BardsleyPosts

Lake Onslow pumped storage

^{Comment by Earl Bardsley, University of Waikato.}

^{The 8 square kilometre Lake Onslow reservoir as seen on February 21, 2023. This high basin above the Clutha River is currently under consideration by a private consortium to be converted into the upper reservoir of a pumped storage scheme. A tunnel connection would be constructed to the Clutha River, serving as the lower reservoir. The currently estimated construction cost is approximately $8 billion.}

^{The pump/generation capacity is anticipated to be 1000 MW. The main specifications of the scheme as currently proposed are shown below. Further information can be found here.}

^{Simulation studies from Clutha River flow records indicate in the order of 200 days for the first fill of the upper reservoir. There are no low-flow decades in the river flow record that would prevent the first fill operation.}

^{A feature of the scheme is the large 4 TWh energy storage capacity of the upper reservoir. This is of particular value for New Zealand because the existing 4.5 TWh of national energy storage means that hydro power output is vulnerable to occasional dry years. A further 1 TWh could be extracted by drawing down below 730 metres in the event of a rare extreme dry year emergency. This large storage capacity means the scheme would be the world’s largest by energy storage measure.}

^{A fortunate aspect for Onslow’s northward power transmission is that the transmission line was recently upgraded when there was uncertainty over whether the Tiwai aluminium smelter might be closed.}

^{It would be useful to have a large pumped storage scheme located in the South Island because in dry years North Island electricity would no longer need to be diverted south to offset reduced South Island hydro power output, largely offsetting the dry year need for the Huntly power station. The graph below gives relative magnitudes (from Transpower) of south to north electricity transfer (green) and north to south electricity transfer (black). Note the significant transfer to the South Island in the latter part of the 2024 dry winter.}

^{The current state of the Lake Onslow pumped storage scheme is that the private consortium anticipates submitting a substantive proposal before Christmas 2026, with the hope of gaining a decision from an appointed Fast-track panel in the first few months of 2027.}

^{The idea of pumped storage at Lake Onslow originates from the University of Waikato. Selected references and conference presentations are listed below.}

^{Bardsley, W.E. (2025). The hydrology of the lake Onslow pumped storage scheme. New Zealand Hydrological Society Annual Conference, Hamilton.}

^{Karaminik, Y. (2024). Environmental offsets and water resource opportunities with Lake Onslow pumped storage (MSc).}

^{Bardsley, W.E., Karaminik, Y., Majeed, M. (2022). Estimating Teviot River compensation flow to offset evaporation loss from Lake Onslow pumped storage. Journal of Hydrology (NZ), 61, p.179-182.}

^{Kamarinik, Y., Bardsley, W. E. (2020). Onslow pumped hydro: environmental offsets and spinoffs. New Zealand Hydrological Society Annual Conference, Invercargill.}

^{Majeed, M. (2019). Evaluating the potential for a multi-use seasonal pumped storage scheme in New Zealand’s South Island (PhD).}

^{Bardsley, W.E., Majeed, M. (2015). A multi-functional large pumped storage scheme for New Zealand in support of renewable energy development? International Congress on Modelling and Simulation (MODSIM2015). Gold Coast.}

^{Majeed, M., Bardsley, W. E. (2015). Assessment of economic and environmental advantages of a seasonal pumped storage scheme (Onslow, Central Otago). New Zealand Hydrological Society Annual Conference, Hamilton.}

^{Majeed, M., Bardsley, W. E. (2014). Simulation models to evaluate economic feasibility of a possible seasonal pumped storage scheme at Onslow, Central Otago. Electricity Engineers Association Conference Wellington.}

^{Majeed, K. M., Bardsley, W. E. (2012). Prospects for pumped storage in Central Otago. New Zealand Hydrological Society Annual Conference, Nelson.}

^{Bardsley, W. E. (2006). A pumped storage scheme for maintaining hydro electricity against climatic variations? (Invited paper) 8th Annual New Zealand Energy Summit, Wellington.}

^{Bardsley, W. E. (2006). China and New Zealand: Large seasonal pumped storage schemes for an electricity future using wind power and small hydro systems? International East Asia Regional Workshop of the International Academy Panel (IAP) on Water Security with Climate Change and Human Activity, Beijing.}

^{Bardsley, W. E., Leyland, B., Bear, S. F. (2006). A large pumped storage scheme for seasonal reliability of national power supply? Electricity Engineers Association Conference, Auckland.}

^{Bardsley, W. E. (2006). The Onslow seasonal pumped storage scheme revisited: An alternative approach to water level management of the southern hydro lakes? New Zealand Hydrological Society Annual Conference, Christchurch.}

^{Bardsley, W. E. (2005). Note on the pumped storage potential of the Onslow-Manorburn depression, New Zealand. Journal of Hydrology (NZ), 44, p.131-135.}

^{Bear, S. (2005). Hydrological evaluation of pumped storage in the Onslow-Manorburn basin (MSc).}

^{Bear, S. F., Bardsley, W. E. (2004). A large New Zealand pumped storage scheme for reliable power through dry years? New Zealand Hydrological Society Annual Conference, Queenstown.}

^{Bear, S. F., Bardsley, W. E. (2003). A pumped storage/thermal station hybrid for maintaining New Zealand electricity supply through dry years. New Zealand Hydrological Society Annual Conference, Taupo.}

^{Reports produced from the earlier MBIE NZ Battery investigations are currently listed under their heading “Lake Onslow pumped hydro”.}