Protecting Birds, Bats, and Habitats

Closely spaced 3-dimensional H-type vertical axis wind turbines (VAWTs) like arrays of Wind Harvesters are not expected to significantly impact wildlife. When VAWTs are installed in the understories of wind farms, they reduce the need to convert more habitat into renewable energy projects. Because blade tips of VAWTs move much more slowly than the large blades of horizontal axis turbines (HAWTs), they naturally will do less harm to flying animals. 

Saving Habits

Infilling existing wind farms with H-type turbines may be the least damaging, large-scale energy source currently available. Placing H-type turbines under and around tall, propeller-type turbines results in minimal habitat loss in places like California, where wind farms are sited on rangeland or in deserts. In these places, it is not necessary to build new main roads and fences. Additionally, there is no need for new transmission lines when a project is a “capacity factor enhancement” project.

  • Building them in existing wind farms reduces the need to construct roads or add transmission lines that impact many species’ habitats.

  • They should be safer for birds and bats because of their three-dimensional shape and slower, vertically rotating blades.

Habitat of Wildlife and wind turbines
Traditional wind farms are installed across large swaths of land, with varying degrees of harm caused to habitat. Photo by Jason Blackeye, Pastras, Greece.

Impact on Birds

Wind Harvesters are three-dimensional in shape and have slower-moving blades than propeller-type turbines. Scientists hypothesize that this should make them safer for wildlife. Arrays of Wind Harvesters should avoid the problems that propeller-type turbines have with birds of prey. They should be more wildlife-friendly, especially to eagles, condors, hawks, and other soaring birds, in the following ways:

The center of a Wind Harvester is 40 to 65 ft above the ground, the height, and size of many trees. This height means that they run below the flight paths of high-flying birds of prey and migratory birds, and they should not be any danger to those species. Additionally, with their eyes focused on the ground, condors and eagles will see the turbines below and avoid them.

Wind Harvester turbines rotate in three dimensions. Birds and bats should see the moving blades in a row of closely spaced turbines and be able to avoid them whether coming in straight towards them or flying down from above.

The blade tips of Wind Harvesters rotate at half the speed of propeller-type turbines. In general, birds are good at resolving rapid movements, and most species should not have trouble seeing the H-type turbine blades in motion. When high-definition motion detection systems detect birds in the vicinity, the turbines’ controls can quickly slow down or stop their blades. Flying animals should easily see, track, and avoid the blades when slowed down to 5-15 mph.
Birds on vawt
Resting birds safely fly away when Wind Harvester v3.1 slowly starts up. Photo by Pablo Paz, Nordic Folkecenter, Denmark.
Why do birds of prey have problems with traditional turbines?

Raptors like hawks and eagles and some owls can have difficulty seeing and avoiding tall, propeller-type turbine rotors. Genetic variations within certain species may cause this difficulty. For example, vultures have blind spots in their visual field that prevent them from seeing objects—such as wind turbine blades—directly in front of them. Many birds of prey that hunt from high in the sky have eyes that focus on the ground as they track small, running animals. These birds can completely miss the two-dimensional rotors of the traditional, tall turbines as they fly down for the kill.

Did You Know?

Fossil fuel facilities kill more birds than wind turbines

Detection and Avoidance

Wind Harvest is committed to protecting birds and bats and increasing the knowledge base on their reaction to H-Type wind turbines. Because of this commitment, the company will use DT Bird technology when installing Wind Harvester turbines in areas where bird species are of concern.

 

Many bat species nest together in large numbers, resulting in stunning displays of thousands of bats flying together as the sun sets and nighttime feeding begins. Photo by patpitchaya/iStock.

DTBird’s system combines real-time, high-definition image or radar analysis to detect birds with collision risk mitigation actions. It can be programmed to emit warning sounds or slow and stop the turbines to which they are connected. DTBird’s binocular cameras come with night vision and survey 360 degrees around turbines. The cameras detect bird flight patterns and distance away in real-time while recording and storing videos and data. Any actual bird collision is recorded and can be viewed online in videos with sound. Data from an experimental test in Sweden in 2015 showed that the DTBird deference system triggered avoidance behavior in 88% of cases where a bird was on a collision course with the wind turbine.

 

Wind Harvest will hire third-party consulting teams to evaluate the data gathered through the detection and avoidance equipment. They will send trained scientists to conduct regular on-site “mortality studies.” Any conditional use permits that early Wind Harvester projects receive will likely require third-party collected data.

Impact on Bats

In general, bats don’t like to fly when it’s windy because it costs them energy, and any flying insect is harder to catch. However, it is a documented issue that traditional wind turbines can harm some species. Nobody has ever evaluated H-type turbines’ impacts on bats with scientific rigor. However, the following hypotheses make intuitive sense. In addition, Wind Harvester will conduct a survey of wildlife flight paths before beginning every project, and Wind Harvesters installed in bat habitats will include a “chirp” detection system that detects bats in the area and temporarily stops the turbines.

Wind Harvester blade tips travel at less than half the speed (30-90 mph) of large, propeller-type turbines (150-200 mph). The slower-moving blades are easier for bats to echo-locate and avoid.

Most of the time, bats fly in horizontal patterns parallel to the ground, the plane in which H-type turbine blades travel. The bats should hear the turbines’ consistent, 3X/sec echo and trigger an avoidance response. Propeller-type turbine blades coming down on them or up from the ground at 150 mph would be more challenging for bats to track and avoid.

The slower speed of H-type turbine blades should reduce or eliminate barotrauma problems for bats. Their blades create much less extreme air pressure changes.

The lower height of the H-type turbines means they would be significantly below most bat migratory routes.
Wind Harvest will minimize impact on bats from Wind Harvester turbines by surveying potential sites for bat activity and migration paths before beginning project development. Where bats might be around the operating turbines, Wind Harvest will utilize acoustic detection systems that can trigger a deterrence event such as lights or sound, or slow the turbines before bats fly too close.

Why do traditional turbines impact some bats?

Propeller-type turbines can harm bats in two ways. They can fail to hear and “see” and thus miss the downward and upward rotating blades. Bats are also susceptible to “barotrauma” and tissue damage resulting from sudden air pressure changes created by tall, propeller-type turbines’ fast-moving blades.