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Author: Craig Memery
Contributor: Alicia Webb

Following the pre-feasibility activities (desktop study and site visit), the feasibility study looks at the chosen site in more detail. This stage focuses on firming up both financial and technical aspects of the wind farm. Financially, you need to assess costs for various aspects of the development. The technical aspects include layout design, and wind and energy modeling. At the end of this stage you should have a business case that summarises all the information you've gathered. You can present this to investors and the community before you start the more costly detailed assessment and planning application phase.

The feasibility study can take weeks or months, depending on how easy it is to get information, whether you need expert opinions, and the extent of any site constraints. Usually the feasibility study will run alongside discussions with landholders and other stakeholders. You should have a commercial arrangement with the landholder(s) during the feasibility stage and before you start detailed assessments and the planning application.

Main topics covered in this article include:

Engaging specialists

If the feasibility study is relatively straightforward and you don't discover any significant constraints, you might not need to hire specialist consultants at this stage. Specialist consultants can be expensive, so it's best to avoid hiring them until expert reports are needed to satisfy planning requirements. On the other hand, if aspects of your wind farm do require a specialist's involvement, it's best to arrange this early on, rather than find a significant issue later in the process.

If you need an expert opinion in the feasibility stage, you might be able to cut costs by:

  • seeking free advice from companies and individuals involved in wind farm development
  • engaging a TAFE or University, particularly engineering, science or environmental departments, to take on your requirements as projects
  • engaging not-for-profit organisations, retirees, or others who may be able to provide services fat a much lower cost than consultants.

With any of the above approaches you may still need the results verified by a specialist, particularly where there is significant risk or uncertainty, such as for grid connection costs or energy resource assessments.

Wind farm layout and design

Throughout the feasibility and detailed assessment stages you'll need to re-visit your wind farm layout and design. If you plan to have only one or two wind turbines and the optimal locations are obvious from the outset, your final layout may not change too much.

Defining a wind turbine layout is an iterative process. Having started with an initial layout, various technical or planning studies will reveal constraints, opportunities or business decisions that might affect the layout. Remember, each change will affect energy yield predicitons and you may need to make ongoing changes to your business case.

For the feasibility stage you need to come up with an initial layout that:

  • is detailed enough to undertake various investigations
  • satisfies the requirements of your business case
  • you can present to others, including landholders, specialists and other stakeholders.

When you present your layout, remember to emphasise that it's not a final layout and changes may occur based on further detailed studies. This is especially important for landholders, who may start calculating future rent according to the number of turbines planned for their land.

The best way to present the initial layout for your feasibility report is graphically. A scanned or digital copy of the 1:25,000 topographical map is suitable, as is a marked-up image from Google Earth or similar.

Your feasibility report may include relevant features of the site and surrounds, such as:

  • height contours
  • residences
  • property boundaries
  • possible constraints, including known cultural heritage sites, areas of native vegetation and woodland
  • waterways and areas subject to inundation
  • relevant planning and land use overlays
  • proposed wind turbine locations, including possible alternatives
  • existing and proposed roads and access tracks
  • existing and proposed electrical network infrastructure, including underground and overhead cabling, substations, etc.
  • potential locations for site works, including storage and office areas.

Electrical connection

If you haven't already contacted your local electrical distribution business, it's important you do so early in the feasibility process. The first thing you need to know is that the grid has the capacity to accept a generator of your project's size.

Grid connection is a complex area of wind farm development. Dealing with distributors can be difficult and the costs associated with connection may not be apparent until relatively late in the development process. This is a significant risk to the project viability, so it's vital you prioritise investigating grid connection.

There is a separate article on Grid connection in the feasibility section of the wiki.

Energy resource

Wind monitoring is essential for proving the viability of any wind project. Because the process takes at least a year, the feasibility process is often completed at the same time. Depending on how long it takes to put together your feasibility report, you may have already gathered data you can use for calculations and assumptions. However, be very careful how you use and interpret this data.

Interpreting short periods of measured wind data

If you've monitored the wind at the site for three months, stating the average wind speed for that period could misrepresent the viability of the project. Depending on seasonal variations you may have measured in the three fastest months, or the three slowest months of the year. In addition, wind speed varies every year and you need to estimate the wind speed for about 20 years - the project's approximate lifetime.

