Data centre designers at Future-tech know that the resilience and efficiency of an installation are of the utmost importance however a focus should be given to the reuse of waste heat produced by the servers. They understand that this may not always be possible; however this option should always be explored.
Jordan Galloway, design engineer for Future-tech said “No matter how good your PUE is, you are potentially throwing hundreds of kWs of heat energy away, albeit very efficiently”.
The last two data centres completed by Future-tech both have the ability to reuse the heat produced by their servers. The first at St Andrews University, Scotland, can direct the warmth from the water in the cooling system, through a plate heat exchanger, to an under floor heating system. As under floor heating systems run at relatively low temperatures there is no requirement for a heat pump, meaning the data centre can deliver, at full load, 270kW of heating power to the University’s Library. This will result in the conventional heating system merely supplementing the under floor heating system during the very coldest periods of winter.
The second project, for the University of Hertfordshire, uses the return water from the data centre cooling system to help heat the building’s hot water. Although the data centre does not provide enough heat to run the hot water system single-handedly, it does make a substantial contribution to the overall energy used and in turn reduces both energy costs and the University’s carbon footprint.
Jordan Galloway added “The reason I became an engineer was to work on projects like these. It is really rewarding bringing truly innovative solutions to our customers. If new buildings are thought about in a holistic way and the data centre treated as an energy source, we can design buildings that are more efficient, more sustainable and ultimately better value”.
The difficulty in capturing heat for re-use from legacy data centre’s has been two-fold;
Firstly, The legacy data centre has had no form of control in the way the exhaust air that is created by the servers is transported away, generally being allowed to simply mix in the room prior to returning to a perimeter air conditioning unit, thus reducing the useable energy from the exhaust air and making the transportation of the heat energy very difficult
The grade of heat created by servers has been very low, with a typical server only increasing the temperature of the air across its chips by approximately 10 degrees C, so the kW heat output may look very attractive from a re-utilisation perspective, but once diluted across a very high volume of air, the manageability of that heat becomes complicated. Server inlet temperatures are typically maintained at approximately 20 degrees C in a traditional data centre, so with a 10 degree rise that is only 30 degree C air being ejected.. tough to convert into useable heat in another application. The good news is that there is a significant shift in the above limitations from the way that modern data centres are being designed that will allow for a far greater return to be achieved from heat re-use. And these changes are being created by the industries move to be more effective in the use of power in the data centre, this is compounded by the server manufacturers also feeling pressure to reduce the power usage of servers.
Firstly, the need to use air conditioning systems efficiently has caused a significant shift towards close air management in the modern data centre, physically separating the exhaust air from the conditioned air. This new approach has the additional benefit, beyond efficiency, as it allows the data centre owner to consider heat capture due to the concentration of the heat as part of the room design, and the subsequent transportation of the heat away from the facility, initially by passing across an exchanger.
Secondly server manufacturers are moving towards increased exhaust heat temperatures as they reduce fan speeds to improve server efficiencies. A blade server can have twice the heat rise across its chips than a legacy server, increasing the grade of heat significantly, this is compounded even further by a move from the traditional ideals around server inlet temperatures, with every degree of inlet tolerance increase resulting in an additional degree of useable heat energy from the exhaust.