•The applications of phase change materials in buildings are considered.•The experimental papers about PCMs in buildings are reviewed.•Nano-PCMs, as novel storage structures, are taken into account ...in this review.•All the gaps are identified and suggestions are presented for future studies.
Thermal energy storage (TES) systems with phase change materials (PCMs) as a known energy storage technology have a high potential for increasing the energy efficiency of buildings. In fact, the use of PCMs with various approaches, either active or passive, in the building helps to maintain the temperature in the thermal comfort range for occupants through decreasing the temperature swings, and lower energy consumption by the load reduction/shifting. Due to the significance of this issue, many research works have been carried out on the application of PCMs in buildings. In this study, the experimental works in the fields of PCMs in buildings are taken into account. The papers are classified based on heating, cooling, and air-conditioning. Besides these, the applications of nano-PCMs in buildings are reviewed. According to what has been carried out up to now, the gaps are identified and analyzed for preparing useful suggestions for future works. The recommendations and suggestions are presented at the end of the chapters as well as the conclusion, and the literature is summarized in some tables.
In this study, the partial heating supercritical CO
2
power cycle for waste heat recovery is investigated to understand more about the true potential of thermodynamic and economic performance ...improvement of each system component, as well as a more profound comprehension of the simultaneous interactions between the system components using advanced exergy and advanced exergoeconomics analysis. In addition, the affirmative or nugatory impact of the inefficiency of each component on the exogenous exergy destruction and exogenous costs in other system components separately, as well as the effect of the inefficiency combination of other components on the desired component (mexogenous effect) have been determined. The results demonstrated that according to the technological constraints in the system, the maximum exergy efficiency that can be achieved is 59.8%, and 38.4% (926.9 kW) of the total exergy destruction and 46.18% (32.52
$
h
-
1
) of the total exergy destruction cost of the system is avoidable. According to the mexogenous exergy destruction, the simultaneous interplay among other system components affects the turbine performance most. The priority of improving the components based on the highest avoidable endogenous exergy destruction cost is related to the turbine, cooler, and compressor. The results of this study revealed that 97.8% (79.73
$
h
-
1
) of the system's total cost is relevant to the endogenous part, which shows that the cost caused by the interaction among the components is very small. The turbine and compressor have the most significant cost-saving potential, while the heaters have the lowest.
A great significance is attached to the Organic Rankine Cycles (ORCs) as heat recovery technologies and power generation from the low-temperature heat sources. These systems have been utilized in ...diverse applications since their first emergence in 1883. Working fluid (WF) selection exerts enormous influence over the performance of these cycles. A large variety of WFs has been historically tested in the ORCs, from the ordinary organic fluids to the nowadays hydrofluoro chemicals, to find compatible WFs for these systems. The current generation of the ORCs based on the international protocols needs low global warming potential (GWP) WFs to not only reduce their environmental impacts in the operation stage but also the whole life cycle of the system. This study aims to assess the performance of environmentally-friendly WFs in the ORCs through the literature. This paper firstly reviews screening methodologies and WF selection criteria to provide a better understanding of the WF selection procedure. Afterward, proposes three categories of WFs with a GWP value of lower than 150, including hydrocarbons (HCs), hydrofluoro chemicals, and mixture WF, and evaluates their performance in different configurations of the ORCs based on a variety of performance indicators.
Increasing the production of energy in line with industry development, transportation, and life quality improvement is an interesting topic needs to be addressed. Energy policymakers and researchers ...have aimed at energy management, particularly by improving energy systems performance. This review paper explains the rising interest of thermoelectric technology and applications. Nowadays, thermoelectric technology such as thermoelectric generators (TEGs) and thermoelectric cooling systems (TECs) provide heat loss recovery of thermodynamic units for power production of remote areas. Unlimited solar energy can also be employed for thermoelectric power production. This paper describes the principles of thermoelectricity and presents an explanation of current and upcoming materials. Developed models and various performed optimization of thermoelectric applications by using non-equilibrium thermodynamics and finite time thermodynamics are discussed as well. Additionally, a number of topical applications and energy resources are introduced. The main goal of this study is to give a clear overview of thermoelectric technology and applications.
