Renewable Energy (Marine hydrokinetics)

Hydrokinetic energy conversion systems are the electromechanical devices that convert kinetic energy of river streams, tidal currents, man-made water channels or waves into electricity without using a special head and impoundment. This new technology became popular especially in the last two decades and needs to be well investigated. In this study, the hydrokinetic energy conversion systems were reviewed broadly. They have been categorized into two main groups as current and wave energy conversion devices. Their technology, working principles, environmental impacts, source potential, advantages, drawbacks and related issues were detailed.

Hydrokinetic energy is an emerging class of renewable energy that harnesses the kinetic energy of moving water. Distinct from conventional hydroelectric technology, which requires large dams or reservoirs to create significantly high water head to drive the turbine; hydrokinetic technology can be deployed in rivers, streams, or constructed waterways with very low hydraulic head. This characteristic significantly increases the number of potential installation sites and applications possible with hydrokinetic technology. On the other hand, hydrokinetic energy has the advantages of high energy density, very good predictability over other types of renewable energy. This paper reviews the current state of hydrokinetic technology for riverine applications. The hydrokinetic energy theory is reviewed first, with practical examples to illustrate real-world physical meaning of mathematical formulae. Next, maximum power point tracking, turbine’s duct effect are reviewed. Finally, the two most popular categories of hydrokinetic turbines are discussed in detail with focus on advantages, drawbacks and preferable applications

Hydrokinetic energy conversion systems are the electromechanical devices that convert kinetic energy of river streams, tidal currents, man-made water channels or waves into electricity without using a special head and impoundment. This new technology became popular especially in the last two decades and needs to be well investigated. In this study, the hydrokinetic energy conversion systems were reviewed broadly. They have been categorized into two main groups as current and wave energy conversion devices. Their technology, working principles, environmental impacts, source potential, advantages, drawbacks and related issues were detailed.

Abstrack
Flow velocity distribution causes the use of the Savonius turbine in water streams to be less desirable. Tornado Savonius turbine is a new type of turbine developed by the Savonius turbine design. Innovation of the Tornado Savonius turbine is at the bottom of the blade which shrinks and enlarges at the top of the blade. This shape resembles the shape of the flow velocity distribution. This study was conducted by comparing the performance of the Savonius turbine and the Tornado Savonius turbine. It was carried out on a prismatic channel with 5 variations in velocity and 4 variations in depth. Relating to the flow velocity range (v) between 0.172 m/s – 0.453 m/s, the innovation of the Tornado Savonius turbine had elevated the Coefficient of Power (CP) value of the Tornado Savonius turbine to be greater than CP of the Savonius turbine. Based on experimental tests in this study, the Savonius turbine produced RPM values of 12.2–28.9 when the torque range between 0.063–0.213 Nm while the Tornado Savonius turbine produced RPM of 20.7–56.1 when the tested torque values range between 0.038–0.175 Nm. The optimal CP value produced by the Savonius turbine was 0.270 and the Tornado Savonius turbine produced an optimal CP value of 0.422. Based on the gradient of the change in flow velocity to the CP value, the Tornado Savonius turbine could work optimally at the same channel depth as the turbine height. This proves that the flow velocity distribution works better on the Tornado Savonius turbine compared to the Savonius turbine.
Keyword: flow velocity distribution, savonius, tornado savonius , turbine hydrokinetic

