Geothermal Under Street Heating System

Abstract

In 2008 the Rotorua District Council made a block of Tutanekai Street, nearest to the lake, a pedestrian only precinct and the many restaurants located on the block set up "al fresco" dining facilities. The area is named Eat Streat. This move was a great success and widely used by local people and the many tourists who visit the city. Encouraged by this success it was decided in 2012 to further enhance this aspect of the city experience, by providing better shelter and under street heating, using geothermal energy as a heat source, so that outside dining could be carried out for a longer period each year. As the natural geothermal features of the City are a major tourist attraction this move was aimed at showing the environmental benefits of geothermal by tapping the energy using a down hole heat exchanger. The down hole heat exchanger (DHE) used on the project was of novel spiral flute coaxial tube design, with the key design aims being to promote greater turbulence of the circulating water and to maximise the heat transfer surface area of the unit. The unit has a maximum diameter of 80mm and can be installed in a 100mm dia. bore. The bore was drilled at the corner of Tutanekai Street and Pukaki Street with the DHE installed at a depth of 120metres and located in a permeable zone encountering geothermal fluid at 130