The Project

Contact Energy in partnership with the proprietors of Taheke 8C and Adjoining Blocks Incorporation (Taheke 8C) were developing a proposed geothermal power station project on the Taheke geothermal field near Lake Rotoiti.

The developers required a technology study and concept design with various alternatives for location of well pads, pipeline routing, and two power plant locations to optimize environmental constraints as well as resource potentialities. The concept design was to be used for resource consenting as well as for development feasibility and inputs into a business plan.

Our Role

Members of Thorndon Cook Power staff were engaged to perform the concept study which included:

• technology options and selection
• several options for power station sizes and locations
• pipe routings
• interconnection with the nearby high voltage grid
• definition of production and reinjection well pads locations
• water intake for drilling
• project description covering all main characteristics of equipment
• a summary of all inputs and discharges for the binary plant
• environmental assessment of all emissions, including NCGs

Our approach to the technology study was to consider options with a commercial history, and then optimise and evaluate how they would perform on the Taheke resource. Two technology options were carried forward to the project description that would give a consenting envelope that would allow the most economic choice when the project was implemented. The project description was developed in sufficient detail so that the scope and scale of works were fully understood for environmental consultants to assess the environmental effects .

Results

The Project Description was a comprehensive document incorporating equipment descriptions, site and plant layouts and processes. It was finalised following feedback from the environmental consultants on technical modifications to achieve a consentable framework.

At all times options were kept open to develop a consenting envelope that would allow the best solutions to be developed during detail design. This included wet cooling systems for binary plant to improve performance and reduce variations in output during hot ambient conditions. Allowance was also made for acid dosing if needed to prevent silica scaling.

To get a good understanding of the project parameters the plant was modelling with sophisticated plant process modelling software. This gave details of cycle performance and sizing of heat exchangers. Modelling also allowed quantification of the cost and performance benefits of wet cooling on binary plant.

Capabilities

Disciplines:
process design, mechanical engineering, electrical engineering

Roles:
conceptual engineering, feasibility studies, including economic analysis, owner's engineer roles