Harvesting the Winds of Change: The Promising Future of Offshore Wind Energy in Australia

In the last 20 years, offshore wind has come a long way. Two decades ago, it was an early-stage conceptual technology that posed significant economic and technical challenges to the energy industry. Today, globally it is a proven market where developers can take on projects with greater levels of technical certainty. However, each emerging market has its own unique technical hurdles to overcome. Due to global supply chain pressures and infrastructure availability, there are also still real challenges that require navigating to make offshore wind work as a commercial venture.

Around Australia, the Federal government has identified 6 potential areas for offshore wind development:

• The Bass Strait region off Greater Gippsland, VIC.
• The Pacific Ocean region off the Hunter / Newcastle NSW.
• The Southern Ocean region off Portland, VIC.
• The Pacific Ocean region off the Illawarra, NSW.
• The Bass Strait region off Northern TAS.
• The Indian Ocean region off Perth/Bunbury, WA

The Greater Gippsland area was the first area declared with Feasibility Licence applications accepted until the end of April 2023. Since then, the Hunter Region in NSW was declared in July 2023 and the Southern Ocean and Illawarra areas have been announced as proposed areas and are out for public consultation.

A notice of proposal to declare the Perth/Bunbury area will commence the public consultation process is expected to occur November 2023. In addition to offshore Perth and Bunbury, developers have identified sites suitable for offshore wind from Bunbury to the Midwest (Kalbarri) – leading to the opportunity for further declared areas all along the WA coastline.

As Australia is on the brink of establishing offshore wind energy production, it is critical to understand what has been successful — and not so successful — in other regions — and blend these learnings with decades of local expertise and experience with offshore Oil & Gas projects. Each developer will have to assess the feasibility of each site and navigate the site’s strengths and weaknesses to develop an engineering and commercially viable solution. For example, local and regional supply chains, nearby ports, seabed conditions, metocean parameters, wind resource, grid connection opportunities and environmental sensitivities.

Local and Regional Supply Chains

Within Australia, there are aspects of the local supply chain that could lend itself to offshore wind development. For example, with WA’s long-standing expertise with offshore O&G, engineering and design, and offshore maintenance skill sets are well suited to support. Similarly, opportunities for pin-pile and WTG tower fabrication, site survey personnel, onshore infrastructure, installation staging, WTG assembly and smaller support vessel fabrication (e.g., CTVs) etc. exist with current capabilities or moderate investment.

Notably, the Western Australian government has recently allocated $10mill for a full feasibility study to set up turbine manufacturing in the state ​[1]​, including identifying the requirements for a potential manufacturing hub in WA, and government and funding required for WA businesses to transition to manufacturing wind turbine components. For example, establishing a Common User Facility (CUF) at an existing industrial hub, such as the Australian Marine Complex (AMC) or Bunbury.

WA also has several fabricators present with capability to support the offshore wind sector. For example, Civmec at AMC has the capability to manufacture offshore structures including jackets, topsides, and anchoring systems ​[2]​; but may require expansion to undertake complete offshore wind construction.

There are also a significant number of long lead items (greater than 4 years) that require careful consideration and early engagement with suppliers (e.g., cables, turbines and offshore substations, and construction vessel contracts ​[3]​). Due to the significant increase in global demand for subsea cables with the growth of offshore wind, many global cable manufacturing companies are currently operating at full capacity.

Ports and Logistics

During the construction phase of an offshore wind development, a staging port is required for marshalling components, pre-assembly, and support installation activities.

Nominally a port would be required to have a quayside and channel able to accommodate large construction vessels with 8m to 12m draft and lengths of over 200m. In addition, overhead clearance of greater than 140m would be required to facilitate the pre-assembly and vertical transportation of the wind turbine towers to the windfarm. There are further sea access requirements, such as turning basins, tidal restrictions, sufficient channel depths, as well as 24hr access and pilotage. Adequate quayside capacity is also essential for windfarm components (e.g., a minimum bearing capacity of 10te/m2 for turbine components and exceeding 20te/m2 for support structure components).

Land availability is also a critical factor for a successful offshore wind development. Dependent upon the construction execution schedules, ongoing quayside laydown of approximately 10ha to 25ha would be required to support a 2GW development for example. Where offshore construction conditions are more challenging, increased installation staging may be required to assure the greatest installation efficiency whilst favourable weather conditions are present. The more exposed locations from the Indian Ocean could experience from 40% to 60% installation downtime, in comparison to approximately 20% in the nearshore areas. Location is also critical for a port as it affects the time spent transporting components to the wind farm site for installation.

Within the Perth / Bunbury area, the AMC and Port of Bunbury are nearby deepwater ports, that have access to a considerable resource pool and support industries, which may play a vital role in the development of offshore wind. However, existing, and future uses of the ports, as well as shipping lanes would have to be well understood for a successful execution and site selection.

AMC comprises of two development areas. The Southern Harbour includes the CUF, which is an integrated and open-access fabrication, assembly, commissioning, maintenance, and repair facility. The CUF has 3 heavy load-out wharves and approximately 28ha of laydown area ​[4]​. In addition, the undeveloped lots of the Northern Harbour may be suitably dedicated to support offshore wind developments in the future​ [5]​.

