ABB drives at heart of low-energy cooling system for Qatar football stadium
Desiccant dehumidification and evaporative cooling are at the heart of air-conditioning system for the new football stadium in Doha to reduce the air temperature from the 45°C ambient often experienced in the country to a more comfortable level in the stands and pitch areas for spectators and players. To reduce energy consumption even more, the system uses solar energy to provide high-pressure hot water for the absorption chiller and to generate electricity.
The Qatar bid committee for the 2011 Fifa World Cup asked Desiccant Dryair System of Morecambe to provide the air-conditioning systems for the stadium.
Incoming air passing through an air-handling unit is first dried by passing it through a slowly rotating wheel using a silica-gel desiccant to reduce the moisture content from 20 to 10 g/kg of air.
The incoming air then passes through a sensible-cooling wheel to be cooled by the opposing outgoing air flow from the stadium. However, before this stage, the outgoing air passes through an evaporative cooler to reduce its temperature to the wet-bulb value. The outgoing air is saturated with moisture, but only its sensible heat is transferred to the incoming air.
The final cooling is provided by the solar-powered absorption chiller.
Water is removed from the desiccant wheel by a coil that is heated using high-pressure hot water produced by solar energy. The water vapour is removed from the building by a fan.
Each of the two AHUs uses 10 ABB standard drives for HVAC to control the two wheels, the process and regeneration fans and other equipment. The desiccant wheel rotates at an average of 12 rev/h and the energy-exchange wheel at 14 rev/min — depending on the difference in air temperature between incoming and outgoing air. The greater the temperature difference, the faster the rotors spin to transfer more energy.
The solar PV system powers the drives, which can vary their speed according to demand. The system uses 1 MW of renewable power, compared to 1.3 MW of conventionally generated energy used by a mains-powered system.
John Cross, managing director of Desiccant Dryair Systems, says, ‘We always buy ABB motors because of the high level of service and support we receive. We are now also confident in the quality of ABB variable-speed drives and that we can get an equally high level of support form ABB’s drive service network.’