Abstrak
Konsep distribusi kecepatan aliran menyebabkan penggunaan turbin Savonius di aliran air kurang diminati. Turbin Tornado Savonius merupakan jenis turbin baru hasil pengembangan desain turbin Savonius. Inovasi dari turbin Tornado Savonius berada pada bagian bawah blade yang mengecil dan membesar pada bagian atas blade. Bentuk tersebut menyerupai bentuk distribusi kecepatan aliran. Studi ini dilakukan dengan membandingkan kinerja yang dihasilkan turbin Savonius dan turbin Tornado Savonius. Pengujian ini dilakukan pada saluran prismatik dengan 5 variasi kecepatan dan 3 variasi kedalaman. Pada rentang kecepatan aliran (v) antara 0,172 m/s–0,453 m/s, inovasi turbin Tornado Savonius menyebabkan nilai Coefficient of Power (CP) turbin Tornado Savonius lebih besar dari turbin Savonius. Berdasarkan uji eksperimen pada studi ini turbin Savonius menghasilkan nilai RPM sebesar 12,2–28,9 pada saat torsi ( ) sebesar 0,063–0,213 Nm sedangkan turbin Tornado Savonius menghasilkan RPM sebesar 20,7–56,1 pada saat nilai torsi pengujian sebesar 0,038–0,175 Nm. Nilai CP optimal yang dihasilkan turbin Savonius sebesar 0,270 dan turbin Tornado Savonius menghasilkan nilai CP optimal sebesar 0,422. Berdasarkan gradien perubahan kecepatan aliran terhadap nilai CP diketahui bahwa turbin Tornado Savonius dapat bekerja secara optimal pada kedalaman saluran yang sama dengan tinggi turbin. Hal ini membuktikan bahwa distribusi kecepatan aliran bekerja baik pada turbin Tornado Savonius dibandingkan turbin Savonius. τ
Kata Kunci: distribusi kecepatan aliran, savonius, tornado savonius, turbin hidrokinetik

Yudistira, R., Nindito, D.A. and Saputra, R.H., 2021. KINERJA TURBIN HIDROKINETIK TORNADO SAVONIUS. Jurnal Teknika: Jurnal Teoritis dan Terapan Bidang Keteknikan, 4(2), pp.181-186.

DAFTAR PUSTAKA

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Nindito, D. A., Istiarto, I. & Kironoto, B. A. 2009. Simulasi Numeris Tiga Dimensi Kantong Lumpur Bendung Sapon. Journal of the Civil Engineering Forum, 18(1).

Patel, T., Patel, S., Patel, D & Bhensdadiya, M. 2015. An Analysis of Lift and Drag Forces of NACA Airfoils using Python. International Journal of Application or Innovation in Engineering & Management, 4(4), pp. 198–206.

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Wardani, C. S., Nindito, D. A. & Jaya, A. R. 2020. Inovasi Dan Desain Turbin Hidrokinetik Darrieus Berdasarkan Bentuk Distribusi Kecepatan Aliran. Media Ilmiah Teknik Sipil, 9(1), pp. 32–43. doi: doi.org/10.33084/mits.v9i1.1771

Hydrokinetic energy is an unrecognized, low-cost renewable technology that can be deployed in Pakistan through a robust national energy strategy and international investment schemes to tackle the country’s acute energy crisis. This Article will be the first to show how national and local laws can be amended to favor progress in the sustainable energy sector and achieve hydrokinetic energy production in Pakistan, which if actualized, would be nothing short of a game changer – strategically and, even more so, environmentally. Despite current legal regimes that disfavor small scale hydroelectric power production, Pakistan and other less developed countries can adapt and deploy hydrokinetic technology through revamped investment laws, regulatory rules, and renewable energy tax reform.

The cost of utilizing kinetic energy of river stream, tidal and ocean current is considered to be higher than that of wind power generation because of difficulties in construction and maintenance of devices installed in seawater. As a solution to the problem, the authors propose a new concept of water stream turbine. The main idea is in the manner of supporting turbine. Although it is similar to a vertical axis turbine, the direction of turbine axis is not firmly fixed and its tilt angle is passively adjustable to the stream velocity. Since it does not have to keep the turbine axis in upright position, required structural strength and weight of the device will be reduced significantly. This paper describes the application ranging from the small hydro power in river streams to large application of tidal and ocean current turbine. In the large capacity plant for tidal stream and ocean current, the main mechanism of turbine axis support is the same as that of the wind turbine authors proposed in the previous paper. It leads to the further opportunity of cost reduction. The sample design of a multi-megawatt ocean current turbine shows the possibility of high economic performance of the concept. The results show that the cost of energy in the concept can be comparable to a land based wind turbine.

