Some like it hot ... very hot: How to use heat to your advantage in your data center

That's not a typo: hot-water-cooled

Yes, hot-water-cooled. And that's not just warm, it's most definitely hot – as in, 40°C or 104°F – which is nearly 20°C above your common-or-garden rack mount hardware's preferred air inlet temperature. You can run that water through an external piping radiator system and cool it in almost any ambient air temperature, without even having to turn on the compressors for the chiller systems to artificially cool the fluid lines.

Originally launched in 2012 by the Leibniz Supercomputing Centre in Germany, in their IBM "SuperMUC" supercomputer this hot-water-cooled beast is reckoned to save around 40 per cent on comparable supercomputer operating costs, with no noticeable decrease in performance. There's no requirement to run it at a lower clock speed or compromise on the computational output; it's designed to run at 40°C without having to back off the throttle.

Raising the inlet temperatures in servers by a couple of degrees was a game-changer. Raising the water-cooling temperature to 40°C? That's remarkable.

So you're running at higher inlet temperatures, taking advantage of the environmental conditions and improvements in HVAC systems, but let's face it: Heat's still going to be produced. It's an inevitability of IT hardware. We might win the odd battle, snatch a few victories and gain a few yards, but we'll never decisively win the war.

Hardware needs power. Hardware produces waste heat as a by-product. But who says heat has to be a waste product?

I can't remember where I first heard the term, but the idea of a "digital furnace" has the potential to be a game-changer. The heat produced isn't simply wasted, it becomes the center of a heat exchange system, and the principle is simple enough; it's essentially the opposite of free-air cooling in an HVAC system.

Using spinning disks and humming boxes to heat offices

Where a free-air cooling system draws air in from the external environment, diverts the ventilation flow, and mixes the lower-temperature external air to lower the internal temperature, the digital furnace does the exact opposite; the waste heat that is inevitably produced by the buzzing power supplies and spinning disks is siphoned out of the data hall, and put to better use.

The obvious application of this is central heating. That wasted heat is pumped into a ducting system that, when combined with a building and environmental management system as clever as your HVAC, is diverted under the floors and over the ceilings of attached offices to maintain a constant, pleasant temperature in the occupied areas.

That's all well and good in cold countries and is generally applicable the world over in winter, but there are some environments where you rarely (if ever) need turn on the heating. In that instance, your waste heat energy could be used to heat water instead – everybody always needs hot water – and in the unlikely event no waste heat is currently needed, can be vented off or diverted to a thermal store. Super-efficient underground thermal stores can hold thermal energy for months, so energy that's not required in July can be still be made use of the following January.

Somebody going down this route is Sainsbury's, with Geoscart (formerly Greenfield Energy). The retailer is cracking open the car parks outside its buildings and installing underground thermal storage systems – and the associated control systems – to recycle the wasted heat produced by the company's vast refrigeration and freezer systems. According to the Greenfield Energy website:

The system was the first ground-source system to be "refrigeration-led." Recognizing that cooling is by far the largest energy consumer in retail applications, we focus on optimizing the refrigeration systems, as this gives greater overall energy savings.

"Refrigeration-led"? That sounds perfect for data centers! The firm claims its Geoscart technologies have delivered 76,836 MWh of clean energy that would otherwise have been wasted, and have a stonking 1,127 GWh of yet-to-be-produced energy on their contracts.

There are no rules to say data centers can be the only ones benefiting from this potentially never-ending source of otherwise-wasted heat energy. Many data centers simply don't have staff numbers needed to re-use this useful heat energy produced. One option, therefore, could be pass on this stored capacity to others.

It sounds fanciful and altruistic, but data centers and information processing centers could provide heating and hot water for their neighbors. Eco-friendly housing developments are winning awards for their energy efficiency by using geothermal energy and networked ventilation systems to provide heating and hot water year-round. Why not data centers?

With a little bit of clever infrastructure diversion, data centers could go from major villains to positively saintly in terms of their environmental credentials. Perhaps if the idea of recycling waste heat were incentivized like solar panels or wind power, then everyone would be a winner.

In that world, heat's gone from being the enemy to something altogether different. ®