The other towers in widespread use by the wind industry are tubular towers mounted on steel plates. Designed specifically for the wind industry, these towers can reach heights of up to 80 meters but cannot be climbed and must be lowered to repair or replace equipment. A 60-meter tower costs between $30,000 and $35,000 to install, maintain and remove, according to Lozanov.
"Climbable lattice towers will likely become more common due to the simple fact that it requires fewer resources to service the towers and accompanying sensors," says Amy Sue Karshbaum, crew leader for CCR. "As a result, it will be less expensive to achieve a higher standard of data quality for the client."
Greater flexibility in wind assessment tools give developers more options, says Katy Briggs, senior engineer at DNV Kema. There are many factors at play which could jeopardize wind projects, including market changes or permitting. Mobile towers, however, can help developers recoup some of their investment because they can move the equipment to another site if a project falls through, Briggs says.
Remote sensing technology is another tool for wind energy assessment. LIDAR uses light waves while SODAR uses sound waves to assess wind speeds up to 200 meters. It is a less reliable technology that is not always well-received by banks when obtaining financing for wind farms. Remote sensing equipment is currently used in conjunction with meteorological towers.
"The value of remote sensing is that you can often get a measurement [of wind speeds] above hub height," Briggs says. "Knowing what is going on across the full turbine rotor helps you better estimate [energy] production. Sometimes the wind doesn't increase as much as you would think up the top of the rotor and you wouldn't know that if you didn't measure the wind across the top of the rotor. Remote sensing can provide that data."
As the wind energy industry continues to advance, accurately assessing hub-height wind speeds is a perennial challenge for developers. Lack of reliable hub-height wind data often results in lower financing levels for a given project, but developers are cautious about investing large amounts of money into a project that might not be built. The new hub-height aluminum lattice towers may help the wind energy industry reach new heights by lowering development costs, while boosting data quality.
"Certainly the trend is going upwards," says Gunn of Baseline Renewables. "Typically, the higher up you go, the stronger the wind."
Image of aluminum tower by Kiril Lozanov.