Reliability-Constrained Optimal Scheduling of Interconnected Microgrids

This paper proposes a Mixed-Integer Linear Programming (MILP) optimization model for the scheduling problem of the interconnected microgrid system. The proposed model is capable of efficiently minimizing the microgrids' total operating costs and improving the entire system's reliability, as it is constrained based on enhancing the interconnected microgrids' reliability. The Expected Energy Not Supplied (EENS) is considered in order to ensure minimizing the interconnected microgrids' power deficiency. Furthermore, the proposed model has the capability to solve the optimization problem considering the islanded operation of the interconnected microgrids, i.e. when disturbances occur on the upstream grid. Numerical simulations on a test system containing three interconnected microgrids are performed to evaluate the effectiveness of the model and the results demonstrate the merits and features of the reliability-constrained optimal scheduling model in minimizing the interconnected microgrids' total operating costs and enhancing the interconnected system reliability

Optimal Operation of Integrated Microgrids

Microgrids\u27 deployments are increasing and projected to increase even more in future due to the significant advantages that are provided by this technology for end-use customers. However, microgrids can be connected to each other to create integrated microgrids system, which can further promote the anticipated and desired benefits. An integrated operation of microgrids can potentially improve the local power system reliability and resilience, increase the individual microgrids\u27 economic benefits, and promote further utilization of renewable energy resources. Integrating microgrids, to achieve a microgrid network or cluster, is expected be an essential application towards smarter power grids and a key operational feature in emerging modern distribution grids. Consequently, finding the optimal schedule of the integrated microgrids during the grid-connected and islanded operation modes is necessary to achieve the most possible economic and environmental benefits. In this dissertation, the integrated microgrids systems\u27 operation is investigated, researched and studied. The impact of elevating prosumers to provisional microgrids (to form an integrated microgrids system) is discussed and examined, and further independent and integrated microgrid optimal scheduling models are developed and mathematically simulated, to identify its merits and importance in the distribution grid. In addition, the value/quantity of the unused capacities in the microgrids is discussed and investigated, and a communicative optimal scheduling model for integrated microgrids systems is developed and proposed, in which the local power exchange between the integrated microgrids is determined through an iterative exchange of relevant information based on unused capacity and unmet power in the microgrids. Moreover, the microgrids\u27 privacy is taken into consideration by a developed optimal scheduling model based on the Lagrange Relaxation (LR) method, where the optimal scheduling problem is decomposed into individual optimal scheduling problems using the LR to take prevailing privacy issues into account. Furthermore, an optimal scheduling model for integrated microgrids systems in holonic distribution grids is developed, where the proposed model is capable of determining the optimal network topology, i.e., optimal connections among the integrated microgrids, to ensure minimum microgrid-specific and system-wide operation cost as well as maximum reliability of the entire integrated system. It should be mentioned that all proposed models are mathematically formulated using mixed-integer programming, and studied through numerical simulations to show their performance and effectiveness

Impact of Net Metering on Customers Saving

The purpose of this study is to investigate the effects of net metering on customers engagement. Brief discussions about net metering, its purpose, its challenges and benefits, and the history of net metering in the United States are included within the thesis. The thesis illustrates the net-metering rules, regulations and policies in the United States, and it shows that they are applied in 43 states plus the District of Columbia. Nevertheless, It has clearly seen that they are not similar in all states. The thesis then identifies the impacts of net metering on utilities and solar power owners in particular. Subsequently, a solution has been proposed for net metering challenges, which includes a case study on residential net-metered customers. On the basis of the results of this research, it can be concluded that net metering could be a good practice for everyone, and could affect on economic and environmental concerns widely

Portal Vein Thrombosis in a Patient with Type 1 Diabetes Presenting as Acute Pyelonephritis

