Papers by S.M. Sajed Sadati
In the present paper, a complete process from reliability evaluation to design modification is pr... more In the present paper, a complete process from reliability evaluation to design modification is proposed and also applied to a newly designed and manufactured Remotely Piloted Helicopter (RPH) by the authors. First of all, a description of all platform subsystems is presented. After that, function diagram and also product tree of the whole system is depicted for further analysis. Then, the reliability of all parts and components are calculated through standard methods. The procedure is followed by FMEA/FMECA execution and determination of critical components and failures. Then, the reliability of the whole platform is calculated using standard block diagrams. Finally, in order to improve the mission operational reliability of the considered RPH, some modifications are implemented to the platform including configuration and mechanisms design changes. Nomenclature C = criticality number d = possibility of failure detection FMEA = failure modes and effect analysis FMECA = failure modes, effects and criticality analysis MTBF = mean time between failures MTTF = mean time to failure n = severity of failure P = probability of failure pdf () = probability density function PN = probability number of component failure R S (t) = reliability function RPH = remotely piloted helicopter T = lifetime of item (Fig. 2) UAV = unmanned aerial vehicle = failure rate
Confronting snowfall at airports is a long-standing challenge for the aviation industry. To addre... more Confronting snowfall at airports is a long-standing challenge for the aviation industry. To address these concerns, electrically conductive portland cement concrete (ECON) is currently a
focus in pavement design. This method applies a potential difference to a surface or near-surface conductive concrete layer, heating the pavement to melt the snow. Due to the complex nature of performance measurements, most studies use experimental methods to examine the ability to remove accumulated snow. However, these methods are resource intensive. This study addresses this challenge through the development of an experimentally-validated 3D finite element (FE)
model of ECON for evaluating its thermal performance. Predicted surface temperatures of the FE model are consistent with the data, indicating that a FE model is a promising method for
feasibility studies and control strategy development.
The use of renewable energy with storage systems is particularly important in small and unreliabl... more The use of renewable energy with storage systems is particularly important in small and unreliable grids, such as islands. This paper reports sizing of a photovoltaic (PV) power plant with storage system for Middle East Technical University Northern Cyprus Campus through technical and economic analyses. PV system was modeled considering fixed tilted, one-axis and two-axis tracking systems using hourly data. Energy storage system was included in the model to overcome the temporal mismatch between the electricity demand of the campus and the electricity supplied by the PV system. The reduction in CO 2 emissions by deploying these systems was studied. The results showed that although it would not be economically feasible to meet the entire demand of the campus, a PV system of 4.5 MW with 15 MWh of storage size would generate enough electricity to meet the demand for 83% of the time in a year, yielding the cost of 0.25 USD/kWh.
As the main source of local nonlinearities, joints can lead to drastic changes in dynamic behavio... more As the main source of local nonlinearities, joints can lead to drastic changes in dynamic behavior of structures in a global scale. Finite element (FE) models often lack these nonlinearities and are incapable of representing nonlinear behavior. Therefore, the identification of nonlinear dynamic mechanical properties of the joint is necessary, in order to develop a faithful FE model of the structure. In the present work, dynamic parameters of a nonlinear joint are identified using an optimum equivalent linear frequency response function of the structure. A test rig, which includes a beam that can produce cubic stiffness spring characteristic as a nonlinear joint, is built, and nonlinear dynamic characteristics of the beam are identified. In addition to hardening behavior related to cubic stiffness, softening effects were also observed in some measured modes in which further investigation attributed that behavior to the presence of a bolt in the test rig.