•Explains the rising interest of thermoelectric technology and applications.•Describes thermoelectricity principles and current and upcoming materials.•Developed models and various performed optimization are discussed.•Includes non-equilibrium thermodynamics and finite time thermodynamics.•A number of topical applications and energy resources are introduced.
A novel hybrid system, including photovoltaic, wind turbine, diesel generator, battery, electrolyzer, gas turbine cycle, Rankine cycle, absorption chiller, and hot water line, is introduced in order ...to supply electricity, cooling, and heating simultaneously for a town in Istanbul. The dynamic method is employed for different parts of the system dependent on meteorological information, and the steady-state situation is considered for the other parts, such as the gas turbine cycle, Rankine cycle, absorption chiller, and hot water line. Therefore, every operational parameter of the proposed system is evaluated monthly based on the meteorological information of 2019 in Istanbul. Also, the combination of the non-dominated sorting algorithm and multi-criteria decision-making of TOPSIS is employed in order to obtain the optimum rates of monthly operational parameters. Accordingly, the maximum rates of energy and exergy efficiencies can be acquired, which belong to September, October, and November, approximately 54–60%. Furthermore, exergy destruction can be achieved at the lowest rate. The highest exergy destruction is dedicated to December, with 1925.7 MW and the combustion chamber in the gas turbine cycle has the highest contribution (48%) in the exergy destruction related to this month. At the end, the COE and NPC of the system based on the optimum operational parameters are obtained 0.05147 $kW h
−1
and 579.3 M$, respectively.
In this study, a thermal model for a turbojet engine is proposed. Besides the engine’s performance, the cost flow rate of each component is evaluated by performing the energetic, exergetic and ...exergoeconomic analyses. The compressor pressure ratio (
π
AC
), flight Mach number (Ma) and turbine inlet temperature (TIT) are three operating variables, which affect the performance of the whole system. Therefore, a sensitivity analysis is carried out to survey the effect of these variables on objective functions (i.e., energy efficiency, exergy efficiency, and exergy destruction). It is found that there are some contradictions between exergy efficiency and exergy destruction, which by increment in TIT energy efficiency increases, while the exergy destruction decreases. Therefore, an optimization should be applied on the presented system. The results show that the highest exergy destruction, unit exergy cost, and cost rate are 34.96 GJ h
−1
, 34.85 US$ GJ
−1
and 437.37 US$ h
−1
occur in the combustion chamber, compressor’s outlet flow and combustion chamber outlet stream, respectively. The energetic and exergetic optimization solution is obtained as the Pareto frontier. Final decision-making methods such as TOPSIS, LINMAP are employed for choosing the optimal solution. Design points of LINMAP and TOPSIS having 65.86%, 66.95% thermal efficiency and 12.51 GJ h
−1
, 12.65 GJ h
−1
exergy destruction, respectively.
In this research, nitrogen-doped carbon nanotubes (N-CNT) were prepared through the low-temperature thermal method and used as the support material for the bimetallic catalyst PtRu and Pt ...nanoparticles. A passive single-cell direct methanol fuel cell (DMFC) was designed and fabricated to investigate and compare the performance of three discrete membrane electrode assemblies (MEA) with carbon black (CB), CNT, and N-CNT as the catalyst support, respectively. Adding N to the structure of CNTs remarkably improves the physical and electrochemical characteristics of the catalyst. More active sites and stronger interaction between support and metal particles lead to the formation of smaller metal clusters and higher surface area as well as superior electrochemical activity. Compared to PtRu/CB and PtRu/CNT, PtRu/N-CNT illustrate 32% and 12% higher surface area, 3 and 1.9 times higher MOR activity, and 62% and 18% higher power output (26.1 mW/cm2), respectively. Moreover, it is revealed that PtRu/N-CNT has long-term stability in the MOR. The research work presented in this paper exhibits the outstanding performance of Pt and PtRu supported on N-CNT in a passive single-cell DMFC.
