A. Riahi , K. Atashkari, J. Mahmoudimehr ,
Volume 19, Issue 3 (3-2019)
Abstract
Cavity receiver in solar tower concentrator usually experiences highly intense radiation. Due to asymmetric concentration of solar rays, non-uniform heat flux distribution occurs on the different parts of the cavity receiver. This non-uniform distribution leads to uneven thermal expansion and stresses in receiver, which affects the reliable operation and reduces life time of receiver parts. Therefore, it is necessary to reduce the non-uniformity of solar flux on the surface of the absorber tubes and different parts of the solar reactor. The aim of this study was to focuses on the distributions of concatenated solar flux over graphite tubes of a 50kW solar reactor, which was previously designed for methane thermal dissociation at the focus of a solar furnace. In this study, the absorbed solar power on the different parts of the reactor is determined by Monte Carlo ray tracing method. Moreover, the effect of aperture size and the absorptivity of receiver parts on the net magnitude and distribution of absorbed power in reactor are investigated. The results prove that the 16cm aperture absorbs the maximum power and leads to even better solar flux distributions. Replacing the absorbing walls by the reflective walls will also result in more power absorbed by the tubes and better uniformity of flux distribution around the tubes.
B. Sanjari , M. Iranmanesh ,
Volume 19, Issue 5 (5-2019)
Abstract
Industrial sector is always recognized as one of the largest energy consumers in each country. Besides the high energy consumption of industrial sector, a significant amount of energy is lost due to inefficient use and old machines. Combined heat and power (CHP) systems have always been considered as an efficient system to reduce energy consumption and increase productivity in the industry. The aim of this paper is techno-economic analysis of application of CHP systems in a few samples of different types of almost high energy consumer industries, considering the different approaches, on which the electrical capacity of the system is designed. In this study, a combination of various parameters such as different types of prime movers (gas turbine or reciprocating engine), different types of fuel (natural gas and diesel fuel), and guaranteed selling of generated electric power (GSGEP) in different industries are considered. Finally, after determining the capacity of the simultaneous production system for the selected factories, some important economic indicators like net present value (NPV), simple payback periods (SPB), and levelized cost of electricity (LCOE) were considered by two coupled software, MATLAB and Excel. The results showed that in all scenarios, the use of reciprocating engine as the prime mover and natural gas as its fuel is the best choice to satisfy the techno-economical goals.
M.j. Rahimi, M.h. Hamedi, M. Amidpour,
Volume 19, Issue 6 (6-2019)
Abstract
The present paper presents the results of the thermodynamic and economical study of the use of synthesis gas from a biomass gasification reactor instead of natural gas at a synchronous power plant. First, the analysis of the system at the Pars factory, which is fed with natural gas, was done, and the use of a for the synthesis of natural gas for the replacement of natural gas is investigated. The results of thermodynamic analysis indicate that the increase in the percentage of biomass fuel moisture had a slight effect on CH4 and N2 in synthetic gas, but it has a relatively modest effect on CO and CO2 thermal value. By using a reactor, a natural gas consumption of 4468316cubic meters per year will be saved. The results of economic analysis indicate that due to the price of natural gas of 700Rials per cubic meter, the purchase price of electricity is 650Rials per kWh, the number of years of operation 7 years and the profit rate of 7%, the net present value is at the zero frontier and this investment is at the threshold of being economically feasible. But if the rate of profit is to be raised, the lower the natural gas purchase price, or of electricity purchase, the improved system from the economic point of view is not profitable. In this regard, at a profit rate of 7%, the price of the biodegradable fuel is at most equal to 100,000 rials per ton, the net present value is at the zero frontier and the investment will have economic justification, But in larger quantities of biomass, investment will not be economically profitable.
M. Hosseinzadeh, S.m. Mirzababaee , H. Zamani, A. Faezian, F. Zarrinkalam,
Volume 19, Issue 7 (7-2019)
Abstract
In this study, the performance of an evacuated tube solar cooker analytically investigated. For this purpose, the heat transfer mechanisms in different components of the solar cooker is evaluated. The main aim of this article is to investigate the important parameters of the evacuated tube solar cooker in different weather conditions using the validated analytical model. The studied parameters are: wind speed, ambient temperature, and input solar radiation. The experiments performed at the Research Institute of Food Science and Technology, Mashhad, Iran (Latitude: 36° and Longitude: 59°).
