COST MODEL | DATA CENTRE COOLING Cost model Data centre cooling In this months cost model, Aecoms engineering services cost-management team explores the options for cooling large data centres from traditional air cooling with chiller and Crac units, to free cooling and water-based systems C ooling of data centres has evolved from cooling small clusters of servers to giant server farms. While these modern large data centres are vital components of the information services economy, they consume a formidable amount of energy worldwide. Its been widely documented that the cooling systems the chiller, humidifier and computer room air conditioning (Crac) units account for 45% of the total energy consumption of a data centre, while the IT equipment accounts for 30%. This means that 1kWh consumed by the IT equipment requires another 1kWh of energy to drive the cooling and auxiliary systems. From environmental and cost-efficiency perspectives, selecting a cooling method that can reduce this energy demand is clearly beneficial. Traditionally, data centres have been air cooled with chillers, humidifiers and Crac units, in a variety of cold aisle/hot aisle approaches that arent terribly efficient and that can result in hot spots within the data hall. Over the years, server equipment has become more resilient and can now tolerate a greater range in temperature and humidity levels than older technology allowed. These days, legitimate alternatives to cooling are routinely considered in most data centre projects looking for greener and more efficient strategies. Currently, in the northern hemisphere, aircooling solutions are looking more towards free cooling, which works by using air from outside combined with reclaimed heat (winter) and evaporative cooling (summer) to provide the total cooling solution throughout the year. Water-based cooling options are a more modern approach, and cool the inside of the servers by pumping cold water through pipes or plates. Water-cooled rack systems work well, but have an inherent risk of leaks. Understanding the cost drivers and benefits of each are crucial to advising clients effectively. There are many factors that drive the selection of any particular option, not least capital and life-cycle costs, but also the location of the data centre and the feasibility of incorporating innovations such as free cooling or aquifer thermal energy storage (ATES). Parameters that drive these decisions include the requirement for power usage efficiency (PUE) levels to hit planning stipulations, and for acoustics and total cost of ownership (TCO) levels to be optimised. Chiller C r a c R a c k s R a c k s C r a c Air cooling by chiller and Crac units 68 November 2019 www.cibsejournal.com CIBSE Nov19 pp68-70 Cost Model.indd 68 25/10/2019 15:55