Wind Energy Overview

Wind energy – introduction

People have harnessed the energy from wind for hundreds of years. Today, wind turbines are
constructed to generate renewable electricity. Wind turbines can be constructed and operated
individually, or grouped together to form a wind farm.

What is a wind turbine and how does it work?

A wind turbine is comprised of a tower, topped by an enclosure called a nacelle which holds the
propeller-like structure known as the rotor. Air flows past the turbine causing the rotor to spin.
The rotational energy is transferred via a gear box to the generator. The generator converts
the rotational energy to electricity. Most wind turbines have three blades which turn when
facing into the wind. The nacelle is designed so that it can rotate around the tower allowing
the turbine to produce electricity regardless of the wind direction.

What does a wind turbine look like?

Typically wind turbine towers in Australia are 50 to 80m tall. Wind turbines operate most effectively
in consistent winds. These winds are found at 50 – 80m from the ground surface. Towers are mostly
made of steel tubes and are held in place by large concrete footings. The rotor blades are made from
light composite materials such as fibreglass. The blades are up to 40m long.

Is a site windy enough for a wind farm?

For a wind farm to operate efficiently and be commercially viable, the site needs to have a
consistent wind resource. Wind monitoring is carried out to assess the nature of the wind
resource at sites which have the potential for wind energy development. Wind turbines begin
generating electricity when the blades start turning, typically in wind speeds of about 4 metres per second (m/s). A 1 MW turbine reaches its maximum power output at a wind speed of about 14m/s. At very high wind speeds (25m/s or 90km/hr) wind turbines shut down so that damage is not caused to the gearbox and generator.

Benefits of Renewable Energy and Wind Farms

Why develop wind energy projects?

Producing energy from sustainable sources such as wind reduces our heavy reliance on fossil fuel based sources. Moving toward renewable energy sources also reduces the total emissions of greenhouse gases’ which contribute to climate change. Both the Federal and NSW State governments have recognised the need to address climate change, and consequently have set upschemes to promote the use of renewable energy. The Federal government has passed legislation that requires electricity retailers, such as ActewAGL, to purchase a proportion of their electricity from renewable energy sources. These sources can include wind farms.

How much electricity can wind energy provide?

Wind turbines capable of generating 1-2 megawatts (MW) of electrical energy are now relatively common.

A 1 MW turbine would provide sufficient electricity to power approximately 300 homes, and save over
2000 tonnes of greenhouse gas emissions per year.¹

Local Benefits

Wind energy developments can create positive benefits for the local community through:

• increased tourism opportunities resulting from people making trips into the local area to view the wind farm once operational and associated increase of spending on local goods and services;
• employment opportunities for the local community both during construction and potentially for ongoing maintenance and management;
• spending in the local economy by construction employees (up to 80) during the construction period;
• local purchase of services (e.g. materials transport) and supplies (e.g. aggregate) for the wind farm both during construction and operation; and
• opportunities to inform and educate the public about renewable energy and the local environment through the proposed viewing platform and interpretive displays.

Potential Environmental Impacts

What are the potential environmental impacts of wind farms and what can
be done to reduce them?

The development of any infrastructure project such as a wind farm will result in some level of
environmental impact. Developers are required by law to carry out an environmental impact
assessment to consider the potential impacts of their project. The increased use of wind
energy around the world has lead to a greater understanding of the potential environmental
impacts of wind turbines and what can be done to reduce these impacts. Issues which have been
raised on previous wind farm schemes and the response used to lessen the impacts are
shown below:

Visual
Some people are concerned about the impact wind farms have on the landscape. During
environmental impact assessment the visual impact of a wind farm is considered. Visual
specialists determine where the wind farm will be seen from, the distance from where it will be
seen and the duration for which it will be seen. Visual specialists then determine the significance
of the visual impact. Where necessary, measures are taken to reduce the visual impact of wind
farms, such as sensitive siting of turbines and positioning of related infrastructure.

Shadow flicker
In some cases, when the sun is just above the horizon, the shadow cast by the rotating blades
can cause a flickering effect. The time at which this may occur and the exact position of the
shadow can be accurately calculated, and measures can be taken to reduce the effect.

Noise
A wind turbine has two potential sources of noise:
the noise of the turbine blades passing through the air and the mechanical noise of the gearbox and generator in the nacelle. Noise from the blades is minimised by careful attention to the design and manufacture of the blades. The noise from the gearbox and generator is contained in the nacelle by sound insulation and isolation materials. Wind farm developers in New South Wales must ensure
that the noise from wind farms complies with the Environmental Protection Agency's requirements
for noise. Well designed wind farms are generally quiet in operation and when turbines are positioned sensitively they do not impact on the surrounding community.

Birds and bats
Birds and bats may collide with wind turbines. Assessments can be undertaken to identify the
impact on any threatened or migratory species. Placing turbines to avoid flight paths and
incorporating spacing to allow for birds and bats to coexist with the wind farm minimises
impacts. Food sources can be relocated to draw birds and bats away from wind farms. Initial
monitoring results from wind farms in Victoria has found minimal deaths of common bird species,
with no deaths to rare, endangered or threatened birds.²

TV, radio and mobile phone interference
Wind turbines can interfere with analogue television reception, radio signals and mobile phones due to
either obstruction or reflection of the signal. Measures such as sensitive siting of turbines and
the use of fibreglass or epoxy resin in rotor blade construction can minimize the risk of interference.

1 Sustainable Energy Development Authority,
NSW Government, 2004. (www.seda.nsw.gov.au)
2 “Surveys indicate low risk to birds from wind farms“
Environment Victoria, 2 March 2004.