Renewable Energy Resources and Technologies
Chunhyun Paik; Yongjoo Chung; Young Jin Kim
Abstract
The power generation sector accounts for a significant portion of GHG emissions, and many countries strive for the large-scale adoption of renewable generation. Although the intermittent nature of renewables brings about complications in energy system planning, the share of renewable generations is increasing ...
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The power generation sector accounts for a significant portion of GHG emissions, and many countries strive for the large-scale adoption of renewable generation. Although the intermittent nature of renewables brings about complications in energy system planning, the share of renewable generations is increasing to the greatest extent. The wind generation has drawn increasing attention to expanding the use of renewable energy to reduce carbon emissions from the power generation sector, and the estimation of capacity factor is crucial in energy system modeling. This study develops a mathematical model for estimating the capacity factor of a wind farm with the consideration of outage probability of individual turbines. In addition, the power curves and wind speed distribution of the wind farm need to be estimated, which is demonstrated with a wind farm in Korea. It is asserted that the proposed method may render the wind farm capacity factor effectively. Thus, the results from this study can be useful for energy system modeling involving wind generations.
Renewable Energy Resources and Technologies
Farhad Amiri; Mohammad Hassan Moradi
Abstract
In the power system, frequency stability is critical. The wind turbine oscillates (depending on the wind speed) and is of low inertia. Thus, wind turbines face the issue of power system frequency stability. Since the power system's resources are interconnected via communication networks, the presence ...
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In the power system, frequency stability is critical. The wind turbine oscillates (depending on the wind speed) and is of low inertia. Thus, wind turbines face the issue of power system frequency stability. Since the power system's resources are interconnected via communication networks, the presence of time delay also affects the frequency stability of the power system. When a disturbance occurs in the power system due to load or distributed generation sources (wind turbine), it leads to frequency deviations in the power system, exhibiting low damping speed. Although large conventional generators in the power system provide sufficient inertia and reduce frequency deviation, the damping speed of frequency fluctuations is slow, which may be due to time delays between power system resources. In this paper, virtual damping (a proposed method) is used to accelerate the damping of frequency deviations caused by load disturbances, distributed generation source disturbances, and the time delay between power system resources. The results of the proposed method are compared to those obtained using the conventional method in this field, demonstrating the superiority of the proposed method. The proposed method reduced frequency deviations in the power system caused by disturbances and time delays by 67 % (a 67 % improvement over existing methods in this field) and increased the damping speed of the frequency deviations by 62 % (a 62 % improvement over the methods used in this field).
Renewable Energy Resources and Technologies
Ehsan Hosseini; Neda Behzadfar; Mahnaz Hashemi; Majid Moazzami; Majid Dehghani
Abstract
Wind turbines can be controlled by controlling the generator speed and adjusting the blade angle and the total rotation of a turbine. Wind energy is one of the main types of renewable energy and is geographically extensive, scattered and decentralized and is almost always available. Pitch angle control ...
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Wind turbines can be controlled by controlling the generator speed and adjusting the blade angle and the total rotation of a turbine. Wind energy is one of the main types of renewable energy and is geographically extensive, scattered and decentralized and is almost always available. Pitch angle control in wind turbines with Doubly Fed Induction Generator (DFIG) has a direct impact on the dynamic performance and oscillations of the power system. Due to continuous changes in wind speed, wind turbines have a multivariate nonlinear system. The purpose of this study is to design a pitch angle controller based on fuzzy logic. According to the proposed method, nonlinear system parameters are automatically adjusted and power and speed fluctuations are reduced. The wind density is observed by the fuzzy controller and the blade angle is adjusted to obtain appropriate power for the system. Therefore, the pressure on the shaft and the dynamics of the turbine are reduced and the output is improved, especially in windy areas. Finally, the studied system is simulated using Simulink in MATLAB and the output improvement with the fuzzy controller is shown in the simulation results compared to the PI controller. Fuzzy control with the lowest cost is used to control the blade angle in a wind turbine. Also, in this method, the angle is adjusted automatically and it adapts to the system in such a way that the input power to the turbine is limited. Compared to the PI controller, by calculating different parameters, the power quality for fuzzy controller is enhanced from 2.941 % to 4.762 % for wind with an average speed of 12 meters per second.
Advanced Energy Technologies
Marzieh Moein; Somayeh Pahlavan; Mehdi Jahangiri; Akbar Alidadi Shamsabadi
Abstract
The electricity economy and its excessive consumption have become one of the main concerns of the Iranian government for many years. This issue, along with recent droughts, shows the need to use renewable energy that is free and clean and does not require water. In addition, due to the high cost of cable-laying ...
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The electricity economy and its excessive consumption have become one of the main concerns of the Iranian government for many years. This issue, along with recent droughts, shows the need to use renewable energy that is free and clean and does not require water. In addition, due to the high cost of cable-laying and maintenance of power lines, it is not at all an option at all distances over the development of the national electricity grid. Therefore, it is important to find a distance for farther distances so that the use of renewable energy systems can be superior to the national electricity grid. According to related studies conducted so far, nothing has been done in this regard in Iran untill private-sector investors realize that, for what distances from the national grid, the network development is not cost-effective compared to using renewables. Therefore, in the present work, by using NASA's wind and solar data, 102 stations in Iran were investigated using the HOMER software. The studied system is a solar-wind one backed up by batteries and diesel generator for emergency conditions. The results showed that the average total net present cost of the solar-wind hybrid system in Iran was to provide a daily average electricity load of 5.9 kWh of a residential building with a peak load of 806 W equal to $ 12415, which could on average provide 95.3% of the building's needs by renewable energy. The average minimum distance from the national grid is 593 m for the cost-effective use of renewable energy.
