Sharif Digital Repository

One of the most important operating parameters which affects the performance and efficiency of active solar stills is brine depth. In all of the previous experimental or theoretical studies, effects of water depth were investigated during only the first 24-hour period (or even shorter periods) of the operation of active solar stills. In other words, only the first day was taken into account. However, the production of an active solar still depends on several parameters such as brine temperature at sunrise (initial temperature), which are all affected by the depth variation after the first day of operation. However, the present research experimentally investigates the long-term effects of... 

Increasing energy demand has led to a substantial growth in the use of wind energy across the world, which can be attributed to the low initial and running costs and rapid and easy deployment of this technology. The development of hydrogen from wind energy is an excellent way to store the excess wind power produced, as the produced hydrogen can be used not only as clean fuel but also as input for various industries. Considering the good wind potentials of Yazd province, the variety of industries that are active in this area, and the central location of this province in Iran, which gives it ample access to major transport routes and other industrial hubs, hydrogen production from wind power... 

A technical-economic assessment was carried out in this study to determine the possibilities for wind and solar power generation in Afghanistan’s Helmand province. The results showed that most of the province has a solar irradiance of over 400 W/m2, and also showed that wind and solar power generated in the province can be up to twice as cheap as the official price of renewable power in Afghanistan. The most suitable site for solar and hydrogen production was found to be Laškar Gāh, where solar and hydrogen can be produced at a cost of 0.066 $/kWh and 2.1496 $/kg-H2, respectively. In terms of wind power production and hydrogen production from wind, the most suitable site was Sangīn, where... 

Herein, we report a new strategy for improving the efficiency and reducing the fabrication cost of dye-sensitized solar cells (DSCs) by elimination of the three- or four-fold layer deposition of TiO2. This is performed by replacing a single layer deposition of mesoporous TiO2 beads, with sub-micrometer size, high surface area and tunable pore size, synthesized by a combination of sol-gel and solvothermal methods. Furthermore, superior electronic properties gained by a reduction in electronic trap states are achieved through doping of pristine TiO2 beads with lithium. The beads have a spherical shape with monodispersed texture consisting of anatase-TiO2 nanocrystals and ultra-fine pores. The... 

Battery energy systems are playing significant roles in smart homes, e.g., absorbing the uncertainty of solar energy from root-top photovoltaic, supplying energy during a power outage, and responding to dynamic electricity prices. For the safe and economic operation of batteries, an optimal battery-management system (BMS) is required. One of the most important features of a BMS is state-of-charge (SoC) estimation. This article presents a robust central-difference Kalman filter (CDKF) method for the SoC estimation of on-site lithium-ion batteries in smart homes. The state-space equations of the battery are derived based on the equivalent circuit model. The battery model includes two RC... 

In modern heat transfer systems, thermal storage not only causes the balance between demand and supply, but also improves the heat transfer efficiency in these systems. In the present study, a comprehensive review of the applications of micro- or nano-encapsulated phase change slurries (MPCMs/NPCMs), as well as their effects on thermal storage and heat transfer enhancement, has been conducted. MPCMs/NPCMs have a myriad of applications and various usages such as pipe and channel flows, photovoltaic/thermal, solar heaters, air conditioning systems, storage tanks and heat pipes that have been categorized and studied. It was found that there are many advantageous adding MPCM/NPCM to the base... 

In modern heat transfer systems, thermal storage not only causes the balance between demand and supply, but also improves the heat transfer efficiency in these systems. In the present study, a comprehensive review of the applications of micro- or nano-encapsulated phase change slurries (MPCMs/NPCMs), as well as their effects on thermal storage and heat transfer enhancement, has been conducted. MPCMs/NPCMs have a myriad of applications and various usages such as pipe and channel flows, photovoltaic/thermal, solar heaters, air conditioning systems, storage tanks and heat pipes that have been categorized and studied. It was found that there are many advantageous adding MPCM/NPCM to the base... 

Pulsating heat pipes (PHPs) are compact cooling equipment used for various applications. This type of heat pipes can be used in renewable energy systems, cooling electronic devices, heat recovery systems and many other applications. Since PHPs have superior thermal performance, by applying them in energy systems enhance their efficiency. In addition, PHPs are a reliable medium for cooling various devices which have high heat flux. In this study, various works conducted on the applications of PHPs are reviewed and analyzed. It is concluded that PHPs are efficient and reliable devices for utilization in various energy systems. Moreover, at very low temperatures, such as cryogenic applications,... 

One of the primary factors affecting the amount of worldwide energy consumption and greenhouse gas emissions is cooking. Solar cooking is an appropriate solution because it is both inexpensive and expandable. To illustrate modern advancements and the current status of solar cooking technology, this paper presents a review of recent experimental and analytical socioeconomic studies on solar cookers. The experimental studies have been divided into three categories based on different solar cooker structures: (i) box types, (ii) concentrating types, and (iii) panel types. Next, different designs are investigated according to their direct or indirect heat transfer modes and optional equipment for... 

Because of the low outflow temperature of the conventional photovoltaic thermal systems and lack of electrical production of the solar thermal collectors, a novel combined system is proposed to solve the two mentioned drawbacks. This novel system is achieved by connecting a photovoltaic thermal unit to a solar thermal collector in series. To increase the overall performance of this novel combined system, different hybrid nanofluids include (1) multiwall carbon nanotube-aluminum oxide (2) multiwall carbon nanotube-silicon carbide (3) graphene-aluminum oxide, and (4) graphene-silicon carbide are compared. The investigation is performed based on the three-dimensional simulation, and the... 

