Natural Power has launched DARC (Detection and Active Response Curtailment) – a bat curtailment technology to simultaneously reduce bat fatalities and energy losses at wind farms. Following a proof-of-concept deployment in 2019 and supported by the U.S. Department of Energy (DOE) as well as the National Renewable Energy Laboratory (NREL), Natural Power worked with Alliant Energy to install and operate a full system from August to October 2020 at the English Farms wind farm in Iowa.
The acoustic monitor sits on top of the nacelle and listens for bat calls. When it detects bat activity, it sends a signal to the DARC server where it is processed alongside other SCADA signals from the turbine and meteorological data. The server then decides whether the turbine should shut down or not. If it forces a shutdown, the blades will slowly come to a stop before lying motionless for 30 mins. If more bat activity is detected during this time, the turbines will continue to lie still for ten-minute increments until no activity is detected. The turbines will then start up again.
Using bat monitoring data and wind measurements from a wind farm site, DARC is able to quantify the impact of various curtailment strategies, comparing the impact on energy loss and bat fatalities of blanket curtailment and DARC.