DATA CENTRE MANAGEMENT In the loop – recovering waste heat in data centres


Data centres generate a significant amount of waste heat. Tim Mitchell explains how this can be captured by water-cooled systems or air-to-water heat exchangers and transferred to an ‘ambient loop’, which distributes it within a local network.


Tim Mitchell www.klima-therm.co.uk


Sales director for Klima-Therm


T


he data centre sector is booming. There were 10,978 or so worldwide locations noted in December 2023,


but this rocketed to a whopping 11,800 just three months later. The dramatic expansion in the number of data centres has brought with it a corresponding growth in power requirements. International management


consultancy giant Boston Consulting Group reckons global demand for data centre power will grow at around 16% on a compound annual basis from 2023 to 2028 – 33% faster growth than from 2020 to 2023 – and forecasts it will reach an eye-watering 130GW by 2028. As data centres swell in both size and


number, their energy consumption and environmental impact have become increasingly pressing concerns. That’s why, in an era where sustainable practices are a priority, the concept of ‘ambient loops’ has emerged as a promising solution to enhance energy efficiency within these facilities. Ambient loops offer a classic


win-win. By optimising cooling and heating processes, they not only cut operational costs but also contribute to more ecologically friendly data centre operations. However, these are not the only benefits of ambient loops; they also offer an innovative method for capturing and reusing excess heat from data centres.


Ambient loops are essentially piping


networks that circulate a heat transfer fluid – typically water – around a local area, whether that be through storeys of a single building, or around a number of buildings in a development or locality. They operate at relatively low temperatures (usually between 10°C and 30°C), making them compatible with various heat sources and ‘sinks’. Ambient loops are often used with heat pumps to raise the local delivery temperature to useful levels. But how? Since heat pumps extract heat from one place and transfer it to another, they can move and amplify the heat from the ambient loop to provide the required heat for a building. Of course, the reverse is also true: they can remove heat from the building and transfer it into the ambient loop, thereby cooling the building. In short, the ambient loop circulates


water at a moderate temperature. The heat pump then extracts this low- grade heat and upgrades it to a usable temperature for space heating or hot


water. This is highly efficient because the loop operates at a low temperature, so heat losses are minimised. The heat pumps then efficiently boost the temperature, making the system cost- effective and sustainable. Ambient loops are often part of district heating and cooling systems where multiple buildings share the same loop. In this case, each building’s heat pump individually adjusts the temperature as needed. But there are also other ways to harness the energy saving benefits of recycled heat in data centres to improve energy efficiency and reduce environmental impact. As well as the integration of excess


heat from servers into district heating systems, which can warm residential buildings, offices, leisure centres,


Heat recovery in London data centre project


There are various strategies for enhancing energy efficiency in data centres. One key approach is integrating energy efficient technologies and innovative solutions to optimise energy consumption and useful output, reducing operating costs in the process. Alternatively, relocating data


centres to the outskirts of urban areas can help balance the cooling demand of the facilities with environmental concerns. Smaller, local data centres offer


significant energy-saving potential. Instead of rejecting and wasting the heat generated, it can be used for local district heating systems or to


EIBI | MAY 2025


hospitals or greenhouses in colder climates, on-site heating can also be covered. In this case, heat generated from data centre servers is used directly to heat office spaces or other parts of the same facility, reducing the need for separate heating systems. Alternatively, in some cases where


high temperature heat is recovered, that heat can be transformed into cooling to improve energy utilisation by using waste heat to drive absorption chillers that cool the data centre itself or nearby buildings. In short, the waste heat from data centres can be picked up by a liquid cooling system or air- to-water heat exchanger, and fed into the ambient loop. The ambient loop transfers this heat to an absorption chiller, often located in the same facility or nearby. ■


‘smart cities’ concept, where the by-product of one process is used to perform another job. Combinations of four-pipe and


Rhoss EXP heat pumps provide a heating and cooling solution in Tower H amlets


serve neighbouring properties. This concept is exemplified by a


project completed by Klima-Therm in Tower Hamlets, London. Here, planning


conditions required the installation of a heat recovery loop to serve a residential development adjacent to the data centre. This aligns with the


six-pipe Rhoss EXP heat pumps and ‘booster’ machines can be used to manage the temperature of the water in the heat recovery loop and deliver it to local systems on demand. These provide simultaneous and independent cooling and heating from the same plant. This means that a cooling system can easily become a complete cooling and heating solution, even including domestic hot water production.


By obtaining a double output from a single unit with a single expense, these heat pumps optimise energy efficiency and reduce costs.


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