Development of an optimizing tool for design of tailored PV modules through Cell To Module (CTM) factor modelling

Abstract

The advancement of innovative PV technologies has led to an all-time high integration of the same in the urban environment. Furthermore, development of decentralized power systems complements this rise as it supports in-situ power consumption. Due to space availability constraints in urban environments and a need for appealing aesthetics, tailored PV modules is gaining importance. However, it is desirable to achieve maximum power out of these tailored PV modules to ensure efficiency in space usage.
Literature suggests that one of the most apt performance metric for estimating the goodness of design for PV modules is the CTM ratio. However, various challenges incurred upon implementing the present CTM analysis algorithms on tailored PV modules suggests the need for development of a different approach to estimate the same. The presented work strives towards the development of a tool for the prediction of various performance metrics, including the CTM ratio, of both standard and tailored PV modules to aid its user to make educated design choices to develop optimum modules.
The methodology used for development of the tool encompasses various steps which occur in a pre-programmed flow. Firstly, a developed script automatically creates the module structure based on user inputs. Hereafter, ray tracing is implemented and its results furnishes optical performance of the module. Furthermore, an electrical loss calculation model is developed, using differential element method, which when coupled with the optical performance data enables the estimation of the CTM ratio and other performance metrics. The tool is programmed in Matlab to ensure easy integration of the same with the PVMD toolbox for future research on module designs.
Firstly, an attempt is made to optimize the parameters of the mini-module for maximizing its performance. For a white backsheet test mini-module, optimization through the usage of the tool, leads to a 5.52 % gain from the worst case design. This gain is realized by achieving an optimal tuning between the cell-cell and cell-edge spacing. Moreover, when compared, the white backsheet module’s power production capacity outperforms the black backsheet module by around 13.93 %. Additionally, effect of busbars on the performance of the module is investigated.
Furthermore, the tool is able to derive novel empirical formulas which, for different module architectures, predict the effect of cell top metallization on the cell photocurrent density in an encapsulated environment.
Secondly, efficacy of the tool is demonstrated for a comparative study between a 60 cell module and its corresponding 120 half-cut cell module. The tool suggests the half-cut cell module to have a 2.91 % gain in CTM ratio as compared to its full cell counterpart.
Thirdly, the tool demonstrates modelling and simulation of glass-glass modules and achieve optimization. The tool also recommends an increase of the dimension size for the test module to 20×20 cm2 to achieve the exemplary target transmission of 14 %.
Lastly, the tool efficacy is demonstrated for a triangular PV module. This module with a white backsheet is found to outperform its black backsheet counterpart by 9 % in CTM ratio.