An analytical and comparative study of the charging and discharging processes in a latent heat thermal storage tank for solar water heater system

Over the last decades, the science of solar cells has been substantially soared; however, the existence philosophy needs to follow almost the same mechanism due to the known limitations. Building upon this fact, until now, several generations of solar collectors have been introduced to the field of renewable energies. This current study reports an analytical investigation of the new compact design of evacuated heat pipe solar water heater integrated with latent heat storage tank. This device has a set of evacuated heat pipe solar collector (ETHPSC) arrays directly connected to a tank, which is filled by paraffin wax as the phase change materials (PCM). This work is carried out in two steps. Firstly, the system is modeled theoretically by applying the mathematical equations by using MATLAB in order to study the thermal performance of the thermal battery. Afterwards, a parametric and comparative investigation is conducted to study the performance of the system with different PCMs, different climate condition and different flowrates. This study is also carried out to compare the model with the conventional system. In the baseline system, and for the best chosen PCM, the system efficiency is between 32 and 42% in low solar radiation days, while it is in the range of around 40 ± 3% in the high radiation intensity days, whereas these magnitudes are ∼57% and higher than 50% in the new design, respectively. The efficiency of the new design, for all three types of PCMs, in a typical sunny day is in the range of the 36–54%, while, interestingly and positively, this efficiency increases to the range of 47–58% in a typical cloudy/rainy day. On the other hand, this trend happens reversely for the conventional system. Overall, the average efficiencies of the proposed system are increased from approximately 10% to 58% for three different PCMs in compared to the baseline.