117 research outputs found
Effect of wind speed gradients on AEP in a wind farm cluster
No full textThe engineering flow models used to estimate annual energy production (AEP) in offshore wind farm layout optimization typically assume inflow homogeneity over the model domain. This assumption lies in contrast with observations of horizontal wind speed gradients in coastal regions where many offshore wind farms are being constructed. Accounting for wind speed gradients in wind farm models may lead to reduced uncertainty in AEP estimates and reduced bias inoptimized wind farm layouts. This thesis examines whether accounting for horizontal wind speed gradients with WRF simulated wind resource inputs to engineering wake models impacts AEP prediction for a wind farm cluster in the Irish Sea by comparing results with calculation methods which assume homogeneous inflow. Analysis of a wake free two turbine case under a gradient shows that the assumption of homogeneity leads to errors with the true power which a gradient based method is able to predict. Despite this, results suggest that the overall impact of modelling wind speed gradients on AEP predictions in the Irish Sea cluster is small. Homogeneous and gradient methods using the same wind resource data predicted differences in AEP of between 0.1% and 0.75%, with most cases below 0.75%. Filtering by wind direction reveals AEP differences larger than the assumed wake model uncertainty for two sectors with inflow from land. The AEP contribution from sectors with mean wind speed gradients is limited by low frequencies and mean wind speeds. Additionally, positive and negative power differences predicted by homogeneous and gradient methods were found to balance over the year.Rotor Design TrackEuropean Wind Energy Masters (EWEM
Akad Murabahah Bil Wakalah menurut hukum ekonomi Syariah dan Fatwa DSN MUI serta penerapannya pada Lembaga Keuangan Syariah
Get PDFINDONESIA :
Lembaga keuangan syariah (LKS) merupakan lembaga keuangan yang prinsip maupun oprasionalnya dilandaskan berdasarkan nilai-nilai hukum ekonomi Islam. Perkembangan LKS di Indonesia menghadapi tuntutan zaman yang semakin kompleks, sehingga LKS tertuntut untuk menyajikan produk-produk inovatif agar dapat bersaing dengan lembaga keuangan konvensional. dengan tetap berpegang kepada prinsip-prinsip syariah. Sebagai jawaban dari tantangan tersebut LKS mengeluarkan produk Murabahah bil Wakalah. Penyertaan akad wakalah pada pembiayaan murabahah dalam perspektif hukum ekonomi Islam termasuk dalam jenis hybrid contract. Oleh karena itu, perlu untuk dilakukan penelitian guna mengetahui mengetahui perspektif hukum ekonomi Syariah dan fatwa DSN MUI serta penerapannya pada LKS.
Penelitian ini merupakan penelitian empiris. Penelitian ini bertumpu pada dua sumber data, yaitu data primer dan data sekunder yang dianalisis menggunakan metode analisis deskriptif. Data skunder diperoleh peneliti dari hasil wawancara dengan karyawan Mandiri Syariah, BTN Syariah, BPRS Al Ihsan dan BMT ItQan sebagai sampel dari LKS. Dari hasil wawancara tersebut peneliti memperoleh data tentang bagaimana LKS tersebut menyertakan akad wakȃlah pada produk pembiayaan murȃbahah. Sedangkan data sekunder peneliti peroleh dari buku-buku, laporan-laporan tertulis yang diperoleh dari perusahaan, dan literatur lain yang sesuai dengan tujuan penulisan.
Penelitian ini menggunakan metode kualitatif, yang bertujuan untuk mengetahui bagaimana perspektif hukum ekonomi syariah dan fatwa DSN MUI atas penerapan akad Murabahah bil Wakalah pada LKS. Selain itu penelitian ini juga dilaksanakan dengan tujuan untuk mengetahui adakah perbedaan antara praktik dan teori pada akad Murabahah bil Wakalah pada LKS. Penelitian ini menggunakan teknik content analysis untuk untuk mengetahui dan menganalisis kesyariahan penerapan akad Murabahah Bil Wakalah pada LKS.
