ENERGY FOUNDATION technology developed in Austria could offer a sustainable answer to the problem of keeping underground metro systems cool, an invited audience at a Mott MacDonald seminar was told last month.
Professor Dietmar Adam from the Technical University of Vienna explained the technique, which is based on the casting of high density polyethylene pipes into concrete piles, base slabs or diaphragm walls in contact with the ground.
A water/glycol mixture is circulated through the pipes to heat buildings, bridges and underground structures in winter and cool them in summer, especially if a heat pump is included in the circuit. Special geomembranes and geotextiles have also been developed to allow heat extraction from around tunnels and under roads.
Two cut and cover stations on the Vienna Metro extension already have the system installed, and a similar system in a rail tunnel on the city's outskirts is heating a local school.
Research at the Technical University of Vienna suggests that for every watt of energy needed to operate the system between 3.5W and 5W is returned as heat energy.
Despite its significant environmental benefits, the concept has yet to catch the imagination of engineers, said Mott MacDonald transport group director Alan Powderham.
'In central Europe there are around 400 energy foundation projects already completed or under construction. In the UK and the US there are almost none.'