Solar energy is an abundant source of energy for generating electricity. One of the main challenges in using solar energy is that solar photovoltaic (PV) panels are typically used in regions where solar radiation is high; consequently, the temperature of the panels will increase, and the efficiency of the panels will decrease. Adding cooling tubes to the PV panel is a possible approach to cool it down. To design such cooling systems, CFD simulations may be used; however, this approach tends to be time-consuming. In this paper, we report a new algorithm for designing straight cooling tubes. The algorithm can be used to determine important design parameters such as tube center-to-center length, diameter of the tube, and the minimum tube length needed to achieve a desired outlet temperature. The accuracy of the algorithm was tested using real-world data (including various ambient temperatures and solar radiations) and the maximum temperature difference between desired outlet temperature and CFD simulation for the designed cooling system was found to be 1.7 degrees K.