judgecorp writes "IBM has said that water-cooled servers could become the norm in ten years. The company has lately been promoting wider user of the forty-year-old mainframe technology (e.g., here's a piece from April 2008), which allows faster clock speeds and higher processing power. But IBM now says water cooling is greener and more efficient, because it delivers waste heat in a form that's easier to re-use. They estimate that water can be up to 4,000 times more effective in cooling computer systems than air. However, most new data center designs tend to take the opposite approach, running warmer, and using free-air cooling to expend less energy in the first place. For instance, Dutch engineer Imtech sees no need for water cooling in its new multi-story approach which reduces piping and saves waste."