Wind power
New Zealand's climate makes wind power ideal for many properties.
Wind turbines range from 1kW systems for households to 20kW systems for farms or communities, to large systems of up to 5000kW for commercial power generation.
On the right type of property in the right location, a small-scale wind turbine can be a cost-effective and environmentally friendly way to generate your electricity.
However, it is unusual to depend only on a wind turbine. A backup system (such as photovoltaics and batteries or a diesel generator) is needed for when there isn't enough wind.
How does wind power work?
Wind generators come in different shapes and sizes, but they all work according to the same principle: wind spins a turbine (which is generally shaped like a propeller) and the turbine, in turn, drives an alternator to generate electricity. The stronger the wind blows, the more electricity is generated (within limits and depending upon the turbine design).
To make the most of the wind, the turbine has to be atop a tower and a good distance from obstructions such as buildings and trees.
For a stand-alone system, the electricity is stored in a battery for use when it is needed.
How much power can a wind system generate?
The amount of power generated depends on the system you use, the location of the wind turbine and the average wind speed.
A typical small, 1kW, wind generator can produce about 12kWh per day (500W on average) in high average wind speeds of 10 metres per second, and just 0.7kWh per day on sites with low average wind speeds of 3 metres per second. So it makes a big difference whether you live on top of a hill near Palmerston North or on the plains around Blenheim.
The average New Zealand household uses about 10,000kWh of electricity a year - which equals just under 27.5kWh per day.
A rural home using as little electricity as possible may use only 5kWh of electricity per day. The NZ Wind Energy Association suggests a 1kW generator is about right for many locations, so long as there is photovoltaic and battery back-up.
Grid connection
You may be able to connect to the grid and sell power back to your retailer. However, your ability to do this will depend on whether the retailer can accommodate the variable output that will result from changes in wind speed.
Is wind power suitable for all properties?
Wind speed
A wind turbine is only worthwhile where the wind is reasonably strong and steady.
Proper testing of wind resources is expensive, but you can often judge average wind speed by looking at the shape of trees. If the branches are clearly growing more in one direction than another, you've probably got enough wind. The NZ Wind Energy Association's Introduction to Wind Energy (PDF, 277kB) has more detail on what to look for.
An average wind speed of 4-5 metres per second at 10m above ground level is probably enough for a wind turbine to meet a low electricity demand. Higher average wind speeds will be better for a stand-alone system powering a typical home.
Location
Wind turbines are best in non-urban areas because of the space taken up by the tower, the noise they make, and the higher wind speed out in the open without effects of turbulence caused by obstructions. They must not be sited near airstrips.
Why get a wind turbine?
On the right type of property, wind is a cost-effective and environmentally-friendly way to generate electricity. For remote rural properties, it can be far more cost-effective than buying and running a diesel generator or connecting to the grid.
Wind power also has significant environmental benefits. It doesn't produce greenhouse gases and saves the transmission losses that occur when electricity is generated at a power station and sent to your property over the local lines network.
Cost-effectiveness
A very basic small wind generator system might cost about $5000. This includes the turbine, tower, battery and other equipment, but not installation.
If you also have photovoltaic or micro-hydro systems, some control equipment will be shared.
Environmental benefits
Wind turbines produce no greenhouse gas emissions, and they reduce the amount of electricity that needs to be supplied by the local lines system, therefore reducing its emissions.
Choosing a system
What size turbine?
This depends on:
- your electricity use, and
- how windy your property is.
You can find out your annual electricity use by checking your power bills if you are grid connected already. Note that you’ll need a system that can meet your needs in winter, when usage is higher, and in summer, when wind speeds may be lower.
Once you’ve figured out the capacity you need, check the turbines on offer from different suppliers to see which ones are suitable. Typically, a turbine’s actual annual electricity output will be about 25-30% of its theoretical maximum output because the wind doesn’t always blow strongly - so, if you think you need a 1kW system, you’ll need a turbine that has a maximum capacity of about 3kW.
Type of turbine
There are many manufacturers of turbines. The most common have three-blades and are propeller-like. Some spin on a vertical axis, which means they don’t always have to turn to face the wind - but they’re less efficient.
