Author: Alicia Webb
Contributors: Chris Blanksby, Natalie Lukies
Once you've identified a potential site for a wind power project, it's important to measure the wind resource to see how much renewable energy the project is likely to produce — before final feasibility and design work goes ahead.
Here we detail the process of designing and installing a wind monitoring mast. It's pretty technical, and you'll probably need to consult experts along the way, but this article can help community groups understand what's involved, decide which aspects they can take on themselves, and which to outsource to the experts. It can also give you a rough idea of costs.
Commercially, wind monitoring is carried out by professional wind engineers. However, hiring consultants to choose a site, and design and procure the mast and instruments, can be expensive and is not always necessary. To save money, community group members can get involved in aspects of the design process, and simply get a consultant in for final checking and the more complex technical tasks, such as installation supervision.
Safety and risk
You will need to be aware that erecting wind monitoring masts is hazardous. It is a complex procedure requiring skilled and experienced personnel (with mandatory rigging qualifications). It also requires attention to detail and established operating procedures and safety plans, which should be checked carefully beforehand. Calm and fine weather conditions are also required for it to be safe to erect the mast. There is also a commercial risk to be considered if the mast collapses. Responsibility for costs should be established contractually beforehand.
Monitoring mast basics
Typically, wind conditions are measured with various instruments at different heights on a tall tower. They monitor wind speed and direction, and often temperature, humidity and pressure. All the data is recorded on a 'logger' — a simple computer at the bottom of the mast, which can then be transferred to a normal computer.
Anemometers measure wind speed, and look like three small cups spinning on a central axis. Usually, there are several anemometers mounted at different heights on the mast - one or two at the very top, with another two or three mounted further down. This will show how wind speed varies at different heights, and can help you predict average wind speeds for various wind turbine heights.
It will also allow the calculation of the wind shear at the site, how the wind speed varies with height, which will be required to assess the loading over the wind turbine rotor blade area. This is important to ensure the wind turbines chosen can withstand the wind loads at the site.
Wind vanes measure wind direction, and are also mounted at different heights. Two vanes are adequate for most community-scale projects.
Because the instrument tower is an obstacle, it interferes with the wind flow the instruments are there to measure. There are strict standards on how the whole set-up is arranged so the instruments don't just measure the effect of the tower's interference. For example, instruments are mounted on horizontal 'boom' arms, to keep them away from the mast. It's also important to point these boom arms in the right direction. For example, if the site generally experiences strong winds from the west, the boom arms should face west.
Measuring wind speed and direction at the hub height of the turbine you propose reduces uncertainty in the measurements, and this is recommended for complex or large wind sites. At a community scale, however, it can be much more affordable to simply erect a 50 or 60-metre tubular mast that tilts up and down.
Where to put it
Your wind monitoring mast should be as close as possible to where the wind turbines will be. For small community-scale projects with very few turbines, this should be reasonably straightforward. If the precise turbine locations aren't finalised yet, try to choose somewhere that's approximately central to where your turbines will be.
Your monitoring site should be ‘representative’ of the overall site - not at its highest or lowest points, but somewhere similar to where the turbines will be in terms of elevation and proximity to obstacles. Basically, the monitoring site needs to be as close to, and as similar to, the final turbine locations (on average) as possible.
Access to the site to install and deconstruct the mast (and possibly regularly collect wind data from the logger) should also be considered, particularly if there are several options for the mast location.
What a consultant will do
Choosing the wrong location can’t be corrected easily. A consultant will likely request a site visit to verify and sign off the suitability of a monitoring location. However, if the site isn't too complex, it’s possible to achieve this with good maps and photos.
What the community group can do
The best way to be absolutely sure of choosing the best monitoring location is to write a report that details the suggested location, and send it to a wind engineering consultant for verification. Your report should include:
- a clear outline of the site boundary
- GPS coordinates of the suggested site, and any alternatives
- photos and GPS coordinates of any surrounding obstacles
- any information about site constraints, such as noise, flora and fauna
- information about wind farm layout and design, even if it’s only at concept stage
- contour data for the site or a map showing contour information.
