Overview of direct air free cooling and thermal energy storage potential energy savings in data centres

• The total annual hours for direct air free cooling in data centres are calculated.
• The potential of TES integration in data centres is evaluated.
• The implementation of TES to store the ambient air cold is not recommended.
• TES is feasible if combined with redundant chillers and off-peak electricity price.
• The cooling electricity cost is being reduced up to 51%, depending on the location.

In the last years the total energy demand of data centres has experienced a dramatic increase which is expected to continue. This is why data centres industry and researchers are working on implementing energy efficiency measures and integrating renewable energy to overcome energy dependence and to reduce operational costs and CO2 emissions. The cooling system of these unique infrastructures can account for 40% of the total energy consumption. To reduce the energy consumption, free cooling strategies are used more and more, but so far there has been little research about the potential of thermal energy storage (TES) solutions to match energy demand and energy availability. Hence, this work intends to provide an overview of the potential of the integration of direct air free cooling strategy and TES systems into data centres located at different European locations. For each location, the benefit of using direct air free cooling is evaluated energetically and economically for a data centre of 1250 kW. The use of direct air free cooling is shown to be feasible. This does not apply the TES systems by itself. But when using TES in combination with an off-peak electricity tariff the operational cooling cost can be drastically reduced.