Doha stadium to keep cool on carbon neutral aircon plant 31 January 2011

Football fans in Qatar – which is undertaking a major refurbishment programme ahead of the 2022 Fifa World Cup – will soon be kept cool with ABB variable speed drives.

The Qatar 2022 bid committee asked Desiccant Dryair Systems of Morecambe in Lancashire to provide air conditioning systems for the new stadium in Doha, to reduce the temperature from 45C on the stands and pitch.

John Cross, managing director of Desiccant Dryair Systems, says that the system will be nearly carbon neutral – using sunlight to provide high pressure hot water for the absorption chillers and electrical power, via PV (photovoltaic) arrays.

Desiccant's cooling AHU passes hot air through two slowly rotating wheels – the first removing moisture via a silica gel desiccant, which halves moisture content to 10g/kg of air, and the second recovering sensible heat from the opposing airflow, using chilled water from an absorption chiller. Fans then supply conditioned air to the stands and pitch areas.

Cross explains that the opposing airflow is the return from the stadium and is already lower in temperature and moisture than the fresh air being introduced. On entering the machine it passes through an evaporative cooler which drops the air temperature to the wet bulb value. This then passes through the sensible heat wheel.

Meanwhile, he says, regeneration of the desiccant wheel uses high pressure hot water from the solar field via a heating coil, with water vapour removed via a regeneration fan.

Each of the two units uses 10, ABB standard drives for HVAC, to control the rotors, as well as the process and regeneration fans and other ancillary equipment. The first rotor moves at an average speed of 12 revolutions per hour, while the second revolves at 14 revolutions per minute, depending on the difference in air temperature between the opposing airflows.

Temperature sensors feed signals to the ABB drives via the building management system, ensuring they drive the rotors and fans at an appropriate speed to suit the ambient conditions. Because the drives alter speed according to demand, the power drain is minimised.

Overall, the system uses 1MW of renewable energy, compared to the 1.3MW of conventionally generated energy used by a mains powered system.

"ABB provides the best quality and we always buy ABB motors, because of the high level of service and support we receive," says Cross. "We are now also confident in the quality of ABB variable speed drives and that we can get an equally high level of support from ABB's drive service network."

Brian Tinham

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Desciccant DryAir Systems

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