Solar dryers assisted with phase change material (PCM) speed up the drying process by compensating the negating effect of reduced or absence of solar energy under cloudy or non-sunshine hours respectively. The study of the relevant and recent literature indicated that the minimum quantity and proper placement of this PCM have not been explored to take full advantage of using them in solar dryers. Hence in this research work, experimental investigations on banana slice drying were carried out with 4 and 10 numbers of copper tubes filled with 176 and 494 kg of commercial paraffin wax respectively (correspondingly designated as SD-PCM1 and SD-PCM2). The copper tubes were placed in vertical and horizontal orientations on the inner wall of the drying chamber so that the upward movement of air would not disturbed. A comparison of the drying performance of a PCM-based unit with a natural convective solar dryer without PCM (SD) was also presented. As no appreciable differences between the mass loss during drying under SD and SD-PCM1 modes were observed, it was concluded that a mass of PCM greater than 176 g would enhance drying rates. Thus for the same final mass of dried banana slices, the drying time was about 15 and 9 h with SD and SD-PCM2 respectively. As the operating conditions of SD and SD-PCM vary considerably in terms of the thermal energy supplied during the drying process, the concept of a generalized drying curve with dimensionless time was used to study the drying kinetics. A close alignment of experimental data of moisture content ratio with the generalized drying curve under SD and SD-PCM modes indicates similar dryer performance irrespective of the differences in thermal energy supplied. The average exergetic efficiency of SD, SD-PCM1 and SD-PCM2 was 21, 26 and 28 % respectively. The sustainability index and environmental impact factor for SD-PCM2 were 1.41 and 2.5 respectively which was better compared to the respective values of 1.27 and 3.77 in SD mode favoring the use of PCM in solar dryers.