convert temp coeff to %/C (#433)

* convert temp coeff to %/C

* update whatsnew

* Update solarforecastarbiter/pvmodel.py

Co-authored-by: Will Holmgren <[email protected]>

Co-authored-by: Will Holmgren <[email protected]>

Author: alorenzo175

docs/source/whatsnew/1.0.0rc1.rst

@@ -11,6 +11,9 @@ API Changes
 * Added support for week-ahead persistence forecasts with
   :py:func:`solarforecastarbiter.utils.get_data_start_end` and
   :py:func:`solarforecastarbiter.main.run_persistence` modifications. (:issue:`55`) (:pull:`392`)
+* :py:func:`solarforecastarbiter.pvmodel.calculate_power` and
+  :py:func:`solarforecastarbiter.datamodel.Site` expect a ``temperature_coefficient``
+  with units of % of DC capacity/C instead of 1/C (:issue:`350`) (:pull:`433`)
 
 Enhancements
 ~~~~~~~~~~~~

solarforecastarbiter/conftest.py

@@ -300,7 +300,7 @@ def site_text():
         "max_rotation_angle": null,
         "surface_azimuth": 180.0,
         "surface_tilt": 45.0,
-        "temperature_coefficient": -0.002,
+        "temperature_coefficient": -0.2,
         "tracking_type": "fixed"
     },
     "name": "Power Plant 1",
@@ -359,7 +359,7 @@ def many_sites_text():
             "max_rotation_angle": null,
             "surface_azimuth": 180.0,
             "surface_tilt": 45.0,
-            "temperature_coefficient": -0.002,
+            "temperature_coefficient": -0.2,
             "tracking_type": "fixed"
         },
         "name": "Power Plant 1",
@@ -386,7 +386,7 @@ def many_sites_text():
             "max_rotation_angle": 90.0,
             "surface_azimuth": null,
             "surface_tilt": null,
-            "temperature_coefficient": -0.002,
+            "temperature_coefficient": -0.2,
             "tracking_type": "single_axis"
         },
         "name": "Tracking plant",
@@ -498,7 +498,7 @@ def powerplant_metadata():
 
 def _powerplant_metadata():
     modeling_params = datamodel.FixedTiltModelingParameters(
-        ac_capacity=.003, dc_capacity=.0035, temperature_coefficient=-0.003,
+        ac_capacity=.003, dc_capacity=.0035, temperature_coefficient=-0.3,
         dc_loss_factor=3, ac_loss_factor=0,
         surface_tilt=30, surface_azimuth=180)
     metadata = datamodel.SolarPowerPlant(
@@ -673,15 +673,15 @@ def ac_power_forecast_metadata_label(request, site_metadata):
 
 def fixed_modeling_parameters():
     modeling_params = datamodel.FixedTiltModelingParameters(
-        ac_capacity=.003, dc_capacity=.0035, temperature_coefficient=-0.003,
+        ac_capacity=.003, dc_capacity=.0035, temperature_coefficient=-0.3,
         dc_loss_factor=3, ac_loss_factor=0,
         surface_tilt=30, surface_azimuth=180)
     return modeling_params
 
 
 def tracking_modeling_parameters():
     modeling_params = datamodel.SingleAxisModelingParameters(
-        ac_capacity=.003, dc_capacity=.0035, temperature_coefficient=-0.003,
+        ac_capacity=.003, dc_capacity=.0035, temperature_coefficient=-0.3,
         dc_loss_factor=3, ac_loss_factor=0,
         axis_tilt=0, axis_azimuth=0, ground_coverage_ratio=2 / 7,
         backtrack=True, max_rotation_angle=45)

solarforecastarbiter/datamodel.py

@@ -361,8 +361,8 @@ class PVModelingParameters(BaseModel):
     dc_capacity : float
         Nameplate DC power rating in megawatts
     temperature_coefficient : float
-        The temperature coefficient of DC power in units of 1/C.
-        Typically -0.002 to -0.005 per degree C.
