نشریه انرژی های تجدیدپذیر و نو
سال نهم شماره 1 (پیاپی 17، بهار و تابستان 1401)

Reliability assessment of renewable energy systems is a key step in evaluating the feasibility of renewable energy projects. The assessment can provide valuable information on the availability and reliability, operation and maintenance strategies, and operating costs of systems. In this regard, the present study analyzes the reliability parameters of a wind turbine system using a statistical / simulation approach. To this end, the Reliability block diagram has been used for modeling the problem which has the capability of analyzing complex systems with a high number of components while providing simplicity and transparency in the concept presentation. For the modeling and simulation, RAM Commander software developed by ALD software company was utilized. The block diagram model was developed considering a series arrangement (8 subsystems and 94 components) and taking into account the probability distributions of failure time, repair time, and other reliability data for each block. results were then obtained by implementing the Monte Carlo algorithm. The results of this study contain the values of reliability, availability, and failure rate for a turbine during its lifetime. According to the results, the average availability of a turbine over a 20-year life span was more than 0.999. At 25 points, the turbine needed repairs, and the mean time between failures was calculated to be 7008 hours. The mean time between system critical (catastrophic) failures is 77928 hours. Also, the sensitivity analysis of the model to changing input variables is presented.

In recent years, for reasons such as the limitation and pollution of fossil fuels, as well as the growing electricity demand, the international community has paid more attention to the use of renewable energy. On the other hand, the use of renewable energy in the electricity generation requires the provision of appropriate infrastructure and platform in power system. This has led to the emergence of a concept called microgrids. A microgrid is a local group of electrical resources and loads normally operating in conjunction with a traditional integrated power grid and can effectively integrate distributed generations, especially renewable energy resources. Due to the structural differences between microgrids and traditional power systems, microgrids face several challenges. This paper presents the concept of microgrids, equipment used, challenges and research gaps. The research shows that, by removing the technical barriers and addressing the challenges ahead, microgrids can be considered as a suitable platform for maximum utilization of renewable energy resources. It is expected that power systems in the future will be of microgrid type.

This study investigates the effect of land use change for bioenergy production by considering the cost of value added and water quality in random conditions using waste and wheat residues that have produced biofuels. Therefore, a linear model for land use change was presented with the aim of reducing total costs and increasing production efficiency. In random conditions, the model was solved using GAMS software and the computational results and comparisons show the optimal performance of the effect of land use change for biofuel production based on value added cost and water quality in different scenarios. By selecting Ajabshir city as a study area and selecting 9 different products and examining the products in terms of costs and added value of each product, we came to the conclusion that planting and producing wheat for biofuel production It is both cost-effective and cost-effective and has less of an impact on water pollution. Due to the need for less fertilizer, which leads to a lower amount of nitrate in the soil, which also reduces the percentage of water pollution during biofuel production, less damage to the environment and be economically affordable for the residents of Ajabshir city.

Nowadays, due to the population growth and the developed economy of most countries, there is increasing need for energy consumption in the industry and agriculture sector. Over the past decades, supplying this energy with fossil fuels has led to environmental pollutions and climate changes. So, it has imposed a lot of cost on different countries. Over the recent decades, many countries have tried to supply energy with renewable energy resources. Due to the significant role of agriculture sector in the countries’ food security and the increased non-petroleum export of oil-producing countries, it is necessary to develop this sector more than in the past. The important issue in this area is focusing on sustainable energy supply. The present research aims to study and identify different technologies that are related to agricultural industries in which, the necessary energy is supplied by renewable resources. The results showed that different types of renewable energies, can be used in devices such as solar desalination system, solar dryer, solar seeder robot, water supply pneumatic pump, wind farm, Solid biofuels, biogas and biodiesel systems, greenhouse heating systems using geothermal water resources, and ground source heat pump. Using these systems can result in the significant reduction of fossil energy consumption, reduction of air pollutants, development of the related jobs, energy security, and the decrease in the social costs of using fossil fuels. These findings can be widely used in designing and management of different energy systems in agricultural industries.