Hasil dari teknik content analysis didapatkan bahwa penerapan akad Murabahah bil Wakalah telah diterapkan sesuai ketentuan dan regulasi yang berlaku, namun dalam penelitian ini juga ditemukan ketidaksesuaian dengan skema alur pembiayaan yang diberikan oleh pihak LKS itu sendiri. Dalam penerapannya keluar dari beberapa prinsip akad Murabahah bil Wakalah dari segi waktu pelaksanaan akad murabahah yang dilaksanakan sebelum akad wakalah sehingga menyalahi ketentuan fatwa DSN MUI tentang wakalah dalam murabahah yang secara prinsip barang adalah milik LKS. Namun pada hakikatnya, terlepas dari bagaimana aplikasi pada LKS, penyertaan akad wakalah dalam murabahah menjadi solusi dalam penerapan akad murabahah biasa pada LKS. Dimana adanya regulasi pajak pembelian sehingga penerapan murabahah murni tanpa adanya wakalah dapat menimbulkan pengenaan double tax sebagai akibat terjadinya dua kali pembelian, yaitu antara penjual sebagai pihak ketiga dengan LKS dan antara LKS dengan nasabah. Penerapan akad wakalah dipandang lebih menguntungkan kedua belah pihak.
ARAB :
عقد المرابحة بالوكالة بمقهوم القانون الاقتصادي الإسلامي و فتوى هيئة الشرعية القومية التابعة لمجلس العلماء الإندونيسي وتطبيقه في المؤسسات المالية الإسلامية
ملخص
المؤسسات المالية الإسلامية (LKS) هي مؤسسات المالية تستند مبادئها وعملياتها إلى قيم القانون الاقتصادي الإسلامي. يواجه تطوير هذه المؤسسات في إندونيسيا متطلبات حقبة متزايدة التعقيد ، بحيث يُطلب منها تقديم منتجات مبتكرة من أجل المنافسة مع المؤسسات المالية التقليدية عن طريق التمسك بمبادئ الشريعة, استجابة للتحدي أصدرت المؤسسات المالية الإسلامية منتجات المرابحة بالوكالة تدرج مشاركة عقود الوكالة في تمويل المرابحة في منظور القانون الاقتصادي الإسلامي في نوع العقد الهجين. لذلك ، من الضروري إجراء بحث لمعرفة منظور القانون الاقتصادي الشرعي وفتوى هيئة الشرعية القومية التابعة لمجلس العلماء الإندونيسي وتطبيقه في المؤسسات المالية الإسلامية.
هذا البحث هو البحث التجريبي و يعتمد هذا البحث على مصدرين للبيانات هما البيانات الأولية والبيانات الثانوية التي تم تحليلها باستخدام طرق التحليل الوصفي. تم الحصول على بيانات ثانوية من الباحثين من المقابلات مع موظفي Mandiri Syariah و BTN Syariah و BPRS Al Ihsan و و BMT ItQan كعينات من المؤسسات المالية الإسلامية, من نتائج المقابلة حصل الباحث على بيانات حول كيفية قيام المؤسسات المالية الإسلامية بتضمين العقد الزمني في منتج تمويل المرابحة. في حين أن البيانات الثانوية التي تم الحصول عليها من الباحثين من الكتب والتقارير المكتوبة التي تم الحصول عليها من الشركة ، وغيرها من الأدبيات التي تتوافق مع الغرض من الكتابة.
تستخدم هذه الدراسة طريقة نوعية ، تهدف إلى معرفة كيفية منظور القانون الاقتصادي الإسلامي وفتوى هيئة الشرعية القومية التابعة لمجلس العلماء الإندونيسي على تطبيق عقد المرابحة في وكيل المؤسسات المالية الإسلامية, بالإضافة إلى ذلك الحال تم إجراء هذا البحث بهدف معرفة ما إذا كانت هناك اختلافات بين الممارسة والنظرية في عقد المرابحة بالوكالة في المؤسسات المالية الإسلامية ,تستخدم هذه الدراسة تقنيات تحليل المحتوى لتحديد وتحليل تطبيق عقد المرابحة على المؤسسات المالية الإسلامية.
