**4. Conclusions**

A hydronic evacuated tube solar heating system is fabricated and installed to match the domestic requirements and uses throughout the day by using PCM latent heat. In the analysis of the hydronic solar system, the influence of the weather and operating conditions was considered. The thickness of the PCM shell in the bottom portion is greater than that of the top, minimizing the water temperature difference at the top and bottom to 5 ◦C.

The water and ambient temperatures through the system testing are presented and discussed in three cases: the first one was at normal conditions on clear days with water consumption, the second was without water consumption, and the final case was the effect of sudden and complete consumption of hot water while observing the behavior of PCMs in heated water. The results show increasing water temperature after a short period for domestic water temperature values.

The thermal efficiency of the hydronic solar system in December, March, and June was 80%, 81%, and 84%, respectively. This conclusion is higher than that of the experiments conducted by Kumar et al., 2020 [21]. Thermal efficiency depends linearly on ( <sup>Δ</sup> *<sup>T</sup> <sup>I</sup>* ). The hot water for domestic use is available throughout the day, which is achieved by using PCMs.

**Author Contributions:** Methodology, D.S.M. and R.I.R.; Software, M.S.M.; Formal analysis, D.S.M. and M.S.M.; Investigation, D.S.M. and R.I.R.; Data curation, D.S.M., M.S.M. and S.J.A.R.; Writing—original draft, D.S.M., R.I.R., M.S.M. and S.J.A.R.; Writing—review & editing, R.I.R. and S.J.A.R.; Supervision, R.I.R.; Funding acquisition, R.I.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Jordan University of Science and Technology/Deanship of Research grant number [50/2018].

**Institutional Review Board Statement:** Not applicable.

**Acknowledgments:** The authors are immensely grateful to the Jordan University of Science and Technology/Deanship of Research for their financial support of this project.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Nomenclature**


