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Wind is a sustainable and renewable source of energy, so we will continue to see more and more wind turbines dotting our landscape as we harness this power for our energy. Developers must consider many restrictions and constraints, including characteristics of the wind in the area, availability of land, existing buildings and infrastructure, species and protected land, Federal Aviation Administration (FAA) clearance and the Department of Defense (DOD) and the geographic landscape surrounding the proposed locations.

Visual inspections of individual sites, a process called a microsite, must be performed before a wind turbine and the site of its associated infrastructure can be chosen. The microsite is essential for maximizing the efficiency of a turbine and for identifying potential obstacles when setting up turbines.

The geographic landscape can be a complicated consideration when determining a potential site for a wind turbine. Wind turbines contain many components, and long, oversized vehicles are used to deliver these components to each site. Delivery vehicles require large areas to perform turning movements and cannot traverse steep terrain or negotiate roads that have rapid changes in terrain.

In addition, large cranes are required to erect the components necessary for the construction of the wind turbine. It is best to move cranes, fully assembled, from one wind turbine site to another to help control costs and save time. This process requires additional planning.

To accommodate large delivery vehicles and optimize the crane route, civil engineers constructed access roads to each wind turbine site during the preliminary design. The preliminary design is usually created using high resolution aerial imagery data and aerial topographic survey data to illustrate the geographic landscape. Many visible features such as drainage patterns, tree masses or other physical restrictions can be identified from this remotely obtained data.

After the preliminary design of the access road is complete, engineers typically perform an in-person field examination as part of the microsite. During the field examination, each wind turbine site is examined more closely for areas that should be avoided or altered to allow access to the site by large delivery vehicles.

Some sites are visible from existing roads and the design can be checked quickly. But many sites are not visible from the existing roads, and, even further, some sites are not easily accessible even by all-terrain vehicles.

In these cases, project engineers should verify the proposed delivery route on foot. Between walking and driving, engineers can examine 25-30 sites a day, but large-scale wind farms are growing and typically consist of more than 100 wind turbine sites. Depending on the size of the project, the microsite process can become inefficient in terms of time and cost.

One solution to reducing the time and costs associated with the microsite process is to use an unmanned aerial vehicle (UAV) during the in-person field exam. A single drone operated by a pilot can survey over 100 sites in a day.

The UAV provides high-resolution live, real-time video to the developer’s project team. This video can easily be viewed on monitors in the field or streamed live to team members at the home office. The drone’s visual feed in the field and the proposed access road design plans can be placed side by side to understand the geographic landscape in real time.

If different areas along a proposed access route need to be further investigated or modified during the review, the project team is in direct communication with the UAV pilot, who can immediately respond and modify UAV flight plan to include additional areas for review. Data is recorded and stored so that microsite information is available at all times for reference and use.

Case study

Mike Laird is a Senior Surveyor in Olsson’s Overland Park, Kan., Office and has spent hundreds of hours in the cockpit as a private pilot. Drone experts like Laird combine their piloting skills with computer networking and global positioning system (GPS) technology to produce dramatic results in microsite field data, in real time.

We recently brought together several clients and performed tests of our microsite process to demonstrate the geographic accuracy that can be achieved with drones. Laird uses a specialized UAV that can handle wind gusts of up to 45 mph – a requirement for the proposed wind power sites.

Rather than riding on ATVs, customers sat comfortably in a sport utility vehicle (SUV) as the UAV flew from one proposed site to another. Inside the vehicle, customers watched a live broadcast of each site inspection, noting the location of every fence, irrigation system, utility pole, oil well, livestock feeder, or other potential obstacle. Customers were able to input changes to the proposed site map directly into their laptops, reducing the need for future design adjustments.

Rather than doing all three dozen standard site assessments in one day, one pilot was able to complete over 100.

Another microsite tool is a terrestrial light sensing and ranging (lidar) scanner. Lidar scanning with drones offers an alternative way to capture and create high definition 3D models or computer aided design (CAD) drawings of any object or space using multiple scans from different viewpoints to create a dense point cloud.

Compared to traditional surveying methods for topography and contours, UAV lidar scanning services create 3D models much faster and with a higher level of detail, providing survey documents that capture up to 100,000 points per second with an accuracy of 3 mm. This equipment can be used in all light levels, including total darkness. High resolution images are also acquired during the flight of the UAV, from which a virtual ‘flyover’ can be generated.

No other technology can produce detailed, high-definition 3D surface models like those obtained by lidar scanning. A lidar scanner can obtain measurements in a horizontal movement of 360 degrees and a vertical movement of 270 degrees.

The large amount of data acquired using this equipment reduced and / or eliminated the prior need for additional field visits. Lidar scanning can also reduce the number of project change orders that occur when actual site conditions differ from the design plans, saving time and money.

Rod Hanson works at Olsson, an engineering and design company that serves a number of markets, including onshore and offshore wind.

Photo courtesy of Sulzer Schmid, leading experts in UAV technology for rotor blade inspections