Bats and wind energyCan bat activity patterns make them vulnerable to wind turbine impacts
Tiffany Thwaits NMMU
Prof. G. Kerley Dr. N. Mzilikazi
Energy Postgraduate Conference 2013
WIND ENERGY
RenewableRenewable
CleanClean
Environmentally Environmentally friendlyfriendly
88 applications for SA
40 31
BUT HAS NEGATIVE IMPACTS ON
WILDLIFE
Migratory & tree roosting species at greater risk
Wind farm/facility Total fatalities Reference
Mountaineer Wind Energy Centre (West Virginia, USA)
2092 (over 2 yrs) Kerns & Kerlinger (2004)
Casselman Wind Project (South-central Pennsylvania, USA)
784/yr Arnette et al. (2009)
Coega test turbine (Eastern Cape, SA)
17 (1 yr) Doty & Martin (2012)
Wind turbine associated mortality greater than Natural mortality
Slow to recover from adverse
effects
Long livedSlow reproductive rateSlow population growth
SO WHAT?SO WHAT?
SO WHAT?SO WHAT?
HEIGHTTIME WEATHER
BAT ACTIVITY
MONITORING BATS
BAT PASS
STUDY SITE
MITIGATION & MANAGEMENT
Different bat groups are active at different seasons and occupy
different aerial habitats
BIMODAL PEAK• activity highest 1-2hrs after sunset• 1-2hrs before
sunrise
SINGLE PEAK• activity highest 1-2hrs after sunset
• reduced activity in winter months
WEATHER & BAT ACTIVITY
Variables in global model
▪ Month
▪ Overnight average temperature
▪ Overnight average wind speed
▪ Temperature:Wind speed
▪ Month:Temperature
▪ Month:Wind
▪ Month:Temperature:Wind
Predictor variable χ2 d.f. P
Month* 121.52 4 <0.001Overnight average temperature* 51.55 1 <0.001
Overnight average wind speed 5.96 1 0.016
• Final model = weak High degree of variation in data
• Model may be dependent on other variables not quantified here
Lang et al. 2006Milne et al. 2005
Another factors involved
Temperature
Wind Speed
Barometric Pressure
Humidity
Precipitation
Season
Time of night
Insect abundanc
e
Moon Phase
Cloud cover
MODEL
Mitigation & Management
Bat activity & Monitoring
Mitigation Management
• 2hrs after sunset• High flying bats at great risk (55m)• Autumn = peak season
Increase cut in speed of blades
Curtailment
Blades spin fast so that they are more
“visible” to bats
Switch off turbines during peak seasons
or when wind conditions
unfavourable
• Post construction monitoring (fatalities)• Feasibility of mitigation methods• Evaluations of next turbine locations