400 bat carcasses scattered under wind turbines

 As one of the important clean and renewable energy sources, wind energy has developed rapidly worldwide in recent years. At present, the global cumulative installed capacity of wind power has exceeded 650 GW (1 GW = 109 watts); in 2019 alone, the newly added wind power installed capacity worldwide reached 60.4 GW, which is equivalent to the power generation of 2.7 Three Gorges Project. However, a wind farm with a calm surface is actually undercurrent.

　　 From Australia to the United States and Europe, bat deaths caused by wind turbines have been reported one after another. According to statistics, there are about 600,000 bats killed by wind turbines in the United States each year, mainly the gray fluffy bat (Lasiurus cinereus), red fluffy bat (Lasiurus borealis) and other species. Most of these bats do not live in caves. It is used to migrating and living in trees.

Bats rarely collide with signal communication towers, buildings, etc., but they often die under wind turbines. The autopsy results showed that half of the bats died from direct collisions with wind turbine blades, and the other half died from lung damage caused by changes in air pressure. What's incredible is that the investigators also discovered during the field investigation that some bats would even take the initiative to approach these three-bladed "executors"-the wind turbine seemed to have some magic power to seduce the bats and make them willing to be killed.

　　According to the characteristics of wind turbines and the living habits of bats, scientists have put forward a series of hypotheses, but it is always difficult to draw a definite conclusion. The whole incident is still confusing and confusing.

　　 Damaged lung tissue(2021 hermes bags)?

　　 Among the bat corpses collected, about 50% of the corpses did not have any wound marks on the surface. This non-collision-caused death comes from the sudden internal injury of the bat-lung pressure injury. The wind turbine looks demure, but its lethality is hidden in the invisible air currents. Due to the rapid rotation of the blades, the air velocity near the blade tip is extremely high, close to 80 meters per second, resulting in a rapid drop in air pressure. Erin Baerwald, a professor of biology at the University of Calgary in Canada, pointed out that a large drop in local atmospheric pressure can easily cause the lungs of bats to expand rapidly and induce damage to their lung tissues.

Not only that, but the lung damage of bats also has a mystery. The high-speed rotating wind wheel of a wind turbine will form a huge wake area in the rear, where the airflow is complex and turbulent; at the same time, the tip of each blade will continuously induce a tip vortex (similar to a vortex in a river). Although the size is small, the rotation speed is extremely high. Once the bat gets close, it may be involved. When trapped bats try to escape by waving their wings, the sparse oxygen around them and the short-term sharp struggle will force the lungs to overload their work, eventually leading to a tragic death.

Most bats use echolocation for navigation and predation, and emit low-frequency sound waves to attract mates, summon similar species, and expel natural enemies. However, the huge noise generated by large wind turbines seriously interfered with the normal information exchange of bats. These noises include aerodynamic noise generated by the blade tip side, mechanical noise generated by gear meshing, etc. The sound intensity is high, and there is a partial overlap with the frequency domain of the ultrasonic wave emitted by bats (concentrated at 20-60 kHz). When receiving a sound with a frequency similar to that of the sound wave, in order to ensure the reception of the information, the bat may be forced to "change the channel" and change the sound wave frequency used.

　　Researchers have adopted the strategy of "confronting poison with poison" and developed an ultrasonic sound that can continuously emit huge noises with a frequency of 20-100 kHz to deter bats from keeping them away from noise sources. The test results show that after the installation of the wind turbine, the number of deaths of bats has dropped by 21%-51%. However, the roar of this kind of sound is not essentially different from the noise of wind turbines, and it will also have a certain impact on the health of bats.

Modern large-scale wind turbines are generally white all over, and their huge size makes them exceptionally conspicuous, becoming an embellishment of the beautiful scenery in the eyes of tourists. But in fact, as a large-scale man-made machine, wind turbines cannot be integrated into the ecological environment around them. The light source of the wind turbine at night and the heat emitted from the cabin will attract a large number of insects to gather on the surface of the wind turbine. At the same time, the boundary area formed by the small open space around the wind turbine and the jungle still has the "jungle boundary effect", and the daily activities of insects in the boundary area are even more active than in the complete jungle environment. Those bats whose main food is insects may follow the food footprint and approach dangerous wind farms.

　　 For migratory bats, large wind turbines are not only the tallest building on their path, but also have a steady flow of heat inside. They are ideal places for habitation and courtship, which further intensifies the "fatal attraction" of wind turbines.

The large-scale substations of wind farms and the erected cables and other equipment affect the propagation of electromagnetic waves to a certain extent and interfere with the signals received by mobile phones, televisions and other equipment-this is one of the reasons why wind farms are prohibited from being built near airports and ports. Some migratory bats do not completely rely on echolocation. Similar to pigeons, they also determine the direction based on the geomagnetic field. Therefore, the turbulent electromagnetic fields around the wind farm may disorient these bats and go astray.

　　 In addition to the powerful auditory system, bats have a very sensitive sense of smell. Long-term stable operation of wind turbines is inseparable from lubricating oil and grease. In a long-term high-pressure environment, lubricating oil will slowly permeate from gearboxes and other components, and even leak into the external environment. The smell of these oils may also interfere with the sense of smell of bats or attract their attention.

Some migratory bats may abandon the use of echolocation and rely only on vision when traveling through familiar routes in order to save energy. However, bats belonging to nocturnal animals have degraded eyes and poor vision. When they are far from the wind turbine, it is difficult to see the rotating blades. We can see the light and shadow patterns produced by the spinning of the fingertips, and observe the reversal of electric fans and car tires. This kind of "illusion" produced by persistence of vision may also appear in the visual system of bats, making them see It is not clear about the rotating blades in front, so it is impossible to avoid obstacles in time.

　　 Why are the solutions not promoted?

　　 The various reasons listed above are derived from the speculation of scientists. According to the evidence obtained so far, the casualties of bats may be the result of a combination of multiple causes. Of course, there are still a lot of unsolved mysteries in the bat itself. We still don't fully understand its relationship with wind turbine generators. Related exploration work still has a long way to go. The problem that needs to be solved is how to avoid such casualties again.

　　The wind farm is far away from the active area of ​​bats, which can protect the life safety of bats to the greatest extent. However, the vast areas where birds and bats frequently move are also ideal locations for wind farm development. Even if extremely demanding wind farm site selection strategies are required, wind farm developers will not easily give up a large area of ​​high-quality wind resources because of the existence of a small portion of wild animals.

It is almost impossible for the wind farms that have been constructed to be relocated. At this time, the solution to “remedy the situation” is particularly critical. Tests have shown that increasing the starting wind speed of large wind turbines from 3 meters per second to 5.5 meters per second can reduce nearly 60% of bat deaths. Use the monitoring system to scan the airspace within 4.8 to 12.8 kilometers around the wind farm. When radar, ultrasonic microphone, camera, GPS and other equipment detect that the bat colony is about to fly in, adjust the operation strategy of the wind turbine in advance, or even shut down the wind turbine directly. Reduce the casualties of bats. However, these measures will seriously affect the power generation efficiency of the entire wind farm, and these bat carcasses in hidden corners can often only become victims.

　　 Compared with fossil energy, new energy represented by wind energy is more environmentally friendly. But new energy is not flawless, and these need to improve the space is the driving force to promote our continuous progress.