To obtain maximum exergy and energy efficiencies of photovoltaic-thermal (PV-T) systems, innovative configurations of coolant tubes are proposed and simulated numerically. The tubes' configuration is modified using non-uniform wavy tube concept, which forms different styles, including ascending and descending amplitude of coolant tubes. Besides, the influences of geometrical parameters, extending PV panel length, sensitivity analysis on the operating conditions and a comprehensive investigation of different types of heat transfer fluids are analysed for the innovative systems. The results demonstrate that the PV-T performance develops in terms of electrical, thermal, and exergy efficiencies using ascending wavy tubes compared with straight, uniform wavy and descending wavy tubes. The electrical and thermal efficiencies are promoted from 10.94% to 61.04% for the straight tubes to 11.32% and 65.21%, respectively, for the system in which ascending wavy tubes are utilised. A comprehensive study of different coolant fluids proves that when SiC and MPCM-28 are simultaneously employed, the best cooling fluid is achieved, leading to a 0.4% higher electrical efficiency than the case in which water is used. (C) 2021 Elsevier Ltd. All rights reserved.