In the present paper, a two dimensional axisymmetric Finite Element Method (FEM) is developed to carry out a thermo-mechanical analysis on a horizontal storage tank intended to storage hot water for a domestic application. The purpose of these numerical simulations is to assess the thermo-mechanical behavior of a horizontal tank with evacuated tube collectors, and consequently to suggest a new design which ensures an optimum mechanical strength according to severe applied operating conditions in terms of temperature and pressure. To achieve this goal, a thermo-mechanical 1-way sequential coupling has been used as a solving method. The physical model suggested in this study and the simulations procedure was described under detailed assumptions. In fact, the main hypotheses in the current formulation were the thermo-elastic behavior of the tank's materials and the steady state assumption analysis. This paper outlines three studies that were performed to extend the lifespan of the horizontal storage tank, through the definition of a suitable material and an optimal design. The main conclusions of the assessment are that the optimal configuration which avoid the appearance of the stress concentration zones is the configuration (c), where Ri = 11 mm and Re = 14 mm, because the stress on the tank's shell was better applied. Moreover, the effect of the material's selection was carried out, and it was found that stainless steel is the optimal material. Last but not least, a set of simulations were conducted to investigate the tank shell thickness on which the thermo-mechanical constraints were applied. The thickness t = 2 mm was presenting an optimal mechanical behavior with regard to the studied operating conditions. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.