The growing demand for electricity and the increasing size of the carbon footprint of data centers worldwide bring a severe challenge to sustainable development of human civilization. The cooling energy consumption takes up around 30–50% of the total consumption of data centers due to the inefficient cooling system. Free cooling is an effective solution for reducing the power consumption of cooling systems. 

Scientists of TIPC,CAS reviewed the advancements of data center free cooling mainly focusing on configuration features and performances. Three kinds of free cooling methods, airside free cooling, waterside free cooling and heat pipe free cooling are discussed and performance characteristics of each are analyzed. Further, the criteria of performance evaluation for free cooling of data centers are summarized, and an overview of free cooling systems based on these criteria is demonstrated in order to help researchers acquire the latest developments in this area.

Renewable and Sustainable Energy Reviews, 2014

Example of data center energy split 

ASHARE environmental classes for data centers