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Air conditioning Efficiency
For Daikin product executive Simon Keel, the association with a chiller and a boiler to give heating
A rooftop cooling unit.
Carrier’s Andrew Keogh says
largest contributor to energy efficiency gains in air and cooling.’
better system design and
conditioning has been direct expansion inverter heat
deploying other strategies
pumps and especially those in multi-split VRV systems: Mixed mode can lead to improvements.
‘Being direct, there is no need for extra pump or fan Unsurprisingly, John Staunton of chilled beam supplier
power to be used to circulate the heating or cooling SAS agrees that this technology is in the ascendant. He
around a building. The hundreds of thousands of such says: ‘The British Council for Offices’ updated Guide to
systems operating throughout the world have proved Specification has introduced a design target for mixed
the point.’ mode and naturally ventilated offices of not more than
However, he believes that the next 20 years could 25C for more than five per cent of the occupied hours,
see the decision-making landscape change, resulting and 28C for not more than one per cent.
in a shift of emphasis in the air-con sector: ‘Chilled ‘Many in the industry see the likely consequence
beams that only started to become popular five or so of this being the next generation of office buildings
years ago have replaced variable air volume systems adopting a mixed-mode approach to cooling and
in the majority of cases. These will be operated in ventilation, with probably greater use of free-cooling >
www.cibsejournal.com December 2009 CIBSE Journal 41
CIBSEdec09 pp40-42,44 aircon.indd 41 19/11/09 16:26:52
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