Design of a low-cost measuring and plotting device for photovoltaic modules

Abstract

The photovoltaic module testing apparatus being used presently for photovoltaic measurements acts principally on the method of photovoltaic module loading with resistive, capacitive, and electronic elements. In this work, a new method is described using a supercapacitor as the load to the photovoltaic module. This technique of characterization has proved to generate reliable V–I characteristics as validated by statistical and mathematical analyses in this article. Heat dissipation affecting the functioning of the photovoltaic modules is a common occurrence with resistive and capacitive loading techniques. It is reduced significantly in this method using supercapacitors, and curve tracing time is extremely modest and easily controllable. In effect, a low-cost, portable, and reliable I–V plotter is developed, which is operational from an embedded systems platform integrated with smart sensors. This I–V tracer has been used for the performance assessment of solar modules ranging from 10 to 100 Wp under varying climatic conditions in the eastern region of India. This test kit so developed in the photovoltaic engineering laboratory at Indian Institute of Engineering Science and Technology, Shibpur, is estimated to be useful for practicing engineers and photovoltaic scientists and in particular for photovoltaic module manufacturers. The performance parameters such as fill factor and performance ratio of photovoltaic modules measured by the device have been found to have almost identical values as the measurements from a reference commercial testing apparatus. The data pertaining to peak wattage as measured by the designed plotter have been found to be closely converging with an industry-friendly YOKOGAWA Power Meter (WT 330). Such peak values of power as measured and claimed by the datasheets will help reduce the uncertainties in measurement, leading to increased confidence of photovoltaic module manufacturers and investors. With this backdrop, the necessary work for scaling up of the low-cost I–V plotter has been taken up for assessing the performance of higher wattage photovoltaic modules.