A 115 kilometre 220-kilovolt overhead transmission line will connect the Renewable Energy Parks to the Tasmanian transmission network. Planning with TasNetworks has started, including exploring a potential route.
It’s important we find the best pathway that minimises impacts to properties, public land and the environment as much as possible.
Photomontages of the transmission line
To understand the changes in the visual landscape associated with the proposed transmission line, we’re undertaking two key work elements, one of which is called viewshed analysis.
Viewshed analysis measures the geographical area that may be visible from a specified location, in this case the tower locations. This analysis provides a map of the area the transmission line may (or may not) be visible from.
To develop the viewshed analysis, we’ve taken the proposed locations for towers, and used computer mapping software (ArcGIS) to determine surrounding points in line-of-sight with each tower location, based on a digital terrain model. The mapping is a worst-case scenario, using the tallest potential height for each tower (55 m).
To ensure we consider all potentially visible locations, the viewshed analysis ignores any obstruction from trees or buildings of the view of the transmission line. The viewshed analysis also ignores obstruction due to the influence of the horizon. It also assumes perfect atmospheric conditions.
Viewshed analysis isn’t a definitive tool to determine exactly whether a point can or can’t be seen, it’s a tool to indicate areas where a point is likely or unlikely to be visible, in order to determine suitable locations for further analysis, using photomontages.
The viewshed analysis has been used to determine specific locations for photomontages, based on the visibility of the development from different areas. Photomontages provide a detailed tool to understand the change in view from key viewpoints, such as roads (both tourist and non-tourist routes) and significant locations.
The second key work element we’re completing to show the visual impact of the towers and turbines is called a photomontage.
A photomontage involves combining two or more images to make one image. They allow us to show how the turbines and transmission line will appear in the landscape, precisely matching between site photographs, 3D models and digital terrain models.
The photomontage technique we’re using uses computer software and digital terrain models to add 3D models of infrastructure, that are based on their proposed location within the terrain. These models are then applied to photos taken of the terrain from key viewpoints.
They present what the turbines and transmission line would look like once constructed.
There’s no scale on the photomontage as scale bars provide a visual indication of the size of features, and distance between features, on a 2D plan or map only. In the case of the photomontages, it’s impossible to provide a single scale for each image, as the scale would vary with distance from the location the photo was taken from.
For example, heights of the turbines are all the same in the photomontages, but turbines in the foreground appear taller than turbines in the background.
Plans for a new transmission line
Our current plan for the new transmission line:
- Cables embedded into the bridge to move electricity from Robbins Island to mainland Tasmania
- Cables connect to an overhead transmission line that continues to the Jim’s Plain substation
- A transmission line connects Jim’s Plain Substation to the TasNetworks Hampshire to Staverton line at Hampshire
TasNetworks will be developing the Hampshire to Staverton line as part of its planned North West Transmission Development design to optimise renewable energy potential for Marinus Link and the Battery of the Nation developments. You can learn more at the TasNetworks website.
How the transmission line route is determined
The transmission line route is being determined through studies and consultation with directly affected landowners, stakeholders and planning authorities.
A preferred route will be subject to further consultation and planning approvals. We’ll continue to share information along the way.
What we consider when planning the route:
- Built up and sensitive areas: areas where people live and have property
- Public land: reserved land, timber production areas and forests
- Vegetation and threatened species: flora and fauna, vegetation communities and environmentally protected species
- Planning schemes relevant zones and overlays
Other options we explored for the connection
We also looked at some other options for how to connect to the Tasmanian transmission network. These include:
- Option 1: a new transmission line to the existing Smithton Substation
- Option 2: a new transmission line to the existing Burnie Substation
Our analysis of these options showed us that neither substation has capacity for the extra power generated by the Renewable Energy Parks.
Connecting to the National Electricity Market
We also explored the possibility of a direct connection across Bass Strait to the National Electricity Market in Victoria, including a T-connection to Marinus Link.
The cost of directly connecting across Bass Strait was approximately $1.5 - $2 billion which was too expensive and would make the project uneconomic.
The ability to T-connect to Marinus Link was also explored and found to be technically difficult and cost prohibitive. It would also be subject to Marinus Link's viability which is still to be confirmed.
Connecting to the strongest part of the Tasmanian transmission network and developing in conjunction with Marinus Link and Battery of the Nation will maximise project value. It will create jobs and economic activity, eventually lower power prices and allow for the export of excess energy to the mainland.
The transmission line towers will likely be 45 to 55 metres high.
On average they will be 400 metres apart, but these distances will vary depending on the route and landscape.
Each tower is micro-sited, meaning we'll look at the on-the-ground conditions and plan the route to minimise impacts.