+        The temperature coefficient of DC power in units of %/C.
+        Typically -0.2 to -0.5 % per degree C.
     dc_loss_factor : float
         Applied to DC current in units of %. 0 = no loss.
     ac_loss_factor : float

solarforecastarbiter/io/reference_observations/rtc.py

@@ -33,7 +33,7 @@ def adjust_site_parameters(site):
     modeling_params = {
         'ac_capacity': 0.00324,  # no clipping
         'dc_capacity': 0.00324,
-        'temperature_coefficient': -0.00420,
+        'temperature_coefficient': -0.420,
         'dc_loss_factor': 0,
         'ac_loss_factor': 0,
         'surface_tilt': 35,

solarforecastarbiter/pvmodel.py

@@ -277,6 +277,7 @@ def calculate_power(dc_capacity, temperature_coefficient, dc_loss_factor,
     ----------
     dc_capacity : float
     temperature_coefficient : float
+        Specified in units of %/C to be converted to 1/C
     dc_loss_factor : float
     ac_capacity : float
     ac_loss_factor : float
@@ -291,7 +292,7 @@ def calculate_power(dc_capacity, temperature_coefficient, dc_loss_factor,
     pvtemps = pvlib.temperature.pvsyst_cell(poa_effective, temp_air,
                                             wind_speed=wind_speed)
     dc = pvlib.pvsystem.pvwatts_dc(poa_effective, pvtemps, dc_capacity,
-                                   temperature_coefficient)
+                                   temperature_coefficient / 100)
     dc *= (1 - dc_loss_factor / 100)
     # set eta values to turn off clipping in pvwatts_ac
     ac = pvlib.pvsystem.pvwatts_ac(dc, dc_capacity, eta_inv_nom=1,

solarforecastarbiter/reference_forecasts/main.py

@@ -77,7 +77,7 @@ def run_nwp(forecast, model, run_time, issue_time):
     >>> modeling_parameters = datamodel.FixedTiltModelingParameters(
     ...     surface_tilt=30, surface_azimuth=180,
     ...     ac_capacity=10, dc_capacity=15,
-    ...     temperature_coefficient=-0.004, dc_loss_factor=0,
+    ...     temperature_coefficient=-0.4, dc_loss_factor=0,
     ...     ac_loss_factor=0)
     >>> power_plant = datamodel.SolarPowerPlant(
     ...     name='Test plant', latitude=32.2, longitude=-110.9,

solarforecastarbiter/reference_forecasts/tests/test_persistence.py

@@ -27,7 +27,7 @@ def load_data_base(data, observation, data_start, data_end):
 def powerplant_metadata():
     """1:1 AC:DC"""
     modeling_params = datamodel.FixedTiltModelingParameters(
-        ac_capacity=200, dc_capacity=200, temperature_coefficient=-0.003,
+        ac_capacity=200, dc_capacity=200, temperature_coefficient=-0.3,
         dc_loss_factor=3, ac_loss_factor=0,
         surface_tilt=30, surface_azimuth=180)
     metadata = datamodel.SolarPowerPlant(

solarforecastarbiter/tests/test_pvmodel.py

@@ -180,11 +180,11 @@ def test_calculate_poa_effective(aoi_func_system_type, apparent_zenith,
 @pytest.mark.parametrize(
     'dc_capacity,temperature_coefficient,dc_loss_factor,'
     'ac_capacity,ac_loss_factor,expected', (
-        (10, -0.005, 0, 10, 0, (0., 7.58301313763377)),
-        (5, 0.005, 0, 10, 0, (0., 5.)),  # pvwatts_ac max out is pdc0
+        (10, -0.5, 0, 10, 0, (0., 7.58301313763377)),
+        (5, 0.5, 0, 10, 0, (0., 5.)),  # pvwatts_ac max out is pdc0
         (10, 0.000, 20, 10, 20, (0., 6.1789760000000005)),
         (10, 0.000, -20, 10, -20, (0., 12.)),
-        (15, -0.005, 0, 10, 0, (0., 10.)),
+        (15, -0.5, 0, 10, 0, (0., 10.)),
     ),
     ids=[
         '10:10 DC:AC, neg temp co, no loss',