AIR CONDITIONING, COOLING & VENTILATION Achieving sustainability in data centres
Data centres play a significant role in an increasingly digital world, and their energy consumption does have a substantial carbon footprint. By implementing innovative solutions and embracing sustainable practices, data centres can contribute to a greener digital future, writes Bradley Stone, data centre vertical manager UK & Ireland, Carrier
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he energy consumption required by data centres is primarily driven by the need to power and cool the number of servers and other infrastructure required to store, process and transmit data. These facilities have never faced greater scrutiny regarding efficiency, availability and flexibility. Data centres account for 1% of the world’s electricity consumption and 0.5%of carbon dioxide emissions. Computing hardware gives off vast amounts of heat, and requires specific conditions to operate safely and efficiently. Keeping an
ambient temperature is crucial to the smooth- running of a data centre. HVAC systems consume 30 to 40%of the overall energy in a data centre facility. Although HVAC systems are the largest single category in energy usage, efforts are continuously being made to improve their energy efficiency. As the data centre industry grows, and as climate change sees temperatures rising across the globe, more sustainable operations are needed. To achieve this goal, data centres need lifecycle solutions for complete data centre optimisation.
There are four key elements to data centre decarbonisation with HVAC systems:
• Enhancing energy efficiency and optimising free cooling
• Repurposing waste heat • Water consumption • Refrigerant technology
Enhancing energy efficiency
Data centre operators are adopting several measures to enhance energy efficiency. One such approach is the use of hot aisle/cold aisle containment systems. By segregating hot and cold airflows and preventing mixing, these systems enable more precise cooling, reducing the workload on HVAC systems. Advanced monitoring and control systems
are also being employed to fine-tune HVAC operations. Machine learning algorithms and artificial intelligence can analyse vast amounts of data in real-time, allowing for dynamic adjustments to cooling requirements based on workload and environmental conditions. These intelligent systems optimise energy usage, maximising efficiency without compromising performance.
Free cooling
With lower ambient temperatures – those that are lower than the water temperature set point – free cooling and be used in lieu of mechanical cooling. It involves using the cooler outside air to directly cool the water or other heat transfer fluid in a cooling system. This can be achieved through various methods, such as air-side economizers, evaporative cooling or heat exchangers. Free cooling can provide cooling capacities that exceed the requirements of the design, allowing for optimization of multiple chillers. Multiple chillers can be operated in parallel or independently, depending on the cooling load, to further enhance efficiency and flexibility.
6 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2023
As an example, Carrier’s AquaForce® 30XF air-cooled screw chiller for data centres operate between 100% hydronic free cooling, hybrid (free/mechanical) cooling and 100% mechanical cooling to maximise the efficiency of the system. Data centres are also being situated underwater as a way of reducing the amount of mechanical cooling. Submerged data centres take advantage of the natural cooling properties of water to dissipate the heat generated by the servers.
Re-purposing heat
Data centres have the potential to be more than just power-hungry facilities. They can contribute to energy efficiency and sustainability efforts by leveraging their excess heat. Traditionally, heat has been discharged into the air. The heat from data centre cooling systems can be used for heating nearby buildings, homes, public building spaces and even swimming pools.
The heat generated by the data centre is being used to heat a public pool in South West England’s Devon. The computers are surrounded by oil to capture their heat, which is pumped through a heat exchanger which warms the Exmouth Leisure Centre pool to 30oC, 60% of the time. Building data centres in cooler regions like the Nordics, is another approach for taking advantage of free cooling. The lower ambient temperature in this region reduces the need for excessive cooling and saves energy. Nordic data centres also use heat pumps to
recover heat. The excess heat provides power to thousands of nearby homes and generates hot water for district heating systems. This solution helps to reduce overall energy demand and the carbon footprint in the region. Servers have also been stored in caves beneath a cathedral in Helsinki, with water warmed, while cooling the servers providing heat for hundreds of homes. Carrier’s AquaForce® 61XWHZE high-temperature water source screw heat pump, which has a low GWP R1234z refrigerant, covers heating capabilities from 300kW to 1600kW and can re-use data centre heat to generate up to 85oC hot water for district heating systems.
Water
Water is a precious resource for data centres, especially those with water-based cooling systems. Cooling towers and chilled-water systems are common in large-scale data
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