Kawerau Geothermal Power Station Hero

Kawerau Geothermal Power Station: the largest geothermal project to occur in New Zealand for over 20 years

A surge in demand for renewable energy and increasing concern over energy security has focused international attention on geothermal energy. Current global geothermal generation is around 11,000 MW. Estimates suggest this will more than double in the next 10 years – an investment of some US$40 billion.

In 2006 Mighty River Power commissioned a NZ$300 million geothermal power station at Kawerau as part of its strategy to meet the government’s objective of achieving 90% renewable electricity by 2025. This was the largest geothermal project in New Zealand for more than 20 years.

Hawkins Infrastructure was the ‘onshore partner’ for a consortium which included Sumitomo Corporation and Fuji Electric Systems to turn Mighty River Power’s vision into reality.

 

Mighty River Power’s aim:

  • To add 400MW of new generation by 2013 through a major, strategic geothermal power expansion programme.

What we did:

Acting as the ‘on-shore partner, we were responsible for the design and construction of the civil, structural, architectural and building services elements of the facility.

Site establishment and bulk earthworks commenced in January 2007. In order to protect the power plant from liquefaction and settlement issues in the event of a major earthquake, the 6-hectare site was excavated to a depth of 3 metres and re-compacted.

The erection of steel structures for the turbine building starting in July 2007, while commissioning work began in mid-2008. We were involved right to the end with roading, ground finishes, fencing and landscaping.

The project required: 

  • 8000m³ of concrete,
  • 1100 tonnes of reinforcing steel
  • 700 tonnes of structural steel

27 companies, and over 400 people, were employed on site at the peak of construction.

Unique challenges:

  • The powerhouse structure and turbine / generator pedestal required significant piling. Each pile was different and difficult to place as a result of large boulders (undiscovered in original soil investigations) and a hot and high water table. Although technically a relatively simple engineering exercise, the volume of information was immense and we decided to build a structural 3D model to integrate the interface of the pipe support with the foundations.
  • The pedestal structure was supported on a 1.6 metre raft foundation, 9 metres underground with 40 piles extending some 30 metres downwards. In order to prevent high internal temperatures from damaging the mix and causing cracks, as can happen with such depths of concrete, we developed a special concrete mix and methodology.

The outcome:

The Kawerau geothermal power station boosted the country's geothermal capacity by 25 percent and significantly increased local generation capacity in the Eastern Bay of Plenty. The plant meets approximately one third of residential and industrial demand in the region.

The project delivered best practice in many areas of sustainable development and energy efficiency, from sustainable geothermal reservoir management, distributed generation, engineering design and construction, to environmental management and community participation.

The project was completed three weeks early in August 2008. Originally specified as a 90MW power station, when delivered it produced in excess of 100MW. It’s success led to Hawkins working on the $430M, 140MW Nga Awa Purua geothermal power station at Rotokawa.