This will help your consultant consider your choice, and ensures it's technically suitable.
Planning permission
Before putting up a wind monitoring mast, it's important to contact the local Council about planning requirements. In Victoria and New South Wales, you don't need planning permission to put up a wind monitoring mast, as long as it's taken down after three years. However, if vegetation clearing is required, a permit may be required to allow the vegetation to be cleared. It is always worth checking with the local council before you start.
In South Australia, you'll need development approval from the local Council for installing a wind monitoring mast. The local council can help you with the correct forms and payments. It's not usually expensive to apply - around $100-$200.
Your application should detail the location with a detailed description of the wind monitoring mast, any technical drawings, and a brief statement of how the mast complies with the Development Plan for the relevant Local Government area. If the development application is required to go on public exhibition, you will need to prepare your community consultation strategy beforehand.
A building permit, which signifies that a building surveyor has approved the mast and its installation prior to the erection of the mast, is always required.
Choosing a mast
You can buy wind monitoring towers from several Australian manufacturers, some of whom can install them for you. Or you can buy them from overseas instrument suppliers, either separately or as part of full monitoring kits. It's always worth calling a few companies and getting a good range of quotes.
At a community level, it’s likely the mast will be 50-60 metres tall and tubular. This offers the best balance between cost and the accuracy of measurements. If the community can afford it, a 60-metre mast offers more accuracy than a 50-metre one.
Instrument selection and configuration
A monitoring system usually includes several wind speed and direction sensors, mounted at various heights. Also, there should be a temperature sensor and possibly other weather sensors, all connected to a simple computer called a 'logger'. Instruments are manufactured by several brands around the world, and vary in price and quality. A top-of-the-range Danish anemometer will cost around $3,000 AUD, whereas a cheap, servicable unit from the United States can cost as little as $300 AUD.
The number of instruments and how they’re mounted is important. The design will need to follow international standards that minimise flow disturbance caused by the mast. Fewer instruments will be more affordable, but using more will capture the behaviour of the wind more accurately. Using more instruments will also allow for better data reliability if some instruments fail. There are technical details for different instruments in the wind monitoring reference document.
The wind monitoring requirements of a community are different to a commercial developer's. Often the monitoring phase is a relatively expensive step for a community wind farm, so price is an important consideration when deciding on instrument type and configuration.
What the community can do
A community group can get quotes from instrument suppliers as part of its design and decision-making process. Instrument suppliers are accustomed to talking to customers without in-depth technical knowledge of wind monitoring, and they can help design a monitoring system that meets the relevant standards. Many instrument suppliers can also recommend an entire system, including cables, logger and power supply. This is preferable as it's much simpler.
What a consultant can do
A consultant can suggest different instrument brands, configurations and suppliers, and price up the alternatives. However, if the community has already undergone some or all of this process, the consultant can simply verify the suitability of the suggested design. It's important to get expert sign-off before installing the mast.
An example system design
The most important instrument on your monitoring mast is the top anemometer. It's often mounted on top of the mast so it measures undisturbed wind. It's customary to mount another anemometer near the top for back-up reasons, as well as a wind vane. Lower down, there is usually another anemometer and vane and at 10 metres above ground, one more anemometer for noise calculations.
A suggested 60-metre mast configuration features:
- a top-mounted anemometer
- a backup anemometer at 60 metres
- a wind vane at 55 metres
- an anemometer at 40 metres
- a wind vane at 35 metres
- an anemometer at 10 metres.
Mast and instrument suppliers and installers
Towers
Here are some approximate costs for the tower. Contact individual suppliers for more accurate quotes. Installation costs can vary significantly, depending on how remote or accessible your site is.
|
Tower or service |
Price |
|---|---|
|
60-metre mast including guy wires and lightning protection |
$11,000 |
|
50-metre mast including guy wires and lightning protection |
$9,000 |
|
Installation |
$9,000 |
|
Vehicle and trailer hire, and equipment insurance |
$2,000 |
It's a good idea to ask the tower installer how much they'd charge to visit and maintain the tower every 12 months. As a guide, it should cost approximately one day’s wages for two people, plus travel and accommodation.
