Cementation Skanska worked with GECCO2, a U.K.-based GSHP/geothermal installed three Energy Piles design and build contractor, which has ® for The Leadenhall Building in London. The piles, measuring 2.1 m (6.9 ft) and 2.4 m (7.9 ft), are considered some of the largest energy foundation piles in the U.K., said Matt Love, managing director of GECCO2. Each pile will contain a total of 300 lm (984 ft) of collector pipe. Known as the “Cheese Grater” because of its tapered shape, the 50-story building is expected to be completed in 2014. GECCO2 also is involved in energy Current design practices, the authors said, typically do not allow thermal fluid temperatures to fall below 0°C and require a 2° safety margin. In contrast, the authors’ calculations of typical operational temperature patterns applied to a 600 mm (24 in) diameter pile determined that, even for a fluid temperature of -1°C, the edge of the pile remained at least 1°C above freezing. Thus, the authors concluded that less-conservative fluid temperature limits could be adopted because: • A temperature gradient between the fluid and the pile edge always exists. • Short-term, high-magnitude heat fluxes do not reach the pile edge; the concrete is effectively insulating the ground from these variations. Professor Brandl comments that while a fluid temperature of -1°C is of course possible, he is not much in favor of “squeezing” theoretical limits in practice, noting his concern about additional risk of long-term detrimental effects to concrete. The Austrian energy pile limit of 0°C, he said, “is still economical.” New Thermal Pile Standard. In September 2012, the U.K.’s Ground Source Heat Pump Association (GSHPA) released a thermal pile standard. GI’s Tony Amis said the new GSHPA standard provides information for the materials and general specifications of a closed-loop thermal pile system. The standard also covers internal pipe work up to and including manifolds, flushing valves, arrangements up to the entrance of header pipes into the plant 52 • DEEP FOUNDATIONS • MAR/APR 2013 room. The standard is available for purchase at www.gshp.org.uk/shop.html. High-Profile Projects. EFPL’s Professor Laloui said roughly 50 projects have been completed in Switzerland since the early 1990s. The most impressive, he said, is the Dock Midfield, Zurich Airport. The terminal, completed in 2003, is 500 m (1,640 ft) long and founded on 350 cast-in- place piles with diameters of 0.9-1.5 m (3- 5 ft), 306 of which are thermally activated with 5 U-loops vertically distributed around the pile perimeter, he said. The geothermal piles coupled with the heat pump, geocooling scheme, and a refrigerant tower, provide 85% of the building’s heating and cooling demand. The Spring 2011 Deep Foundations featured the largest energy foundation project in the U.K. for “One New Change,” a $250 million mixed-use development in London. Authors Julian Crawley and Tony Amis of GI, and Peter Smith of Cementation Skanska reported the ground source heating and cooling scheme 400% efficient compared to the 90% efficiency of a standard gas condenser boiler. “The system provides upward of 10% of the building’s energy needs, but meets all the stringent new planning requirements for CO reduction,” said Smith, Cementation 2 system, with 219 Energy Piles and two waterwells, has been operating for the past three years and delivers 1.6 MW of heating and 1.7 MW cooling. The process is estimated to save 900 tonnes (1,000 tons) of CO emissions annually.” 2 Skanska’s geothermal manager. The ® foundation projects at three Crossrail stations and the Shell Centre, all in London; and an energy pile research and development project in Rugby, Love said. He added that 30% of GECCO2’s business is devoted to energy foundations, partnering not only with Cementation Skanska, but also with Bauer Technologies, Expanded Piling, and Balfour Beatty Ground Engineering (BBGE). The Crossrail development is currently the U.K.’s largest civil engineering project, Piles and Energy Walls are being installed into several of the underground station walls and piles for [future] over site developments.” Amis, business development director said Cementation’s Smith, noting Energy ® at GI, said his company is installing geothermal loops at five Crossrail stations across London. Placing geothermal loops into foundation elements “is seen as the only method for meeting various planning requirements,” he said. “Renewable energy targets have to be met on the subterranean installations in order to meet [future] requirements for above- ground developments once station work is complete.” “We have recently started energy pile design work at London Bridge Station for Network Rail, and expect to start installing loops into piles in the middle of 2013 with Bachy Soletanche, to provide a cooling solution that will save [roughly] 80 tonnes (88 tons) of CO annually,” 2 Amis continued. “London Bridge Station is currently being upgraded following the opening of the Shard, the tallest building in Europe.”
