12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaDISTRICT HEATING PIPES 200 MM BELOW SURFACEIN A STREET WITH HEAVY TRAFFICAnders Fransson 1 and Sven-Erik Sällberg 21 Göteborg Energi AB, Sweden2 Building Technology and Mechanics, SP Technical Research Institute of SwedenABSTRACTThis article reports the results from a field experimentinitiated by Göteborg Energi AB with an extremeshallow burial of district heating pipes 162/76,1 (DN 65)casaflex under a street with heavy traffic designed foran average of 2000–4000 passes of vehicles a day andline. The pipes were laid only 200 mm below thesurface. The backfill was of 0–40 mm particle size.Several consecutive measurements were done to studythe effects from instant and long term loads from thetraffic. The tests were done on a test pipe preparedwith displacement gauges and on operating pipes.The aim is that the results will inspire and give input formaking district heating and cooling more cost effective.The tests showed that both the instant and long turndeformation of the pipes are small at the actual layingdepth and also that the acceleration in the ground asheavy vehicles passes does not seem to be alarming.sales (i.e. less district heating, d.h. to be sold). Toconnect new district heating customers in the future,with the competition of other heating suppliers, it is notenough to use just smaller pipes because of thesmaller demands. Building the grid and maintaining thegrid needs to become more cost efficient.The purpose of this article is to inspire and if possiblehelp whoever is interested in making district heatingand cooling in the world more cost effective using theideas or test results from this article.1.2 Cost-cutting due to shallow burial in roadsWhen reducing costs, it is important to maintain thequalities that are required. The road owner needs theroad to be functional and has its standards. The districtheating supplier is responsible for its pipes anddeliveries of heat and has its standards. Finally thereare workers (contractors and maintaining staff) whoneed acceptable working conditions.The conclusion is that shallow burial is technicallypossible if the road and backfill is done properly.1. INTRODUCTION1.1 New conditions for district heatingThe branch of district heating is in need of a newgeneration of district heating pipes.The conditions for selling district heating are slowlychanging due to new legislation, harder competition,new technique and climate changes. Since 2003Göteborg Energi AB is connecting more and morecustomers but is selling less and less energy. Newlegislation from 2006 allowed new buildings inGothenburg to use a maximum of 110 kWh/m2externally supplied energy for heating (,cooling) andproducing domestic hot water. Today the municipalityof Gothenburg wants new buildings to use 60 kWh/m2at most.These changes are not unique. New houses are usingless and less energy per square meter. There arealready households that are not using but producingenergy. The former energy suppliers in Europe arefinding themselves not as suppliers but distributors,buying and selling energy. Climate changes are globaland have already measurable effects on district heating96Fig. 1 Standard shaft sectionIn a standard shaft section the drainage may be takenaway in roads. A properly built road has a hard top andis drained as it is. You do not need to drain it anymore.It is also possible to make the shaft more narrow andmaintain acceptable working conditions if either longpipes with no joints are used or if the joints are weldedon top of the shaft.Less coverage is also an alternative. Earlier studies[1]–[3] shows that the pipes are solid enough to beplaced with very little coverage (180 mm) and in roughmaterials. It is also shown that there is less settling in