In order to reduce energy consumption in air conditioning and refrigeration systems, in this research, a system based on the vapor compression refrigeration cycle and ground energy use has been proposed. This system centrally supplies the energy needed for the air conditioning unit, refrigerator and freezer of a building. The condensing unit of this system is cooled separately and in series by two heat exchangers using outdoor air as well as ground energy. The energy consumption for a sample building is simulated by analytical calculations as well as the use of HYSSIS and TRANSYS softwares. The results of the calculations, which include the system performance coefficient, compressor power consumption, refrigerant quality and mass flow rate, have been compared with the values ​​of the conventional system. The results show that using the water cooled condenser unit, the inlet refrigerant temperature to the reducer valve is significantly lower than the outdoor air temperature. This significantly increases the performance of the proposed system and significantly reduces the refrigerant mass flow rate. The effect of reducing the exit refrigerant temperature of the condensing unit on the exergy of the refrigerant has also been investigated.

Shading and using shade to cool the building has long been considered by humans, and self-shading of buildings in hot climates is a good solution for passive cooling; In this regard, the shape of the building bodies is an important factor in creating shadow on the body. On the other hand, the angle of orientation and placement of the building is another very effective item that can affect the amount of self-shading and, consequently, the amount of energy received. This article intends to study the self-shading in different angles of the building orientation and the desired amount of protrusion of the floors in the facade to obtain the maximum amount of shading. The studied city and climate is Kish city in the hot and humid climate of Iran. The research method in this research is descriptive-analytical, in which simulation has been done with the help of Ecotect software. According to the findings, while changing the degree of protrusion of the floors causes a significant change in the amount of self-shading, the orientation towards the east and west and also the difference in positioning angle does not cause a significant change in the average annual amount of shaded areas. Still, in both cases, the amount of radiant energy received changes significantly. The results show that the four-story building with the protrusion of the floors by 0.3 meters relative to each other, with an angle of 30 degrees to the west, is considered the optimal model in terms of passive cooling.

The role of energy for welfare and economic development of countries highlights importance of energy. So far, no major study was conducted on the effects of energy on economic welfare in Iran. Hence, this study surveys the effect of the consumption of renewable and non-renewable energy on economic welfare in Iran during the period 1981-2018. ARDL model and cointegration approach had used to determine the existence of short-term and long-term relationships among variables. Estimation results show adjustment speed of error correction model to long-term equilibrium is about 61%. The relationship between economic welfare and exogenous variables such per-capita GDP, labor force, Gini index and types of renewable and non-renewable energy sources (solar, wind, water, geothermal, oil, gas and gasoline) is straightforward in short and long terms. One percent incraseing in the exogenous variables of research leads to an increase of 0.85, 0.66, 0.45, 0.61, 0.56, 0.36, 0.31, 0.72, / 76, and 0.34 percent in the welfare of society. Despite the relative abundance and non-optimal use of non-renewable energy (oil and gas) in Iran, the positive effect of renewable energy on economic welfare indicates use of this type of energy along with non-renewable energy will increase economic welfare.

The All Porous Solid Oxide Fuel Cell (AP-SOFC) is a concept that links the dual and single chamber Solid Oxide Fuel Cell (SOFC), combining advantages of both. The AP-SOFC does not need any sealant and crack generation in its electrolyte component does not terminate cell operation. In this study, the performance of a hydrogen-fuelled co flow planar AP-SOFC is investigated numerically for the first time. Governing equations include species, mass, momentum, charge and energy solved fully-couple with electrochemical equations. Due to lack of study on hydrogen-fuelled AP-SOFC, first the performance of a conventional hydrogen-fuelled SOFC is modeled and the results are compared with experimental results for the validation purpose, then changes in the model are made to apply the electrolyte porosity. Results show a 29% decline in maximum power density produced by the AP-SOFC compared to its conventional scheme with the same inputs. The main reason for this reduction in the cell performance is mostly the flow leakage of oxygen from the near air channel inlet to the fuel channel side. This leakage leads to displace the maximum cell temperature point.

An essential component in the construction and operation of solar power plants is identifying the factors affecting power generation in the desired areas based on the season and the amount of radiation in each season for the construction of solar power plants. Therefore, in this study, by examining the output capacity of a small 1kW power plant and analyzing effective data in different seasons, as well as by comparing practical and simulation results, we could identify useful and consistent data about factors affecting the production capacity of the plant. Then, the effect of temperature changes on each cell unit was investigated. Using a 100W YH100W-18-M panel, a practical study of the data was performed based on the STC rate. Meanwhile, the data were simulated and matched, and the final results were extracted. Finally, the diagram of the impact on the power and current of the power plant in all seasons of the year was extracted. The obtained results, namely the effective parameters in compiling this article, indicated the effectiveness of parameters such as the ambient temperature and the amount of radiation, yielding significant results in the output power of the power plant in different seasons.

