pvlib IV curve - TypeError: must be str, not int

Question

I'm trying to make an IV curve from pvlib but am getting the error:

TypeError: must be str, not int.

Running on Spyder. Could you advise please? This example taken from the web.

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
rom pvlib.pvsystem import singlediode, v_from_i, i_from_v, retrieve_sam

def fivepoints_to_frame(pnt):
    """
    Converts a 1 dimensional, dict-like singlediode or sapm result
    to a 5 row DataFrame with columns current and voltage.
    Users can iterate over the rows of a multidimensional
    singlediode or sapm result, if necessary.
    """
    ivframe = {'i_sc': (pnt['i_sc'], 0),
               'p_mp': (pnt['i_mp'], pnt['v_mp']),
               'i_x': (pnt['i_x'], 0.5*pnt['v_oc']),
               'i_xx': (pnt['i_xx'], 0.5*(pnt['v_oc']+pnt['v_mp'])),
               'v_oc': (0, pnt['v_oc'])}
    ivframe = pd.DataFrame(ivframe, index=['current', 'voltage']).T
    ivframe = ivframe.sort_values(by='voltage')

    return ivframe

resistance_shunt = 16
resistance_series = 0.094
nNsVth = 0.473
saturation_current = 1.943e-09
photocurrent = 7
module_parameters = retrieve_sam('cecmod')['Example_Module']

v_oc = v_from_i(resistance_shunt, resistance_series, nNsVth, 0, 
saturation_current, photocurrent)
voltage = np.linspace(0, v_oc, 100)

current = i_from_v(resistance_shunt, resistance_series, nNsVth, 
voltage,saturation_current, photocurrent)

fivepnts = singlediode(
    module_parameters, photocurrent, saturation_current, resistance_series, 
resistance_shunt, nNsVth)
ivframe = fivepoints_to_frame(fivepnts)

fig, ax = plt.subplots()
ax.plot(voltage, current)
ax.scatter(ivframe['voltage'], ivframe['current'], c='k', s=36, zorder=10)
ax.set_xlim(0, None)
ax.set_ylim(0, None)
ax.set_ylabel('current (A)')
ax.set_xlabel('voltage (V)')

Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it in the question itself. Questions without a clear problem statement are not useful to other readers. See: How to create a [mcve]. — ImportanceOfBeingErnest, Jun 04 '17 at 15:07

score 1 · Answer 1 · answered Jun 04 '17 at 16:36

From the (Docs)

pvlib.pvsystem.singlediode(photocurrent, saturation_current, resistance_series, 
                           resistance_shunt, nNsVth, ivcurve_pnts=None)

The first parameter to singlediode() is incorrect. If I remove it like:

fivepnts = singlediode(
    photocurrent, saturation_current, resistance_series,
    resistance_shunt, nNsVth)

I get:

pvlib IV curve - TypeError: must be str, not int

1 Answers1