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Tapping Water for Energy Efficiency

In the 19th-century, the textile industry in this region of the city drew heavily from the water table. Now that the thirsty factories are gone, the water has risen again, as high as 23 feet (7 meters) below ground level, creating intrusion problems in some of the district's deeper basements.

This unwanted water surplus has been creatively tapped in the BCN@ctiva project. Two 100-foot- (30-meter-) deep wells at opposite ends of the site harness up to 18,000 gallons (70,000 liters) of water per hour. Some of this goes to non-potable water functions such as landscape irrigation and sanitary services. Some of the water contributes thermal energy and is returned to the water table.

The wells provide water at a constant temperature of 64 degrees Fahrenheit (18 degrees Centigrade), which is higher than the outdoor air temperature in the winter and lower than that in the summer. Depending on the season, heat or cold is mechanically extracted from the water.

Thermal storage tanks totaling 3500 cubic feet (100 cubic meters), located two and three levels below grade, hold the heated or cooled water before it is circulated through the buildings' climate control systems.

When the system is operating, the output is 4 kilowatts of cold or 5.3 kilowatts of heat for every kilowatt of electricity used in the extraction process. This hydrological exploitation system becomes, in a sense, a hidden vertebral column that "supports" the whole site.

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Miguel Roldán and Mercedes Berengué are principals of R+B Architects. They received the commission for this project as a result of a design competition in 2000. Construction was completed in 2003.

The visually horizontal Barcelona Activa, by R+B Architects, holds an underground secret to its energy efficiency. Photo: Eva Serrats Transverse section, Barcelona Activa. Image: R+B Architects Plaza-level floor plan, Barcelona Activa. Image: R+B Architects Light-filled interior of Barcelona Activa. Photo: Eva Serrats   Click on thumbnail images to view full-size pictures.