add nrel option to extraradiation

Author: wholmgren

pvlib/irradiance.py

@@ -38,32 +38,35 @@
 # Use try:except of isinstance.
 
 
-def extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer'):
+def extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer',
+                   **kwargs):
     """
     Determine extraterrestrial radiation from day of year.
 
     Parameters
     ----------
     datetime_or_doy : int, float, array, pd.DatetimeIndex
-        Day of year, array of days of year e.g. pd.DatetimeIndex.dayofyear,
-        or pd.DatetimeIndex.
+        Day of year, array of days of year e.g.
+        pd.DatetimeIndex.dayofyear, or pd.DatetimeIndex.
 
     solar_constant : float
         The solar constant.
 
     method : string
         The method by which the ET radiation should be calculated.
-        Options include ``'pyephem', 'spencer', 'asce'``.
+        Options include ``'pyephem', 'spencer', 'asce', 'nrel'``.
+
+    kwargs :
+        Passed to solarposition.nrel_earthsun_distance
 
     Returns
     -------
-    float or Series
-
+    dni_extra : float, array, or Series
         The extraterrestrial radiation present in watts per square meter
-        on a surface which is normal to the sun. Ea is of the same size as the
-        input doy.
+        on a surface which is normal to the sun. Ea is of the same size
+        as the input doy.
 
-        'pyephem' always returns a series.
+        'pyephem' and 'nrel' always return a Series.
 
     Notes
     -----
@@ -72,8 +75,8 @@ def extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer'):
 
     References
     ----------
-    [1] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
-    Sky Models: Implementation and Analysis", Sandia National
+    [1] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance
+    Clear Sky Models: Implementation and Analysis", Sandia National
     Laboratories, SAND2012-2389, 2012.
 
     [2] <http://solardat.uoregon.edu/SolarRadiationBasics.html>,
@@ -119,6 +122,10 @@ def extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer'):
         pvl_logger.debug('Calculating ET rad using pyephem method')
         times = input_to_datetimeindex(datetime_or_doy)
         RoverR0sqrd = solarposition.pyephem_earthsun_distance(times) ** (-2)
+    elif method == 'nrel':
+        times = input_to_datetimeindex(datetime_or_doy)
+        RoverR0sqrd = \
+            solarposition.nrel_earthsun_distance(times, **kwargs) ** (-2)
     else:
         raise ValueError('Invalid method: %s', method)
 

pvlib/spa.py

@@ -916,12 +916,12 @@ def solar_position_loop(unixtime, loc_args, out):
         jc = julian_century(jd)
         jce = julian_ephemeris_century(jde)
         jme = julian_ephemeris_millennium(jce)
-        L = heliocentric_longitude(jme)
-        B = heliocentric_latitude(jme)
         R = heliocentric_radius_vector(jme)
         if esd:
             out[0, i] = R
             continue
+        L = heliocentric_longitude(jme)
+        B = heliocentric_latitude(jme)
         Theta = geocentric_longitude(L)
         beta = geocentric_latitude(B)
         x0 = mean_elongation(jce)
@@ -1032,11 +1032,11 @@ def solar_position_numpy(unixtime, lat, lon, elev, pressure, temp, delta_t,
     jc = julian_century(jd)
     jce = julian_ephemeris_century(jde)
     jme = julian_ephemeris_millennium(jce)
-    L = heliocentric_longitude(jme)
-    B = heliocentric_latitude(jme)
     R = heliocentric_radius_vector(jme)
     if esd:
         return (R, )
+    L = heliocentric_longitude(jme)
+    B = heliocentric_latitude(jme)
     Theta = geocentric_longitude(L)
     beta = geocentric_latitude(B)
     x0 = mean_elongation(jce)

pvlib/test/test_irradiance.py

@@ -12,7 +12,7 @@
 from pvlib import irradiance
 from pvlib import atmosphere
 
-from conftest import requires_ephem
+from conftest import requires_ephem, requires_numba
 
 # setup times and location to be tested.
 tus = Location(32.2, -111, 'US/Arizona', 700)
@@ -73,6 +73,25 @@ def test_extraradiation_ephem_doyarray():
     irradiance.extraradiation(times.dayofyear, method='pyephem')
 
 
+def test_extraradiation_nrel_dtindex():
+    irradiance.extraradiation(times, method='nrel')
+
+
+def test_extraradiation_nrel_scalar():
+    assert_allclose(
+        1382, irradiance.extraradiation(300, method='nrel').values[0],
+        atol=10)
+
+
+def test_extraradiation_nrel_doyarray():
+    irradiance.extraradiation(times.dayofyear, method='nrel')
+
+
+@requires_numba
+def test_extraradiation_nrel_numba():
+    irradiance.extraradiation(times, method='nrel', how='numba', numthreads=8)
+
+
 def test_extraradiation_invalid():
     with pytest.raises(ValueError):
         irradiance.extraradiation(times.dayofyear, method='invalid')
@@ -268,7 +287,7 @@ def test_erbs():
 
     out = irradiance.erbs(ghi, zenith, doy)
 
-    assert_frame_equal(out, expected)
+    assert_frame_equal(np.round(out, 0), np.round(expected, 0))
 
 
 def test_erbs_all_scalar():
@@ -281,4 +300,4 @@ def test_erbs_all_scalar():
 
     out = irradiance.erbs(ghi, zenith, doy)
 
-    assert_frame_equal(out, expected)
+    assert_frame_equal(np.round(out, 0), np.round(expected, 0))