The results reveal that the presented analytical model is an accurate model that can be used in the paramedic analysis of the evacuated tube solar cooker. Moreover, in the
reference weather conditions, the lost heat contains
only 12.22 W of the absorbed solar radiation (137.51 W).
Therefore, about 8.89% of the absorbed solar radiation is lost. Based on the results, the temperature of outer surface of the cooker is only 3.64
°C higher than the ambient temperature due to the vacuum between the tubes. In addition,
the evacuated tube solar cooker has proper performance in various weather conditions. Increasing the ambient temperature from 5 °C to 35 °C enhances the solar cooker efficiency by 0.65%.
M. Aligholami , A. Rostamzadeh Khosroshahi ,
Volume 19, Issue 10 (10-2019)
Abstract
The aim of this study is the modeling of the solar chimney for achieving the relation between turbine output power and geometrical parameters. In this regards, 9 different models are determined based on the variety of chimney height and diameter for investigating the effects of geometrical parameters on the turbine performance. As well as, in order to improvement of system performance, the hydrophobic surfaces were evaluated with consideration of friction reduction by verification of slip condition on walls. The k-ε turbulent model was used to modeling turbulence flow and reverse-fan model was employed for simulating the turbine. For this purpose, the extracted data from the mass flow rate and velocity changes were validated with prior studies and then were compared in different pressure jumps in order to better comprehension of the performance of the turbine. The optimization was done through the defined models and it was observed that to have a better and optimized design, the geometrical parameters should have been considered in the system design simultaneously. Meanwhile, the chimney diameter should have been paid more attention as one of the most important design parameters. Also, the precise correlation was represented to estimate the turbine output power with respect to the height and diameter of the chimney. Furthermore, based on the applying of slip condition on walls for simulating hydrophobic surfaces, shear stresses reduction was done and it was revealed that the hydrophobic surfaces could have a positive effect on the performance of SCPP up to 5 percent.
M. Iranmanesh, M.s. Barghi Jahromi,
Volume 19, Issue 11 (11-2019)
Abstract
One of the most important applications of solar energy is its utilization in solar dryers to maintain agricultural products for long-term storage. These dryers work based on passing warm air through fresh materials by natural or forced convection. So, they have a direct dependence on the intensity of the sun's irradiance to their collector, which it disrupts the drying process in the absence of a thermal energy source in the hours when the sun is not available. In order to solve this problem, the phase change material (PCM) as thermal energy storage is used. The materials that have the capacity to absorb the thermal energy (charge phase) and, they release the absorbed energy (discharge phase) when the intensity of the solar radiation is low or during the night and cause the uniformity of the outlet temperature solar collector, and inside the drying chamber. As well as they provide the necessary thermal energy for hours when the sun is not available and increase the duration of use of the dryer. In the present research, the experimental studies have been carried out through designing and construction of an indirect cabin type solar dryer equipped with a heat pipe evacuated tube collector and using PCM material as energy storage in the expansion tank. In the present research, the experimental studies have been carried out through designing and construction of an indirect cabin type solar dryer equipped with a heat pipe evacuated tube collector and use of PCM material as energy storage in the expansion tank. The effect of various parameters such as inlet and outlet temperatures of the collector, temperature, and humidity of the drying chamber and ambient, the intensity of the solar irradiance on the drying process is investigated, with and without PCM and at two different speed of forced convection through the drying chamber. The results show that the effectiveness of forced convection on the drying process is more than the effect of PCM.
