Lisbon: Solar cooling system for office complex

CGB Bank in Lisbon with solar cooling Solar thermal installation on top of this huge banking complex in Lisbon: The Portuguese state bank Caixa Geral de Depositos (CGD) commissioned the Austrian engineering company S.O.L.I.D. to design the solar cooling plant.
Photo: S.O.L.I.D.

Europe’s largest solar cooling system for an office complex was inaugurated in mid September in Lisbon. Even the country’s head of government attended this special occasion. The client for this system, planned and installed by the Austrian company S.O.L.I.D GmbH, was the Portuguese state bank Caixa Geral de Depositos (CGD).
Their huge headquarters in the centre of Lisbon has 100,000 m2 of office space for 5,000 people, a theatre, an out-patient clinic and two restaurants, and used to be heated and cooled using electricity alone. That made things expensive in the long run, and so S.O.L.I.D was charged with planning a solar cooling system in the autumn of 2006.

It seemed natural to use the collector array in all three main areas that showed potential and so the total area of 1,592 m2 (1.1 MWth) is firstly to be used to heat the service water previously heated using electricity. Additionally, the solar energy will ‘reheat’ the incoming air after it has been dehumidified. Finally, the solar heat will drive an absorption chiller rated at 585 kW. These are optimal conditions for solar heat, as there is thus a continuous high demand at different temperature levels. S.O.L.I.D.-head Christian Holter has calculated in an annual yield of 650 kWh/m2 of collector area. In absolute terms the solar system will only reduce the total electricity demand of the complex, including computers and lighting, by 5 %, however.

“Unfortunately we only had a limited area of roof space available for installing the collectors,” regrets Holter. Architects in Portugal have a lifelong right to oppose measures on the facades of their buildings, and the architect of the eleven-storey office block with its two inner courtyards made use of this to banish the collectors onto the roof areas of the rear parts of the building. The planners had to respect this, but they were able to get their way with the changes to the cooling system. This was being driven by around 40 over-dimensioned, stepless pumps. “The cooling system had absolutely no range: input was at 7 °C and output was at 7.5 °C,” explains Holter. “We thus had to install rpm controllers in the existing cooling system during full operation, or else we wouldn’t have been able to connect up our coolers,” says Holter on the problems they had. It took weeks and several exchanges by post before the customer’s fears were allayed.

The solar thermal and cooling system, including storage, planning and installation cost € 1.3 million. S.O.L.I.D. reckons with an amortisation period of 14 years.

Further information: www.solid.at

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