Rotokawa upgrade project: Midlife geothermal power plant development and optimisation

Abstract

Mercury operates the Rotokawa and Ng? Awa P?rua geothermal power plants on the Rotokawa geothermal field located in the North Island of New Zealand. Over time, the geothermal fluid enthalpy has declined. The Rotokawa
Upgrade project was initiated to mitigate the impact of this enthalpy decline on the generation output of the two power stations.
This midlife upgrade project sought to rebalance the steam and brine flows from the Rotokawa reservoir between the two power stations. The rebalancing was completed through the installation of two new separators and by increasing the brine processing capability of the Rotokawa Power Station. The project has extended the operational life of Ng? Awa P?rua at design enthalpy and has resulted in a generation uplift at the Rotokawa power station.
The upgrade project was fully commissioned at the end of 2021. This paper presents the upgrade objectives, specific design aspects of the upgrade project, the performance of the generation equipment and ongoing optimisation efforts implemented over the two plus years since its completion.