Around New Zealand, TrustPower owns and operates 36 small to medium-sized hydroelectric generation stations. We called on this experience to successfully develop two small power stations in the Hawkes Bay - when others decided not to proceed. Esk Hydropower Project is named after the famous wine-growing valley, about 20km from the site. Two stations, Rimu and Toronui, will provide electricity for about 2,000 households. Rimu is the highest-head generation station in the North Island.
Innovative Thinking in Action
The Esk project is located in the headwaters of the Esk River, north of Napier, and is planned to be commissioned in July 2013. The scheme consists of two separate high head stations, drawing on separate Esk tributaries. They will produce a combined 3.8MW and an estimated 15GWh per annum: enough power for up to
Local Contractors: MAP Projects, AIE Hydroworks and Unison Contracting
The project's 16-month civil build is planned to be completed in July 2013. Conditions were at times highly challenging, with temperatures down to minus 5 degrees, and winds over 140km/hr.
The specialist civil contractor working on Esk, MAP Projects, is based in Raetehi, near Ohakune. Their experience in working in extreme environments, such as on the Mt Ruapehu ski fields and at National Park, proved a real asset. MAP Projects has worked with TrustPower on a number of previous schemes, and our strong relationship has been a cornerstone to the project's success.
Allied Industrial Engineering and Hydroworks (AIE/HW) are a joint venture. They bring together specialist fabrication, installation and management (AIE), with specialist water turbine design (HW). The two companies, based in Kawerau and Christchurch, produce world-class hydro-generation equipment for clients in New Zealand, Australia and the South Pacific. They provided turnkey hydro-generation equipment for the project.
Unison Networks, and their construction arm Unison Contracting, designed and built 17km of 33kV transmission and connected the scheme to the local grid. This challenging build included crossing Darky's Spur, where a steep 350m ascent tested the team's skills and resources.
Back in 2003, Toronui sheep and beef station owner Chris Pask conceived a hydro scheme that would utilise streams to power the local community. Over the next five years, he developed the proposed scheme to include Rimu scheme, located on the neighbouring Rimu station, owned by Dennis Bell.
TrustPower joined these local landowners in 2009, and progressed the Esk Hydropower Project through design, procurement and construction. The landowners wanted to ensure the Rimu waterfall, and upper Sutherland stream, were kept intact and we were pleased to develop the concept around these desires. Between 2009 and 2013, we worked with the landowners and local contractors to bring together a unique hydro development project.
Rimu has a gross head (vertical elevation difference between the intake and the power station) of 346m and a maximum consented flow of up to 1.0 cubic metres of water per second (cumec). Even with this modest flow, the station will be able to generate 2.4MW of clean green electricity.
Water is transported from the intake to the power station by a 2.4km penstock pipe. This is buried underground so farming activities can continue unaffected by the scheme, with no visual impact.
Toronui is smaller, with a design output of 1.4MW. The station has a gross head of over 140m, with a 900m penstock, and a maximum consented flow of up to 1.2 cumecs. There's a 4,000 cubic metre reservoir, enough to cater for twice daily periods of peak demand. As required by the consent, flow will be continuously released from the weir back to the streams.