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Caution! Bat Crossing

The goals of a wind power operator are to optimize switch-off times and increase yield. Where winged animals rule the skies, it has been necessary to reckon with costly downtimes – but Senvion is showing how to change that. With the help of WAGO, the wind turbine manufacturer offers operators the possibility of reacting even more flexibly to changes, for example: bat conservation.

Date information, wind speeds, temperatures: What functions as the basis for the weather forecast is really a kind of flight plan – for bats. “All this information is required in order to be able to make reliable statements about the activities of bats,” explains WAGO engineer Nino Flottmann. But for what purpose? The short answer: animal protection.

The Forest Becomes a Wind Power Zone

The background is that, from a purely legal point of view, forests have also become a substantial zone for wind energy. This was unthinkable at the start of the era of wind power, simply for nature conservation reasons and due to technical hurdles. However, the targets of energy and climate policy need to be met. That’s why only five percent of the about 26,000 wind turbines in Germany are located in forests – but there is an upward trend.

However, these wind turbines must share the space with the forest dwellers. In the turbines, which currently stand up to 200 meters high, the nacelles extend far above the forest canopy, and the ends of the enormous rotor blades move far above the treetops. However, they reach so far down that they cross the airspace of bats, since most of the 25 native species prefer trees as their habitat.

Adaptable algorithms allow us to react in swift, flexible and straightforward manner to changing conditions.

Jochen Poitzsch, Senior SCADA Engineer at Senvion

Bats on a Collision Course

“We have to and want to avoid injuries to bats on our wind turbines,” says Jochen Poitzsch, Senior SCADA Engineer at Senvion, a wind turbine manufacturer that has already installed more then 7,800 onshore and offshore turbines. Not only collisions with the rotor blades are deadly for the bats – even the air turbulence represents a danger.

The only way to protect the bats is to switch the wind turbines off temporarily – as required by the Federal Immissions Control Act (BImSchG), the most important set of environmental protection regulations. The federal states implement this in their wind power ordinances. However, this protection requirement applies not only to turbines in forests, but to all onshore sites. In particular, the common pipistrelle bat and the Common long-eared bat, which are on the red list of endangered species, can also be found in unforested areas.

“When certain temporal and meteorological conditions under which bats are active are met at the location of the wind turbine, it is necessary to switch them off. But the operators have a natural interest in minimizing the downtimes of their systems. Every kilowatt hour counts,” explains Poitzsch, the expert for Supervisory Control and Data Acquisition (SCADA).

Flexible Algorithm Instead of Sensors

In this area of tension, WAGO controllers offer a way out: Instead of always putting wind turbines in idle mode under certain conditions in general, a programmable logic controller (PLC) from WAGO helps to adapt the switch-off times to every individual site, optimizing them.

The reasons for having an external controller handle this are quite practical. “The statutory developments are very dynamic; and the requirements are constantly changing and also differ by federal state,” explains Jochen Poitzsch. The alternative would have been updating the SCADA controllers of the wind turbines for every change to the requirements – too time-consuming, Senvion decided.

Therefore, the solution that has been developed now works as follows: “The decision to switch off is not made on the basis of costly sensors that detect the actual presence of bats,” explains WAGO engineer Nino Flottmann. Instead, it is based on a flexible algorithm that takes numerous scientifically determined factors into account such as sunrise and sunset, temperature, wind speed, and precipitation among other things. The scientific factors trace back to the WINDBAT research initiative, which investigates the risk of bat collisions with onshore wind turbines. As part of its investigations, this research group also developed the “ProBat” software tool, which can be used to calculate bat-friendly operating algorithms for wind turbines. This tool also forms the basis for the solution used at Senvion.

“We then apply local weather data directly from the SCADA system of the wind turbine,” adds Flottmann. That is no problem, thanks to the open interfaces of the WAGO PLC. Nino Flottmann parameterized all the other data through the Web interface. If all the switch-off conditions are met, the SCADA system of the wind turbine receives the stop command from the WAGO controller, and the rotors quickly come to a standstill.

All switch-offs, including the current states of the system, are stored in a file and sent to the plant operator monthly. The system status can be queried at any time through the Simple Network Management Protocol (SNMP). If the legal requirements change, the operator can bring the controllers up-to-date without significant time and effort: The operator changes the default values in the algorithm accordingly and stores the file on an SD card or online. As soon as this data has been loaded onto the WAGO controller, the new values are applied automatically.

Optimizing Switch-Off Times

Senvion has now equipped about 100 wind turbines in Germany with the more flexible controller, and the project is far from over. First of all, the application is currently being internationalized and prepared for Europe-wide launch. Secondly, this technical solution is not limited to just bats: It can also be used for bird protection.

However, it is difficult to determine how much this controller improves the annual return of a wind turbine. “Nonetheless, it is clear that the switch-off times are optimized,” says Jochen Poitzsch in summary, since the adaptable algorithms allow wind turbine operators to react in a swift, flexible and straightforward manner to changing conditions.

Text: Heiko Tautori | WAGO
Photo: Getty Images

Jochen Poitzsch is a “Senior SCADA Engineer” at the wind turbine manufacturer Senvion.

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