat exchanger. Water-based systems can be divided again into two: water source heat pumps (WSHP) that harvest heat from surface water, such as lakes, rivers and seawater, and ground source heat pumps (GSHP) that utilise heat from the soil or groundwater.
Selecting the right heat pump system There is no one-size-fi ts-all commercial solution and it will often
depend on what needs to be achieved. WSHP or GSHP systems deliver more consistent performance throughout the year as ground and water temperatures remain much more stable than air temperatures across the seasons. The UK market is, however, predominantly ASHP systems as there is not always a suitable water source or the correct geology near the building, meaning WSHP or GSHP are not applicable for many projects. The requirements of the building are also a factor. Most commercial heat pump systems will be able to fulfi l space heating requirements relatively easily, especially for buildings where a lower temperature heating system, such as underfl oor heating, is installed. Achieving the higher temperatures of above 70ºC for domestic hot water (DHW) generation has been more challenging for heat pump systems originally designed for HVAC. However, with the move towards lower GWP and natural refrigerants coupled with products in heat pump technology there are now ASHP products, such as Daikin’s new CZ-HT high temperature heat pump, that can directly achieve domestic hot water of 70ºC across the UK ambient range. For commercial projects that have comfort cooling
requirements, heat pumps can deliver this as the refrigerant cycle can be reversed for cooling. This is one of the key benefi ts of heat pumps over conventional heating systems. For buildings with more complex heating and cooling requirements, there are ‘four pipe’ multipurpose heat pump units that can achieve heating, cooling or a mixture of both taking advantage of heat recovery. These multipurpose 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. Often a mix of diff erent types of heat pumps will result in
14 November 2024 •
www.acr-news.com
the most effi cient solution. A combination of ASHP in cascade with a WSHP as a booster to cover the domestic hot water allows the comfort elements of a project to be run at lower more effi cient temperatures and only the required DHW demand to be covered at higher temperatures.
Key design considerations To ensure that the selected heat pump system can be
successfully integrated into a new or existing building, there are several factors that must be considered. Energy effi ciency: Due to the lower fl ow temperatures and
delta-T that heat pumps operate at, it is important to ensure that a ‘fabric fi rst’ approach is taken to maximise the thermal effi ciency of the building. The hydraulic design will also need to be evaluated to ensure it adequately covers the diff erent delta T’s and fl ow rates. Power demands: Utilising heat pumps instead of gas boilers
is an excellent way to reduce the use of fossil fuels, but they will increase the electrical demand for the building or development, which may have an impact on the electrical infrastructure and connection to the local electrical grid. Therefore, early engagement with the distribution network operator (DNO) is essential to ensure requirements can be met.
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