If the tubular mast needs to be lowered and raised again it could cost significantly more.
Instruments
NRG Systems
One of the most affordable wind measurement suppliers is NRG Systems, based in the United States. Visit NRG Systems for all their products and prices. They even supply entire systems with every component included including the tower. For example:
- a 60-metre tower kit costs US$16,650 plus postage
- a 50-metre tower kit costs US$15,350 plus postage.
These kits include a temperature sensor, but not humidity or pressure sensors, and the anemometers aren't MEASNET-calibrated (although this is optional). They don't include a telemetry system (also optional), so someone will need to visit the site monthly to download data. An installation kit, including winch, pulleys and a gin pole is US$8,000. However most tower contractors will have this equipment already. Note that the installation of the tower should only be done by qualified installers.
Here's a basic cost breakdown of NRG parts. Typical shipping cost is around $500 AUD.
|
NRG Instruments |
Price |
Quantity |
Total |
Currency |
|---|---|---|---|---|
|
NRG #40C anemometer with boot and MEASNET cert |
395 |
4 |
$1,580 |
USD |
|
NRG #200P vane with boot |
205 |
2 |
$410 |
USD |
|
NRG RH sensor |
345 |
1 |
$345 |
USD |
|
NRG #110S temp sensor with sheild |
195 |
1 |
$195 |
USD |
|
NRG #BP20 barometric pressure sensor |
325 |
1 |
$325 |
USD |
|
NRG booms for tubular towers |
95 |
6 |
$570 |
USD |
|
Cables to suit 60-metre mast |
615 |
1 |
$615 |
USD |
|
Lightning protection kit |
439 |
1 |
$439 |
USD |
|
Subtotal |
|
|
$4,479 |
USD |
|
NRG Logging Equipment |
Price |
Quantity |
Total |
Currency |
|---|---|---|---|---|
|
NRG SymphoniePLUS with MMC and accessories |
1350 |
1 |
$1,350 |
USD |
|
Shelter box |
135 |
1 |
$135 |
USD |
|
SCM cards for enviro sensors |
39 |
3 |
$117 |
USD |
|
Extra MMC card for swapping |
50 |
1 |
$50 |
USD |
|
Subtotal |
|
|
$1,652 |
USD |
|
Optional — NRG Telemetry Equipment |
Price |
Quantity |
Total |
Currency |
|---|---|---|---|---|
|
iPack for GSM with PV |
1440 |
1 |
$1,440 |
USD |
|
Phone plan* |
|
|
|
|
*The correct phone plan should be negotiated with phone companies, dependent on local area and network strength.
Second Wind
Another affordable supplier is Second Wind, who you can visit online at www.secondwind.com.
They sell a complete 60-metre tower system for USD$14,985 plus postage.
Much like the NRG kit, this does not include installation gear or telemetry for remote communications.
Their price list is available as a PDF from their website. Some basic component costs are:
|
Second Wind Instruments |
Price |
Quantity |
Total |
Currency |
|---|---|---|---|---|
|
SWI C3C anem with MEASNET cert |
375 |
4 |
$1,500 |
USD |
|
SWI PV-1 vane |
245 |
2 |
$490 |
USD |
|
Vaisala temp and hum sensor with shield |
475 |
1 |
$475 |
USD |
|
SETRA pressure sensor |
325 |
1 |
$325 |
USD |
|
Booms |
200 |
6 |
$1,200 |
USD |
|
Cables |
444 |
1 |
$444 |
USD |
|
Lightning protection kit |
50 |
1 |
$50 |
USD |
|
Subtotal |
|
|
$4,484 |
USD |
|
Second Wind logging equipment |
Price |
Quantity |
Total |
Currency |
|---|---|---|---|---|
|
Logger with software, box, etc |
1499 |
1 |
$1,499 |
USD |
|
Extra MMC card for swapping |
40 |
1 |
$40 |
USD |
|
Subtotal |
|
|
$1,549 |
USD |
|
Optional – Second Wind Telemetry Equipment |
Price |
Quantity |
Total |
Currency |
|---|---|---|---|---|
|
GSM pack |
1180 |
1 |
$1,180 |
USD |
|
Phone plan* |
|
|
|
|
*The correct phone plan should be negotiated with phone companies, dependent on local area and network strength.
