Operation of a Test Facility for the Direct-Heat Use of Geothermal Energy

Abstract

The Rotorua Geothermal Task Force has recognised that the level of geothermal drawoff in Rotorua could be substantially reduced using simple energy conservation techniques. The Task Force has built a geothermal test facility to demonstrate the more effective utilisation of geothermal energy for direct-heat use. This facility incorporates a geothermally heated secondary system providing space heating through radiators and domestic hot water to a 100 m2 house. The heat loads, temperatures and mass flowrates throughout the heating system can be monitored using a data aquisition system. This facility has provided information on the minimum levels of geothermal drawoff necessary to provide continuous space heating in Rotorua's climatic conditions. The savings available through the use of thermal insulation, modern heat exchanger design and temperature control equipment are described. The facility has been open for public in spection since April 1985.

The test bed has also provided a means to measure the performance of different heat exchangers and temperature control devices under controlled conditions. Both shell- and- tube and plate type heat exchangers have been tested at a range of heat loads up to 15 kW. The temperature control equipment tested includes thermostatic steam condensate traps and teqerature actuated valves. Tiping was set up to show different insulatior. cladding materials; aluminium, malthoid and PVC products have been used to assess their suitability to geothermal applications in Rotorua.