Further engineering insights and refinements*
The Baw Baw Pumped Hydro Energy Storage (PHES) scheme, as described when first put forward here two years ago, would draw water from Lake Thomson to a new reservoir approximately 15 kilometers, and almost 700m higher, across the Baw Baw masiff. During times of peak demand water would return through the same underground tunnels, forming an energy storage scheme on a similar scale to Snowy 2.0, and the ‘Battery of the Nation’ proposal for Tasmania. As discussed in the previous post, such projects will be vital to accelerate Australia’s transition to a low emission, low cost, reliable energy supply, and will create and support regional jobs along the way.
The reservoir originally proposed is one of 22,000 found across Australia as part of a 2017 ANU study. Coupled with a two Gigawatt hydroelectric plant it would have a run-time of 28 hours – a ‘deep storage’ system that could smooth out variation in energy supply across months and seasons. Bringing this configuration online in one stage could, however, present challenges: as our energy supply transitions to become increasingly variable, shallow and medium-depth storage will be needed first, followed by more deep storage as the last coal plants come offline. Construction of the large, remote reservoir, and the 5km of tunneling under the Baw Baw range, would also be a significant undertaking, needing a compelling business case to justify it.
The scheme is now envisaged as being developed in two key stages. In the first stage, a smaller, 8GL reservoir (also found in the ANU study) situated on the east side of the Baw Baw range would be developed, much closer to the Thomson dam, as shown in the screen grab above.
If built initially with a one Gigawatt generation capacity, the scheme would run for 14 hours on a full charge: providing the medium-depth storage needed in the next phase of transition in the electricity market. The proximity to lake Thomson means underground tunneling would be limited to 1600m; the pressure race (pipes carrying water downhill) could be constructed above-ground; and the powerhouse close to the surface on the shore of the existing lake. These minimise cost, and together with the improved efficiency of shorter piping distance bolster the project’s business case. As coal plants progressively retire, additional generation capacity could be added: at two Gigawatts, this one-reservoir configuration would have a 7-hour depth of storage.
As the need emerges, the west reservoir (which, at 30 GL, would be much larger, and slightly higher) could be built – either to enhance the depth of storage, support further increases in power capacity, or both. This scheme could also provide an important insurance policy for Victoria for cases of extended ‘wind droughts’ or major network failures: the combined scheme would have 70 Gigawatt hours of dispachable generation.
No energy project is without its drawbacks, and environmental impacts of such a scheme would be unavoidable. In the next post we will consider these, and the context of projects of similar scale.
* Our guest contributor is a Gippsland-bred engineer, working in the power industry. The previous post is (1) the growing need for deep and medium storage. To follow on over the next month are (3) environmental impacts and (4) how to progress