Journal Papers by S.M. Sajed Sadati
Pakistan is going through a severe energy crisis due to an increasing gap between demand and supp... more Pakistan is going through a severe energy crisis due to an increasing gap between demand and supply. Its current energy needs are heavily dependent upon conventional thermal power plants which mainly use oil and gas. In addition to the economic problems associated with importing oil for Pakistan, the burning of fossil fuels for the production of electricity releases vast amounts of greenhouse gases. As an alternative to the current scenario, in this paper the energetic and economic performance of green energy technologies such as photovoltaic (PV), parabolic trough collector (PTC) with and without storage, and wind energy systems are analyzed and compared with respect to their potential for electricity generation for the city of Multan, Pakistan. Each system is designed taking a nominal 10 MWe capacity as a reference. Hourly meteorological data are used to estimate hourly insolation on a fixed PV module and for PTC's with East–West and North–South tracking. Results show that PV and PTC systems without storage have approximately the same output with capacity factors of approximately 20%. The electrical energy output of the wind turbines was very low with a capacity factor of $2%. PTC's with 7.5 h storage and a solar multiple of 3.5 showed the best result for electrical energy output with a capacity factor of 46%. A cost analysis is performed assuming a 30 year lifetime for PV and a 35 year lifetime for PTC. The Levelized Cost of Electricity (LCOE) is found to be 0.192 USD/kWh for PV systems, 0.273 USD/kWh for PTC systems without storage, and 0.226 USD/kWh for PTC systems with 7.5 h of storage. The results of the economic study show that based strictly on economic considerations green energy technologies can be utilized if the government supports the investment by giving incentives and subsidies.
As the main source of local nonlinearities, joints can lead to drastic changes in dynamic behavio... more As the main source of local nonlinearities, joints can lead to drastic changes in dynamic behavior of structures in a global scale. Finite element (FE) models often lack these nonlinearities and are incapable of representing nonlinear behavior. Therefore, the identification of nonlinear dynamic mechanical properties of the joint is necessary, in order to develop a faithful FE model of the structure. In the present work, dynamic parameters of a nonlinear joint are identified using an optimum equivalent linear frequency response function of the structure. A test rig, which includes a beam that can produce cubic stiffness spring characteristic as a nonlinear joint, is built, and nonlinear dynamic characteristics of the beam are identified. In addition to hardening behavior related to cubic stiffness, softening effects were also observed in some measured modes in which further investigation attributed that behavior to the presence of a bolt in the test rig.
The impact of ice and snow on transportation infrastructure adds significant expense to the U.S. ... more The impact of ice and snow on transportation infrastructure adds significant expense to the U.S. economy through the cost of snow removal, pavement deterioration, and profit lost due to travel delays, particularly for airport travel. Therefore, alternative snow removal practices are needed to reduce the costs and increase re-siliency of communities when faced with harsh snowfall conditions. This study investigates the economic viability of electrically conductive concrete (ECON) heated pavement systems (HPS), based on construction and operational experiences with the first full-scale ECON HPS at a U.S. airport (Des Moines International Airport (DSM)). Monte Carlo simulation-based analysis was also conducted to quantify the most significant variables influencing the overall economic viability of ECON HPS. The results of analysis indicate that benefits of implementing this system would outweigh its costs with more than 70% reliability. The results of sensitivity analysis indicate that number of aircraft operations would strongly affect the benefit-cost ratio (BCR). The simulation was also designed and run for the Minneapolis-St. Paul International Airport, MN (MSP), which has six times more enplanements than DSM. The simulation results showed a 92% relative likelihood that the BCR ratio of implementing ECON HPS in MSP would be greater than one.
Deploying renewable energy systems (RES) to supply electricity faces many challenges related to c... more Deploying renewable energy systems (RES) to supply electricity faces many challenges related to cost and the variability of the renewable resources. One possible solution to these challenges is to hybridize RES with conventional power systems and include energy storage units. In this study, the feasibility analysis of a grid-connected photovoltaic (PV)-wind-battery hybrid system is presented as a microgrid for a university campus-scale community on a Mediterranean island. Models for PV and wind turbine systems are presented to estimate energy production, and net present cost (NPC) and levelized cost of electricity (LCOE) are used as economic metrics. A parametric study is performed with hourly time-steps to determine the sizes of energy generation and storage units to minimize the NPC for a small community as the case study. Two alternate configurations with and without storage are proposed. In both cases, the resulting LCOE is 0.15 USD/kWh while the current electricity tariff for the analyzed location was 0.175 USD/kWh in 2015. This lower unit cost of electricity leads to a lower NPC considering a 25-year lifetime. Different estimated and measured solar irradiance and wind speed data sets are used to evaluate the performance of the designed microgrid. Sensitivity analysis on different available weather data sets shows that the uncertainty in wind resource estimations is much higher than the uncertainty in solar resource estimations. Moreover, the results show that solar and wind resources could be utilized synergistically for the studied location.
