Value of tilt in case of single-axis tracking


I need to simultate a gound-mounted CSP-plant with 1-axis tracking. I’ve chosen the azimut to 180 degrees. How should I define an angle for the tilt in case of variable positions over the day? Below I have attached the parameters of the simulation. Thank you for any help!

args = {
‘lat’: lat,
‘lon’: lon,
‘date_from’: date_from,
‘date_to’: date_to,
‘dataset’: ‘merra2’,
‘capacity’: 1.0,
‘system_loss’: 0.1,
‘tracking’: 1,
‘tilt’: ?,
‘azim’: 180,
‘raw’: ‘true’,
‘format’: ‘json’