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Selection of the optimum values for net zero energy buildings (NZEB) is a complex task, due to the existence of multiple objectives. In the current study, cold and semi-arid climate was considered for investigation, and DesignBuilder was used for simulating a residential NZEB in Shiraz, Iran, as a case study. First, optimum solutions for minimising the cooling and heating demands were obtained by obtaining a Pareto front including 21 points. Then, phase changing materials (PCMs) were integrated to the envelope to further optimise energy consumption. The obtained results illustrated that using PCMs on both sides of the envelope can significantly reduce the energy consumption. Findings of this study are beneficial for the future plans of Iran, particularly with regards to improving sustainability within the building sector. • Integration of multi-objective optimisation algorithm with dynamic simulation tool. • Discussion of design criteria for residential NZEB in semi-arid climate. • Minimisation of energy demand by considering discomfort as constraint. • Discussion on innovative configurations of novel passive strategies. [ABSTRACT FROM AUTHOR]

• The presence of PCMs reduces temperature fluctuations and heat transfer to the room. • Performing sensitivity analysis for HTR based on variation in properties. • Thermal conductivity of PCM plays most significant role in selecting the appropriate PCM. • For equal thermal conductivity, closer melting point to room temperature is preferred. • When PCM is closer to the exterior, a larger portion of it melts, HTR is greater. Passive latent heat thermal energy storage approach incorporating phase change materials (PCM) is a brilliant technique to tackle high energy consumption issue in buildings. This paper investigated the thermal performance of the conventional walls of buildings in Isfahan, Iran with the inclusion of thirteen different phase change materials. The studied base wall was composed of plaster (2 cm), clay brick (15 cm), and cement (3 cm). The effect of PCM position inside the wall on the heat transfer was assessed in two scenarios, namely: close to the interior and close to exterior. The nonlinear governing equations were solved using the finite volume method. The results show that the performance of PCM-based wall is strongly influenced by the thermal conductivity, phase-change enthalpy and melting temperature of PCM. A PCM can more efficiently reduce the heat transfer to the interior space in case it has a lower thermal conductivity, has a higher latent heat of phase-change, and its phase-change temperature is closer to the room temperature. Moreover, the thermal conductivity has priority over other PCM thermophysical properties. The lower PCM thermal conductivity leads to transfer the lower amount of heat to the interior space. A two-fold increase in the thickness of the PCM leads to less than a twofold reduction in the heat transfer. Among the studied PCMs, the heat transfer reduction by Enerciel 22 was within the range 15.6–47.6%, while this range was 2–7.8% for CaC l 2. 6 H 2 O. [ABSTRACT FROM AUTHOR]

In this study, a series of experimental runs performed under different conditions in order to evaluate the effectiveness of a household refrigerator. Two eutectic phase change materials (PCMs) arranged in a cascade configuration have been tested on the performance of the system. The PCMs were placed on the back-side of the wire-and-tube condenser in a decreasing order of their melting temperatures along the refrigerant flow direction to achieve a high heat transfer rate and to reduce energy consumption. The operating characteristics of the novel refrigerator were studied and compared with the results of a refrigerator equipped with a single PCM and two ordinary refrigerators with and without measurement packages (M-packs). All the tests have been performed in standard condition in Philver Company in Tehran, Iran. For the novel refrigerator, the temperature of the condenser surface significantly decreased, which led to a lower condensing temperature during the refrigeration cycle and improved the coefficient of performance (COP). Also, the ratio of the on-time to the total experiment time was considerably shorter compared to the refrigerator equipped with a single PCM and two ordinary refrigerators. According to the results, integration of two different PCMs on the condenser surface in a cascade arrangement decreases the compressor work time percentage from 32.7 to 27.6, while this parameter was decreased to 29.6 with a single PCM. Finally, the energy consumption was reduced by 13% in the novel refrigerator whereas it was only reduced by 8% in the refrigerator equipped with a single PCM. • Efficiency enhancement of a household refrigerator has been studied. • Eutectic phase change materials with cascade configuration have been used in the system. • The compressor off-time of the novel system lowered significantly. • Energy consumption of the refrigerator with single PCM was reduced by 8%. • Further energy consumption reduction up to 13% has been achieved in cascade configuration. [ABSTRACT FROM AUTHOR]

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]

• The SSPCM was employed to prepare cement mortars for plastering masonry brick walls. • An experimental setup was utilized to perform thermal performance test on the wall specimens. • The wall specimens were under ambient temperature conditions of two different cities of Iran. • The physical and mechanical properties of SSPCM-incorporated mortars were measured and analyzed. • The developed SSPCM incorporated in plaster mortar provides thermal energy storage capability. Phase change materials (PCMs) have been widely proven to provide thermal energy storage (TES) capacity in building systems. However, some potential problems associated with the incorporation of PCMs in building materials may cause uncertainty about their real performance. Among such problems, the leakage possibility of PCMs in the molten state has been greatly addressed in the literature. In this regard, this study is aimed to evaluate the mechanical and thermal behavior of a shape-stabilized PCM (SSPCM) as a TES component in the conventional wall system of buildings in Iran. For this purpose, PEG 600 was shape-stabilized in the porous structure of the silica fume as the supporting material using the vacuum impregnation method. The SSPCM was further employed to prepare cement mortars for plastering masonry brick wall specimens. The mechanical experiments on the SSPCM-incorporated mortars indicated satisfactory results to be used as the finishing plaster for masonry walls. Moreover, a novel experimental setup was utilized to perform thermal performance test on the wall specimens plastered with SSPCM-incorporated mortar under ambient temperature conditions of two different cities. Accordingly, the developed SSPCM exhibited the promising potential to provide TES capacity in external masonry wall systems by reducing the peak temperature as well as mitigating indoor temperature fluctuations. [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]

• An integrated system is proposed to produce power, cooling, and freshwater. • Novel Thermal Energy Storage (TES) is suggested using phase change material (PCM). • Using high temperature PCM for TES, continuous operation of system is feasible. • The overall energy and exergy efficiencies are 40.52% and 14.40%, respectively. • The LCoE of the plant follows the downward trend of concentrated solar plants. In this article, three different modes of a novel integrated system would be evaluated by the application of high temperature Thermal Energy Storage (TES) to produce electricity, cooling, and freshwater. Freshwater is produced using the reverse osmosis (RO) desalination unit while Absorption Refrigeration Cycle (ARC) provides cooling. In this system, a high temperature Phase Change Material (PCM) is utilized to make the system working continuously even at nights. The output heat of gas turbine (GT) is also recovered utilizing the Organic Rankine Cycle (ORC). According to exergoeconomic analysis, the efficiencies, exergy destructions and product cost rates are computed. The multi-objective optimization has also been performed considering six different ORC working fluids and the changes in the direct normal irradiation of a city in Iran. In the trigeneration condition, the optimum values of the GT's compressor pressure ratio and ORC's turbine inlet pressure were obtained 9.06 and 3300 kPa, respectively. The exergy efficiency of the suggested system at the optimal condition is computed to be 14.40%, while that of energy is 40.52% with the total product cost rate of 30.524 $/GJ. The produced cooling capacity of the absorption system is also 1.62 MW whereas the output amount of freshwater and electricity for the users are about 5209.5 m3/day and 2.42 MW, respectively. The Levelized Cost of Electricity (LCoE) is also calculated to be 0.2341 $/kWh, which shows promising economic performance. [ABSTRACT FROM AUTHOR]