Fixes #129 (#131)

Author: sasanjac

windpowerlib/wind_turbine.py

@@ -78,7 +78,7 @@ class WindTurbine(object):
         corresponding power curve value in W. Default: None.
     nominal_power : None or float
         The nominal output of the wind turbine in W. Default: None.
-   
+
     Notes
     ------
     Your wind turbine object needs to have a power coefficient or power curve.
@@ -170,9 +170,9 @@ def __init__(
                     logging.debug(msg.format(self.turbine_type))
 
                 if self.nominal_power is None and turbine_data is not None:
-                    self.nominal_power = float(turbine_data["nominal_power"])
+                    self.nominal_power = float(turbine_data["nominal_power"].iloc[0])
                 if self.rotor_diameter is None and turbine_data is not None:
-                    self.rotor_diameter = float(turbine_data["rotor_diameter"])
+                    self.rotor_diameter = float(turbine_data["rotor_diameter"].iloc[0])
 
         if self.rotor_diameter:
             if self.hub_height <= 0.5 * self.rotor_diameter: