About the Mahinerangi Wind Farm
TrustPower has Resource Consents for a 200MW wind farm at the Mahinerangi site, which were granted by the Otago Regional and Clutha District Councils. The Resource Consents allow for a maximum of 100 turbines at a maximum height of 145-metres.
In May 2010 TrustPower’s board of directors approved the first stage of development at the site. Stage One of the Mahinerangi Wind Farm will be a 36 MW development, which will include the installation of twelve 3MW Vestas V90 wind turbines. Construction of stage one started in September 2010, with the first power expected to be produced in February 2011 and the development completed and fully commissioned by May 2011.
The output of this stage will feed directly into an existing line, used by the Waipori hydro scheme, which is connected to Dunedin’s Halfway Bush substation, and then into the Dunedin local network. The long term expected annual output from stage one of the wind farm is forecast to be 105 GWh per annum, which is enough power to supply approximately 13,000 Dunedin homes.
Due to its location adjacent to the lake supplying the existing Waipori Hydro Scheme, the Mahinerangi Wind Farm will allow TrustPower to make the best of both wind and hydro resources. When the wind is blowing TrustPower will be able to conserve water for use when the wind is not blowing. When hydro storage and wind conditions are both plentiful the scheme will provide excellent peaking capacity.
The Mahinerangi Wind Farm Philosophy
An 'environment first', rather than 'engineering first', philosophy has been adopted for the MWF in order to ensure that the environmental carrying capacity of the site, and any associated thresholds, are respected.
With this philosophy in mind, TrustPower sought consent for a 'development envelope'. This approach provides flexibility, subject to resource consent conditions, for fine-tuning of the MWF in order to accommodate ecological, landscape, geotechnical and other environmental values.
The development envelope, for which consent was granted, consists of:
• A 1,723 ha area of land, as identified in Figure 1 (Volume 1 of the revised application documentation).
• A maximum installed capacity of up to 200 MW.
• A maximum turbine height, to the tip of the blade, of 145 metres.
• A maximum of 100 turbines.
This development envelope has been subject to continual refinement during project development in order to avoid adverse effects on important visual, landscape, ecological and archaeological values.
The approach adopted ensures that the environmental values of the site are not compromised and that the necessary flexibility for the engineering requirements of the scheme is provided for. Given this approach, generation potential can be maximised. Within the development envelope, detailed engineering design can aim to achieve the best mix of turbine capacity, tower height and associated tower spacing while also seeking to minimise, if not avoid, environmental effects.
In addition to the turbines, the MWF will also have the following facilities:
• An electrical transmission system. This will consist of a 33 kV underground cable network connecting each turbine to a substation which will be located within the MWF site. For stage 1 the wind farm will connect into an existing 33kV transmission line used for the Waipori hydro electric scheme. For subsequent stages the wind farm will require a new 110kV transmission line, with transmission poles under 20m in height, will connect the wind farm to Transpower's 110 kV Roxburgh to Halfway Bush line which is located around 7 km south of the proposed substation.
• An operations and maintenance building.
• An underground fibre optic network.
• Roof rain water collection system for a portable water supply.
• An on-site wastewater treatment and disposal system.
• Internal access tracks (approximately 7 km of tracks for stage 1 and 30 km for subsequent stages) within a maximum width of 12 m.
Construction of the facility would take place over 2 to 3 years. Construction will utilise standard construction equipment including large cranes. A concrete batching plant will be established on site and a construction water supply will be required. It is estimated that during the construction activities the total area of earthworks will cover an area of approximately 186.2 ha. However, just under 20 ha (i.e., under 2% of the total area of the site) will be associated with permanent site facilities such as turbine platforms, access tracks and buildings.