A good option is to put a high quality anemometer at the top of the mast with cheaper options lower. The WindSensor P2546A anemometer is regarded as among the best available. It is compatible with either of the systems above and is available to order online at www.windsensor.com. It is also sold by NRG Systems and Second Wind, as well as some Australian distributors.
Installation
Installing a monitoring mast typically takes one or two days in good weather. However, there are plenty of things to get sorted beforehand. You need to get the mast and instrument systems to the site and organise a backhoe for digging the anchor holes. The mast installer can help arrange and oversee this process.
People on site for the installation may include:
- the mast installation team
- a backhoe operator
- an instrument and system installer, usually a consultant wind engineer or electronics technician
- the landowner
- the owner of the mast.
A typical process for installing a wind monitoring mast would be something like this:
- The mast installer puts down a centre-marker for the mast location and lays the mast horizontally on the ground facing prevailing wind — the installer will want to lift into the wind.
- The backhoe operator digs holes for the guy wire anchors.
- The anchors are installed and backfilled.
- Mast and guy wires are put together and laid flat on the ground.
- Arms and instruments are attached to the mast.
- Cables are run down the mast, often wrapped around it.
- The logger, power system and any communications systems are arranged and tested.
- Documentation and photographs are completed.
- The mast is lifted using a winch.
- Instruments are connected to the logger — if this hasn’t already been done.
- Testing is finalised and more site photographs taken.
Installation report
Once your mast is installed, it’s vital to have a completed installation report. This describes in detail the instruments used, how they are mounted on the mast, and the dimensions of the mast, including boom lengths and boom orientations. It should also detail the location of the mast and the guy wires, the type of logger and power system, and how the logger is programed. Photos of the mast and surroundings are also necessary.
A report can help identify any faults in the data, and it is invaluable to any maintenance work on the mast. It also helps a wind consultant verify that the design meets international standards for reducing wind disturbance. Lastly, it accompanies all the data the mast produces and allows wind engineers to confirm the instrument signals have been conditioned correctly.
Things that can go wrong
One of the most common issues with monitoring masts is weather exposure, which can causes rust and moisture damage, loosening booms, failure of electrical and aerial connections and failure of bearings in old instruments. This can stop data logging. Also, rechargeable batteries can simply wear out and stop recharging. You can detect a lot of these issues before they occur, with a proper checking and maintenance schedule.
You may also experience cattle chewing wires and rubbing on mast guys, or protesters intentionally damaging gear. Masts should be fenced off wherever possible, and locks put on the logger box — or mount it high on the mast, out of reach.
Vandalism is also a potential problem in cases where there is community opposition to your project, or wind farms in general. While difficult to prevent, a regular checking and maintenance schedule will minimise loss of data or further damage should vandalism occur.
If instrument failures occur (this happens from time to time, due to lightning strikes for example), a tilt-up mast cannot be climbed and must be lowered and raised to effect a replacement. This can be costly so it is best to ensure a redundant instrument at the top level. If other instruments fail, it may be acceptable not to replace them.
Checklist
- Choose a wind monitoring site that is representative of the overall site
- Obtain planning permission (if required) for installing the mast
- Choose mast, wind monitoring instruments and design configuration on the mast
- Obtain quotes for, and purchase tower and monitoring instruments
- Obtain quotes for, and organise the installation of the mast
- Install mast
- Obtain and keep completed mast installation report
- Carry out regular checking and maintenance