Offshore wind farms

OWFs are now proposed around as much as 75% of Australia’s coast.

A recent Blue Economy CRC report identified Bass Strait as a key wind resource, and the current suite of proposals in Australia’s EEZ extends from near Broome to Cape Leeuwin off Western Australia, areas of the Great Australian Bight, Bass Strait and from Gippsland to Cairns – the Southeast Trade winds in tropical seas are seen as an attractive resource.

A 2020 map of proposed Australian Renewable Energy Zones (REZs:) only showed one OWF area off the Southeast Victorian coast. State waters extend to 3 nautical miles from shore, so by constructing OWFs in Commonwealth waters, proponents avoid dealing with State Governments.

The Australian Federal Government formally proposed an area in Commonwealth waters off Gippsland, Victoria for offshore renewable energy projects in October this year that was declared with some changes in the areas involved – an interactive map of the declared area can be viewed here

There are now more than 20 companies looking to develop OWFs around Australia. Bass Strait is likely to see the greatest interest and construction effort, with relatively shallow waters (but see below) and proximity to major energy users on the mainland. While much of the interest in Bass Strait is in very preliminary stages, and likely that some proposals may not eventuate, some proposals are with the Federal Government for assessment under the EPBC Act.

Until recently, OWFs were constrained to waters shallower than 50-60m or so. The shallow waters of the North Sea allow relatively easy construction of OWFs there, but Australia’s continental shelves are relatively narrow and deep, limiting options for the placement of OWFs. However, earlier this year, an OWF with floating turbines commenced operating 140km off the Norwegian coast in 260-300m of water more details are here. It is presently unclear what the limits are to OWFs in terms of bathymetry around Australia, if any.

The engineering predictions are for larger turbines, with blade lengths of 125m+ by the mid-2030s, giving a rotor swept area diameter of 250m or greater, and a maximum tip height of ~300m ASL. There may be some benefit to the larger turbines as there is some preliminary evidence that the greater distance between the water surface and the lower tip height associated with larger turbines may allow for the birds to fly safely under the turbines. However, much more work is needed, and particularly so for Australasian species.

There is a range of behavioural responses by birds to the presence of turbines and associated infrastructure, including support vessels. Within the spectrum of behavioural responses, the reviewed literature places most of the emphasis on avoidance behaviour that occurs in both the horizontal (flying around a wind farm) and vertical (flying over or under a wind farm) planes. However, birds can also be attracted to windfarm infrastructure and support vessels as potential roosting sites or in response to a localised increase in food availability.

Birds may be displaced during specific migration periods or throughout some or all of the year during foraging trips. The behavioural responses are species-specific, and involve flying birds (e.g., species migrating or dispersing across Bass Strait) and feeding birds (such as penguins and other seabirds). At its most extreme level, an adverse impact would see a wind farm acting as a barrier to migration of birds or excluding birds from a foraging area.