•A low-temperature thermal method was used to prepare nitrogen-doped CNTs.•The N-CNTs were used as catalyst supports for the PtRu & Pt nanoparticles in a DMFC.•The performances of various electrocatalysts were compared together.•Results exhibit the outstanding performance of N-CNT supported catalyst in DMFC.
Hybrid systems composed of solar photovoltaic (PV) and battery storage units are reliable and clean technologies for utilization in off-grid cases. Optimal sizing of these systems results in more ...cost-effective units, which is the main subject of various researches. The current work focuses on the assessment of an optimization approach for finding the optimum size of PV/battery hybrid unit in order to provide the required electricity of the case study and reach the minimum Total Life Cycle Cost (TLCC). In this regard, the components of the designed systems are modelled; afterwards, the objective function is established on the basis of TLCC. In the optimization procedure, a constraint is considered for the highest possible loss of power in order to have a system with acceptable reliability. In addition, Improved Harmony Search (IHS) algorithm is applied to determine the variables with optimal quantities for satisfying the required electricity in the most cost-effective condition. The calculated results are compared with harmony search and simulated annealing algorithms to evaluate the reliability of the applied method. The outcomes show that employing IHS leads to more promising results and it has higher robustness compared with the HS and simulated annealing algorithms. Moreover, the number of units in the hybrid system reduces by increment in the loss of power supply probability.
Energy accessibility especially electrical energy is considered as one of the most appealing factors to achieve energy sustainability. The purpose of this study is to investigate energy ...sustainability using renewable energies for two high potential cities in the south-east of Iran until the year 2030. In this regard, Homer software is used to evaluate economic and technical analyses of PV-wind-diesel hybrid system for the two cities by the data gathering which was collected from Iran's meteorological organization. Therefore, the average of solar radiation per month for Zabol and Zahak were about 9 and 9.1 (h/d). Also, mean wind speeds are calculated 5.35 m/s and 4.7 m/s for Zabol and Zahak respectively which proposed that these cities have high potential in order to electrical production by a hybrid system. Furthermore, the amount of electricity production by PV array for Zabol and Zahak were 1700 (kWh/yr) and 1669 (kWh/yr) respectively, and the amount of electricity production by wind turbine were 9036 (kWh/yr) and 7263(kWh/yr) for Zabol and Zahak respectively. Consequently, it is of elaborated that the investments on solar and wind energy sectors for both cities would be economically justified.
Solar thermochemical reactors have been considered in recent studies because of converting the solar energy to a fuel, which is called solar fuel. In such reactors, heat transfer is a dominant ...phenomenon in generating products. Providing the optimum thermal energy for the solar thermochemical cycle can be gained by adjusting the size of the solar concentrator. In this study, the sizing of the solar concentrator is studied and the best size of the cavity is calculated by the Monte Carlo method. In this reactor using solar energy, the intermediate metal is converted to solar fuel. ZnO/Zn is considered to be the intermediate metal for the reaction. Next, the solar reactor is modeled in three dimensions and all types of heat transfer mechanisms, i.e., conduction, convection, and radiation along with chemical reaction conditions, are also considered. Sensitivity analysis is done based on the solar concentrator size and the aperture cavity. The results show that the optimum size of the dish collector is 5.168 m and the aperture cavity diameter was gained 5 cm for 10 kW
th
solar reactor. Nanofluid is used as cooling fluid, with the best modeled fluid flow rate for this structure, the ratio of annual fluid flow to nanofluid being 1. By examining the hydrogen production reactor, the amount of hydrogen produced in the system is 34 mol m
−3
. Also, the irradiation distribution of the cavity receiver and the temperature distribution of the solar reactor were modeled and analyzed.
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