Boreholes and tides cool UK office blocks

Copyright: David Lawson– Property Week Feb 1998

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A riddle: how can  a boring project be considered an exciting breakthrough? Answer: when it involves a groundbreaking method of cutting an occupier's rising tide of costs. Puns flow like a gushing stream from a handful of developments on opposite sides of the UK where developers are exploring  techniques for tapping the water beneath our feet to heat and cool buildings.

 One, on the Isle of Man, has turned a problem into an asset. Pumping out a waterlogged site has become a  money-saver. The others are experiments in a technique called ground coupling, widely used in countries like the US but yet to be tried seriously on a commercial project here.  All are a fascinating technical exercise in technology for the engineers involved. But they also hold a lesson for developers and investors. How do you create buildings today which will still be attractive  when energy efficiency  has become an important part of the value attached to commercial property?

 Trevor Silver is passionate about 'green' buildings. 'It is probably my background as a civil engineer,' he says. But as a partner with Akeler Developments, he also has his eyes set firmly on the bottom line. Eco-friendly techniques cannot succeed if they make buildings so expensive that occupiers and investors are put off. 'It is hard to justify radical methods of alternative energy today,' says Silver. 'The cheapest sources are still the electricity and gas grids.'

  But he says tenants  are already thinking forward to a time when carbon taxes and tight conservation rules will add to occupation costs. An inefficient building will be an expensive one when energy ratings are used as part of  local property tax calculations. This is also percolating through to investors, who could see their assets losing value fast in this kind of era unless they feed in such ideas now.

  Akeler's forward planning - and Silver's passion - have already  produced innovations such as high insulation techniques and a solar-panelled facade on an office block in Doxford Park in  north-east England. Now he is breaking ground with  new solutions.

 Ever since man began burrowing for fuel and minerals it has been common knowledge that the rocks below our feet remain at a fairly constant temperature no matter what the season.  'At around 20m to 100m below the UK the temperature is a steady 13degC, plus or minus a degree,' says Silver. Engineers have played around for years with the idea of using this as a regulator for the buildings above.   That involves boring downwards, then pumping water out and through the building. Ity can then be dumped or returned to the ground.

 Akeler will experiment with this technique in two developments now on the cards. One is  a joint venture with Alfa Laval for 300,000 sq ft on its headquarters at Junction 2 of the M4 in west London, and the other a pair of office buildings at 217 Bath Road, Slough  It  involves pumping  water out of a borehole and passing this through a heat exchanger. That extracts  heat from the water in winter and absorbs it from the building in the summer.  This  could save 2.25m kW of energy a year on the Equinox scheme. That is around 35% of annual consumption, or  £16,000 a year.

  'Just as important is the 509,000 kg of carbon dioxide saved each year,' says Silver. This will be significant if carbon taxes are based on CO2 output.

  Could this kind of technique be used elsewhere? 'I don't see why not,' says Silver. It adds marginally to rent levels but Akeler has found that green credentials are in great demand by some forward-thinking occupiers, so this is not expected to affect letting chances.

  There are two problems, however. One is purely technical: the system works 24-hours a day, but buildings are rarely occupied that intensely. Silver solved this by planning to use the sprinkler tanks as 'buffers' to soak up heat during the night.  The other involves red tape: extracting water requires a licence  - which can take a long time to win. The Akeler system avoids this by using a closed loop. Water comes out of the ground but is pumped back through the sealed system without fear of contamination.

 Taming the Tides

Another project which uses water cooling in a different way involves the the old Villiers Hotel in Douglas, on the Isle of Man. It was in terminal decline  long before  engineers and architects arrived on the site. Tourism is giving way to financial services and the Victorian pile  was set  for clearance  by new owner  AXA Equity and Law.

  That should have given Tom Smith of engineers WSP  a free hand to design  services for a spanking new office complex - except for one obvious fact. The site was directly across the road from the sea, and when the tide came in, it filled the old basements. 'I was gobsmacked when I first saw this,' he says. 'It is on land reclaimed over the last century and water comes in under the surface.’  In normal circumstances that would have  involved  tanking the foundation areas  and pumping away the water. But the architects had other ideas.

  AXA, now part of the insurance group Sun Alliance, wanted  a 'green' building, and had chosen architect Haworth Tompkins and WSP for their track record in designing eco-friendly structures. Already schemed in were  opening windows, maximum natural light, exposed floor slabs as thermal 'sponges' and fresh-air ventilation.  The two advisers then  came up with a way of harnessing the tide.

 'The water has to be pumped out anyway, so we decided to link it to the cooling systems,' says Smith. First, however, he had to find out if this was feasible. He had  read about this technique being used  in the landmark Hong Kong & Shanghai Bank building, which is on the former colony's coast. 'But there was nothing like it in the UK,' says Smith.

  The local authorities showed little problem with extraction. 'I don't think they had been asked before whether a licence was needed,' says Smith. A scout around the universities produced some background academic studies.  Site studies also determined how far the water moved - about a foot above ground at high tide and six metres down at low water. A little number-crunching  along with specifications of the planned 160,000 sq ft office complex produced plans for an 18 metre borehole linked to a heat exchanger.

 The water comes in at about 12degC and out of the building at 18degC to be dumped back in the ocean.  This has to be pumped because the tide would not provide enough pressure to push water around the building. It also requires anti-corrosive measures. The heat-exchanger is titanium and the piping is plastic, says Smith.

  The crucial fact, however, is that this is no more expensive than a conventional cooling system. The bore and equipment cost around 100,000 pounds, plus 25,000 pounds for research. Running costs are negligible. Savings also come from the elimination of large plant on the roof.

  Only one phase of the complex has been built so far, and the system is already expected to cut energy consumption by 30% - saving around 5,000 pounds a year. But it is designed to handle all three buildings, so the savings will magnify once  complete.