A wind turbine works in the opposite way to a fan. Instead of using electricity to make wind, like a fan, turbines use the wind to make electricity.
Almost all wind turbines producing electricity consist of rotor blades that rotate around a horizontal hub. The hub is connected to a gearbox and generator, which are located inside a protective covering (called a nacelle).
Most wind turbines have three blades that face into the wind. The wind turns the blades round spinning the shaft which is connected to a generator. This is where the electricity is made. A generator is a machine that produces electrical energy from movement.
Large wind towers are mostly tubular, made of steel and generally painted light grey. The blades are made of glass-fibre reinforced polyester or wood-epoxy. They are light grey because this is the colour which is most inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.
These large turbines generating electricity are the opposite to wind pumps because they don't need a lot of turning force (torque) but do need to operate at high speed. This is why they generally only have two or three blades whereas wind pumps have many blades.
Wind generators are not noisy. It is possible to stand underneath a turbine and hold a conversation without having to raise your voice. When it is very windy, the noise of the wind masks the noise made by wind turbines.
Some of the new innovations in wind generation design include vertical axis turbines and more aerodynamic features or shrouded blades to improve the performance of small horizontal axis systems. Some models can be mounted on your roof in a similar way to roof ventilators.
Generally, you will need both AC and DC power for your home. DC power is produced by the wind turbine and can be stored in batteries. Then it can be converted to AC by using an inverter which also makes it suitable to export to the electricity grid. Check with the wind generator manufacturers for more specific information on configurations to suit your situation.
Conventional wind turbines start operating at wind speeds of 3 – 4 metres per second (around 10 km per hour) and reach maximum power output at around 13 metres per second (around 45 km per hour). At very high wind speeds — that is, gale force winds at 25 metres per second (90 km per hour) — wind turbines shut down.
The blades rotate at anything between 15 – 50 revolutions per minute at constant speed. However, an increasing number of machines operate at variable speed.
Some of the new, smaller models can begin operation at much lower wind speeds.
Small roof-mounted domestic wind generators
A typical wind farm of 20 turbines might extend over an area of one square kilometre. However, less than two per cent of the land area would be taken out of use so the remainder can be used as before. This makes it popular with farmers because their land can continue to be used for growing crops or grazing livestock. Wind turbines can be dismantled after 20 to 25 years and the land returned to virtually its former state.
Some of the smaller domestic wind generators can be installed in much smaller areas, including the roof of your home.
The amount of energy created by a wind turbine obviously depends on the amount of wind, but it can also vary from one turbine model to the next. Also, the higher that the "fan" of your turbine is located from the ground, the greater the wind speed will be and therefore the greater the energy output.
Domestic wind generators are usually used as stand-alone systems and are designed to charge a battery bank. They are usually between 300W – 5kW but in some instances they could include a 10kW or 20kW turbine. With new designs continually coming onto the market, the range of these outputs is also increasing.
To work out the most suitable wind system for your circumstances there are several things that you need to consider:
- How much electricity you will need in a typical day
- The physical aspects of your location
- The costs of purchase, construction (if relevant) and installation
- Total cost of ownership, which includes costs for
- insurance
- regular maintenance
- repair, and
- spare parts.
Working out typical energy needs
Most households use approximately 20 – 30 kilowatt hours per day, but this can vary enormously depending on your particular energy requirements and lifestyle.
More accurate information can be obtained from your electricity bill. It will tell you your average daily consumption for each quarter in kiloWatt hours.
Physical aspects of your location
Next you need to know the wind speed over time in your location.
Wind speeds are often measured in kilometres per hour (kph). Generally, wind speeds greater than 11 kph are needed before a wind turbine can start to generate electricity. Although there are wind generators that begin operation well below this speed.
Finding the wind speeds and directions in your area is simple through the Australian Bureau of Meteorology. Not all locations are listed on their website. If the information for your location is not listed you can contact the Bureau to request this information for your location.
Calculating power generated by different wind turbines
The next step is to work out the amount of electricity each wind turbine generates at different wind speeds. Refer to the manufacturer’s specifications to see how much energy will be generated at different speeds for each wind generator model that you are considering.
The amount of power generated by the turbine increases by a cube factor as wind speed increases. For example, if the wind speed doubles (2 x wind speed), the power generated increases by 2 x 2 x 2 = 8 times. If the wind speed triples (3 x wind speed), you get 3 x 3 x 3 = 27 times as much power.
Calculating the cost
Finally, you need to consider all the costs.
Add up the initial purchase, construction (if relevant) and installation costs. Add this to the ongoing costs including insurance, regular maintenance, necessary repairs and spare parts as required. More detailed information about these costs can be obtained from the generator manufacturers.
Find out if you’re eligible for the NSW Solar Bonus scheme, the ACT Feed-in Tariff scheme, or the Solar Buyback scheme. Of course, you should always check first with your accountant to determine any financial implications if you participate in one of these schemes.
You should also be aware that there are strict guidelines to follow when connecting a small wind generator (PDF, 117KB) to the electricity grid.
Once you have considered all these factors, you will be in a position to determine the best wind generator for your situation.
On a wind farm, when the wind stops blowing electricity continues to be provided by other forms of generation, such as gas. Our electricity system is mostly made up of large power stations and the system has to be able to cope if one of these large plants goes out of action.
It is possible to have up to 10% of the country's needs met by intermittent energy sources such as wind energy, without having to make any significant changes to the way the system operates.
For domestic wind generators, the electricity network continues to provide power as needed.
Generally not. Grid-connected generators typically work on the basis where all generated electricity is exported back to the grid. The system is wired and metered to do this.
While it is technically possible to install a switching mechanism, such a system would most likely be cost-prohibitive for the average householder. If you would like to pursue this option contact ActewAGL Distribution on 02 6293 5856 for more information.
Wind turbines cause very little permanent damage, occupying less than two per cent of the land area within a given wind farm boundary. They can be dismantled after 20 to 25 years and the land returned to virtually its former state.
Sheep, cows and horses are not disturbed by wind turbines and tend to use them for shade.
Any tall structure presents a risk to birds. However, the threat from wind turbines is not only very small compared to other impacts, it is also one of the most intensively studied of all risks to birds. New research at several operational Australian wind farms indicates that the risk to birds may be even less than first expected, and well below the predicted levels from models that were run as part of the approvals process. The research found not a single mortality for rare or significant bird species.
All wind farm developments are accountable under the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999 (EPBC).
Some people wonder why wind turbines aren't put out to sea. It is much more expensive to have offshore wind farms even though this is partially offset by the stronger winds generally found at sea producing more electricity. Australia does not have the space constraints of Europe and is surrounded by deeper seas. So it is unlikely Australia will have offshore wind farms for quite some time.