Evaluating the Potential of Pumped Hydro Energy Storage to Mitigate Dry-Year Hydroelectric Shortfalls in New Zealand
Derek (Xiangwen) Ding
21/07/2026
New Zealand’s electric system relies heavily on hydroelectric generation; thus, the system is vulnerable during dry years due to the shortage of precipitation. Pumped hydro energy storage (PHES) is a proposed option to store surplus electricity in a reservoir and release it when electric generation is limited from environmental factors. This study evaluates the extent to which the proposed Lake Onslow PHES could offset hydroelectric shortages during dry years.
A system-level energy and power model was developed using published design parameters such as a storage capacity of 7 TWh and the average hydraulic head of 615m. This model calculated stored and usable energy, discharge duration, and coverage ratios for dry-year shortfalls between 3 and 5 TWh. Assuming baseline data, the model provides around 5.6 TWh of usable energy and can cover a 5 TWh shortfall. Sensitivity analysis on the model showed storage availability is the greatest key performance indicator, where variations in hydraulic head have a modest effect. This highlights the importance of active storage volume in determining overall system performance.