Alinta cancels 900MW Oven Mountain pumped hydro project in NSW

Alinta has cancelled its 900MW Oven Mountain pumped hydro project in New South Wales. The company cited economic and timing challenges as the primary reasons for the decision.

In a statement, Alinta said that “Economic and timing challenges on key elements of the project, including a critical transmission line, made it unviable to proceed.” The report was first published by RenewEconomy.

This move ends a planned large-scale energy storage development that was intended to support grid stability. The cancellation highlights the complexities developers face when aligning infrastructure timelines with market conditions.

Project Scale and Design

Located northwest of Kempsey in northern New South Wales, the Oven Mountain project was designed as a massive pumped hydro facility. The core of the system relies on a vertical distance of 600 metres between its upper and lower reservoirs. This significant height differential is the primary physical mechanism that allows the plant to store energy efficiently. Gravity drives water from the upper reservoir through turbines to generate electricity when demand is high, while excess power pumps water back up to the top basin when supply is abundant. The 600-metre drop provides the necessary pressure head to convert potential energy into electrical output with high efficiency, a fundamental requirement for any pumped hydro scheme to remain economically and technically viable.

The planned capacity was set at 900 megawatts, with a storage duration of eight hours. This specification indicates the project was intended to serve as a bulk energy storage asset rather than a short-duration frequency control device. An eight-hour window allows the facility to shift large amounts of renewable energy generated during the day into the evening peak period, a time when solar output drops and grid demand typically rises. By holding this volume of energy, the plant could theoretically supply power to over 600,000 homes. This scale classifies Oven Mountain as one of the largest proposed storage projects in the region, aiming to provide substantial grid stability and resilience. The combination of high power output and long duration reflects the industry’s need for firm, dispatchable capacity to balance the intermittent nature of wind and solar resources on the national grid.

Ownership and Construction History

• Alinta Energy received critical state significance status for the project in 2020.
• The project’s parent company, Alinta, was acquired by Singapore-based Sembcorp Industries, with the takeover completing in June 2024.
• In 2024, Alinta selected Gamuda and Ferrovial Construction as its contract partners for the development.

The decision to cancel the Oven Mountain scheme comes after a shift in corporate control that fundamentally altered the project’s strategic context. When Alinta secured critical state significance in 2020, it signaled a strong initial commitment to the site, a designation that typically streamlines environmental and planning approvals for large-scale infrastructure. However, the subsequent acquisition by Sembcorp Industries, finalized in June 2024, introduced a new layer of corporate oversight and potential portfolio reassessment. For large international energy players, integrating acquired assets often involves rigorous re-evaluation of capital expenditure against current market conditions, which may have contributed to the recent withdrawal.

The construction phase had already begun to take shape before the cancellation. By 2024, Alinta had engaged Gamuda and Ferrovial Construction as its primary contract partners. These firms are major players in the construction sector, and their involvement suggested that the project was moving from the planning stage toward active development. The selection of such partners implies that substantial groundwork, including site preparation and initial infrastructure planning, was likely underway or in advanced negotiation. The termination of the project now leaves these contractual agreements and the associated planning investments in a state of limbo, highlighting how rapidly the viability of large-scale energy storage projects can change when economic timing and critical infrastructure dependencies, such as transmission lines, do not align.

What to watch

With the cancellation confirmed, immediate attention shifts to the status of the contracts with Gamuda and Ferrovial Construction. Since these firms were selected as primary partners in 2024, the specific terms governing termination costs and liability allocation will determine the financial impact on Alinta’s balance sheet.

The broader implication extends to the critical transmission line cited in Alinta’s statement. The project’s failure was tied to economic and timing challenges on this infrastructure element, not just the plant itself. This raises questions about the current viability of other large-scale storage proposals in northern New South Wales that rely on similar grid connections. If the underlying transmission constraints remain unresolved, other developers may face similar hurdles in securing project finance. The market will be watching to see if this cancellation triggers a reassessment of regional grid capacity, potentially delaying other renewable integration plans that depend on the same network nodes.

Finally, the corporate context remains relevant. As Alinta operates under the ownership of Sembcorp Industries, future capital allocation decisions may reflect a more cautious approach to long-duration storage assets in Australia. The shift from a critical state significance designation in 2020 to a withdrawal in the current period underscores how quickly strategic priorities can change post-acquisition. Investors and industry participants should monitor whether Alinta or its parent company signals a pivot toward shorter-duration storage technologies or different geographic locations for future storage investments, as the specific conditions that made Oven Mountain unviable may not apply to all potential sites. The resolution of these contractual and strategic questions will define the next phase of Alinta’s portfolio strategy.