DATA CENTRES EVAPORATIVE COOLING
issues were resolved: a series of control and monitoring procedures were set up to deal with the potential for legionella; a visit to a site where similar cooler units had been installed enabled potential noise levels to be assessed; and the contractor gave assurances that the system would be able to cope as designed. The installation of the system was
completed in June 2011 and, to date, the units have performed as expected, with very few teething problems. The problems that were encountered
The system required for the data centre included evaporative cooling cubes from EcoCooling
consume 40 litres of water per hour, which, multiplied over the five cooler units, gives a maximum hourly consumption of 200 litres. At peak load, that means the system would consume approximately 60p of water per hour. It was assumed that this additional cost would be absorbed via the maintenance savings achieved by not using the old cooling system. Figure 2 summarises the energy, cost
and carbon savings of the evaporative cooling system, compared with the split system installed and the forecast payback periods. As the project has a payback period of less than five years, it was possible for the university to fund the project using a loan from the Salix/Higher Education Funding Council for England Revolving Green Fund. This could then be paid back over the next five years from the savings that the project achieved.
Monitoring Prior to the project commencing, there were a number of concerns voiced by the engineers at Nottingham Trent University, including issues about possible legionella, the noise of the system and the ability of the system to cope with the cooling requirements placed on it. All of these
System
150 kWh split cooling system (R407c refrigerant)
Annual electricity consumption (kWh) 219,342 Annual electricity cost (£)
18,425 Annual carbon emissions (kg of CO2
Payback period based on £72,000 installation cost
eq) 119,068 N/A
Figure 2: Costs and payback period of the evaporative cooling system 48 CIBSE Journal October 2011
www.cibsejournal.com
175 kW evaporative cooling system
22,847 1,919
12,402 4.4 years- Saving
196,495 16,506
106,666
l Scott BrookS is energy and carbon engineer, Nottingham Trent University.
scott.brooks@
ntu.ac.uk +44 (0)115 848 2462
were all resolved, and were primarily down to control issues, such as: ensuring that the dampers closed fully when the fire alarm in the room was activated, in order to make sure that the gas suppression system could operate fully; and issues with ensuring that the dampers closed when the back-up generator was activated to prevent smoke entering the data centre. Also, although a number of high
temperature days have been experienced, the system has not yet had any problems with meeting its cooling requirements. Owing to the success of this project,
Nottingham Trent University is currently investigating a number of other locations where this type of system could possibly be installed. However, due to the amount of air being passed through the room, the ducts are 60 cm by 60 cm – and so the locations where the system can be used are heavily restricted. In addition to installing the evaporative
cooling system, due to the relatively low power requirements of the system (7.5 kW at peak load) it became apparent that the project offered an ideal opportunity to install a source of renewable energy – to generate a large proportion of the electricity required by the system throughout the year. As a result, a 10 kW peak photovoltaic
system was installed on the roof of the building where the data centre is located. This was wired directly into the electrical panel that supplies power to the cooling system, to ensure the most direct route available so that the power is used by the cooling system wherever possible. This system was installed in April 2011
and is well on track to produce more than 8,300 kWh per annum, which will replace the demand for approximately 36% of the cooling systems electrical requirements.
Scott Brooks
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