Tasmanian hydropower icon powering towards a new future

05 October 2023



The iconic Tarraleah hydro scheme in Tasmania’s central highlands has been powering the state for more than 85 years. It’s an integral part of our system and needs replacing in the next 10 to 15 years.

 

This is an opportunity to reimagine the scheme to deliver more energy and improve operational flexibility to meet Tasmania’s future energy needs and suit a changing electricity market.

 

After rigorous analysis, we’ve landed on our preferred option for the site: full redevelopment with pressurised conveyance to deliver water from Lake King Williams to the new power station.

 

Of the options considered, this delivers the greatest capacity, storage, flexibility, and reliability for every dollar invested, while addressing environmental risk.

 

A redeveloped Tarraleah hydropower scheme would increase peak capacity from 90MW to 190MW and deliver 30 per cent more energy from the same amount of water.

The iconic Tarraleah penstocks as viewed from the platform near the village

 

The base cost estimate for this option is $1.05 billion (in 2023 dollars). This estimate will increase as we undertake more detailed assessments to progress the final business case and engage with potential suppliers.

 

Redevelopment of the Tarraleah hydropower scheme would be a boost for Tasmania, delivering 250 jobs during construction and helping to deliver the energy security needed to underpin future growth.

 

It’s a flagship project in supporting our Battery of the Nation initiative, our bold vision to maximise our hydro capacity, build long-duration storage and deliver clean, reliable energy for generations to come.

 

Here’s a closer look at the journey to this milestone and what’s next ...

Why does Tarraleah need to be redeveloped?

 

Doing nothing is not an option – the scheme is reaching the end of its life. We need to invest in the scheme to continue to generate enough clean energy to power Tasmania, operate more flexibly, and to mitigate the environmental and reliability risks that increase as the asset ages.

The Tarraleah Power Station control panel

 

1. Risk of an environmental incident

As the scheme ages, there is increased risk of conveyance failure and potential for an environmental incident in the adjacent Tasmanian Wilderness World Heritage Area (TWWHA). 

 

2. Scheme inflexibility

The scheme is manually operated (one of the few stations left that we don’t run remotely from our Hobart headquarters via our Energy Control System) and its generation is inflexible (we can’t turn it off and on as quickly as we’d like). This limits the scheme’s ability to respond to market signals and provide the flexible generation needed to maintain system security and reliability.

 

3. Reliability risk

Many parts of the scheme are now nearing the end of their operational life. This means planned and unplanned shutdowns will occur more frequently, and that represents lost generation from a scheme that is an important part of Hydro Tasmania’s annual generation (around 6.5%).

 

The stunning art deco architectural style is reflected perhaps best in the station foyer

 

    Tarraleah’s long network of canals convey water from Lake King William to the station

    The preferred option

    Redevelopment with a pressurised conveyance is the preferred option to progress to the final business case. A key differentiator of this option is the flexibility to respond to changing energy market conditions.

    it also offers the greatest value due to its inter-seasonal storage capabilities, and maximum flexibility and reliability. 

     

    The redeveloped scheme would include the following key works:

    • A new intake on Lake King William, a 1 km connecting intake tunnel and a spillway upgrade on Mossy Marsh Lagoon. These upgrade works are currently underway.
    • Connection of the new lake intake to a new surface pipeline which would connect to a 9 km long headrace tunnel, incorporating a mid-tunnel surge pond.
    • Construction of a 2.5 km long power tunnel, connecting the headrace tunnel at the base of the surge shaft to the power station. The tunnel will feed directly into a new power station.
    • The new power station would be constructed adjacent to the existing Tarraleah switchyard.
    • Construction of a surge shaft rising from the power tunnel, connected to a 70m high surge tower providing governing capability and surge protection.
    • A new 16 km transmission line connecting the new power station to the existing transmission line.
    • Decommissioning of assets no longer required including Nieterana Mini-hydro Power Station, Butlers Gorge Power Station, the existing Tarraleah Power Station, existing Tarraleah conveyances and Tarraleah No. 1 Pond. 

    An overview of the proposed scheme redevelopment and the upgrade works currently underway

     

    What’s next?

     

    We are preparing a final business case to support a Final Investment Decision currently planned for late 2024.

     

    This will determine how the investment stacks up. The project will only progress if it’s commercially viable for Hydro Tasmania and delivers benefits to Tasmania.

     

    And of course, we’ll continue to invest in our assets to maximise their capacity and to ensure they keep operating safely and reliably. Hydropower will play an increasingly critical and highly valuable role in the transition to renewables, particularly with growing demand in Tasmania and nationally.

     

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