Australia will face significant challenges in connecting offshore wind farms to onshore transmission networks and load centres in the latter part of this decade, a conference has heard.

Speaking at the Climate Smart Engineering Conference hosted by Engineers Australia last November, Charlotte Guthleben, Manager, Sustainability & Climate Change at Aurecon, presented findings from research that she conducted along with several other Aurecon colleagues (refer end of article).

The research focused on learnings which Australia could adopt from overseas in terms of how to connect offshore wind assets to the onshore electricity grid.

According to Guthleben, Australia will face challenges in integrating a large number of offshore wind projects with the onshore grid later in the decade.

“There is an incredible scale of feasibility assessment that is going on at present,” Guthleben said, referring to the large volume of offshore wind projects which are currently in the pipeline.

“While we are not expecting energisation of any of these until the late years of this decade, bringing any of them online is going to be a challenge with the current transmission pipeline.”

Huge Scale of Development

Guthleben’s comments come as Australia is embarking on a major program of construction of offshore wind facilities.

Offshore wind is seen as a critical part of the nation’s push to decarbonise its energy system and to meet carbon reduction targets of 43 percent compared with 2005 levels by 2030 and net zero by 2050.

In Victoria alone, the state has set offshore wind energy generation targets of at least 2GW, 4GW and 9GW by 2032, 2035 and 2040 respectively.

In August 2022, Federal Climate Change Minister Chris Bown announced that six areas had been declared as priority areas for offshore wind development.

These include Gippsland in Victoria, Hunter and Illawarra in New South Wales, the Southern Ocean off Victoria and South Australia, Bass Strait in Tasmania and an area in Western Australia.

Thus far, 60 proposed offshore wind projects have been announced. Of these 37 are in the Gippsland declared zone off the coast of Victoria.

Each of these projects is expected to be in the scale of at least 1-2 GW in capacity.

How Offshore Connection Works

Before discussing challenges, Guthleben provided an overview of the journey of energy from the point of generation at offshore turbines to connection with the onshore grid.

This works as follows:

• First, energy which is generated from offshore turbines is feed to an offshore substation via inter array cables.
• From the substation, the energy is often transmitted via subsea cables to a collector substation which collects energy generated from multiple projects.
• From collector stations, energy is transmitted onshore to a converter substation via export cables. These cables will either be high voltage DC or high voltage AC cables depending on the distance involved.
• Finally, energy travels from the onshore converter station to the existing grid. This is typically done via high voltage AC conductor systems.

(Overview of key network components of offshore wind transmission – refer top part of image. Source: Aurecon)

Technical and Planning Challenges

According to Guthleben, challenges associated with connecting offshore assets revolve around two areas.

First, there are technical difficulties which are inherent in the design of offshore cables.

For several reasons, Guthleben says that offshore cables are more difficult to construct, maintain and upgrade compared with onshore assets.

Compared with onshore counterparts, offshore projects involve higher entry costs in order to deliver projects. This is leading developers to pursue economies of scale and is driving the massive scale that we are seeing on offshore projects (refer above) in terms of project size and cost.

Next, the complex nature of construction is driving challenges in terms of incremental development as multiple projects are developed. In particular, construction and maintenance in the offshore environment requires access, highly specialised engineering services and boat operators.

Added to this challenge is a significant concentration of industry expertise in the Northern Hemisphere. Such a concentration arises as the Northern Hemisphere has thus far been the focus of offshore development activity.

That concentration of resources adds further to repair times as operators may need to be sourced from the Northern Hemisphere.

Next, there are social and environmental challenges.

A particular advantage in placing wind turbines offshore involves reduced impacts which are associated with land use, aesthetics and noise.

However, offshore development can involve additional social and environmental impacts that need to be mitigated when transmission systems land onshore.

For a 2.5 GW wind farm, for example, we could expect six 275 KV lines coming onshore. These may require easements in the length of 100 to 120 meters.  This may affect coastal communities. Where possible, such effects need to be mitigated.

Finally, construction of connecting infrastructure involves working in sensitive marine environments with assets that have not as yet been tested in Australia.

This means that planning will take longer and that impacts which may occur during construction and operation will need to be mitigated where possible.

Taking all these factors into account, Guthleben says that offshore wind connection projects are challenging to plan and construct.

Moreover, she stresses that it is imperative that these projects are carefully planned so as to derive the optimal size and scale of projects at first instance.

Doing this will help to avoid any unnecessary incremental construction and resulting fatigue on communities. Such planning will also help to maximise the benefits from opportunities which are associated with cost efficiency.