Nowadays, population growth, pollution, climate change, depletion of groundwater resources and excessive water consumption are the main reasons for the shortage of fresh water. One of the methods for producing water is the use of solar energy, which is performed on devices called solar still. In this study, the effect of using different masses of sand on the production of double slope single basin solar still with a basin surface of 0.27 m^2 at a constant water depth of 1.5 cm on sunny winter days was investigated. The sand acts as a heat storage and when the solar radiation is low, the heat stored in it returns to the still. The findings of the research show that production in solar still without sand and solar still with a mass of 1 kg of sand is identical, also, with increasing sand mass, from 1 to 2 kg, the amount of still production decreases. On the other hand, the energy and exergy efficiency system have also decreased with increasing sand mass. As a result, putting 1 kg of sand in this solar still is as optimal amount and increasing it has a negative effect on system performance on sunny days.

Clerestory windows are one of the best ways to increase the penetration of light in Low-rise buildings. However, in rainy climates with cloudy skies, receiving daylight will be more critical. Since the physical component of buildings in this climate varies according to the type of roof slope, the shape of the interior roof, and the plan's geometry. The fundamental question is: What physical characteristics can receive the maximum light from the Clerestory window in Pitched low-rise buildings? The research aimed to investigate the potential of Clerestory to improve daylight in a Pitched-roof. In the present study, Rhino software was used to design 3D models, and the Diva plugin in Grasshopper software was used to evaluate the “daylight factor.” Data indicate that; regardless of the geometry of the plan and form of internal reflection, the most effective component is the “roof slope ratio,” which creates the most significant change in interior lighting. Moreover, the 18-degree roof slope with a ceiling ratio (4-12) is the best efficiency, and provides 3.3% (A.DF) among the various. By considering the slope of the roof component and the shape of the interior reflector, the geometry of the square plan creates more appropriate daylight in the interior space.

In this research, thermodynamic modeling of a combined production cycle of heat and power is performed based on a solid oxide fuel cell for building sector applications. Initially, the thermodynamic assessment is explained by introducing the mentioned cycle and its respected modeling technique. Then, cycle simulation is performed using Cycle Tempo analytical software by simultaneously solving the mass, energy, and electrochemical equilibrium equations. Parametric analysis of the main characteristics influencing the performance of the cycle is assessed, and the appropriate operating conditions are determined after presenting the performance results. The results show that using this model, electric power of 14.00 kW, thermal power of 4.56 kW, heat to power ratio of 32% at net electrical efficiency of 58.5%, and total efficiency of 77.3% is achievable. These results also confirm the attractiveness of the proposed systems over other electricity and heat cogeneration technologies, which are based on gas engines or gas micro turbines. The system is highly recommended in administrative buildings and warm and warm/moderate climates considering the functionality of the proposed system in different heat to power ratios.

The environmental crisis has induced experts to develop renewable energy alternatives. Architects have strived to achieve between the proposed alternatives and various climates of different regions. Given the application of Double Skin Façade as an alternative in renewable energy usage, the current study aims to investigate an optimized procedure for utilizing wind energy in the natural ventilation of a building in Manjil city. The velocity and pressure of the wind is literally impossible to control and suppress its force. This study is intended to inquire into the relationship between physical components of the double-skin façade as well as the structure of the openings and the velocity and pressure of wind within the internal environment of mid-rise buildings. Therefore, the main goal is to achieve a method through which the wind pressure and its effects on the building is controlled by the use of the double-skin façade. The parameters’ values are determined and they are assigned to the variables in the Design-Builder simulation software, version 6.1.0.6. Then, the analytical results are compared to the experimental ones. It is revealed that the use of two skins leads to a decrease in the velocity and pressure of the wind within the internal space of the building with respect to the velocity and pressure in the external space. The extent of reduction in wind velocity and pressure is directly related to the distance between layers of skins. It is also worth mentioning that the vertical openings show better performance compared to the horizontal ones.