Google has opened a new data center in Finland where all of the cooling is done with sea water rather than compressors and refrigerants. The building, which was originally built as a paper mill, is located on the Gulf of Finland and using cool sea water is a way to save money while keeping the building cooled with a readily available resource.
Cooling is one of the biggest expenses for data centers. Servers, especially when many of them are stacked close together, generate a great amount of heat, and that heat must be dissipated to keep the equipment running. The Google data center brings in sea water through granite tunnels and into heat exchangers where the water absorbs the heat to keep the equipment cool.
The heated water is further tempered with cool sea water in a separate building before it is returned to the ocean to minimize the impact the heated water might have on the natural environment.
(Source: www.ecogeek.org )