Liquid cooling was once a staple of large-scale computing, but has increasingly been replaced by air cooling. Now, several companies are applying liquid cooling to standard servers to reduce energy. One, through a Swedish research initiative, is also seeking to recapture heat.

US company Green Revolution Cooling claims that "With our fluid-submersion technology, we can reduce cooling energy use by 90-95% while also reducing server power by 10-20%. Greenfield installation costs are significantly lower than comparable air-cooled systems and retrofit paybacks are as low as one year and typically below three years."

The company moved into waste heat recapture this summer with a test at Stockholm's Royal Institute of Technology (KTH). "[The installation] will reliably produce water up to 50°C (122°F) — hot enough to pump to surrounding buildings for building heat. Remarkably, this performance has been achieved with commodity servers and standard CPUs…As testing continues at KTH, researchers will strive to produce 70°C water, which could be used to produce hot tap water, a useful commodity all year long. And if 70°C is achieved, KTH will be able to recapture energy in addition to heat…we expect a full white paper by the end of the year."

There are still deployment hurdles for early adopters of submerged servers to overcome, but this is yet another example of how Green ICT is pushing innovation.

More about reuse of ICT waste heat: Swiss data center heats municipal swimming pool and Finnish data center provides district heating.