Adjusting the wind speed you've measured is an inexact process, but there are things you can do to reduce uncertainties in your business case and feasibility report. The most important thing is to find some wind speed data from the closest Bureau of Meteorology weather station. This data will indicate the seasonal variability at the weather station, which depending on proximity you can use to indicate the seasonal variability at your site. Bureau data will also indicate annual variability, so you can see if you measured in a fast or slow year.

You could ask a wind engineering consultant to help you with these adjustments, or perhaps even a community group member with a solid understanding of mathematics and statistics. At such an early stage of monitoring, the best you can hope for is a range of possible site average wind speeds, perhaps with a tolerance of 1 m/s or 0.5 m/s.

Wind speed modeling

If you've not yet started wind monitoring due to financial constraints, or because you suspect the site wind speed may not be very strong, you can try wind speed modeling. This is a specialist skill, and can be expensive. It's best to only undertake this if you have access to monitored wind speed data from a proximate mast, no more than about 10 km from your site.

Site access

There are two main site access issues to consider: 'onsite' and 'offsite', and you should mention both in your feasibility report.

Onsite access considerations

It's likely you'll need new access tracks on your wind farm site. Large, heavy trucks need to deliver large components to the turbine locations and to other works, such as the substation, sheds and offices.

Also, each turbine location will need what's known as a 'hardstand' or 'laydown area'. These are paved, flat spaces for the crane to stand on while constructing the turbines.

If your site is particularly hilly or complex, it's worth walking around and measuring the flattest route to each turbine location, and how large a hardstand you can accommodate. A helpful rule of thumb is that unsealed roads should be no steeper than a 1:7 gradient. In the case of very steep sites, roads can be sealed — you may need to investigate the cost of this and include it in your feasibility report.

Offsite access considerations

Because wind farms tend to be in rural areas, sometimes this requires upgrading the public roads leading to wind farm sites. The cost is often borne by the wind farm developer. It's worth inspecting the public roads your deliveries will use. Here are some issues to look out for:

  • The strength and width of local bridges. If they will need improving to accommodate heavy vehicles, make sure you look into the cost and feasibility of the work necessary.
  • The gradient of unsealed roads on the delivery route. Up to 1:7 is a good rule of thumb.
  • Roads must be wide enough for large trucks and accommodate their large turning circles - so look for tight bends, too.
  • There may be a requirement for traffic controls or road closures, as some trucks will be long and slow moving.
  • See if you might need access through neighbouring properties.
  • Fences and gates may need to be moved or replaced.
  • You may need to remove native vegetation to gain access.
  • Road surfaces and shoulders may need resurfacing if damage occurs through transportation.

If there are significant questions about any of these issues, it may be worth contacting a traffic or civil engineer to help with feasibility investigations.

Geotechnical

Building a wind farm requires extensive excavation for wind turbine foundations and underground cabling. Most ground conditions are suitable for wind turbines, as foundations are designed specifically for each site. However, very rocky ground, swampy areas with low-strength soils, or environments where underground caves pose a risk, may create issues. In these environments, excavation for foundations can be  a lot more expensive. So it's worth investigating the ground conditions at the feasibility stage. Geotechnical maps are available which may help you establish soil conditions in the area.

You can obtain more precise geotechnical data for wind turbine foundation design by drilling core samples to a depth of a few metres. Drilling is usually done in the design for construction phase, either by the turbine supplier or the civil contractor.

Noise

Noise is one of the most contentious issues surrounding wind farm development, so you need to treat it as a high priority design concern. Pre-feasibility noise concerns are simplified to simple set-back distances between turbines and houses. Preliminary noise studies in the feasibility stage are slightly more complex, but they're still a simplified version of a full noise study. Later, once the project is deemed feasible and you're ready to invest money in the detailed assessment phase, consultants will complete the detailed noise assessment studies you need for planning permission.

Read the article on Preliminary noise modelling in this feasibility section.

Flora and fauna

At the feasibility stage, you need to investigate flora and fauna issues more rigorously than during the pre-feasibility and site selection stages. Your feasibility report needs to include discussion of the regulatory bodies you've spoken with, and the resulting findings. A good place to start is with a call to the state government department responsible for flora and fauna. If you describe the location of your site they may be able to search databases for you and describe any endangered species or other significant environmental issues in the area. If you tell them you're a community group, they may even visit the site for you.