Hydrokinetic is a recently introduced type of hydropower energy, having been proven as the most effective and predictable renewable energy source available around the world, especially in the rural and electrification areas. Most of these sites are dependent on small and micro scale stations to produce cheap but abundantly available and effective electrical energy. Hydrokinetic energy that can be harnessed from the flow of water in the irrigation and rainy channels is a promising technology in countries with vast current energy. Micro hydrokinetic energy scheme presents an attractive, environmentally friendly and efficient electric generation in rural, remote and hilly areas, as effort to reduce the ever-increasing greenhouse gas emissions and fuel prices in these sites. Though potential, this scheme is yet to be fully discovered to the considerable extent, as researchers are still searching for solution for the main problem of low velocity of current in the open flow channels. Deploying acceleration nozzle in the channel is a unique solution for increasing the channels current flow systems' efficiency. Acceleration nozzle channel method has numerous advantages especially on the environmental impact, yet has not been given much attention in the renewable energy field. This paper proposes a novel system configuration to capture as much as kinetic energy from in stream current water. This system, known as bidirectional diffuser-augmented channel functions by utilizing dual directed nozzles in the flow, surrounded by dual cross flow turbines. This type of turbine is commonly used for hydropower applications; and this study proposes the employment of this turbine for hydrokinetic power generation. Numerical investigations had been performed using finite volume Reynolds-Averaged Navier–Stokes Equations (RANSE) code Ansys CFX to investigate the flow field characteristics of the new system approach with and without the turbines. The performance of the twin (lower and upper) cross flow turbines had also been studied. It was found that the highest efficiency of 0.52 was recorded for lower turbine at tip speed ratio (TSR) of 0.5.

Turbulence is inherently chaotic and unsteady, so observing it and modeling it are no easy tasks. The ocean’s sheer size makes it even more difficult to observe, and its unpredictable and ever-changing forcings introduce additional complexities. Turbulence in the oceans ranges from basin scale to the scale of the molecular viscosity. The method of energy transfer between scales is, however, an area of active research, so observations of the ocean at all scales are crucial to understanding the basic dynamics of its motions. In this collection of work, I use a variety of datasets to characterize a wide range of scales of turbulence, including observations from multiple instruments and from models with different governing equations.
I analyzed the largest scales of the turbulent range using the global salinity data of the Argo profiling float network. Taking advantage of the scattered and discontinuous nature of this dataset, the second-order structure function was calculated down to 2000m depth, and shown to be useful for predicting spectral slopes. Results showed structure function slopes of 2 at small scales, and 0 at large scales, which corresponds with spectral slopes of -5/3  at small scales, and −1 at large scales. Using acoustic Doppler velocity measurements, I characterized the meter- to kilometer-scale turbulence at a potential tidal energy site in the Puget Sound, WA. Acoustic Doppler current profiler (ADCP) and acoustic Doppler velocimeter (ADV) observations provided the data for an analysis that includes coherence, anisotropy, and intermittency. In order to more simply describe these features, a parameterization was done with four turbulence metrics, and the anisotropy magnitude, introduced here, was shown to most closely capture the coherent events. Then, using both the NREL TurbSim stochastic turbulence generator and the NCAR large-eddy simulation (LES) model, I calculated turbulence statistics to validate the accuracy of these methods in reproducing the tidal channel. TurbSim models statistics at the height of a turbine hub (5m) well, but do not model coherent events, while the LES does create these events, but not realistically in this configuration, based on comparisons with observations.
Each of the datasets have disadvantages when it comes to observing turbulence. The Argo network is sparse in space, and few measurements are taken simultaneously in time. Therefore spatial and temporal averaging is needed, which requires the turbulence to be homogeneous and stationary if it is to be generalized. Though the acoustic Doppler current profiler provides a vertical profile of velocities, the fluctuations are dominated by instrument noise and beam spread, preventing it from being used for most turbulence metrics. ADV measurements have much less noise, and no beam spread, but the observations are made at one point in space, limiting us to temporal statistics or an assumption of “frozen turbulence” to infer spatial scales. As for the models, TurbSim does not have any real-world forcing, and uses parameterized spectra, and coherence functions and randomizes phase information, while LES models must make assumptions about sub-grid scales, which may be inaccurate. Additionally, all models are set up with idealizations of the forcing and domain, which may make the results unlike observations in a particular location and time. Despite these difficulties in observing and characterizing turbulence, I present several quantities that use the imperfect, yet still valuable observations, to attain a better description of the turbulence in the oceans.

