Liquid Cooling – It All Comes Flooding Back
A couple of years back, we heard that servers would be going to liquid cooling,. The idea seems to be resurfacing, says Peter Judge
When launching its new Xeon E5 range of processors this week, Intel made a lot of how efficient they are, saying that they cut the energy demands of servers by as much as 50 percent.
The server makers in the room all had plenty of tweaks and tips to cut energy use at the system level, including fans which are individually controlled. Cooling at full blast, a fan can use 75W, but can be cut down to 1W stand by if they are not needed.
Why not stop blowing air?
But what are those fans doing there? As 451 Research memorably described it, running a data centre and cooling it by air is like having a room full of electric heaters cooled by a battery of electric fans.
Air is not great for cooling. It takes energy to move it around and it is so thin, that it can’t carry away much heat. A dense liquid will absorb heat better, and can carry it away through convection currents with a minimum of pumping.
High end computers used to be water cooled but, though water cooling is still used in the doors of certain server cabinets, it is rarely seen today. Despite this, brave gurus are predicting that liquid cooling will eventually be the norm.
As well as reducing the energy demands of a data centre, it also has potential benefits, in that heat in liquid form can be re-used more easily. Most systems now don’t use water as a coolant (it’s not great close to electronic systems), but it is easy to run the actual coolant through a heat exchanger, and have a good supply of hot water, for heating or other needs.
In 2009, IBM told us to expect all servers to be cooled by liquid within ten years. We are not sure how seriously to expect that, but Big Blue is certainly putting water cooled servers in very public contracts – for instance in the data processing for last year’s Wimbledon tennis tournament.
Bring on the cool startups
But the idea of bringing liquid cooling into mainstream machines in racks seemed to have gone quiet last year. If it is to happen, it will most likely be the preserve of a startup – and given the extent of the paradigm shift they are attempting, it will have to be a very patient startup. At the moment, we are aware of at least three such “cool” startups.
In the US, Hardcore Computing has backing from Sun founder Scott McNeally, and has been working away at this idea since around 2006.
Green Revolution Cooling has a very simply engineered solution, which places normal blades vertically into a sealed container so they are simply submerged in a large tank of coolant. It recently extended the idea, by showing how the waste heat can be used to heat buildings.
The UK’s contender, Iceotope, was launched in 2009. We’ve not heard much since then, but the company has just re-emerged under a changed management structure, at this year’s CeBIT show in Hanover. Iceotope’s idea is to make the liquid-cooled blades fit into convential racks, but each one is made into sealed container. The coolant (3M’s dielectric coolant Novec) is circulated in each blade individually, through nozzles at the back.
The plus side is that an Iceotope server room is much like a conventional one, with an extra coolant circulation system going up the back of each rack, alongside power and network cables. The downside is that this is at this stage very much a proprietary system, albeit built with very standard electronic components, and built to be as easily serviceable as possible.
Iceotope claims to be able to reduce cooling costs by 95 percent, as well as providing a potential asset in the heat output. Whether this benefit is enough to persuade data centres to adopt a new system (from any of these new cool kids) remains to be seen.
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