(The relatively low density of energy users in Australia (left) compared with the situation in Europe (right) poses challenges in delivering new transmission infrastructure on a cost-effective basis.)

Beyond technical challenges, Guthleben says that sufficient planning is important to ensure that Australia’s onshore transmission network is suitably equipped to manage the additional energy which is coming from offshore.

A particular challenge in this area involves the relatively low density of energy customers in Australia.

In Australia, the East Coast transmission network currently serves around 20 million people over an area of roughly 3,000 kilometres.

In Europe, transmission covering a similar area serves more than 600 million customers.

This presents challenges in terms of financial viability of transmission infrastructure investment along with the need to minimise transition charges for energy consumers.

Recently, both state and national governments have sought to help address this by examining ways to accelerate planning for transmission networks. This has been done through Renewable Energy Zones, planning bodies, new revenue structures to support connecting generators and accelerated planning and approval pathways.

When planning for transmission, however, Guthleben stresses the need to consider offshore generation and how to successfully connect offshore projects to onshore transmission.

As things stand, this is problematic for Australia as the nation does not currently have any national framework to manage the connection of offshore generation to the onshore transmission network.

Taking a look at the overseas situation, Guthleben says there are various models of offshore transmission ownership and planning in relation to core transmission network components (see below).

In countries such as Denmark, the Netherlands, France and Norway, for example, the offshore transmission network (collector substations, onshore converter substations and associated cables etc.) is owned and managed by either the government or a national transmission system operator. These parties act as the central planner and owner for the offshore transmission infrastructure.

Such an approach helps to provide better coordination as planning is performed at a national level with a holistic view of the system.

By contrast, in the US, China and Taiwan, a developer led model sees the planning and development of offshore transmission infrastructure undertaken by developers.

According to Guthleben, such an approach can offer advantages in terms of greater speed of development and delivery in regard to the offshore transmission assets.

Where such approaches are adopted, however, it is important to ensure that there is sufficient onshore transmission capacity to keep pace with the volume of energy which is being generated from offshore sources and delivered into the grid.

(Overview of key network components of offshore wind transmission and ownership structure of key network components. Source: Aurecon)

A Coordinated Approach is Needed

Overall, Guthleben says there are several strategies which Australia needs to adopt.

Above all, the nation needs to adopt a coordinated approach to infrastructure delivery, offshore collector assets and planning and regulation.

In terms of infrastructure delivery, coordination is necessary to help to minimise social and environmental impacts and to de-risk approval processes for projects.

Such coordination will also enable the incorporation of learnings from the Renewable Energy Zone projects onshore.

In terms of offshore collection assets, these need to be carefully considered in order to derive social and environmental gains as well as economies of scale.

In particular, it is important to avoid the need to have multiple export cables coming to land where possible. This will help to reduce not only onshore impacts but also community fatigue.

This will be particularly important within the Gippsland declared offshore wind zone in Victoria on account of the density of projects which are expected to be developed in this area.

Finally, Guthleben says that planning frameworks will need reform to ensure a coordinated approach to regulation and approval.

This will help to deliver certainty to planners and investors.

In particular, Guthleben says that coordination will be needed in order to avoid projects becoming delayed by bottlenecks which may occur as a result of Commonwealth/State duplication.

Such bottlenecks may arise out of a gap in the current regulatory framework that sees state government responsible for planning and approvals up to three nautical miles off the coast beyond which the Commonwealth takes over as waters become Commonwealth waters.

Concluding Remarks

Finally, Guthleben makes several other comments and observations.

“The shared onshore transmission capacity forms the main limit on ultimate capacity of any offshore wind development,” she said.

“We need to make sure that this is invested in at the same time (as offshore assets).

“Secondly, we need to be planning and coordinating onshore and offshore transmission centrally at a state level where possible to minimise impacts on coastal communities.

“Thirdly, the scale of these different declared zones means that there is no one-size-fits-all for what these projects are going to look like (in terms of the connection solution which is appropriate). We need to be carefully considering them in each case.

“Finally, we need to determine effective offshore asset planning and ownership models in order to clarify frameworks for planning.”

Guthleben’s research was conducted in conjunction with her Aurecon colleagues Andreas Laubi, Claire Whiteway, Paul Cann and Chris Amos.

(Reader note: a broader discussion on successful strategies regarding offshore wind projects in Australia was posted by Paul Conn on the Aurecon blog.)

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