Energi terbarukan bisa digunakan sebagai solusi mengurangi ketergantungan pada bahan bakar fosil dengan cara menggunakan sumber hidroelektrik seperti penggunaan turbin vertikal berjenis Darrieus. Turbin Darrieus memiliki kelemahan yaitu kesulitan memulai awal putaran (self starting) pada rotornya karena berbasis gaya angkat. Studi ini menyelidiki pengaruh penambahan pengarah Omni Directional Guide Vanes (ODGV) dengan jumlah guide vanes dan besar sudut berbeda-beda terhadap turbin Darrieus dengan tujuan dapat menekan kelemahannya. Studi ini menggunakan turbin Darrieus 2 (dua) airfoil dan 3 (tiga) airfoil dengan profil NACA 0012 untuk diujikan di aliran air pada saluran prismatik. Hasil uji eksperimental menunjukkan bahwa penggunaan pengarah dengan perbandingan 1/6 celah ODGV (6 guide vanes) dan sudut 0º mengakibatkan bertambahnya nilai Coefficient of Power  (Cp) dan nilai Tip Speed Ratio (TSR), sehingga mampu meningkatkan Cp rata-rata lebih besar 34,25% dari turbin Darrieus konvensional. Namun seiring bertambahnya jumlah guide vanes dan besar sudut membuat performa turbin menurun. Pengarah ODGV mampu meningkatkan nilai TSR sehingga dapat mengoptimalkan gaya angkat pada turbin.

Kata Kunci: Uji eksperimental, sudut guide vanes, turbin hidrokinetik darrieus, coefficient of power , tip speed ratio.

Renewable energy can be used as a solution to reduce dependence on fossil fuels by using hydroelectric sources such as the use of Darrieus vertical turbines. Darrieus turbines have the disadvantage of difficulty self-starting on the rotor because it is based on lift force. This study investigated the influence the addition of Omni Directional Guide Vanes (ODGV) with different number of guide vanes and angles to Darrieus turbines with the aim of suppressing their weaknesses. This study used 2 (two) and 3 (three) airfoils Darrieus turbines with NACA 0012 profile to be tested in water flow in prismatic channels. Experimental test results showed that the use of a guide with a ratio 1/6 ODGV gap (6 guide vanes) and angle of 0º resulted increase the value of the Coefficient of Power (Cp) and Tip Speed Ratio (TSR), so can increase the average Cp 34.25% larger than conventional Darrieus turbines. But as the increase number of guide vanes and large angles can be decreased turbine performance. ODGV is able to increase the TSR value so as to optimize the lift force on the turbine.

Keyword: experimental test, guide vanes angle, hydrokinetic darrieus turbine, Coefficient of Power , Tip Speed Ratio.

Octauria, E.P., Nindito, D.A. and Saputra, R.H., 2021. UJI EKSPERIMENTAL PENGARUH SUDUT OMNI DIRECTIONAL GUIDE VANES TERHADAP PERFORMA TURBIN HIDROKINETIK DARRIEUS. Eksergi, 17(2), pp.95-108.

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The Maine Tidal Power Initiative (MTPI), an interdisciplinary team of engineers, marine scientists, oceanographers, and social scientists, is using a transdisciplinary sustainability science approach to collect biophysical and social data necessary for understanding interactions between human and natural systems in the context of tidal power development in Maine. MTPI offers a unique opportunity to better understand how group structure and process influence outcomes in transdisciplinary sustainability science research. Through extensive participant observation and semi-structured interviews we: (1) describe MTPI’s organizational structure; (2) examine MTPI’s research approach and engagement with stakeholders from different sectors of society (i.e., industry, government, and the local community); and (3) identify challenges and opportunities for involving different disciplinary expertise and diverse stakeholders in transformational sustainability science research. We found that MTPI’s holistic mission, non-hierarchical structure, and iterative stakeholder engagement process led to important benefits and significant challenges. Positive outcomes include knowledge development, a transferable research framework, shared resources, personal reward, and a greater understanding of the local environment and community. Challenges identified include balancing diverse interests and priorities, maintaining engagement, managing stakeholder relationships, and limited resources. Lessons learned from the process of integrative collaborative research in Maine can offer guidance on what should be considered when carrying out similar transdisciplinary sustainability science projects in other research contexts.

