Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-2, 2017 ISSN: 2454-1362, http://www.onlinejournal.in
Floating Water Turbine for Small Scale Power Generation in Remote Areas Rishikesh S Hari Student, Cochin University of Science and Technology Abstract: Even in 21st century, many remote areas of the world are still not electrified. Barriers in setting up of power grids are the main reason for it. Off-grid energy generation is the only solution for this issue. The majority of the off-grid energy solutions are costly and are not environment-friendly. This paper examines on ‘floating water turbine’, an effective alternative to fossil fuel based remote power generation. The paper also discusses on the methodologies chosen while designing the turbine, analysis of the design and future scopes of this technology.
1. Introduction Over 1.2 billion people in the world do not have access to electricity in the modern world [1]. Majority of these people are located in remote areas of the world, where conventional power grid extensions are not possible. Some off-grid energy solutions are required for providing electricity to these areas. Even though such solutions exist, most of these technologies require high capital investment and are too complex. Majority of off-grid power generation depends upon diesel or other fossil fuel based energy source. Fossil fuel based power generation is often costly and is complex. It requires the transportation of fuel from readily available sites to the remote locations for power generation. To tackle these barriers a low-cost, environmentfriendly, simple and maintenance free power generation method is required. Remote power generation using floating turbines is an excellent substitute for the conventional fossil fuel based offgrid power generation. Floating water turbine makes use of the free flow energy available at local water bodies for the generation of electricity. It essentially consists of a hydrokinetic water turbine placed on a floating body across a water stream. As the mechanism is simple, maintenance can be done locally as components are readily available. These turbines require minimum maintenance and operate continuously irrespective of time. Even though the power output of a single unit is marginal, by setting up of multiple units, adequate electricity can be generated for basic uses like water pumping, lighting, refrigeration of medicines in camps, etc.
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2. Literature Review Hydrokinetic energy can be generated from ocean, river or any water stream. Hydrokinetic turbines, produce electricity directly from the flowing water in a river or a stream by making use of the energy. The turbine blades would turn the generator and capture the energy of the water flow. Conventional hydropower generation is done by building dams and making use of the energy of falling water by running the turbine blades. Hydropower generation has its own disadvantages being costly and also due to its negative effects on the environment. Hydrokinetic power generation uses the kinetic energy of the stream of water instead of potential energy. A hydrokinetic turbine used in power generation has a lot of similarities with the wind turbine in terms of the operation, electrical circuitry, and variable speed capability for efficient operation. Since water is almost 800 times denser than air, hydrokinetic turbines are more efficient than wind turbines even at low speed. Hydrokinetic turbines are mainly classified based on the direction of rotation of the turbine rotor relative to the direction of water flow at a site. Conventionally the two types are horizontal axis and vertical axis hydrokinetic turbine. In horizontal axis turbine, the rotational axis of the rotor is parallel to the incoming water stream and whereas in the vertical or cross-flow turbine, the rotational axis is perpendicular to the incoming water stream. It has been observed and proven that horizontal axis hydrokinetic turbines (referred as HAHkT) are more efficient than its vertical axis turbine due to lower inlet losses, less vibration, and more uniform lift forces. The flexibility of installing HAHkT near water surface in rivers, self-starting behavior, absence of vibrational forces and less usage of materials makes HAHkT more efficient than vertical axis hydrokinetic turbines. The primary obstacle to increased widespread usage of different renewable energy sources like solar, geothermal, wind and fuel cells is associated with the economics involved in its production. Although many of this clean energy sources are able Page 916
Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-2, 2017 ISSN: 2454-1362, http://www.onlinejournal.in to address the global environmental concerns (i.e. reduction of greenhouse gas emission) and energy security concerns, they are much more expensive than conventional fossil fuels, making them economically unattractive. The initial cost of energy calculations for hydrokinetic systems are promising from the economic standpoint, primarily because the overall cost associated with the optimal functioning of a hydrokinetic system is comparatively less compared to traditional hydropower or wind systems of same capacity[2]. However, the technical challenges associated with hydrokinetic turbines needs to be assessed to define appropriate technology classes, the design of individual turbine components and power conversion systems for the hydrokinetic technologies before realizing the true commercial success of the present technology.
Figure 4.1 Floating body
3. Mechanism The floating water turbine is a hydrokinetic water turbine making use of the free flow kinetic energy of water for producing electricity via a generator. The turbine is attached to a floating body designed so as to support the turbine and also to maximize the inlet water velocity. Mainly the floating turbine consists of the following parts: Hydrokinetic turbine Floating body Transmission system Generator
Figure 4.2 Turbine
When the whole assembly is placed in a free flow of water, due to the kinetic energy, the blades of the turbine are rotated. The drive of turbine shaft is then transmitted to a DC generator through a gear mechanism for obtaining the optimum speed of the generator. The electricity produced by the generator can be stored in a battery or can be used for small scale purposes.
4. Design Based on the data collected through research, the floating water turbine was designed using Solidworks CAD software. The floating characteristics of the turbine was achieved by making the floating body buoyant enough to support the weight of the turbine with the help of buoyancy calculations. The floating body was designed in such a way that maximum convergence occurs at the inlet thereby increasing the velocity of flow (see Figure 4.1). The turbine was designed to make the inlet angle maximum (see Figure 4.2). By considering the generator specifications, with the help of design calculations, suitable transmission mechanism was also chosen. All the individual design components were finally assembled to obtain the final 3-D model.