تشير نتائج تقنية تحليل المحتوى إلى أن تطبيق عقد المرابحة بالوكالة تم تطبيقه وفقًا للوائح واللوائح المعمول بها ، ولكن في هذه الدراسة أيضًا وجد تعارضًا مع مخطط تدفق التمويل المقدم من المؤسسات المالية الإسلامية نفسه. في تطبيقه ، فإنه يأتي من عدة مبادئ في عقد المرابحة بالاكاد فيما يتعلق بوقت تنفيذ عقد المرابحة الذي يتم تنفيذه قبل عقد الوكالة بحيث ينتهك أحكام فتوى هيئة الشرعية القومية التابعة لمجلس العلماء الإندونيسي المتعلقة بالوكالة في المرابحة والتي تنتمي من حيث المبدأ إلى المؤسسات المالية الإسلامية , لكن في جوهرها ، بغض النظر عن كيفية تطبيق الطلب عليها ، فإن مشاركة الوكالة في عقد المرابحة هو الحل في تطبيق عقد المرابحة العادي علىها, عندما يكون هناك لائحة ضريبة شراء بحيث يمكن أن يؤدي تطبيق المرابحة الخالصة دون وجود وقت إلى فرض ضريبة مزدوجة نتيجة عمليتي شراء ، هما: البائع كطرف ثالث مع المؤسسات المالية الإسلامية وبينها والعميل. يعتبر تطبيق عقد الوصلة أكثر فائدة لكلا الطرفين.
ENGLISH :
Islamic finantical Institution (LKS) are financial isntitutions which the principles and oprations are based on Islamic economic law values. The develovment of the LKS in Indonesia faces the demands of increasingly complec times, so it is required to be able to meet the community's needs by presenting innovative products in order to compete with conventional financial institutions by being based on the principles of sharia. In response to the callenges, the LKS isued a Murabahah Bil Wakalah product. The inclutions of Wakalah contract on Murabahah financing in the perspective of Islamic economic law is included in the type of merger of hybrid contract. Therefore, it is necessary to do research to find out the perspective of Sharia economic law and the fatwa of DSN-MUI and its application to the LKS.
It is an empirical research. The research relies on two data sources, primary data and secondary data which analyzed by using descriptive analysis methods. Secondary data obtained by researchers from interviews with the employees of Mandiri Syariah, BTN Syariah, BPRS Al Ihsan and BMT ItQan as samples of the LKS. The results is obtained data on how the LKS included the Wakalah contract in the Murȃbahah financing product. While secondary data obtained from books, written reports of the company, and other literature which is in accordance with the purpose of writing.
This study uses a qualitative method, which aims to find out how the perspective of Islamic economic law and the fatwa of DSN-MUI on the application of the Murabahah bil Wakalah contract to the LKS. In addition, this research was carried out with the aim to find out whether there were differences between practice and theory in the Murabahah bil Wakalah contract on the LKS. This study uses content analysis techniques to determine and analyze the application of the Murabahah Bil Wakalah contract to the LKS.
