[Easy] Calculate one year of clear-sky irradiance at a location of your choosing.

[kandersolar]

Clear-sky irradiance can be modeled at a selected location using one of pvlib's clear-sky models.

Step 1. - Import some libraries: pvlib, pandas, pytz, and matplotlib. pandas provides date time functions and pytz helps to localize the date times to a timezone.

Step 2. - Choose a location and define a Location object using pvlib.location.Location. Hint: use pytz.all_timezones to list available timezones.

Step 3. - Set up one year of time stamps as a pandas DateTimeindex, using pandas date_range. Be sure to localize the time stamps to the correct timezone.

Step 4. - Calculate a year of clear-sky irradiance using the Haurwitz model. We'll use Haurwitz's model here because it requires the fewest inputs. Do the calculation two different ways:

• using the Location method get_clearsky. Be sure to specify 'haurwitz'.
• using the function pvlib.clearsky.haurwitz. To prepare the inputs for haurwitz, you will need to first calculate solar position (use either the Location method get_solarposition or the function pvlib.solarposition.get_solarposition).

Use matplotlib to visualize the results. Did you get the same answer from both approaches?

In what season is clear-sky irradiance greatest? Least?

Step 5. - pvlib provides several clear-sky models. The default is a model of P. Ineichen's. Use the Location method get_clearsky to calculate clear-sky irradiance by the Ineichen model. Plot the Haurwitz and Ineichen clear-sky results. How are they the same? How are they different?

For a deeper understanding: Look at the source code for the Location method get_clearsky. How does the calculation know what solar position to use?

Bonus challenge: the Ineichen model can adjust clear-sky irradiance for the atmospheric depth at the selected location. If you use the Location method get_clearsky, the adjustment uses the altitude value on the Location object. Vary the altitude and see how much GHI changes with different altitude values.