Renewable Energy Resources and Technologies
Nemat Keramat Siavasha; Gholamhasan Najafi; Teymour Tavakoli; Barat Ghobadian; Esmail Mahmoodi
Abstract
Ducted wind turbines are a kind of small wind turbine having a diffuser or any other shape around the rotor which increases the air flow through the blades and absorbs more power. In the present study, a small wind turbine was ducted with a relatively simple ring and its performance was investigated ...
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Ducted wind turbines are a kind of small wind turbine having a diffuser or any other shape around the rotor which increases the air flow through the blades and absorbs more power. In the present study, a small wind turbine was ducted with a relatively simple ring and its performance was investigated in a wind tunnel. The duct is shaped using rolling steel sheets on a sloping surface and finally fabricated in double-glazed surfaces. The turbine utilizes polyester resin glass fiber-armed composite hollow blades. Bare turbine produces 165 watts in its highest power generation mode which can reach 282 watts when it is ducted. The evaluation of the system in the wind tunnel showed that the power generation of the ducted system compared to a conventional turbine was 14 % higher on average. Furthermore, the rotor speed of the ducted turbine was 45 % higher than the bare one which increases the tip speed ratio (TSR). In this study, TSR increment raised the absorbed power in the developed wind turbine.
Ali Mostafaeipour; Mohammad Saidi-Mehrabad; Mostafa Rezaei; Mojtaba Qolipour
Abstract
The energy insecurity, environmental pollution, climate change and even reduced rainfall in some countries are prime examples of consequences of the world’s excessive reliance on fossil fuels. This study suggests that in some southern islands and coastal areas of Iran, two such problems, ...
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The energy insecurity, environmental pollution, climate change and even reduced rainfall in some countries are prime examples of consequences of the world’s excessive reliance on fossil fuels. This study suggests that in some southern islands and coastal areas of Iran, two such problems, namely the growing shortage of potable water and air pollution can be addressed by building a wind-powered seawater desalination plant at the locations. To evaluate such project, first the sites that may provide the highest efficiency need to be identified. In this study, 10 ports and 5 islands in southern Iran, which suffer from water shortage but have access to seawater, are identified as preliminary candidate sites for such project. The criteria influencing the suitability of a location are considered to be wind power density, economic feasibility, topographic condition, frequency of natural disasters, population, and the wind farm’s distance from desalination facility. After analyzing and weighting the criteria, the locations are ranked using the ELECTRE III method, and the results are validated using the PROMETHEE method. In conclusion, the results of ranking techniques show that Qeshm Island is the best location for construction of a wind-powered seawater desalination plant.
Gholam Reza Arab Markadeh; Nasrin Banimehdi
Abstract
This paper proposes an improved direct active and reactive power control (DPC) strategy for a grid-connected doubly fed induction generator (DFIG) based wind-turbine system under unbalanced grid voltage condition. The method produces required rotor voltage references based on the sliding mode control ...
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This paper proposes an improved direct active and reactive power control (DPC) strategy for a grid-connected doubly fed induction generator (DFIG) based wind-turbine system under unbalanced grid voltage condition. The method produces required rotor voltage references based on the sliding mode control (SMC) approach in stationary reference frame, without the requirement of synchronous coordinate transformation, and therefore causes a simpler design for power control system. Under unbalanced grid voltage condition, two control targets obtained simultaneously, i.e., removing stator active and reactive power oscillations. Moreover this method reduces the THD of stator current. Also it is shown that the proposed control method not only has a high-speed dynamic response but is stable during wind speed and system parameters variations. Simulation results for a 2kw DFIG confirm prominence of proposed control strategy.
Mojtaba Tahani; Pouria Servati; Ahmad Hajinezhad; Younes Noorollahi; Emad Ziaee
Abstract
In recent years, energy predicament and environmental problems in the world caused by fossil fuels combustion make us to pay serious attention to optimizing energy consumption and using renewable energies. One of the potential renewable energies which can be helpful in electricity generation is harness ...
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In recent years, energy predicament and environmental problems in the world caused by fossil fuels combustion make us to pay serious attention to optimizing energy consumption and using renewable energies. One of the potential renewable energies which can be helpful in electricity generation is harness wind and water energy or using these two kinds of energy simultaneously. In this study, to provide a part of electricity in Azadi complex, 2 wind turbines with 12 different scenarios are used. In addition to provide some parts of the consumed electricity, they provide consumed electricity for water pumps which pump the sport complex lake water to a reservoir with 30000 cubic meters capacity and 20 meters height which provides remainder the consumed electricity. In this model, with regard to the uncertain amount of electricity consumption, 3consumption scenarios with three probabilities are pumped every day into a pool and a few of it is used for electricity consumption and the surplus is sold to the agricultural sector and irrigation of green spaces. The GAMS software and two stage optimization methods in two states, with and without considering the risk for optimization are used and in both states, profit and net profit in each scenario are computed.
