I'm often asked questions about the cost and benefits to a data centre of going green. There are plenty of sobering predictions about energy consumption, so reducing your carbon footprint and improving your image, as well as your bottom line, is an attractive proposition. As McKinsey points out, data centres are expected to overtake the airline industry as the largest source of CO2 emissions in 2020. So how do you green a data centre retrospectively?
Hot and cold aisles
Keeping the air temperature of a data centre at 19 degrees Celsius is very hard work and requires a lot of cooling power. Creating 'cold aisles' can reduce the amount of cooling needed for the racks. Ensure that all the server-fronts are in a cold aisle and the rears are in a hot aisle.
The principle works around cold air coming out of the sub floor plenum near the fronts of the servers. This cold air is then sucked into the front of the server (cooling the equipment) and hot exhaust air coming out of the rear of the racks is fed into a specific area for the cooling units to control. To improve this further the cold aisle can be contained by installing doors either end.
Uninterruptible power supply (UPS)
Modern UPSs are considerably more efficient than models created a few years ago. The latest ones have high performance filters, protecting upstream power supply sources from harmonics and they can also provide high input power factor correction of up to 0.99. Wherever possible it's worth investing in the best unit available to suit your configuration.
Switchgear and cabling
Very old or underspecified switchgear and cabling is not only an operational risk, but can also be a source of inefficiency from overheating. Regular thermal imaging checks and partial discharge testing (for cracks in the insulation) can identify inefficient hot spots that may require maintenance or replacement.
LED lamps are much more efficient than traditional bulbs. They offer both a longer lifespan and lower heat output. The lower heat output of LEDs also helps to cut the amount of cooling needed within the data floor.
Many data centres use computer room air conditioning (CRAC) units. These, however, consume huge amounts of power and therefore carry a weighty carbon footprint.
A better option is evaporative cooling (also called adiabatic cooling) which works on the principle that when water evaporates it draws energy and heat away with it. Just as in the same way that people sweat to cool themselves down, this technology draws warm ambient air through a wetted filter or fine mist, which in turn causes some of the water to evaporate and cool the air.
By recirculating exhaust air from the servers to help regulate the incoming air temperature and filtering the external air, the system as a whole can maintain a cold aisle temperature of 20–23 degrees throughout the year. It is a completely natural way of producing cool air with a far lower carbon footprint.
This form of cooling uses up to 90 per cent less power. This allowed our data centre to achieve a PUE of 1.1, an efficiency figure previously impossible with traditional cooling methods.
There are a number of other ways that data centres can be made greener, including the use of power factor correction (or PFC) unit on the mains power supply, blanking of plates and floor grommets in all racks, using power-efficient servers and virtualisation and recycling cardboard packaging, plastic and paper.
- Jack Bedell-Pearce has over 12 years of commercial, operational and technical experience. He is responsible for the day-to-day running of 4D Data Centres, a colocation and connectivity supplier for SMEs in the South East.
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