This technology has been used for decades to cool mainframes and supercomputers, and more recently, gaming PCs. However, it has only gained popularity in recent years as a means of cooling high-density data centers, with applications ranging from scientific computing to Bitcoin mining.
 Liquid cooling refers to products that remove heat directly at the chip or server level, either by immersing an entire server in a liquid coolant or by placing a heat exchanger on or next to the chip inside the server, called Direct-to-Chip (D2C) cooling. Major immersion cooling providers include Green Revolution Cooling, Icetope, and LiquidCool. A few companies that specialize in direct-to-chip heat removal are Asetek, Chilldyne, and CoolIT.
 The real benefit of liquid cooling is the technology's ability to dramatically reduce electricity costs, by almost half in some cases. Liquid cooling occurs at the chip/server level, meaning it's physically closer to the heat source. The closer heat rejection occurs to a heat source, the more efficient the heat removal. No other heat removal method can get that close. Moreover, liquid is a significantly better heat transfer medium than air. Liquid cooling is the only method for cooling data centers that completely avoids air in the heat removal process.
 However, these electricity savings don't come cheap. Liquid cooling products cost considerably more than other cooling solutions. While it's difficult to make exact comparisons, IHS finds that the initial investment can be five times the cost of a traditional chilled water solution. This initial cost serves as a significant deterrent to purchase. In addition, the fear of water near electronics is a widespread concern. However, educational and case studies can help reduce this aversion. Other obstacles to wider adoption include the maintenance of IT equipment, the requirement for special support infrastructure, and the need for server modification in some situations.
 The extremely small current market penetration indicates that the perceived drawbacks still outweigh the potential for increased efficiency for most major data centers. However, there is a growing number of high-performance computing data centers, with rack densities in the 15-kilowatt range or higher, that find the electricity savings worth the investment and tend to be more comfortable with radical technologies. These are the applications that will drive growth in the near term and result in a market size that will double between 2013 and 2015.

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