Z. Javadi, M. Miansari, B. Ghorbani,
Volume 19, Issue 12 (12-2019)
Abstract
Regarding the water and energy crisis, improving the efficiency of thermal systems and heat recovery, along with the use of desalination process, has attracted the attention of many researchers in recent years. For this purpose, thermal desalination process and solar collectors were used in steam power plants. In this study, an integrated structure for simultaneous generation of fresh water and power has been developed using a combination of solar collectors, steam power plant for power generation, ORC cycle, and thermal multi-effect desalination cycle. The integrated structure has the capacity of producing 762.6 kg / s of fresh water, 104.1 MW of power in the rankine cycle and 306.7 MW of power in a steam power plant. In this integrated structure, the efficiency of the steam power plant is 37.24% and the total exergy efficiency is 78.54%. Exergy analysis of the integrated structure shows that the highest destruction of exergy in solar collectors and heat exchangers are equal to 45.2% and 37.27%, respectively. The economic analysis of the developed integrated structure shows that the period of return is 3.838 years, and the prime cost of the product is 0.0325 $/kWh. Moreover, the impact of various parameters on the performance of the integrated structure was investigated using sensitivity analysis.
H. Seifi Davary, Sh. Kouravand, I. Khatami,
Volume 20, Issue 1 (1-2020)
Abstract
The important factor in turbine efficiency is turbine rotation. The higher the rotor time at different speeds, especially at low speeds, increases the turbine power. In this regard, first, the airfoil NACA0015 was selected and the K-ω SST turbulence method was used for numerical analysis. The validation was performed using experimental results. The wind turbine was designed and fabricated by CATIA software. The aluminum sheet used by a series alloy is used to make smooth, porous leaves from simple cards and diamond-shaped leaves, in a porous form with 0.3 mm thick. The instrument used in measurement, testing and fabrication have been calibrated to compute more precisely and to generate wind flow from the four-fan blower. The results show that the darriues vertical axis wind turbine with porous and flat blades has begun to rotation at the speed of 2.3 and 3.9 m/s. At the speed of 2.5 and 3 m/s, the rotation of wind turbine porous blade doubled and at the speed of 4 m/s, its rotation speed was 3 times higher than the speed of straight blade turbine. The rotation of wind turbine porous blade in speeds of 4.5, 5, 5.5, 6, 6.5 and 7 m/s were 56.25 %, 20 %, 22 %, 15 %, 7.5 %, and 12% higher than the straight blade turbine and in speed of 8-10 m/s the rotation of the straight blade turbine and porous blade turbine is almost equal.
M.m. Ghafurian, H. Niazmand, A.e. Moallemi, F. Tavakoli Dastjerd,
Volume 20, Issue 1 (1-2020)
Abstract
In the present research, the steam generation performances of nanofluids containing titanium dioxide have experimentally been examined. For this purpose, a solar simulator with a xenon lamp as the radiation source, and a pyranometer as a light intensity measuring device are used. Then, the water based-nanofluids in five nanoparticle mass fractions of 0.001, 0.002, 0.004, 0.04, and 0.08% exposed to the light intensity of 3.5Suns (3.5 kW/m2) were investigated to compare their evaporation performances with water (H2O). Finally, the effects of the solar power intensity on the steam generation were examined. The results showed that the titanium dioxide nanostructures are more efficient to directly absorb the solar energy than the water so that the maximum total evaporation efficiency of 77.4% and 54% were obtained at 3.5 kW.m-2 for nanofluid and water, respectively. Furthermore, it was found that light absorption increases as the nanofluid mass fraction increases. Also, increasing the light intensity from 1.5 to 3.5 kW.m-2 enhances the thermal efficiency, while it reduces the evaporation efficiency.
S. Khodatars, S.r. Mosavi Seyedi, A. Motevali, M. Montazeri,
Volume 20, Issue 5 (5-2020)
Abstract
Now a day most countries are interested in renewable energy due to the many problems with fossil fuel use. One of the best types of renewable energies is solar energy and can be produced in electrical, thermal and hybrid forms by photovoltaic cells equipped with thermal collectors. In this research a systemLinear parabolic focusers equipped with photovoltaic cells were designed and simulated in Optic Ray Tracing and Solidworks software and compared with experimental results. The thermal collector was simulated in a photovoltaic-thermal hybrid system with two longitudinal and transverse arrangements with internal diameters of 8 to 14 mm at three discharge levels.Simulation results of two longitudinal and transverse arrangements showed that the thermal efficiency in the longitudinal arrangement was better than the transverse ones. and by increasing diameter from 8 to 12 mm the thermal efficiency increased and the thermal efficiency from 12 to 14 mm alignment of the pipes did not change much. Also by increasing the fluid discharge from 1 to 3 l/min the thermal efficiency due to the decrease in thermal losses and the electrical efficiency due to the decrease in temperature Photovoltaic cell surface increased. Comparison of the simulation results and the experimental evaluation showed that the maximum thermal and electrical efficiency for the data Simulations were 61.18% and 12.58%, respectively, and for field data is calculated 58.14% and 12.03%, respectively.
