fixes

Author: cwhanse

pvlib/snowcoverage.py

@@ -10,7 +10,7 @@
 
 def _time_delta_in_hours(times):
     delta = times.to_series().diff()
-    return delta.dt.total_seconds.div(3600)
+    return delta.dt.total_seconds().div(3600)
 
 
 def snow_nrel_fully_covered(snowfall, threshold=1.):

pvlib/tests/test_snowcoverage.py

@@ -24,12 +24,13 @@ def test_snow_nrel_hourly():
                        freq='1h')
     poa_irradiance = pd.Series([400, 200, 100, 1234, 134, 982, 100, 100],
                                index=dt)
-    temperature = pd.Series([10, 2, 10, 1234, 34, 982, 10, 10], index=dt)
-    slide_amt = sliding_coefficient * sind(surface_tilt)
+    temp_air = pd.Series([10, 2, 10, 1234, 34, 982, 10, 10], index=dt)
     snowfall_data = pd.Series([1, .5, .6, .4, .23, -5, .1, .1], index=dt)
     snow_coverage = snowcoverage.snow_nrel(
-        snowfall_data, poa_irradiance, temperature, surface_tilt,
+        snowfall_data, poa_irradiance, temp_air, surface_tilt,
         threshold_snowfall=0.6)
+
+    slide_amt = sliding_coefficient * sind(surface_tilt)
     covered = np.append(np.array([0., 0.]),
                         1.0 - slide_amt * np.array([0, 1, 2, 3, 4, 5]))
     expected = pd.Series(covered, index=dt)
@@ -41,16 +42,20 @@ def test_snow_nrel_subhourly():
     sliding_coefficient = 0.197
     dt = pd.date_range(start="2019-1-1 11:00:00", end="2019-1-1 14:00:00",
                        freq='15T')
-    poa_irradiance = pd.Series([400, 200, 100, 1234, 134, 982, 100, 100],
+    poa_irradiance = pd.Series([400, 200, 100, 1234, 134, 982, 100, 100, 100,
+                                100, 1000, 1000, 0],
                                index=dt)
-    temperature = pd.Series([10, 2, 10, 1234, 34, 982, 10, 10], index=dt)
-    slide_amt = sliding_coefficient * sind(surface_tilt)
-    snowfall_data = pd.Series([1, .5, .6, .4, .23, -5, .1, .1], index=dt)
+    temp_air = pd.Series([10, 2, 10, 1234, 34, 982, 10, 10, 10, 10, 10, 10,
+                             10], index=dt)
+    snowfall_data = pd.Series([1, .5, .6, .4, .23, -5, .1, .1, 0., 1., 0., 0.,
+                               0.], index=dt)
     snow_coverage = snowcoverage.snow_nrel(
-        snowfall_data, poa_irradiance, temperature, surface_tilt,
-        threshold_snowfall=0.6)
-    covered = np.append(np.array([0., 0.]),
-                        1.0 - slide_amt * np.array([0, 1, 2, 3, 4, 5]))
+        snowfall_data, poa_irradiance, temp_air, surface_tilt,
+        threshold_snowfall=0.5)
+    slide_amt = sliding_coefficient * sind(surface_tilt) * 0.25
+    covered = np.append(np.array([0., 1., 1.]),
+                        1.0 - slide_amt * np.array([1, 2, 3, 4, 5, 6]))
+    covered = np.append(covered, np.array([1., 1., 1., 1. - slide_amt]))
     expected = pd.Series(covered, index=dt)
     assert_series_equal(snow_coverage, expected)