Amethyst Hydro Scheme
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Amethyst Hydro Power Station - a 7.6 MW run-of-river facility commissioned by Westpower in June 2013 and jointly owned with Harihari Hydro Ltd.
The 7.6 MW Amethyst Hydro Power Station was successfully commissioned by Westpower in June 2013. Amethyst Hydro Ltd, which owns the station, is a joint venture between Westpower (88% ownership) and Harihari Hydro Ltd (12% ownership).
The Station is situated 5 km east of Hari Hari adjacent to State Highway 6 near the Wanganui River Bridge. This page contains all the information you need to know about the Amethyst scheme.
What is Amethyst Hydro?
The 7.6 MW Amethyst Hydro Power Station was successfully commissioned by Westpower in June 2013. Amethyst Hydro Ltd, which owns the station, is a joint venture between Westpower (88% ownership) and Harihari Hydro Ltd (12% ownership).
The Station is situated 5 km east of Hari Hari adjacent to State Highway 6 near the Wanganui River Bridge. Water is taken from a stream bed intake high up in the Amethyst River and transported to the powerhouse via a tunnel and penstock with a total length of 2.5 km. The hydro scheme is located in challenging terrain and the Powerhouse is within 500m of the main Alpine Fault.
The station produces 50 GWH of energy per annum, enough to power 6,000 West Coast homes and businesses, significantly reducing losses in transmitting electricity to the West Coast. Additionally, the Station can run isolated from the National Grid to supply the South Westland load independently, greatly improving the security of supply to the South Westland area.
Who is involved with running it?
The station is operated by the Westpower Asset Management team, part of the ElectroNet Group, on behalf of Amethyst Hydro Limited.
It is remotely operated from the Network Operating Centre (NOC) in Greymouth. Regular check, maintenance and fault response is carried out by ElectroNet Contracting, with mechanical maintenance carried out by ReGenerate NZ based in Christchurch.
Other West Coast based contracting companies, along with technical specialists throughout New Zealand are engaged in various activities at the station.
How does it work?
Discover the innovative engineering behind the Amethyst Power Scheme, a testament to Westpower's commitment to sustainable energy New Zealand.
Low Level Weir
A low-level weir is used to extract water from the Amethyst River, eliminating the requirement for a dam structure and minimising the environmental footprint. Specially designed screen bars provide a self-cleaning action. This major civil construction effort was carried out with helicopter only access, requiring innovative management of plant and materials.
Isolated Running Capacity
Deflector governing capability gives superior frequency regulation. Innovative, fast-moving deflectors that can respond within 0.5 seconds, were specially designed to allow the station to respond to rapid load changes so South Westland can be supplied from Amethyst when isolated from the National Grid.
Remote Black Start Capacity
The station has been designed from the ground up to provide a remote black start capacity. This means the station can be restarted even when there is no supply from the National Grid.
Fast Response Synchronous Generator
The turbine is connected to a 9250 kVA 11 kV Synchronous Generator with full static excitation, providing fast and stable voltage supply.
Removable Powerhouse Roof
The Powerhouse roof has been designed to be easily removed for maintenance of the generator. This avoids the need for a much taller Powerhouse, which would otherwise be required to house an internal crane.
Tunnel
One of the biggest construction risks involved construction of the tunnel through uncertain rock conditions. The grade of the tunnel is 1 in 4.4, which is extremely steep and is at the maximum grade thought to be constructable using rubber-tired vehicles. The tunnel construction company (Geotech) was chosen due to their experience and familiarity with West Coast underground conditions.
New Zealand Designed Six-Jet Vertical Pelton Turbine
Deflector governing capability gives superior frequency regulation. Innovative, fast-moving deflectors that can respond within 0.5 seconds, were specially designed to allow the station to respond to rapid load changes so South Westland can be supplied from Amethyst when isolated from the National Grid.
This view from the tailrace shows water exiting from the turbine along a buried box culvert after powering the generator. From here it flows via a short tailrace directly out to the Wanganui River
General Information
The output from the station is stepped up to 33 kV via a small substation for connection into the nearby Westpower 33 kV sub transmission network.
Most of the scheme has been constructed in public land administered by the Department of Conservation and particular attention has been paid to minimising the environmental footprint, which is also in line with Westpower's commitment to the environment.
No dam is involved in the scheme, with a low-level weir used to abstract the water from the Amethyst River. This weir had to be constructed solely by helicopter access as the terrain precluded the installation of any roadway, which presented some difficult engineering challenges.
The Amethyst Power Scheme will provide benefits to South Westland electricity consumers for many years to come and demonstrates Westpower's ability to develop small, efficient run-of-the-river hydro schemes in an environmentally sensitive manner.
History of the project
The original 250 kW Amethyst Power Station, which was developed to supply the Harihari area, was commissioned in 1954 and decommissioned in 1991. It took water from the same river and was situated approximately 1 km upstream from the current site.
Construction of the current station commenced in 2010, with commissioning completed in June 2013.
