Due to the latent heat performance of the phase change materials during the phase change process, if they are used in a solar energy storage tank, the heat storage efficiency and the heat release capacity of the tank can be effectively improved. In this study, a water storage tank containing two types of phase change materials with different melting points was proposed. Then, based on simulation calculation, the tank with the highest performance of thermal storage was obtained by changing the thickness of the phase change materials. Finally, three water storage tanks with different contents of phase change materials, respectively equipped with a circulating water system were established; the time of storing and releasing heat as well as the total amount of heat release were measured at releasing heat temperature of 40 and 45 degrees C. Results show that the presence of the phase change materials with different melting points can significantly shorten the time of storing heat. An increase in the contents of phase change materials in the tank leads to evident growth of heat release. At 40 degrees C, the amount of heat release are 21.35, 27.01 and 29.78 MJ at the contents of 0, 11.12% and 19.17% respectively, which are larger than those at 45 degrees C. The storage tank can reduce the use of electric heating devices and can be used in solar hot water systems. (C) 2017 Elsevier B.V. All rights reserved.