Turbine blades are made of various materials including wood, polymers, fibreglass, and carbon fibre. The blades should be light to reduce friction and strong to resist wind gusts.
Types of tower
Towers can be made of steel, concrete or wood.
Some can be raised and lowered using guy cables so you never have to climb the tower. This is probably the easiest for most people, but takes up a larger area. Also, the cables must extend outwards a large distance.
Self-supporting towers take up less room but are usually more expensive.
Where to put it
Nearby trees and buildings will create turbulence and also slow the wind speed. This means the turbine is harder to start and produces less power.
Install a wind generator as far as possible from objects that might block the wind to it, especially in the prevailing wind direction. The clear distance should be at least 10 times the height of the object, preferably double that.
Speed protection
A wind turbine needs some sort of over-speed protection for extreme wind speeds. Blades can be feathered, or the rotor can be turned away from the wind. Some turbines also have automatic brakes.
Cable protection
As the turbine at the top of the tower continually rotates to face the wind it is possible that the cables connecting it to the rest of the system will become twisted. Some turbines use slip rings to avoid this problem. Others may need the tower to be rotated manually.
Backup system
If you are not connected to the grid, you may need to have another generating system as well, for when the wind is not blowing. This will share the battery bank and electronics. This also makes more economic sense than having a larger wind turbine with more battery storage.
Cut-in speed
The “cut-in” speed is the wind speed where the turbine starts to turn. A turbine design with a low cut-in speed (below 3m/sec) is good if you get a lot of light wind.
Choosing a supplier
Deal with suppliers who have experience and really understand their products.
Ask for references and contacts of previous customers.
Some suppliers have experience of different types of renewable energy technologies, and can advise on a complete system tailored for your situation.
Different suppliers include different components in their quotes, and specify outputs at different wind speeds. So compare quotes carefully to ensure a fair comparison.
Installation
Electrical work involving mains voltage (230V) must be done by a registered electrician.
You can get a supplier to install your system, or - in many cases - you can do much of it yourself.
The turbine will come with manufacturer’s instructions for assembly, erecting the tower, and connection to the storage batteries. Follow these instructions carefully.
Legal
To install a wind turbine, you may need:
- a building consent from your local authority - neighbours may object if it is too close to them
- a resource consent in some regions
- a consent from the electricity supplier if you’re connecting to the grid.
You’ll also need to talk to the lines company and power retailer if you are planning to connect to the local lines network.
Maintenance
Wind turbines have moderate maintenance requirements and can give long service, possibly 20 years or more. However, storms can destroy them before this, and batteries will need replacing every 6-8 years.
Turbines need at least an annual service, and will also need to be checked after very strong winds or lightning in the area.
Electrical work involving mains voltage (240V) must be done by an electrician.
Also:
- Follow the manufacturer’s instructions.
- Check brakes and slip rings every so often - they’ll wear out.
- Unwind the cables as necessary.
- Check guy wire tensions frequently.
- Add lightening arrestors to protect electronics.
- If you have to climb a tower, take appropriate safety precautions.
- Keep livestock away - they can do a lot of damage to the cables, and themselves.
- Keep children and other unauthorised people away - a wind generator is potentially dangerous.
More information
From Smarter Homes
From ConsumerBuild
From other sites
The Electricity Commission’s website has sample contracts for electricity customers, which include clauses relating to sale of electricity back to an electricity retailer.
The New Zealand Wind Energy Association’s website has information about wind power systems for farms and domestic use.
The New Zealand Wind Energy Association’s website has a map showing average wind speeds at 10 metres above ground level.
The National Institute of Water and Atmospheric Research’s website has a page on wind speeds at various New Zealand locations.
The Massey University Centre for Energy Research website has information about a ‘zero emissions’ community using wind turbines for power and solar energy for hot water.
Find wind energy information and links to suppliers at www.yes2wind.co.nz.
The government’s EnergyWise website has a page on wind energy.
The Energy Efficiency and Conservation Authority’s website has a page about renewable energy and a factsheet Factsheet 6:Standalone Power Systems (PDF, 330KB).
