IBM will license its technology for cooling servers with water instead of air to Panduit, a global networking and electrical manufacturer, hoping to encourage adoption of IBM energy-saving techniques for data centers.Panduit will license IBM\u2019s Rear Door Heat eXchanger, a 5-inch-deep cooling door that mounts on the back of a conventional server rack. Water courses through the door, cooling the processors in the server hardware. IBM\u2019s water-cooled system reduces server heat output in data centers by up to 55 percent, compared to air-cooled technology, says Tom Bradicich, chief technology officer for IBM\u2019s BladeCenter and System x server product lines.The heat exchanger is part of IBM\u2019s CoolBlue portfolio of products aimed at slicing data center energy costs.Data center operators have been slow to embrace the idea: "It\u2019s difficult to do water cooling inexpensively," Bradicich says. But in the past 18 months, the number of servers used in data centers "has been getting extremely out of hand," he says. As electricity bills for cooling grow, water-cooled solutions become more viable.Some CIOs now give water cooling a closer look, though they still have some reservations, says Michael Bell, a Gartner analyst.Water cooling can be initially more expensive to introduce into a data center than air cooling, and IT managers worry about water systems leaking and causing damage, Bell says. Some CIOs are sticking their toes in the water cautiously\u2014clustering their highest-powered servers into one part of the data center and introducing water-cooled technology only in that area.As power bills grow, Bell says, water usage will rise.Hewlett-Packard introduced a water-based cooling system for its high-density servers in January. Also, blade server maker Egenera introduced CoolFrame, which integrates Liebert\u2019s X-Treme Density cooling technology into a blade architecture. American Power Conversion also makes data center cooling systems using water.