Highbank Power Station Redevelopment – Design Process for a Concrete Encased Turbine and Generator Plinth Replacement

Abstract

Manawa Energy, a renewable energy provider in New Zealand, operates a network of 26 power schemes from the Bay of Plenty in the North to Otago in the South. The Highbank Power Station stands as one of Manawa’s highest strategic value assets, featuring a 26.5MW generator and turbine scroll case assembly. Undertaking the full replacement of these components, particularly the concrete-encased turbine, presents a unique challenge not previously attempted in New Zealand. The total volume of concrete is approximately 310 m3, with a maximum diameter of 10m and a height of 7m. Collaborating closely with Manawa Energy, WSP has been engaged in a transformative project aimed to bring a new life to Highbank Power Station, which has been in operation for approximately 80 years.

The key challenges that design engineers faced included soil-structure interaction, the interaction of the existing station superstructure with the mass concrete, and the design of mass concrete to transfer seismic and operational loads. The design engineers utilized a 3-dimensional strut-and-tie model to quantify actions in the mass concrete, along with a combination of force and displacement-based analysis to ensure compatibility between the various components.

This paper describes the analysis, design, and methodologies deployed by design engineers to address the challenges for the replacement of the concrete-encased turbine and generator plinth.