The Port of Bunbury is a part of Southern Ports group and has the largest land holding of any port in Australia and capacity for significant organic growth ​[6]​. The Port is working in conjunction with State government and other agencies to assist in the development of initiatives such as the Advanced Manufacturing Hub with an increased focus on renewable energy​ [7]​.

Site Characterisation

Due to the nearshore Indian Ocean water depths offshore WA, developments are likely to be fixed-bottom foundations (i.e., jackets, monopiles or Gravity-Based Structures (GBS)), rather than the floating foundations anticipated for offshore NSW.

Offshore Australia nominally has ground conditions comprising high percentage carbonate soils. As such, Oil & Gas fixed-bottom foundations (i.e., in Bass Strait and North-West Shelf) have utilised drilled and grouted piles. This is due to the risk of cemented layers resulting in the inability to install driven piles to target depth and potentially leading to pile tip buckling, as well as the very low axial capacities and poor cyclic performance of driven piles in carbonate materials. Piles for offshore wind would be subjected to a significantly more intense cyclic loading regime than those in Oil & Gas applications and therefore the risk of poor performance under cyclic loading would likely be further increased.

Experience in the offshore wind industry to date in Europe is that axial capacity is not a governing factor for monopile sizing. This state of affair may not apply to offshore Australia in carbonate materials, which would lead to a very low shaft resistance for a driven monopile, potentially meaning the soil could have insufficient capacity to support the deadweight of the monopile and turbine. Furthermore, the risk of pile tip buckling for these structures with very large D/t ratios in potentially unevenly cemented materials warrants careful attention.

(Concrete) GBSs were utilised in the early stages of offshore wind developments globally and more recently with the Fécamp offshore wind farm. When considering GBS, the feasibility of local construction and installation requires careful considerations as the overall structure weights and footprints are often much greater than monopiles and jackets. There are limited dry docks and suitable construction areas in proximity of Perth / Bunbury to support float out installation of GBS’s likely leading to requirements for large and costly construction vessels requiring to be mobilised from Europe to facilitate lift installations.

To understand the risks posed by the local ground conditions, desktop geophysical and geotechnical studies are recommended to be undertaken at the earliest stage of a project with one of the many specialist outfits familiar with the local conditions based in WA. As the project develops, the desktop study would be followed by geophysical and geotechnical surveys.

The local wind resource will have a considerable impact on the energy yield at the site and as such the Levelised Cost of Energy (LCoE). The more exposed regions of the Perth / Bunbury area to the swell of the Indian Ocean may be subject to increased construction durations; however, this may be counteracted by increased wind resource and ultimately energy yield.

Inter Array, Export and Grid Connection

For a site to be deemed suitable for the establishment of offshore wind, the site is ideally located near to a utility grid for a reliable and secure grid connection at high efficiency levels.

There are numerous prevailing challenges associated with offshore wind developments including:

• How to best transmit and deliver energy into the grid and how to establish a safe grid connection.
• Establishing a preferred option for transmission (i.e., a HVAC or HVDC system). Where there are long transmission distances, the preferred option would be HVDC, due to reduced losses over longer transmission routes compared to HVAC cables. Although, it is also possible to increase the transmission capacity of HVAC cable system by careful design and application of reactive compensation techniques.
• Identifying an optimum Point of Connection (POC) to the grid. In many areas, the electrical system close to the coastline is not sufficient to carry large amounts of power from the offshore wind farms further into the grid. However, transmission capacity may be available in the future when traditional power generation plants retire.
• Cable failures are costly, both due to the actual repair cost but also the potential downtime and lost generation due to long lead items and the remoteness of Australia from the supply chain. Therefore, cable reliability and protection require careful consideration.

Site and Technology Concept Selection

Through holistically assessing potential sites considering the physical environment, local niches, wind energy yield and wind farm costing – informed decisions regarding the selection and layout of a wind farm area can be made at the very earliest development stages.

Kent’s own expertise, in addition to our in-house Virtual Wind Farm Tool (VWFT) supports this process and assists developers to understand the impact of uncertainties and unknown data at the early stages of development, elevating design agency and decisions making.

The VWFT facilitates wind farm configuration design, energy production, estimation of wind farm CAPEX & LCoE, and optimisation of wind farm configurations to desired criteria. The software allows the infrastructure to be interactively and automatically designed, the VWFTs capabilities include:

• Definition of site-specific boundaries, constraints, bathymetry, soil data, environmental conditions, wind resource, etc.
• Evaluation of wind energy yield, including wake modelling.
• Design approximations of turbine, substructure, and foundation.
• Through-life costing covering design, fabrication, transportation & installation, O&M and decommissioning.

There is a comprehensive set of data files and settings that input to the software analysis defining soil strengths, turbine information, wind resource, substructure characteristics backed by in-house as-built design data, fabrication costs, installation vessels rates and durations, O&M costs etc.

Every wind farm development has its own unique characteristics, as such the databases for the VWFT can be collaboratively tailored to suit the specifics of each site based on Kent’s knowledge and experience, internal and external networks, and other project stakeholders.

To support the understanding of the relative LCoE across the Perth / Bunbury area considering the local site conditions. Kent has comprised a holistic relative LCoE heat map as a function of the mean (see below) that demonstrates the potential variability across the Perth / Bunbury area.