Free air cooling

Improving point 4:

Reduce electricity consumption for cooling by increasing free air cooling

In principle, data centres can be cooled directly with ambient air. Particularly in countries with temperate climate conditions this is not a problem.

                                                                           (Bron: The Green Grid)

In Dutch climate conditions, 97% of the time sufficient cooling can be achieved with a supply temperature of 24°C using ambient air.

There is, however, much resistance to direct cooling with ambient air. Most objections relate to risks associated with dust, air pollution and air humidity. This is why a barrier medium is needed. This is usually a water system with air/water heat exchangers. In order to achieve the largest share of free air cooling it is important to keep the conversion losses of the heat exchangers as low as possible. This means investing in sufficient heat exchange surface. Free air cooling is not a new concept, it has been in use for years already, achieving about 30% of cooling.



Aquifer Thermal Energy Storage (ATES) is another way to realise 100% renewable energy exchange. This system pumps cold groundwater from a well sank in deep layers of sand (an aquifer) to cool the data centre. The now warm water is injected back into the aquifer at a (hot) well at an appropriate distance. In winter the warm water is pumped back up, chilled by external air, and returned to the cold well. On an annual basis, the ATES energy balance must be neutral, to ensure uninterrupted long term cooling and to meet environmental requirements. Another option is to use the heat for sustainable heating of neighbouring buildings. ATES is a proven technology and applied widely in heating and air-conditioning systems for offices and industries.

                                                                   Direct air cooling (Source: Stulz)