The government has set the goal of having all electricity generated in New Zealand from renewable sources by 2035.
MainPower has been investigating options for renewable distributed generation in and around the North Canterbury region since 2004. In that time we have built a mini-hydro station at Cleardale and gained resource consent for a wind farm at Mt Cass.
Mini-hydro at Cleardale
MainPower’s first power station is at Cleardale on the north flank of Mount Hutt near the Rakaia River. The power station was constructed in 2010 and operates 24hrs a day, seven days a week, to produce around 4 million kWh's each year, enough energy for around 500 homes. To produce this, the station diverts up to 450 l/s (litres per second) from the upper reaches of Little River and transports it 2.3 kilometres via a buried pipeline to the power station, at which point the water pressure is around 30 bar (300m).
At the power station, the water is injected into a pelton wheel turbine rotating at 1000 rpm (revolutions per minute), which converts the energy into electricity via a 1 MegaWatt generator. Some water is diverted to a nearby irrigation scheme with the remainder discharged back into Little River.
In 2018, MainPower created Kakariki Power, so that the electricity generated at Cleardale could be used to power our head office, depots and substations. Our staff are also able to sign up for our Kakariki Power retail offering.
Mt Cass wind farm
MainPower holds resource consent for a wind farm site located on the Mt Cass ridge near Waipara in North Canterbury. We have been collecting wind data from the site since 1997 and were granted consent in 2012 to build a wind farm. When completed, the wind farm will be located along a 7.5km stretch on the ridge crest of Mt Cass at elevations of 400m to 560m.
In 2019, we lodged an application with the Hurunui District Council to vary some of the conditions of our existing consent. Essentially, technology has progressed since 2012 and we wanted to make sure we will be using the best possible resources. We now plan to use 22 of General Electric’s new 4.2-117 wind turbines.
The new technology has allowed us to reduce the original number of turbines down from 26 to 22. They are slightly larger turbines overall, with the tip height of the newer model increasing from 130m to 135m.
The turbines will be capable to producing 93MW of energy (up from 78MW), enough to power 40,000 homes.
When complete, the Mt Cass Wind Farm will be the largest wind farm in New Zealand's South Island, providing greater resilience to North Canterbury's electricity supply. It will be the largest wind farm owned by a non-gentailer in the country and has the capacity to offset 100,000 tonnes of greenhouse CO2 gas emissions.
For more information, visit the Mt Cass Wind Farm website.