The estimated solar resources are important for designing renewable energy systems since measured... more The estimated solar resources are important for designing renewable energy systems since measured data are not always
available. The estimation models have been introduced in several studies. These models are mainly dependent on local meteorological data and need to be assessed for different locations and times. The current study compares the results of
Angstrom’s model and a neural network (NN) model developed
for this study with measured data for four cities in Iran.
The time resolution for the estimated global horizontal insolation
is monthly. The results show that the developed NN
model has promising performance and considering the calibration
process for Angstrom’s model it can be used as an alternative.
The NN model uses climatic data to estimate the solar insolation which makes it more flexible in terms of being applicable for different regions.
Deploying renewable energy systems (RES) to supply electricity faces many challenges related to c... more Deploying renewable energy systems (RES) to supply electricity faces many challenges related to cost and the variability of the renewable resources. One possible solution to these challenges is to hybridize RES with conventional power systems and include energy storage units. In this study, the feasibility analysis of a grid-connected photovoltaic (PV)-wind-battery hybrid system is presented as a microgrid for a university campus-scale community on a Mediterranean island. Models for PV and wind turbine systems are presented to estimate energy production, and net present cost (NPC) and levelized cost of electricity (LCOE) are used as economic metrics. A parametric study is performed with hourly time-steps to determine the sizes of energy generation and storage units to minimize the NPC for a small community as the case study. Two alternate configurations with and without storage are proposed. In both cases, the resulting LCOE is 0.15 USD/kWh while the current electricity tariff for the analyzed location was 0.175 USD/kWh in 2015. This lower unit cost of electricity leads to a lower NPC considering a 25-year lifetime. Different estimated and measured solar irradiance and wind speed data sets are used to evaluate the performance of the designed microgrid. Sensitivity analysis on different available weather data sets shows that the uncertainty in wind resource estimations is much higher than the uncertainty in solar resource estimations. Moreover, the results show that solar and wind resources could be utilized synergistically for the studied location.
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Papers by S.M. Sajed Sadati
focus in pavement design. This method applies a potential difference to a surface or near-surface conductive concrete layer, heating the pavement to melt the snow. Due to the complex nature of performance measurements, most studies use experimental methods to examine the ability to remove accumulated snow. However, these methods are resource intensive. This study addresses this challenge through the development of an experimentally-validated 3D finite element (FE)
model of ECON for evaluating its thermal performance. Predicted surface temperatures of the FE model are consistent with the data, indicating that a FE model is a promising method for
feasibility studies and control strategy development.
Journal Papers by S.M. Sajed Sadati
available. The estimation models have been introduced in several studies. These models are mainly dependent on local meteorological data and need to be assessed for different locations and times. The current study compares the results of
Angstrom’s model and a neural network (NN) model developed
for this study with measured data for four cities in Iran.
The time resolution for the estimated global horizontal insolation
is monthly. The results show that the developed NN
model has promising performance and considering the calibration
process for Angstrom’s model it can be used as an alternative.
The NN model uses climatic data to estimate the solar insolation which makes it more flexible in terms of being applicable for different regions.
focus in pavement design. This method applies a potential difference to a surface or near-surface conductive concrete layer, heating the pavement to melt the snow. Due to the complex nature of performance measurements, most studies use experimental methods to examine the ability to remove accumulated snow. However, these methods are resource intensive. This study addresses this challenge through the development of an experimentally-validated 3D finite element (FE)
model of ECON for evaluating its thermal performance. Predicted surface temperatures of the FE model are consistent with the data, indicating that a FE model is a promising method for
feasibility studies and control strategy development.
available. The estimation models have been introduced in several studies. These models are mainly dependent on local meteorological data and need to be assessed for different locations and times. The current study compares the results of
Angstrom’s model and a neural network (NN) model developed
for this study with measured data for four cities in Iran.
The time resolution for the estimated global horizontal insolation
is monthly. The results show that the developed NN
model has promising performance and considering the calibration
process for Angstrom’s model it can be used as an alternative.
The NN model uses climatic data to estimate the solar insolation which makes it more flexible in terms of being applicable for different regions.