The results of the content analysis technique show that the application of the Murabahah bil Wakalah contract has been applied in accordance with the applicable regulations, but this study also found a discrepancy with the financing flow scheme provided by the LKS itself. The application comes out of several principles of the Murabahah bil Wakalah contract in terms of the time of implementation of the Murabahah contract which is carried out before the Wakalah contract so that it violates the fatwa of DSN-MUI provisions concerning Wakalah in Murabahah which in principle that the commodity belongs to the LKS. But in essence, regardless of how the application on the LKS, the participation of Wakalah in Murabahah contract is the solution in the application of ordinary Murabahah contract to the LKS. Where there is a purchase tax regulation, so the application of pure Murabahah without the presence of time can lead to the imposition of a double tax as a result of two purchases, first between the seller as a third party with the LKS and the second between the LKS and the customer. The application of the Wakalah contract is seen as more beneficial to both parties
Improving Annual Energy Production of Doubly-Fed Induction Generators
No full textDoubly fed induction generator (DFIG) based wind turbines are most employed for onshore applications because of their cost-effectiveness. The drivetrain improvement is barely studied due to the maturity of the DFIG based systems. This paper investigates two methods for improving the annual energy production (AEP) of the DFIG based wind turbines. They are referred to as short-circuited and -Y-connected DFIGs. The origins of the AEP improvement are elaborated from the drivetrain perspective. The improvement is quantified by the aerodynamic model of the turbine and the steady-state model of the DFIG. The two methods are then compared when applied to six regions with different wind speed distributions. The AEP improvements at six regions are evaluated and compared to derive the feasibility of the methods for different locations.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-car Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
Clustering Wind Profile Shapes to Estimate Airborne Wind Energy Production
No full textAirborne Wind Energy (AWE) systems use tethered flying devices to access higher altitudes, typically up to 500 meter, where wind is generally stronger and more persistent. To estimate the Annual Energy Production (AEP) of AWE systems, the wind speed statistics close to the ground are typically extrapolated to higher altitudes, introducing substantial uncertainties. A methodology is developed for characterising a site’s wind resource using a set of wind profile shapes. It is demonstrated how this wind resource representation is used together with a performance model to do fast AEP calculations for flexible-kite pumping AWE systems.greenWind Energ
A frequency-time domain method for annual energy production estimation in floating wind turbines
No full textA new method is proposed to estimate a floating wind turbine's annual energy production (AEP) using frequency and time-domain design techniques. The approach demonstrated herein estimates the AEP by performing a convolution between the floating platform response and the response power operators (RPOs) that map the average power produced by the turbine as a function of the amplitude and frequency of the platform motions. One advantage of this approach is that it can be performed early in the conceptual design phase to help discover design space trade-offs between the platform and rotor design. The methodology is applied to the IEA Wind 15 MW WindCrete spar-buoy model using OpenFAST. The RPOs are obtained by prescribing single-DOF platform motions to the turbine with a given amplitude and frequency. This methodology is then validated by comparing the AEP estimation from the RPOs with the AEP estimation from fully-coupled simulations. The results indicate that the method is able to estimate the value of AEP for a realistic sea-state and regular waves. However, further validation is needed as, in the first case, the turbine is moving too little and, in the second case, the contribution of the controller may be dominant. Wind Energ
Minocycline-induced acute eosinophilic pneumonia: A case report and review of the literature
No full textAbstractAcute eosinophilic pneumonia (AEP) can be a challenging diagnosis and is often initially misdiagnosed as one of the more common pneumonia syndromes such as acute respiratory distress syndrome. Early bronchoalveolar lavage (BAL) is critical in distinguishing the diagnosis to initiate proper management. The etiology of AEP is unknown, though many drugs have been implicated, including minocycline.Minocycline is commonly used for pneumonia, acute bronchitis, urinary tract infections, and acne and is likely the cause of AEP in our patient. There are 26 case reports of minocycline-induced AEP. In most cases, outcomes were favorable and symptoms rapidly resolved upon discontinuation of minocycline, with 11 cases employing steroids, one case twelve hours of CPAP and another 5 days of intubation. None resulted in mortality. Although it is difficult to evaluate without further studies, steroids should be recommended for minocycline-induced AEP, especially for those with severe or persistent symptoms
Clustering wind profile shapes to estimate airborne wind energy production
