Ventilation New-build case study
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The building’s data centres will also use outside air
for cooling. Unlike conventional data centres, which use minimum amounts of fresh air to keep the loads constant, BSkyB has specified more than 400 servers able to cope with minor temperature variations to enable the rooms to be cooled using outside air whenever possible. It is a simple solution, with fresh air ducted to a mixing box on the computer room air conditioning (CRAC) units’ intake. A pressure relief duct and extract fan allows the system to remain balanced when operating in full fresh-air mode. All this natural ventilation has helped the building’s
All this natural
ventilation has helped the building’s design to exceed the minimum requirements by 67%
design to exceed the minimum requirements of Part L2A, 2006, by 67%. It has been awarded an Energy Performance Certificate A rating, which Beaven expects to rise to A+ once the CCHP and wind turbines are installed (see box). On paper it is an impressive achievement, and the solution appears to be robust, but will it live up to expectations? The big question is whether or not Sky’s studio operators will utilise the natural ventilation option, or whether they’ll default to the safe alternative of mechanical ventilation. If they do embrace the natural ventilation system, without a similar scheme for comparison, it will be a steep learning curve for the users to get the best out of the system under both summer and winter conditions. l
Energy Keeping the studios running round the clock
Wood BSkyB was keen for the building to exceed the 10% renewable energy target in place at the time, even though the site is outside the GLA’s jurisdiction. This will be achieved using a 1MWe CCHP system, currently being installed close to the site’s perimeter. The solution is compatible with the building’s 24-hour operation and its continuous demand for electricity and cooling. All the power, heat and cooling are utilised by the building which, as a result, does not have boilers or a gas supply. Mike Beaven, of Arup Associates, says that there
is no point in having on-site generation ‘if it is going to produce much more carbon than buying power from a wind farm’. As a result, the CCHP will derive its energy from biomass, which should ensure the building’s carbon emissions are reduced by at least 20%. However, like every other system on the site, the CCHP is backed up with a full contingent of generators and chillers.
Wind In addition to CCHP, the site will also make use of wind power. The scheme has planning permission for two giant wind turbines situated in front of the building’s northern facade. It was touch and go whether these would actually be given planning permission. An extensive planning process addressed concerns including light-flicker from the turbines, birds, bats and noise, but the biggest challenge was National Air Traffic
Services (NATS). It objected to the turbine’s location on the flight path into Heathrow on the basis that turbine blades reflect radar. NATS was eventually persuaded to withdraw its objection and permission was finally granted. At 100kW each, the two turbines are expected to
provide enough energy to meet the building’s lighting load. However at 56 metres high, the turbines are also significantly taller than a standard turbine to ensure 10 metre clearance beneath the turbine’s blades and the building’s roof. The turbine bases have already been built and Arup has produced a sculptural design for the extended towers. All that remains is for the manufacturer to finalise the turbine’s design for this unique application.
Electrical The building’s entire power supply system is designed as an N+N installation – everything is doubled. Two 11kV ring mains serve the building, so that if one fails the other will pick up the entire load. There are eight transformers; four will support the building’s 8MVA maximum load. Should the power supply fail, the in-line UPS system has double the number of units needed to support all the equipment, and more than is needed to continue broadcasting until the standby generators kick in. There are four 2.5 MVA generators, three to support the building load, plus a spare in case a generator should fail – and space for two additional generators should the building’s load increase further.
32
CIBSE Journal February 2011
www.cibsejournal.com
Christian Richters
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