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Properties of desirable weight, latent heat capacity, and energy storage capability of phase change materials (PCMs) have led to extensive use of these materials in the building industry as productive thermal mass. This study investigated the feasibility of the utilization of PCMs through numerical simulations in residential buildings located in different Iranian climates in Tehran, Tabriz, Yazd, and Bandar Abbas. In so doing, the optimal PCM for each city was selected based on its impact on annual energy consumption, and then its effects on the indoor temperature and thermal load of the model in the hottest and coldest months of the year were examined. The results showed that the use of PCMs does not lead to significant energy conservation in the hot and humid climate of Bandar Abbas compared with other climates. In the second part of the study, the economic feasibility of PCMs and the payback period of such investment were investigated based on the current local electricity and natural gas prices. It was found that although the use of PCMs leads to significant energy conservation in most of these climates, with the current prices of energy and PCMs in Iran, the use of these materials will not be cost-effective, as the return periods for such investment in Tehran, Tabriz, Yazd, and Bandar Abbas will be 42, 179, 102, and 114 years, respectively. [ABSTRACT FROM AUTHOR]

One of the most common issues associated with wind energy penetration as a viable resource is high instability under diverse amplitudes and frequencies. Compressed air storage systems (CAES) and thermal energy storages (TES) not only are promising alternative solution for renewable resources generally, but they are also used with the aim of peak shaving to provide cleaner and affordable power. Due to high storage density with low temperature gradient between storing and retrieving in comparison with sensible heat storage, phase change material (PCM) is selected considering their thermophysical properties. This work, presents a recovery approach by using PCM during 12 h' compression periods to retrieve it in 12 h' expansion as a case study in November for Baladeh (a city in north of Iran). It is worthy to mention that, in order to use PCM in multiple mentioned stages, auxiliary heaters facilitate system to provide constant heat load in each used stage. This concludes system to be more efficient, sustainable and can reduce irreversibilities. Temperature of PCMs and amount of heat stored and released versus time are modeled. A good agreement between PCM model and reported results of related articles was seen. Following to the energy and exergy balances calculation, round-trip efficiency (RTE) and total exergy efficiency of system, reach 70.83%, 80.71%. Exergy analysis showed that near 60% exergy destruction occurred in PCMs with major contribution of second ones in both charge and discharge times. Sensitivity analysis is also investigated assuming the effect of number of wind turbines which shows a reduction in RTE, steeper slope in increasing TES volume for PCM3 and amount of heat stored, by increasing them. Image 10372 • A hybrid renewable energy storage system using phase change materials is investigated. • Compressed air storage and thermal energy storage methods are integrated. • RTE and total exergy efficiency of the system, reach 70.83%, 80.71%. • A city in north of Iran is considered for design of wind farm integrated to the energy system. [ABSTRACT FROM AUTHOR]