No full textAirborne wind energy (AWE) systems harness energy at heights beyond the reach of tower-based wind turbines. To estimate the annual energy production (AEP), measured or modelled wind speed statistics close to the ground are commonly extrapolated to higher altitudes, introducing substantial uncertainties. This study proposes a clustering procedure for obtaining wind statistics for an extended height range from modelled datasets that include the variation in the wind speed and direction with height. K-means clustering is used to identify a set of wind profile shapes that characterise the wind resource. The methodology is demonstrated using the Dutch Offshore Wind Atlas for the locations of the met masts IJmuiden and Cabauw, 85 km off the Dutch coast in the North Sea and in the centre of the Netherlands, respectively. The cluster-mean wind profile shapes and the corresponding temporal cycles, wind properties, and atmospheric stability are in good agreement with the literature. Finally, it is demonstrated how a set of wind profile shapes is used to estimate the AEP of a small-scale pumping AWE system located at Cabauw, which requires the derivation of a separate power curve for each wind profile shape. Studying the relationship between the estimated AEP and the number of site-specific clusters used for the calculation shows that the difference in AEP relative to the converged value is less than 3 % for four or more clusters.Wind Energ
Overall design optimization of offshore wind farms
No full textThe objective of this thesis is to build an optimization algorithm with the aim of optimizing layouts for two objective functions - Annual Energy Production (AEP) and Levelized Cost of Energy (LCoE), for large offshore wind farms. The algorithm considers the four main factors that are taken into account when creating a preliminary system design for an offshore wind farm. They are - the geographical location of the turbines, the hub height of the turbines, the type of the turbine, and the total number of turbines in the design space.The annual energy production (AEP) of the wind farm is calculated using PyWake which uses the simple NOJDeficit wake model combined with the required superposition and blockage models to resolve wind turbine wakes. This AEP is then fed into TOPFARM, an economic solver developed at DTU which uses scaling factors to derive the total cost of the wind farm. Constant factors such as the discount rate, distance from shore, foundation type, and drivetrain type are also considered when deriving the total cost of the wind farm.The results of this process are used to determine whether a system design is better than another. Several constraints are applied when changing each optimization variable to keep each iteration as realistic as possible. The boundary is assumed to be a square. Both algorithms arrive at similar results, with random search providing a much better solution with approximately a 40\% reduction in LCoE.European Wind Energy Masters (EWEM
Performance analysis of wind turbines with leading-edge erosion and erosion-safe mode operation
No full textFor offshore wind turbines, Leading-Edge Erosion (LEE) due to rain is posing a serious risk to structural integrity and can lead to a performance loss of the order of a few percent of the Annual Energy Production (AEP). A proposed mitigation strategy is the so-called Erosion-Safe Mode (ESM). In this work, the AEP losses caused by LEE or by operating in the ESM are compared for two reference turbines, i.e. the IEA 15MW and the NREL 5MW turbines. For both turbines, the performance is evaluated in uniform and sheared inflow conditions. The effects of erosion are modeled by creating clean and rough airfoil polars in XFOIL. It is assumed that erosion occurs once a critical blade element section speed is exceeded. Power curves for LEE and ESM are calculated by using the free-wake vortex method CACTUS. Results show that LEE negatively affects the power production below rated capacity, while operating in ESM predominantly sheds performance at rated power of the turbine. This study, therefore, shows that a break-even point for the ESM exists. The AEP loss due to erosion can be successfully mitigated with the ESM at sites with low mean wind speed, however, at sites with higher mean wind speed, operation with erosion leads to a lower AEP loss. The break-even point shows little sensitivity to the blade design and to mean shear variations, but strongly depends on the frequency ESM needs to be applied. The latter is driven by the predicted amount of damaging rain events. In conclusion, erosion-optimal operation is strongly governed by the site characteristics and much less by turbine design, and the viability of an ESM strategy can be significantly expanded by a better understanding of blade damage mechanisms and improved forecasting of the related weather events. Wind Energ
Predicting the benefit of wake steering on the annual energy production of a wind farm using large eddy simulations and Gaussian process regression
Get PDFIn recent years, wake steering has been established as a promising method to increase the energy yield of a wind farm. Current practice in estimating the benefit of wake steering on the annual energy production (AEP) consists of evaluating the wind farm with simplified surrogate models, casting a large uncertainty on the estimated benefit. This paper presents a framework for determining the benefit of wake steering on the AEP, incorporating simulation results from a surrogate model and large eddy simulations in order to reduce the uncertainty. Furthermore, a time-varying wind direction is considered for a better representation of the ambient conditions at the real wind farm site. Gaussian process regression is used to combine the two data sets into a single improved model of the energy gain. This model estimates a 0.60% gain in AEP for the considered wind farm, which is a 76% increase compared to the estimate of the surrogate model.Team Jan-Willem van Wingerde
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