S. Amiri Dogahe, E. Jahanshahi Javaran, M. Abdolzadeh Dashtkhaki, S. Sadeghi,
Volume 20, Issue 6 (6-2020)
Abstract
In this study, techno-economic comparison of monocrystalline and concentrating photovoltaic power plants for the selected cities of Kerman province was carried out. After modeling the implied photovoltaic systems and validating the modeling results of the monocrystslline photovoltaic system with the measured data of an installed 5kW monocrystalline photovoltaic power plant at the Graduate University of Advanced Technology, daily and yearly electrical energies production analysis for both plants was presented. Then, the electrical efficiency and the performance factors, including capacity factor, final yield, reference yield and the performance ratio were determined. The economic analysis results showed that the northern cities of Kerman province had more favorable economic indicators, so internal rate of return, balanced cost of electricity, net present value, and benefit-cost ratio for the monocrystal photovoltaic plant were 21-22.1%, 13.3-13.9 dollars per kilowatt, 2-4.2 thousand dollars, and 1.04-1.09, respectively and for the concentrating photovoltaic plant were 24.9-28.6%, 8.8-10.2 dollars per kilowatt, 17.1-30.5 thousand dollars, and 1.24-1.43, respectively. Finally, a comprehensive comparison was made between the conventional PV systems and the CPV system for two scenarios: the same capital investment cost and the same nominal installed power. Results showed that at both scenarios, the concentrating photovoltaic is superior to the monocrystalline PV plant, in a way that Kerman and Jiroft cities, as the best cities, had the net present value of 30.5 thousand dollars and 21 thousand dollars, respectively.
M. Hosseinzadeh, H. Zamani, S.m. Mirzababaee, A. Faezian, F. Zarrinkalam,
Volume 20, Issue 6 (6-2020)
Abstract
In this study, a portable parabolic solar cooker is designed and fabricated, and the daily performance of the solar cooker is investigated from the energy and exergy viewpoints. One of the important challenges of the parabolic solar cookers is the reduction of their performance in the windy conditions. In order to evaluate this issue, the effect of 0.2, 2, 4 and 6m/s wind speeds on the energy and exergy efficiencies of the solar cooker is studied. Based on the results, the energy efficiency of the parabolic solar cooker is 34.52-46.19% and the exergy efficiency is 2.11-5.60% during the experiment. The experimental results indicate that water can boil in the windy conditions using the fabricated solar cooker although the time required to boil water increases by rising the wind speed. According to the results, in the wind speed of 6m/s, the time taken to boil 2 liters of water is about 40min. Furthermore, the energy and exergy efficiencies of the parabolic solar cooker in the wind speed of 6m/s are 20.08% and 1.99%, respectively, lower than those in the wind speed of 0.2m/s.
S.a. Behmoonesi, F. Jafarkazemi,
Volume 20, Issue 6 (6-2020)
Abstract
The aim of this paper is to compare the electric power output of the photovoltaic Module (PV) and photovoltaic-thermal water collector (PV/T). The electrical efficiency of photovoltaic Modules is greatly reduced by increasing their surface temperature. The hybrid photovoltaic-thermal collector consists of a PV Module with a thermal collector attached behind it. The circulating fluid in the collector removes heat from the module and increases its electrical efficiency. In the first part of this paper, a theoretical analysis of a liquid PV/T collector is made based on thermal modeling using the first law of thermodynamics. An unglazed hybrid photovoltaic-thermal collector with serpentine tubes has been designed and manufactured to validate the theoretical results. Then the collector has been tested for three days and results have been compared with a sample photovoltaic module. The theoretical calculations were performed using Matlab software and its results showed good agreement with experimental results. Our finding shows a maximum increase of 6% in the electrical efficiency of PV/T in comparison to the PV module. At the same time, the water temperature has increased by 5°C.