There are a number of resources, studies and maps available online you can use to identify potential flora and fauna constraints:

  • The federal government's Protected matters search tool.
  • State government maps or databases for threatened species.
  • Local government maps or studies of local environmental values.
  • Websites of local environmental groups, such as catchment management authorities, resource management authorities and bird watching groups.
  • Recent planning applications and environmental assessments for any large infrastructure projects in the local area.

If you avoid areas like waterways and native vegetation identified in your feasiblity study, this will substantially reduce potential issues in the development assessment and approvals stage. If you find significant issues at your site, you may need to hire a consultant to visit the site, which can cost up to $10,000. See the 'engaging specialists' section at the top of this article for ways to cut costs on consultancy.

Cultural heritage

At the feasibility stage, you also need to investigate cultural heritage at your site more rigorously. Your feasibility report should include details of discussions with relevant heritage groups, and the resulting findings. A good first step is to contact the Aboriginal representative body for your state. Often these organisations have databases of discovered cultural heritage sites.

There are a number of resources, studies and maps available online you can use to identify areas of cultural heritage significance:

  • The Australian Heritage Database.
  • State or local government maps or databases for cultural heritage.
  • Websites of local cultural heritage groups, such as local history organisations.
  • Recent planning applications for other large infrastructure projects in the local area.

If there have been many culturally significant findings near your wind farm site, there may be an issue, and you'll need to investigate further. For more information, see the Cultural Heritage article in the Detailed Assessments section of this wiki. If there are very few or no previously recorded cultural heritage sites near your wind farm site, it's sufficient to detail this in your feasibility report and move on.

Land use and planning

You'll need to check the planning provisions for the wind farm site under the local council development plan or planning scheme to make sure that a wind farm is not a prohibited form of development.

Record the land use, and zoning for the site in the feasibility report, along with any relevant planning provisions or overlays.

Shadow flicker

Shadow flicker occurs when the sun is low on the horizon behind a rotating wind turbine, which can cast moving shadows onto nearby residences. Depending on the time of year, this effect can last for several minutes each day. The best practice guidelines limit shadow flicker to a maximum of 30 hours per year on any surrounding residences.

Shadow flicker assessment, undertaken by an expert, is usually part of any planning application, and should be completed as part of the detailed assessment phase. At the feasibility stage however, it is usually adequate to assume that if your wind farm meets the conditions of the preliminary noise study, then shadow flicker will not be an issue.

Aeronautical assessment

During the detailed assessment phase of developing a wind farm it's important you communicate with aeronautical authorities. At the early feasibility stage, it's usually adequate to do an online search for local airports and to note the locations of these. If they are nearby, you may need to do some further investigation. For more information, see the Aeronautical assessment page in the detailed assessment section of this wiki.

Visual assessment

A feasibility study will involve describing the details of the community engagement undertaken to date, highlighting any potential visual issues or concerns. Usually, a key aspect of community engagement is preparing images of the proposed wind farm. These images are typically created using photos of the wind farm site taken from vantage points well known in the community (for example, an intersection in the centre of a nearby town, or the top of a hill). Wind engineers can model an image of the turbines on top of these backgrounds.

A consultant can do this modeling to a very high standard, including the use of specific wind turbine models, and GPS data of the photo location and the turbine locations. However, this can be quite expensive. The 'engaging specialists' section at the top of this article shows how you might have this work done more affordably.

Landholder engagement

Discussions and negotiations with landholders usually take place during the feasibility stage. An access licence agreement, giving you access to the property for the purposes of undertaking further studies, is sufficient for the feasibility and detailed assessment and approvals stages. You will usually have entered into an agreement about this before you start wind monitoring.

See the Landholder engagement article in this feasibility section for more information.

Community engagement

The level of community engagement at this stage will depend on several factors, which will influence the level of information you make publicly available. Importantly, most sites that undergo a feasibility assessment don't reach the construction stage.

Community wind farms are very different to commercial wind farms, and as such the community is probably already aware and supportive of the idea, if not the specifics. You'll find plenty of information about building community support in the Community engagement section of this wiki.

Common to all project stages is the need for careful and appropriate management of community relations. Refer to Planning consultation for more about this.

More information

Engaging specialists for environmental and technical studies