Abstract We design a thermo-photovoltaic Tandem cell which produces high open circuit voltage (Voc) that causes to increase efficiency (η). The currently used materials (AlAsSb-InGaSb/InAsSb) have thermo-photovoltaic (TPV) property which can be a p-n junction of a solar cell, but they have low bandgap energy which is the reason for lower open circuit voltage. In this paper, in the bottom cell of the Tandem, there is 30 quantum wells which increase absorption coefficients and quantum efficiency (QE) that causes to increase current. By increasing the current of the bottom cell, the top cell thickness must be increased because the top cell and the bottom cell should have the same current. In... 

The application of the solar energy in thermal desalination devices is one of the most beneficial applications of the renewable energies. In this study, a novel solar desalination system is introduced, which is benefited from the undeniable advantages of pulsating heat pipe (PHP) as a fast responding, flexible and high performance thermal conducting device. Results show a remarkable increase in the rate of desalinated water production and the maximum production reaches up to 875mL/(m2.h). However, the optimum water depth in basin and the filling ratio of the PHP are measured 1cm and 40%, respectively  

In this study, a latent heat storage unit and built-in condenser were integrated with a solar still. Storage of dissipated latent heat of vapor during the day and using it after sunset prolongs system operation. During the day, the entire solar radiation was consumed to heat the saline water and only the heat coming from the condensation of vapor was stored in the phase change material (PCM). The dissipated heat from the condenser body was transferred to the PCM and stored. Additionally, the existence of PCM on the outer surfaces of the condenser prevented the rise of condenser wall temperature during the day and kept the condenser temperature low. After sunset, the heat stored in the PCM... 

The use of solar energy concentration systems for achieving performance enhancements in the Photovoltaic/thermal hybrid solar systems and reduction of initial costs is an idea that has been studied for years. In this article a new structure for parabolic trough photovoltaic/thermal collector is proposed and its thermal and electrical performances are experimentally investigated. The receiver of this concentrator contains a triangular channel with an outer surface covered with photovoltaic cells and thermoelectric modules with a specific arrangement so that in addition to absorbing heat, a larger portion of the solar radiation is directly converted to electricity. Hence, the performance of... 

Solar heating and cooling technologies can have a vital role to play in understanding the targets in energy security, economic development, and mitigating climate change. This study aimed to investigate the performance of the combined solar cooling/heating system using a Photovoltaic Thermal collector (PVT) for residential applications. The main advantage of using PVT is the conversion of the maximum amount of solar energy into electricity and thermal energy. In this work, water is used to cool the panel and, consequently, increase the efficiency. The cooling cycle comprises a hybrid ejector-compression refrigeration cycle with two evaporator temperatures. To reduce the effect of the global... 

The present study conducts a comprehensive comparative techno-economic analysis of some near-term sensible thermal energy storage (TES) alternatives to the ‘standard’ two-tank molten salt system for concentrated solar power (CSP) plants. As such, we conducted detailed, relative annual transient simulations for single-medium thermocline (SMT), dual-media thermocline (DMT), and shell-and-tube (ST) systems. To be consistent with recent literature, the DMT and ST systems use concrete with a porosity of 0.2 (e.g. where concrete occupies 80% of the system) as their low cost filler material. The systems were integrated into a validated 19.9 MWe Gemasolar CSP model, which has a solar multiple of... 

A precise model of the behavior of complex systems such as solar chimney power plants (SCPP) would be much beneficial. Also, such a model would be quite contributing to the control of solar chimney operation. In this paper, the identification and modeling of SCPP utilizing ANN and Adaptive Neuro Fuzzy Inference System (ANFIS) are discussed. The modeling is based on the data of three working days which were taken of a built pilot in University of Zanjan, Iran. The input parameters are time, radiation and ambient temperature, while the output is the air velocity at the inlet of the chimney. The results of ANN model and ANFIS model were compared; it was found that ANFIS model exhibited better... 

This research work presents a novel integrated structure for the cogeneration of electricity and renewable syngas. The base structure of the process is developed by solid oxide cells in which electricity is generated by the natural gas-fueled fuel cell unit, and renewable syngas is produced by the electrolyzer cell unit. Direct integration between fuel cell and electrolyzer cell units is established for optimal use of fuel cell off-gases. To improve system's sustainability, a solar power cycle, including solar collectors coupled with an organic Rankine cycle (ORC), is designed to provide renewable electricity for steam and CO2 co-electrolysis operation. 1D mathematical approaches are... 

This study attempts to investigate a new way for cooling PV cell using natural vapor as coolant. The performance of solar cell was examined on simulated sunlight. The natural vapor encountered backside of PV cell vertically in various distribution and different mass flow rates. Also, the effect of natural vapor temperature in cooling performance was analyzed. Results indicated that the temperature of PV cell drops significantly with increasing natural vapor mass flow rate. In detail, the PV cell temperature decreased about 7 to 16°C when flow rate reaches 1.6 to 5grmin-1. It causes increasing electrical efficiency about 12.12% to 22.9%. The best performance of PV cell can be achieved at high... 

An experimental study was conducted on a solar hybrid system to transform the waste heat of photovoltaic module (PV module) into a useful heat which could be used in a solar desalination (SD) system in order to produce freshwater (scenario 1). Then, different parameters such as the amount of the produced freshwater by condensed vapor on the glass cover and basin side walls were taken into consideration after the fabrication of the SD system. Furthermore, the effect of water depth in the tray and the effect of the presence of a fan inside the basin (scenario 3) on water yield (kg/m2hr) were evaluated. In addition, the effects of using a mirror to lead the reflected light on the PV module and...