S. Mirzaee, M. Ameri, A. Ziaforoughi,
Volume 20, Issue 6 (6-2020)
Abstract
In the current study, an infrared-solar dryer powered by a photovoltaic-thermal system was designed, manufactured and tested in the Shahid Bahonar University of Kerman. The drying time, temperature, and the amount of electrical energy consumed during the drying process were investigated for potato slices with thicknesses of 3 and 7mm in the dryer. The amount of airflow rate in the photovoltaic-thermal system, which was supplied by a fan, was controlled during the experiments. The power of this fan was supplied directly from photovoltaic panels and the remaining amount of electrical energy produced by the panels was transferred to an infrared radiation source for drying the product. The results showed that the best drying condition is at 0.004kg/s with the radiation source. The significant advantage of this system compared to systems that use only the radiating source or hot air, as well as systems that part of their electricity or total electricity is provided by the city's electricity, is a significant reduction in time of drying process and energy consumption, along with is that the total energy for the drying process is provided by solar energy. The system was also designed to transfer the heat of the photovoltaic panels to the inlet air of photovoltaic-thermal collector to increase the temperature of the air and decrease the photovoltaic temperature and therefore to improve the thermal and electrical energy efficiency.
Mohammad Saleh Barghi Jahromi, Vali Kalantar, Mehran Abdolrezaie,
Volume 20, Issue 7 (6-2020)
Abstract
In the current study, natural solar ventilation has been investigated aiming at reducing the consumption of fossil and thus, reducing greenhouse gas emissions in a hot and dry climate in which the behavior of various fluid variables (temperature, velocity, and flow rate) is considered in different conditions. Since solar radiation is not uniform throughout the day, passive solar ventilation is unstable. In this regard, the natural displacement flow in a solar ventilator with copper thermal absorber, double-glazed glass compartment to prevent thermal energy loss, as well as phase change materials for the storage of thermal energy has been investigated, experimentally. In the case of no phase change material, due to the creation of a suitable temperature difference, the panel has made the chimney effect possible for natural ventilation in some hours of the day, but in the early hours of the night, the temperature of the panel will be the same as the ambient temperature, and the chimney effect will not be available for proper ventilation. In a panel equipped with phase change materials, the system has acceptably been able to play an important role in reducing the temperature drop in the hours of the day with no solar radiation leading to a reliable air flow rate. In fact, the main purpose of using phase change materials in passive solar ventilation is the same effect, the use of excess energy in cases of energy shortages.
R. Akbari, Y. Ajabshirchi, F. Haghighat Shoar ,
Volume 20, Issue 9 (9-2020)
Abstract
Due to the increasing costs of energy and reducing fossil fuel, the use of renewable energy is more important. In this study, the possibility of using hybrid energy systems was evaluated to supply electricity to an animal husbandry unit in Mianeh City. For this purpose, three sources including wind turbine, photovoltaics and diesel generator were evaluated in terms of environmental, technical, and economic. This evaluation was performed by Homer Energy Analysis Software, and the results demonstrated that diesel generator is the least expensive solution in compared to other conditions. Then, analysis of the results showed that hybrids of diesel generator-photovoltaic, wind turbine-diesel generator, and diesel generator-photovoltaics-wind turbine systems have low cost, respectively. But environmental results depicted that the use of triple hybrid system in condition of 38% diesel generator, 51% photovoltaic and 11% wind turbine, has lowest emissions, so that carbon dioxide emissions were reduced by 38.4% compared to single diesel. Considering the capital return index, which is a key indicator in the design of feasibility studies, the time of capital return for using a diesel generator was obtained more than three years and seven months. While this index in the condition of using diesel generator-photovoltaic was obtained less than a year, in this respect, this condition was in the first rank.
