As pari of the Sustainable Region Initiative (SRI) the Greater Vancouver Regional District (GRVD) Policy and Planning Department has commissioned this study to investigate the use of district sewers as heat sources or heat sinks. This conceptual study examines the technology available for sewer heat transfer, and provides a mathematical and physical model of a heat transfer system, in order to ascertain the feasibility, ecological benefits, and cost effectiveness of such a system.
Possible sites for implementing a sewer heat transfer system within the GVRD are also considered, with particular attention given to the Sapperton force main and the Trout Lake Trunk.
A thorough literature search revealed two practical, proven methods for heat transfer in raw sewage mains: a mechanically intensive system in place in Japanese cities, and a less obtrusive system with heat transfer panels in the sewer invert (termed 'Rabtherm') in use in Zurich, Switzerland. The latter was selected as being most applicable in GVRD sewers and was studied further.
Other methods of heat recovery in use were 'GFX' heat exchangers, for use in recovering heat at a residential level, and heat recovery systems in place on treated sewer flows or at industrial sites; these were not examined further.
Feasibility study of Using GVRD sewers as heat sources and sinks