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DATA CENTRE AIR CONDITIONING BSEE


TRIED AND TESTED Take control of your costs


Reliable performance is a significant consideraon during the planning and design of precision air condioning for data centres. Sebasan Beyer, Test Centre Manager at Stulz, explains why


knowing the actual capabilies of equipment under temperature and air humidity condions is vital and how individual performance tests help to achieve an energy ecient configuraon.


W


ith utility bills rising, growing pressure to reduce carbon emissions and increased demand on power


networks, data centre owners and operators are faced with a major challenge when it comes to energy consumption.


Although organisations such as Google and Microsoft are leading the way in measuring and improving energy use, mainly because they consume such vast amounts and it makes economic sense, the fact is that all enterprises need to do the same, at least until such a time as we develop 100 per cent renewable energy sources. It’s widely accepted that data centres consume almost as much energy for non-computing resources – such as cooling and power conversion – as they do in actually powering their servers. Air conditioning solutions must be planned and implemented meticulously, and it is not just the investment costs of cooling solutions that have to be considered but the operational expenditure associated with them. Planners must also consider how to achieve energy savings by dimensioning their systems appropriately.


Legislation is increasingly putting pressure on data centre owners and operators and this will only increase. Germany, in particular, is leading the way in this area and its Energy Saving Ordinance (EnEV) legally obliges operators of air conditioning solutions to subject all systems over 12kW to an energy inspection on initial installation, on the replacement of important components, or every 10 years. This type of legislation is expected to become more widespread across the globe, as countries try to reduce energy usage and lower CO2


differences in cooling capacity. This is mainly due to different environmental influences, which cannot be taken into consideration in the standard performance test.


Data centres around the world have varying requirements for their air conditioning units. Therefore, a system's performance is determined not just by the quality of the individual components, but also by its location. Ambient conditions, such as the temperature and humidity of the return air at the unit intake or the supply air at the outlet, have a significant influence on the performance of the entire system. In practice, changes to the equipment's temperature and air humidity parameters may have a negative influence on actual cooling capacity and efficiency. This affects the operating points of vital components such as pumps, fans and compressors.


If planners rely on the theoretical manufacturers‘ data, they run the risk of reduced capacity for cooling their data centres. The result can be incalculable additional expense, as electricity costs spiral out of control and upgrades or conversions become necessary. As well as jeopardising cost efficiency, badly planned precision air conditioning can also be detrimental to the ability of a data centre to operate efficiently in the future and meet its Power Usage Effectiveness (PUE) targets.


emissions.


Therefore, the challenge is to implement high performance, efficient and future proof dimensioning for these systems in data centres.


Cooling capacity


uThe Stulz tesng facility has two separate climac chambers and four condioning systems.


Although manufacturers of air conditioning units ascertain the technical specifications of their equipment in accordance with DIN EN 14511 by testing to determine total cooling output and energy efficiency, in practice there can be considerable


To address the problem of air conditioning systems performing inefficiently once in-situ, some manufacturers offer simulation and performance tests under realistic operating conditions. This allows the planners to gain essential data on actual performance and efficiency ratings during the planning stages of large air conditioning systems.


Field based informaon


In the UK – due to strict rules governing the accuracy of the stated performance data – tests of this kind are now standard procedure, with customers increasingly demanding field based information on cooling capacity and energy efficiency, so that they can remain economically competitive. For this reason, manufacturers now also offer individualised customer tests. Stulz built its Test Centre for the internal


testing of prototypes in the design and development phase as well for customers, data centre planners and operators to test their facilities. With an area of over 700sq m, it features four conditioning systems, where airflow rates from 500cu m/h to 55000cu m/h can be achieved. It has two separate climatic chambers, in which air conditioning systems can be put through technical tests either individually or connected via both chambers. Here, different operating parameters, such as environmental influences (-20°C to +50°C) and return air conditions, can be set precisely to match a customer’s requirements, thereby simulating realistic operating conditions. While this is taking place engineers in the control room record and document test data in real time, and analyse it if necessary. Specialist planners can use these results as verification of cooling capacity, efficiency and power, creating an important aid to decision making during the specification of precision air conditioning solutions. Technical tests of air conditioning units in accordance with DIN EN 14511 (performance of air conditioners, liquid chilling packages and heat pumps), EN 1216 (heat exchangers and forced circulation air cooling and air heating coils), and ISO 9614 (sound power levels), can be completed.


System performance


Using the air enthalpy method, system performance is ascertained by measuring the airflow rate and the associated intake and outlet conditions of the air. The calorimetric method, on the other hand, is particularly suitable for simulating partial load conditions during full load tests.


Here, three important scenarios are used – conditioning mode, simulation of data centre cooling with supplementary cold or hot aisle enclosure, and environmental simulation mode that tests entire air conditioning systems with indoor and outdoor units. As all scenarios permit the variable setting of heat and air volumes, air humidity and return air temperature, a customer's specific local requirements can be simulated with great precision.


These individual tests enable precisely the right dimensioning of air conditioning systems in data centres, under consideration of local environmental influences. This way users have full cost control regarding investment sums and expected future running and energy costs.


Another advantage is that the extensive accompanying


documentation can be used not only to verify the performance of air conditioning systems, but also as a basis for configuring the data centre cooling. It is therefore worthwhile for all customers of air conditioning solutions to take up services of this kind that are offered by manufacturers.


www.Stulz.co.uk/en/ VISIT OUR WEBSITE: www.bsee.co.uk BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2018 31


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If planners


rely on the theorecal manufacturers‘ data, they run the risk of reduced capacity for cooling their data centres. The result can be incalculable addional expense, as electricity costs spiral out of control and upgrades or conversions become necessary.


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