Create plot_ghi_transposition.py example

docs/examples/plot_ghi_transposition.py

@@ -0,0 +1,75 @@
+"""
+GHI to POA Transposition
+=========================
+
+Example of transposing clearsky GHI to POA
+"""
+
+# %%
+# This example shows how to use the get_clearsky method to generate clearsky
+# GHI data as well as how to use the get_total_iradiance function to transpose
+# GHI data to Plane of Array (POA) irradiance.
+
+from pvlib import location
+from pvlib.irradiance import get_total_irradiance
+import pandas as pd
+from matplotlib import pyplot as plt
+
+# For this example, we will be using Golden, Colorado
+tz = 'MST'
+lat, lon = 39.755, -105.221
+
+# Create location object to store lat, lon, timezone
+site = location.Location(lat, lon, tz=tz)
+
+
+# Define a function to handle the transposition
+def get_irradiance(site_location, date, tilt, surface_azimuth):
+ # Creates one day's worth of 10 min intervals
+ times = pd.date_range(date, freq='10min', periods=6*24, tz=tz)
+ # Generate cleaersky data using the Ineichen model, which is the default
+ # The get_clearsky method returns a dataframe with values for GHI, DNI,
+ # and DHI
+ clearsky_ghi = site_location.get_clearsky(times)
+ # Get solar azimuth and zenith to pass to the transposition function
+ solar_position = site_location.get_solarposition(times=times)
+ # Use the get_total_irradiance function to transpose the GHI to POA
+ POA_irradiance = get_total_irradiance(
+ surface_tilt=tilt,
+ surface_azimuth=surface_azimuth,
+ dni=clearsky_ghi['dni'],
+ ghi=clearsky_ghi['ghi'],
+ dhi=clearsky_ghi['dhi'],
+ solar_zenith=solar_position['zenith'],
+ solar_azimuth=solar_position['azimuth'])
+ # Return DataFrame with only GHI and POA
+ return pd.DataFrame({'GHI': clearsky_ghi['ghi'],
+ 'POA': POA_irradiance['poa_global']})
+
+
+# Get irradiance data for summer and winter solstice, assuming 25 degree tilt
+# and a south facing array
+summer_irradiance = get_irradiance(site, '06-20-2020', 25, 180)
+winter_irradiance = get_irradiance(site, '12-21-2020', 25, 180)
+
+# Plot GHI vs. POA for winter and summer
+fig, (ax1, ax2) = plt.subplots(1, 2)
+summer_irradiance['GHI'].plot(ax=ax1, label='GHI')
+summer_irradiance['POA'].plot(ax=ax1, label='POA')
+winter_irradiance['GHI'].plot(ax=ax2, label='GHI')
+winter_irradiance['POA'].plot(ax=ax2, label='POA')
+ax1.set_xlabel('Time of day (Summer)')
+ax2.set_xlabel('Time of day (Winter)')
+ax1.set_ylabel('Irradiance (W/m2)')
+ax2.set_ylabel('Irradiance (W/m2)')
+ax1.legend()
+ax2.legend()
+plt.show()
+
+# %%
+# Note that in Summer, there is not much gain when comparing POA irradiance to
+# GHI. In the winter, however, POA irradiance is signifiacntly higher than
+# GHI. This is because, in winter, the sun is much lower in the sky, so a
+# tilted array will be at a more optimal angle compared to a flat array.
+# In summer, the sun gets much higher in the sky, and there is very little
+# gain for a tilted array compared to a flat array.

docs/sphinx/source/whatsnew/v0.7.2.rst

@@ -67,6 +67,7 @@ Documentation
 * Add example of IV curve generation. (:pull:`872`)
 * Add section about gallery examples to Contributing guide. (:pull:`905`)
 * Add section with link to Code of Conduct in Contributing guide. (:pull:`922`)
+* Add example of GHI to POA transposition 
 
 Requirements
 ~~~~~~~~~~~~
@@ -81,3 +82,4 @@ Contributors
 * Kevin Anderson (:ghuser:`kanderso-nrel`)
 * Karthikeyan Singaravelan (:ghuser:`tirkarthi`)
 * Siyan (Veronica) Guo (:ghuser:`veronicaguo`)
+* Eric Fitch (:ghuser:`eric.f900`)