Radiative free cooling for energy and water saving in data centers

Data centers consume large amounts of electricity and water specifically for cooling purposes. Integrating free cooling technologies is an essential part of broad efforts to reduce data centers' energy, carbon, and water footprints. Adding a new technique to the existing portfolio of free cooling technologies for data centers, we present how all-day passive radiative cooling can reduce energy and water consumptions of data centers. All-day passive radiative cooling is a free cooling technique, in which sky-facing surfaces with high solar reflectivity and midinfrared emissivity spontaneously reject heat into the sky, without consuming electricity and evaporating water. Using custom-built physics-based models, we simulate three configurations that integrate all-day radiative free cooling into data centers. We show that data center cooling energy and water consumptions differ substantially depending on the integration configuration. Particularly, direct free cooling of data center return air gives the highest energy saving with an annual average of around 20.0% under the tropical climate of Singapore which hosts a large number of data centers, whereas free cooling of compressed refrigerant prior to the chiller condenser gives the highest water saving with an annual average of around 84.0%. These results offer multiple viable options for integrating radiative free cooling into data center cooling systems to simultaneously achieve water and energy savings.