| Title | Surface Heat Loss Assessment of Rotorua Geothermal Field |
|---|---|
| Authors | A. Seward, R. Reeves, P. Doorman, F. Sanders, S. Lor, N. Macdonald, T. Brakenrig and D. Graham |
| Year | 2020 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Rotorua, Geothermal Surface features, heat loss, heat flux |
| Abstract | Rotorua City is built around the active Rotorua Geothermal Field (RGF) which is valued for its areas of surface activity utilised for cooking, bathing, heating, and tourism. Understanding and monitoring changes in this dynamic geothermal system is crucial in allowing the resource to be used sustainably, while protecting the natural geothermal surface features. Changes in activity of geothermal features over time can indicate changes that may be occurring within the geothermal reservoir due to either natural or anthropogenic causes. Estimating heat loss from a geothermal field provides an indication of thermal activity present in the geothermal system at depth. We present a surface heat loss assessment of the Rotorua geothermal system and compare the results to earlier heat loss surveys, to assess changes in surface heat output. Flow rates, water temperatures and chemistries of major flowing springs and streams were measured, as well as water temperatures and surface areas of large geothermal pools. Calorimetry and ground temperature profiles were also collected from areas of ambient, heated and steaming ground. Evaporative heat loss is a key component of the total heat loss when there is a large surface area of water associated with naturally occurring geothermally heated springs and pools (as occurs in Rotorua). Calculated evaporative surface heat loss from the surveyed geothermal pools is estimated to be 248 MW. Total heat loss (evaporative, discharging flow, convective and conductive heat losses) for the areas surveyed is estimated to be 299 MW. This encompasses approximately 80% of the thermal areas in the RGF. |