The coolest wind farm in the world
Innovative "spider" foundations
The Ross Island turbines' foundations required considerable thought and innovation. Pre-constructed by Leighs Construction in New Zealand, the foundations are an anchored structural steel design developed by structural engineers at Opus International Consultants.
"Our team for this project was selected not only for its technical expertise, but also for its knowledge and experience of Antarctica," explains Hamish Mackinven GIPENZ, a McMurdo Station veteran and Structural Engineer with Opus in Christchurch.
Prefabricating the foundations provided the team with a "practice run" for the real event, and an opportunity to proactively iron out any potential hiccups. However, unlike traditional turbine foundations, these steel versions – designed to sit above ground – needed to be absolutely level, otherwise the turbine towers would be out-of-plumb, making them unstable and unworkable.
Turbine foundations are usually just a poured concrete gravity pad base, to which the turbine tower is secured. It was not that straightforward in Antarctica.
Structural Engineer and Antarctic veteran Murray Mitchell MIPENZ, also with Opus, boasts an amazing quarter of a century's experience on the frozen continent and used his "inside knowledge" to resolve these sorts of problems. "You simply can't make concrete down there," Mr Mitchell says.
"Firstly there is no aggregate or fresh water available to make the concrete, (all the fresh water is made from seawater) and secondly, concrete just doesn't cure in the extremely cold temperatures – even in summer."
The foundations were designed to be level within an accuracy of plus or minus one millimetre over a 2.4-metre diameter flange. As the turbines and their foundations were manufactured on opposite sides of the world, Mr Mitchell's near-obsession with tight component accuracy tolerances is understandable.
Consequently, the Opus engineers worked closely with the German turbine manufacturers to ensure the foundations and turbine towers aligned and fitted correctly. The foundations sit above the ground, with eight legs radiating outwards. Each leg is secured to one of eight 13-tonne pre-cast concrete blocks arranged in a circle in an excavated pit, then backfilled and frozen in so the tops of the blocks are nearly flush with the ground. Each block is fitted with two 12-metre ground anchor bolts drilled and held in place with "Antarctic grout" (a mixture of hot water and sand which freezes rather than sets). This system provides adequate strength to support the turbines in the freezing wind gusts which can reach 240 kilometres per hour.