Karakteristik blade sisi cekung turbin hidrokinetik Savonius yang memiliki nilai torsi negatif mengakibatkan kelemahan berupa efisiensi turbin yang relatif rendah, sehingga diperlukan sistem pengarah aliran berupa rectifier guide vane. Studi ini bertujuan membandingkan performa yang dihasilkan turbin Savonius tanpa guide vanes dan turbin Savonius menggunakan guide vanes dengan memvariasikan lebar rectifier L=Rt/4, L=Rt/2 dan L=3Rt/4, dimana Rt adalah jari-jari turbin. Metode pengujian dilakukan secara eksperimental di saluran prismatik dengan kecepatan aliran 0,111-0,1415 m/s. Hasil studi menunjukkan bahwa penambahan guide vanes dengan variasi lebar rectifier L=Rt/4, L=Rt/2 dan L=3Rt/4 masing-masing menghasilkan peningkatan torsi sebesar 29,9%; 33,3%; dan 36,3%. Turbin Savonius menggunakan guide vanes dengan lebar rectifier L=3Rt/4 menghasilkan coefficient of torque (Ct) dan coefficient of power (Cp) yang lebih tinggi dibandingkan variasi lebar rectifier (L) lainnya, sehingga kinerja turbin meningkat.
Kata kunci: coefficient of power, hidrokinetik, savonius, rectifier guide vanes

ABSTRACT
The characteristic of the concave side blade of the Savonius hydrokinetic turbine which has a negative torque value, it leads to the weakness in the form of a relatively low turbine efficiency, thus a flow steering system is needed in the form of a rectifier guide vane. The aim of this study was to compare the performance of the Savonius turbine without guide vanes and the Savonius turbine using guide vanes by varying the width of the rectifier L=Rt/4, L=Rt/2 dan L=3Rt/4, where Rt is the turbine radius. The test method was undertaken experimentally in a prismatic channel with a flow velocity of 0.111–0.1415 m/s. The results of the study pointed out that the addition of guide vanes with variations in the width of the rectifier was L=Rt/4, L=Rt/2 dan L=3Rt/4 and each of them had an increase in torque of 29.9%, 33.3% and 36.3%. The Savonius turbine used guide vanes with a rectifier width of L=3Rt/4 and it resulted a higher coefficient of torque (Ct) and coefficient of power (Cp) compared to other variations of rectifier width (L), thus, the performance of turbine increased.
Keywords: coefficient of power, hydrokinetic, savonius, rectifier guide vanes

Ichsan, N., Nindito, D. A., & Saputra, R. H. (2021). Uji Eksperimental Pengaruh Dimensi Lebar Rectifier Guide Vanes terhadap Kinerja Turbin Hidrokinetik Savonius. RekaRacana: Jurnal Teknil Sipil, 7(2), 96.

Ichsan, N., Nindito, D.A. and Saputra, R.H., 2021. Uji Eksperimental Pengaruh Dimensi Lebar Rectifier Guide Vanes terhadap Kinerja Turbin Hidrokinetik Savonius. RekaRacana: Jurnal Teknil Sipil, 7(2), p.96.

Reference :
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Alexander, A. S., & Santhanakrishnan, A. (2017). Trapped Cylindrical Flow With Multiple Inlets for Savonius Vertical Axis Wind Turbines. Journal of Fluids Engineerinng, 1–26.

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A metamodel simulation based optimisation approach for the tidal turbine location problem is introduced. The method comprises design of experiments, computational simulations, metamodel construction and formulation of a mathematical optimisation model. Sample plans with different number of data points are used to fit 2nd and 3rd order polynomial as a function of two design parameters: longitudinal and lateral spacing, with a view to approximating the power output of tidal turbine farms with inline and staggered layouts, each Aquatic Science and Technology ISSN 2168-9148 2015 34 of them with a fixed number of turbines. The major advantage this method has, in comparison to those reported in the literature, is the capability to analyse different design parameter combinations that satisfy optimality criteria in reasonable computational time, while taking into account complex flow-turbine interactions.

The Marine Energy Community has been engaged with Standards since 2008 as a necessary adjunct to the development of a maturing industry. This paper seeks to present a brief rationale for standards in this context; to provide a summary of the key events to date and to explain the International arrangements for standards-making and compliance in the Marine Energy sectormaking brief mention of future plans. Finally, the paper is intended to challenge and encourage people to become involved in the making of standards for Marine Energy.

This document presents the experimentally determined power generation efficiency for the drive-train and motor of a 20 kW experimental ocean current turbine. This efficiency assessment was performed using a custom designed dynamometer and covered much of the generator's expected operating range. These measurements are used with numerically modeled rotor performance to predict the overall efficiency of the ocean current turbine when converting kinetic energy flux to electric power.