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Figure 4.3 Assembled design
5. Analysis The proposed design was analyzed in ANSYS software. Floating body analysis, blade profile analysis, 3-D analysis of blade and static analysis of Page 917
Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-2, 2017 ISSN: 2454-1362, http://www.onlinejournal.in the turbine were carried out for ensuring safety at normal load condition and also the efficiency of the design.
5.1. Floating Body analysis The float was designed and optimized so as to ensure maximum flow rate available at the inlet of the turbine. The analysis was carried out in Fluent flow (Workbench) and a suitable design was optimized with the maximum convergence at inlet and hence the velocity of the flow towards the inlet was maximized accordingly (see Figure 5.1). Figure 5.2 2-D flow analysis of flat blade profile
5.3. 3-D analysis of blade
Figure 1
5.2. Blade selection analysis Two profiles were considered for the design of blade profiles that is flat plate profile and circular arc profile. Here the shape of the blade was made as a semi-circular bucket so that maximum flow rate from the stream enters the blade. A semi-circular shape was expected to allow more flow of water to enter bucket as compared to one that could be striking a flat plate. So from the analysis (see Figure 5.1 and Figure 5.2) results and also from further research the circular blade profile was selected over flat plate profile for the turbine design [3].
The 3D analysis of the blade profile was carried out in Fluent Flow (Workbench) by considering a velocity of 1m/s, hence the drag and lift obtained was calculated accordingly. The variation of pressure at the concave and convex regions of the blade was noticeably in the result. From the result (see Figure 5.3), it was observed that a drag force of 38.46N was experienced by a single blade when exposed to a flow of 1m/s. The drag force increases with increase in flow velocity. More the flow velocity more is the experienced drag force.
Figure 5. 3-D analysis of blade
5.4. Static analysis of turbine
Figure 5.4. Deformation experienced by turbine
Figure 5.1 2-D flow analysis of circular blade profile
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From the 3D analysis of blade profile, a drag force of 38.46N was obtained for 1m/s flow. By considering this drag force, a static analysis was carried out on the whole turbine and the total
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Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-2, 2017 ISSN: 2454-1362, http://www.onlinejournal.in deformation experienced by the turbine was obtained. From the results (see Figure 5.4), it can be inferred that the deformation lies in the range 0 to 0.6mm and hence the design was found to be safe.
Figure 5.5 Shear stress on blades
Maximum shear stress was observed at the blade in contact with the fluid. It can also be inferred from the results (see fig. 5.5) that the shear stress lies within the range of -6.8603x106 Pa to 7.5579x105 Pa. By considering the velocity of 10 m/s (assuming it to be the maximum velocity), a drag force of 3746 N was obtained from the 3D analysis of the blade. By inputting this value as the maximum force that will be applied to the turbine during its period of operation, the static analysis of the turbine model was conducted. From the analysis of the blade and its solution for total deformation under the load of 3746 N, the result shows a range from 0-0.060874m for the deformation (see Figure 5.6). It is more experienced on the blades in which the load is felt along with some area of the disc to which they are attached.
The major limitation with the current design is the use of mild steel for the fabricating turbine. Due to this, there is a high risk of corrosion of the turbine. This issue can be tackled by the use of composite materials which are corrosion resistant and also light. Also, the power output from floating water turbine varies according to the variation in velocity of the free flow. So, adequate measures are to be implemented in the system so that the power output remains constant. Small-scale hydropower generation is especially attractive as an alternative to the polluting less efficient diesel power generation that provides electric energy in remote communities across the world. Since many remote communities are situated near moving water bodies these water turbines represent a promising source of clean power as they make use of the free flow energy of water streams. Most of the components, such as a blade, generator, power converter, etc., needed for fabricating the floating water turbine system are locally available and is cheap [4]. Therefore, product development cycle, cost, and level of technical sophistication are expected to be low.
7. References [1] "World Energy Outlook," 2016. [Online]. Available:http://www.worldenergyoutlook.org/media /weowebsite/2015/WEO2016Electricity.xlsx. Accessed: Dec. 6, 2016. [2] S. SUBHRA MUKHERJI, "Design and critical performance evaluation of horizontal axis hydrokinetic turbines," MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY, 2010. [3] K. A.R.Ismail and T. P. Batalha, "A comparative study on river hydrokinetic turbines blade profiles," nt. Journal of Engineering Research and Applications, 2015
Figure 5.6 Total deformation
6. Conclusion and Future Scope Floating water turbines are a renewable source of energy having a minimum impact on the environment. The initial setup cost is less as these turbines operate in a “free flow� environment that does not require damming or diversion of rivers. The maintenance required for these turbines are less and can be done locally. It was also observed that the improved design of the float resulted in a higher efficiency.
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[4] H. Jacobus Vermaak, K. Kusakana, and S. Philip Koko, "Status of micro-hydrokinetic river technology in rural applications: A review of literature," Renewable and Sustainable Energy Reviews, 2013.
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