Data centres and the future of low carbon heat in the UK

Data centres are essential in a world where we rely on a substantial flow of information for almost every part of our lives, including commerce, government, education and even entertainment. But they are significant energy users, and their impact on the global energy supply and the environment is a major challenge. In fact, increasing regulation has slowed or halted some data centre development – the Dutch government banned new hyperscale projects for 9 months, and the Irish government has introduced policies to scrutinize data centres more closely. 

All of this means that decarbonising these spaces is a top priority for the country to reach net zero by 2050.

What’s more, data centre users are increasingly concerned with their carbon footprint. This has created increasing pressure for data centre developers and operators to provide robust, fault-free services while reducing energy use and emissions – a difficult balancing act.

Thankfully, solutions already exist that are able to make data centres more energy efficient and minimise their impact on the environment, including adopting a more sustainable way to generate and use heat.

Reusing heat from data centres

One way that data centres can cut the carbon impact of heat is by reusing it. There has been a great deal of focus on using cooling technologies that meet energy-reduction targets, but shifting the focus onto the reuse of heat energy actually gives data centres the potential to decarbonise further and build a greener future. In fact, excess heat from data centres can be used to heat other nearby buildings – including homes – and provide them a more sustainable heating source. 

A great example of this in action is taking place in Germany. The new German Energy Efficiency Act has made the reuse of ‘waste’ heat a requirement, and data centres in particular will have to achieve 10% heat reuse from 2026, and 20% by 2028.

Several approaches to heat recovery can be applied, depending on a data centre’s heat output and location. One heat recovery model is district heating and cooling as a service: a heat pump recycles the water from the district heat network to cool the data centre. The waste heat from the cooling activity is then collected by the heat pump and pushed to the city network. The reheated hot water from the data centre mixes with the water in the general heat network, increasing the return temperature. Overall, energy consumption across the whole heat network is reduced, and so are energy costs and carbon footprint.

Many leading data centre developers and owners are embracing the benefits of heat reuse. For example, Amazon’s Tallaght data centre located in Dublin uses a system where heat generated by servers is transferred to an air-handling unit and then recycled to warm water. The water is then directed to an energy centre outside the warehouse, where heat pumps further increase the water temperature. This innovative approach not only results in an estimated annual reduction of 1500 tons of carbon dioxide emissions but also provides heating for over 505,000 square feet of local public buildings, 32,800 square feet of commercial buildings, and 133 apartments.

Heat pumps and heat networks to improve energy efficiency in data centres

Embracing technology like heat pumps and heat networks is also critical for reducing the carbon footprint of data centres, and providing heating and hot water more efficiently. 

Heat pumps are particularly useful for making the most of waste heat. Data centre output heat is around 30oC to 35oC. Heat pumps can use water at this temperature as a heat source, topping up the temperature to 70oC or even 80oC. This heat energy can be used in the data centre (or nearby buildings) to meet domestic hot water (DHW) demand in washrooms and showers, for example. 

Alternatively, it can be used on a wider scale in heat networks connected to buildings and homes located further from the data centre. Households can then be provided with heat and hot water via a large network of pipes. The Climate Change Committee (CCC) estimates that 18% of UK heat could come from heat networks by 2050 (up from 2% today).

Making the right choices for heat reuse

When considering heat reuse as an option for a data centre, there are a number of considerations to make from the earliest stages of design and specification. When looking at linking the data centre to a new or existing heat network, the first step is to ensure that there is an outlet for the waste heat a reasonable distance from the data centre – or that there is an existing heat network that can use extra capacity – through heat mapping.

It is then vital to understand what the cooling demand of the data centre is across the year, and to size and specify cooling equipment. The ideal solution is a water-to-water heat pump, or a heat pump chiller. The heat output of the heat pump can then be calculated to establish the annual heat output profile.

A successful match of data centre heat output and local heating requirements is what designers will look for when setting out these projects. Buildings that are close to the data centre, such as nearby offices or public buildings, may not have high heat requirements. However, heat networks which supply domestic customers have higher and more predictable heat demand profiles. Buildings such as hospitals, schools and leisure centres are also sources of heat demand that must be considered.

Energy efficient data centres will lead the way to net zero

There is huge potential for data centres to adopt heat recovery solutions and become part of the UK’s drive to decarbonise heating. Approaches like district heating and cooling allow society to reuse the excess heat from data centres using a heat pump. This kind of process not only enhances energy efficiency in data centres but also contributes to providing neighbourhoods with heat and hot water in a more sustainable way.

As such, framing the data centre sector as part of the solution for our decarbonised future, rather than simply an energy user, has clear benefits for future development and growth.