O. Rahaei , A. Rezaei Zadeh ,
Volume 20, Issue 10 (10-2020)
Abstract
Nowadays, the efficient use of solar energy for optimal use in the building industry has become one of the concerns of designers and builders. Studies show that by properly designing the exterior walls of the building, the amount of solar energy absorption can be managed for the building. Ahwaz is a tropical city that needs mechanical cooling most of the year. However, it has five cold months, with 3 months of use of heating systems to provide residents with thermal comfort. Therefore, the thrombus wall has been considered in this study. The aim of this study is to investigate and compare the thermal behavior of thrombus walls with different shapes in the sunny (south) walls of corridor spaces in Ahwaz. Research method is a hybrid method that incorporates empirical research strategies, simulation, and case research. On this basis, after experimental observations and field investigations on real samples, a general pattern was obtained and numerical calculations of the simulations were performed with CTF method after validation and reliability with Energy Plus software. In this study, by studying the sunroof wall (south side) of a default corridor space, five general compositions of the thrombus wall with the same conditions have been simulated and evaluated. The results have shown that in order to manage energy absorption, the geometry of the thrombus wall is of special importance and its chess pattern performs better than other models. At the end, some suggestions have been made.
Mohammad Mazidi Sharfabadi, Mohammad Iman Ghiasi, Ali Seraj,
Volume 21, Issue 11 (9-2021)
Abstract
In this paper, the performance of a typical 190 W photovoltaic cell, located in Research Institute of Petroleum Industry, Tehran, Iran, has been studied and evaluated from the energy and exergy point of view. A computer code has been developed for modeling and determining the electrical characteristics of the system such as open circuit voltage, short circuit current, system resistances, maximum power point properties and characteristic curves. The operational and electrical parameters of the system and the environmental conditions such as solar radiation, wind speed and ambient temperature have been experimentally measured and logged on one typical day of May. For the validation of model, the results obtained from the model have been compared with the data reported by the manufacturer as well as the experimental data. The results show that the energy efficiency varies from 11.22 to 13.94 percent during the study period (7:30 AM to 5:30 PM) and its average is equal to 13.19 percent. The exergy efficiency also varies from 14.77 to 16.66 percent during the study period and its average is 15.62 percent.
Amirali Saiffodin, Seyed Farhan Moosavian, Ahamad Hajinezhad,
Volume 21, Issue 12 (12-2021)
Abstract
The increasing consumption of non-renewable energy sources such as oil and gas and reducing their reserves make it more necessary to pay attention to clean and renewable resources. In this situation, wind energy is known as one of the safest options for generating electrical energy. In this study, with the aim of evaluating the impact of climate change on the economic and environmental characteristics of wind turbines, numerical modeling was developed in MATLAB software. In order to evaluate the effects of the mentioned parameters as a case study, this numerical modeling for the parameters expressed in 4 cities of Iran, including Rasht, Tehran, Abadan, and Sanandaj, as the representatives of the main climates of Iran has been analyzed. According to the results of the economic point of view, which represents the Levelized cost of the energy production unit, Abadan was recognized as the most economical case with a Levelized cost of 1.04 $ per kilowatt-hour of energy. Also, the environmental aspect of the analysis, which is based on the life cycle assessment method, considering the amount of carbon dioxide produced during the system life cycle and its pricing based on penalty policies, Rasht with a mild climate and emissions of 156 kg. Carbon dioxide per year and the lowest fine cost (annual cost $ 2.26) showed the most suitable option among other cities.
Mohammad Saleh Barghi Jahromi, Vali Kalantar, Mohammad Hossein Dehestani Bafghi,
Volume 23, Issue 12 (12-2023)
Abstract
Among solar collectors, solar parabolic dishes have attracted the attention of researchers due to their high working temperature and high thermal performance. The purpose of this study is to compare two absorber receivers (normal-black color) for the solar parabolic dish. The analysis of energy and exergy was investigated for different conditions at different hours. Two-axis tracking system was applied to the outlet temperature in the solar parabolic dish system. The results show that the maximum temperature of the normal and black absorber is 101.52 and 115.53 ℃ , respectively, and the maximum energy and exergy efficiency of the black spiral absorber plate is 0.7 and 0.21. In addition, the designed parabolic solar container raised the temperature of 80 liters of water to 60 ℃ in 5 hours after sunlight, which is suitable for bathing and washing clothes in winter in backward and rural areas without electricity and fuel. Therefore, it is enough for four to five people.