Background: Few cases have been reported with respect to portal vein thrombosis in non-cirrhotic patients. Asymptomatic or non-specific symptoms of portal vein thrombosis may lead to misdiagnosis or may delay the diagnosis until complications develop. We report a case of portal vein thrombosis in a patient with type 1 diabetes presenting as acute pyelonephritis. Case description: An 18-year-old female with type 1 diabetes on an insulin pump presented with epigastric abdominal pain for 3 days associated with nausea and vomiting. She was a conscious, alert, young female who appeared to be in pain. Vital signs were stable with a random blood sugar (RBS) level of 179 mg/dl. Abdominal examination revealed a soft and lax abdomen with tenderness in the epigastric area and right renal angle, as well as no sign of rigidity or rebound tenderness. No signs of ascites, splenomegaly or hepatomegaly were noted. Investigations showed a WBC count of 10.2, neutrophils at 65%, urine microsopy analysis revealed WBCs between 30–50 per high power field, with culture showing >105 CFU/ml. All parameters of a thrombophilic screen were within normal values. Computed tomography (CT) revealed reduced enhancement of the right kidney, likely indicating acute pyelonephritis, and left portal vein oedema with complete occlusion. Local factors and prothrombotic disorders were ruled out. The patient was managed with ciprofloxacin, enoxaparin and warfarin. Follow-up imaging revealed complete resolution of thrombosis. Conclusions:Portal vein thrombosis is an uncommon condition in the absence of liver disease. Few case reports exhibit sepsis and portal vein thrombosis. Sepsis can create a predisposed environment for hypercoagulability. To our knowledge, this is the first case report of pyelonephritis with portal vein thrombosis

Thermodynamic analysis of absorption refrigeration cycles by parabolic trough collectors

"The purpose of this study is to numerically investigate the performance of a solar physical surface absorption cooling system, in which activated carbon/methanol is used as a working pair, which is placed inside a parabolic-shaped solar collector. The governing mathematical model of this issue is based on the equations of conservation of mass, conservation of energy, and thermodynamics of the physical surface absorption process. The equations are discretized using the fully implicit finite difference method, and the Fortran computer program was simulated. A comparison with the results of previous laboratory and numerical studies validated this model. At each point in the bed, the temperature, pressure, and mass of the refrigerant absorbed during the physical surface absorption/discharge process were calculated. In addition, the effects of the bed diameter, amount of solar radiation, source temperature, temperature, and pressure of the evaporator and condenser were investigated on the solar performance coefficient and the specific cooling power of the system. According to the built laboratory model and the working conditions of the system, the solar performance coefficient and the specific cooling capacity of the system are equal to 0.12 and 45.6 W/kg, respectively.

Multiple sclerosis following bariatric surgery: A report of five cases

Multiple sclerosis (MS) is a debilitating chronic inflammatory demyelinating disease that affects the central nervous system. The underlying cause of multiple sclerosis is unknown, yet there are various predisposing factors. Currently, bariatric surgery is an increasingly common solution for obesity. It has been reported that bariatric procedures result in miscellaneous neurological complications. To the best of our knowledge, this is the first case series to report the occurrence of MS following bariatric surgery. Here we report the cases of five patients who were recruited for inclusion following neurological examination, complete cerebrospinal fluid (CSF) study, enhanced cranial as well as spinal cord magnetic resonance (MR) images. Diagnosis of multiple sclerosis was made based on McDonalds criteria (2010). All cases were diagnosed with relapsing-remitting form of multiple sclerosis (RRMS) after various types of bariatric surgeries

Effect of nocturnal hypoxemia on glycemic control among diabetic Saudi patients presenting with obstructive sleep apnea

