Highbank Power Station

Okay, so I'm here at the Highbank Power Station, which is pretty neat. It's a run-of-the-river hydroelectric station, meaning it gets its power from the flow of water, specifically from the Rangitata Diversion Race, or RDR. It's owned by Manawa Energy.

This place was officially opened by the Minister of Works, Bob Semple, back on June 16, 1945, when he "set the 36,000bhp in motion." What's really interesting is that the RDR scheme was actually built primarily for agricultural irrigation, not electricity generation. So, this station mostly generates power when there isn't a high demand for irrigation water, typically in the winter months. When it's generating, the water gets discharged into the Rakaia River.

Construction started in the early 1940s, beginning with an access road. World War II caused some significant delays because of shortages in manufacturing, materials, and manpower. The project finally finished in June 1945, after the RDR itself was completed in September 1944. There was even a bit of a dramatic story during construction: the ship carrying the original stator for the generator was sunk by enemy action, so they had to get a new one made in England! Flooding in February 1945 also caused a lot of damage, and the village of Highbank had to be relocated 390 meters upstream from the powerhouse.

The powerhouse itself is quite substantial—it’s a modern reinforced concrete structure, about 37 meters long and 16 meters wide, and 16 meters high. This height allowed for a 90-ton crane and a 10-ton auxiliary hoist to be installed. Both the generator and turbine, made by English Electric, were installed between 1942 and 1945. At the time, this generator was the largest single generating unit in New Zealand! It's a 20-pole unit rated for 26.5 MW, driven by a 36,000 bhp Francis turbine.

Power is generated at 11 kV here and then stepped up to 66 kV for transmission via a spur line to Methven.

They've made some upgrades over the years. In the 1970s, generation capacity had dropped quite a bit due to sediment, so they replaced the turbine runner and improved sediment control. More recently, in 2010, TrustPower (now Manawa Energy) added a pump station. This allows them to pump water from the Rakaia River back up the penstock—a 104-meter climb—into the RDR. This is a New Zealand first, apparently, and it helps with agricultural irrigation during peak summer months. They even have six 1.5 MW pumps here for that, and an air-chamber to protect the penstock from pressure fluctuations.

They've been doing a major upgrade lately, too. The original generation equipment, both the turbine and generator, were replaced in a project that started in November 2024 and should be done by May 2026. This new 29 MW turbine and generator are expected to boost output by 8 GWh per year. They also modified the pump station for the Barrhill-Chertsey irrigation scheme during this outage, so those pumps can now also generate 5.8 MW when not needed for irrigation.