Abstract: Flexible copper indium gallium selenide (CIGS) photovoltaic (PV) cells are gradually expanding their applications due to their advantages of flexibility and easy installation. However, they are encapsulated with thermoplastic materials, which have lower thermal stability, faster fire spreading speed and higher fire risk. In this paper, the combustion spread characteristics of flexible PV cells under different tilt angles (-30°~+30°) and ignition positions (top and bottom) are studied, and the changing rules of combustion parameters such as flame morphology, flame angle, fire spreading speed, cell surface temperature, and radiant heat flux are analysed. It is found that: with the increase of the tilt angle of the panel from -30° to +30°, the flame angle and pyrolysis time show the trend of increasing and then decreasing, while the flame length, heat flux, and fire spreading speed show the opposite trend; when the tilt angle is from +10° to +20°, there is a significant surge in the flame length and spread speed, the pyrolysis time is shortened by 40%, and heat flux is increased by 65%. Based on the differences in flame front morphology under different tilt angles and ignition positions, three different radiative heat transfer models are established, and the theoretical and experimental values of radiative heat flux are within 20% of each other, which has good applicability.

Key words: flexible CIGS, PV cell, tilt angle, ignition position, fire spread characteristics, combustion behavior