BackgroundObstructive sleep apnea (OSA) is a prevalent disease that is associated with an increased incidence of type II diabetes mellitus (DM) if left untreated. We aimed to determine the association between glycosylated hemoglobin (HbA1c) levels and both nocturnal hypoxemia and apnea-hypopnea index (AHI) among a Saudi patients with OSA.MethodsA cross-sectional study that enrolled 103 adult patients diagnosed with DM and confirmed to have OSA by full night attended polysomnography between 2018 and 2021. Those who presented with acute illness, chronic obstructive pulmonary disease (COPD)/restrictive lung diseases causing sleep-related hypoxemia, or no available HbA1c level within 6 months before polysomnography were excluded from the study. Univariate and multivariate linear regression analyses between HbA1c levels and parameters of interest were tested.ResultsSixty-seven (65%) of the studied population had uncontrolled DM (HbA1c ≥7%). In univariate regression analysis, there was a significant positive association between HbA1c, and sleep time spent with an oxygen saturation below 90% (T90), female gender, and body mass index (BMI) (p<0.05) but not AHI, or associated comorbidities (p>0.05). In the multivariate analysis, HbA1c was positively associated with increasing T90 (p<0.05), and ODI (p<0.05), but not with AHI (p>0.05).ConclusionNocturnal hypoxemia could be an important factor affecting glycemic control in patients with OSA suffering from DM irrespective of the severity of both diseases

Zonal-Based Optimal Microgrids Identification

Even though many studies have been deployed to determine the optimal planning and operation of microgrids, limited research was discussed to determine the optimal microgrids’ geographical boundaries. This paper proposes a zonal-based optimal microgrid identification model aiming at identifying the optimal microgrids topology in the current distribution systems through zoning the network into several clusters. In addition, the proposed model was developed as a mixed-integer linear programming (MILP) problem that identifies the optimal capacity and location of installing distributed energy resources (DERs), including but not limited to renewable energy resources and Battery Energy Storage Systems (BESS), within the determined microgrid’s boundaries. Moreover, it investigates the impact of incorporating the BESS in boosting the DERs’ penetration on the optimal centralized microgrid. Numerical simulations on the IEEE-33 bus test system demonstrate the features and effectiveness of the proposed model on identifying the optimal microgrid geographical boundaries on current distribution grids as well as its capability on defining the optimal sizes and locations of installing DERs within the microgrid’s zonal area

The Impact of Passive Strategies on the Overall Energy Performance of Traditional Houses in the Kingdom of Saudi Arabia

Communities in nations all over the world must work to address the problem of energy consumption, which has emerged in modern times. Given that domestic consumers account for roughly 49% of the total electricity used annually by all sectors, buildings can be seen as a key player in this conundrum. The architecture field can therefore play a vital role in saving energy, not only through building design but also through the materials used. To minimize architectural programmes’ negative impact on the environment, sustainable design that saves energy is being employed today in traditional Saudi Arabian buildings. This study examined whether current housing designs can effectively integrate four key passive energy-saving strategies: outdoor green area, thermal mass wall, window-to-wall ratio and shading device. This study analysed two types of traditional houses from two different cities in Saudi Arabia’s Najd region, Riyadh and Hail, examining the four passive strategies. Using traditional house designs, this paper created four simulation models for each house, and compared the simulation results with the base case model to determine how well these strategies could affect the energy consumption for residential buildings in Saudi Arabia (KSA). The results indicate that the selected strategies can play an important role in saving energy in residential buildings in the KSA

The Impact of Passive Strategies on the Overall Energy Performance of Traditional Houses in the Kingdom of Saudi Arabia

Communities in nations all over the world must work to address the problem of energy consumption, which has emerged in modern times. Given that domestic consumers account for roughly 49% of the total electricity used annually by all sectors, buildings can be seen as a key player in this conundrum. The architecture field can therefore play a vital role in saving energy, not only through building design but also through the materials used. To minimize architectural programmes’ negative impact on the environment, sustainable design that saves energy is being employed today in traditional Saudi Arabian buildings. This study examined whether current housing designs can effectively integrate four key passive energy-saving strategies: outdoor green area, thermal mass wall, window-to-wall ratio and shading device. This study analysed two types of traditional houses from two different cities in Saudi Arabia’s Najd region, Riyadh and Hail, examining the four passive strategies. Using traditional house designs, this paper created four simulation models for each house, and compared the simulation results with the base case model to determine how well these strategies could affect the energy consumption for residential buildings in Saudi Arabia (KSA). The results indicate that the selected strategies can play an important role in saving energy in residential buildings in the KSA