As we transition to a low emission, low-cost, renewable dominated grid over the coming years and decades, Australia will need to significantly increase its fleet of dispatchable generators. Gas-powered generators can fulfil this function, but despite being touted by many as a ‘transition fuel’ and the supposed key to Australia’s Covid recovery, gas extraction and consumption is increasingly costly – economically, environmentally, and in terms of greenhouse emissions. Pumped Hydro Energy Storage (PHES) schemes offer a long-term, large-scale alternative – and whilst they are not without cost from environmental or economic perspectives, these should be seen in the context of the alternatives. In this post, we consider the environmental impacts of the Baw Baw PHES, and compare its metrics against a high profile gas extraction development.
Unlike traditional Hydro schemes, PHES does not rely on capturing and diverting the flow of natural watercourses. The proposed reservoirs would indeed capture rainwater from upstream catchment, but environmental flows below the dams can be maintained at up to 100% of present-day rate if required. This would not affect the viability of the scheme, as the captured water would represent only a fraction of the total energy passing through the scheme. Habitat, and other uses downstream should not – if managed carefully – be affected. There would be no effect on flows below the Thomson Dam, including the Gippsland lakes: unlike coal plants, PHES does not consume water.
Building the Baw Baw PHES scheme would, however, impact on native vegetation. The footprints of the reservoirs, pressure race, transmission lines, powerhouse, and required upgrades to existing access roads would result in significant modification, or loss, of vegetation and habitat currently within them. This should, however, be viewed in the context of other large-scale projects.
A high-profile Coal Seam Gas (CSG) project in NSW, currently nearing construction after almost a decade of seeking sign off, has approval to clear up to 1000 Hectares of native state forest within its footprint. The proponents estimate, at full production, it will deliver 200 TJ of gas per day: at standard heat rates (10 GJ/MWh for an open cycle turbine) this would represent 20 Gigawatt hours of electricity.
By contrast, stage one of the Baw Baw scheme (14 Gigawatt hours) is estimated to affect in the order of 160 Hectares of forest. The reservoir would have an area of 45 Hectares, and the balance arises from conservative estimates for the 40 km or so of new transmission corridor to the existing network; access road upgrades; and hydroelectric infrastructure. The transmission line would need to traverse approximately 4.5km of the Baw Baw national park north of Rawson- this section, however, may be tunnelled under the park. Once at the Thomson dam, the line would avoid significant forest clearing by stringing the line over the lake up to the powerhouse at the water’s edge.
Stage two, adding a further 56 Gigawatt hours of storage, may impact a further 170 Hectares of forest- comprising the 140 Hectare area of the reservoir, plus widening of existing access roads and a couple of kilometres of new road. The potential Thompson impacts on potential habitat of the endangered Baw Baw frog would need to be assessed, as historical sightings have been made nearby (see map above).
The impacts of the Baw Baw PHES scheme, estimated at about a third that of a Coal-Seam Gas project of comparable size, should be viewed in terms of its lifetime. Where the CSG project has an economic lifetime of only 20 years, the pumped hydro scheme would operate essentially indefinitely- not requiring the endless pursuit of new resource discoveries and extraction, each likely to be more expensive, difficult and environmentally fraught than those that came before it. In the next – and final – post, we consider possible pathways to the Baw Baw PHES coming to fruition.
* Our guest contributor is a Gippsland-bred engineer, working in the power industry. Links to previous posts are (1) the growing need for deep and medium storage and (2) further engineering insights and refinements. Still to come (4) how to progress