Metering geothermal takes in Rotorua – Project update

Abstract

As part of the review of the Rotorua Regional Geothermal Plan, the Bay of Plenty Regional Council (BOPRC)
established a metering project team to develop and effectively implement metering of the geothermal takes for fluid and energy in Rotorua. Currently, data on the actual use of the geothermal takes is of low accuracy and does not reflect the use profile over time. Therefore, this data is not suitable for developing a finer understanding of how different patterns and use levels affect the geothermal system, including the vulnerable geothermal surface features. BOPRC is closing this gap by starting to require continuous metering of ~75% of the water and heat takes from the Rotorua system. To achieve that, BOPRC first developed, trialled and proved a flow loop system that can meter the geothermal water takes with reasonable accuracy. Lately, BOPRC has also identified heat meters as a suitable method for monitoring heat and water takes in Rotorua. Take size thresholds in which different metering requirements would be required (e.g. spot measurements, continuous metering) were defined, based on the distribution of take
sizes, user profile and geographical coverage, to close spatial gaps, particularly on the 1.5 km mass abstraction exclusion zone, which protects the geyser flat. The analysis of the flow loop trial data showed that the actual use profile mirrored the expected profile for the different types of use (e.g. domestic,
commercial). Cost estimates for implementing metering for each user affected by the new metering requirement were carried out to understand the financial implications of those measures to the consent holders. The results showed that the costs are considered reasonable and proportional to the different user profiles and the new metering requirements. This project is now in the stages of rolling out to the largest
users.