c2-7-11-2024.pdf

Chapter 2 CONCEPTUAL FRAMEWORK This chapter provides an overview of the relevant literature and studies gathered through an extensive and detailed search by the researchers. It covers a broad range of theories, find...

Chapter 2 CONCEPTUAL FRAMEWORK This chapter provides an overview of the relevant literature and studies gathered through an extensive and detailed search by the researchers. It covers a broad range of theories, findings, and progressions related to the topic. The content in this chapter helps the reader understand concepts pertinent to the current research. Additionally, this chapter describes the assessment system, explains the data analysis methods, presents the study's conceptual framework, and operational definition of key terms. Review of Related Literature and Studies This chapter discusses the related literature relevant to the development of the design, explains the concept behind principles discussed in the study, analyzing presented findings to outline courses of preferred approach, and scientific terms are defined to facilitate the understanding of the study. Hydrokinetic Systems The global energy landscape is currently dominated by conventional energy sources, primarily fossil fuels, which are major contributors to environmental degradation, air pollution, and climate change (Intergovernmental Panel on Climate Change, 2021). Despite their high energy output, fossil fuels are finite and pose significant risks to both the environment and public health (World Health Organization, 2018). Nuclear energy, another major player, presents issues related to radioactive waste management and potential catastrophic risks, as evidenced by historical incidents like the Fukushima disaster (International Atomic Energy Agency, 2015). Renewable sources such as solar and wind power, although environmentally friendly, face challenges related to intermittency and geographic limitations, making them less reliable without substantial energy storage solutions (International Renewable Energy Agency, 2019). In this context, hydrokinetic energy emerges as a promising alternative. Hydrokinetic energy conversion systems have gained popularity in the last two decades, converting kinetic energy from various sources like river streams, tidal currents, and waves into electricity without the need for special heads or impoundments. The hydrokinetic turbine is a class of Zero Head turbines through which available kinetic energy in the free-flowing water is extracted. Its working principle is similar to a wind turbine; only the fluid medium is changed from wind to water. It uses the free flow energy of water rather than the potential energy available in the water by using a dam. The basic schematic diagram for harnessing energy from flowing water is shown in Fig. 2.1. The following steps are involved in the energy conversion process (Killingtveit, 2019): Figure 1. Hydrokinetic Energy Conversion Process Source: https://doi.org/10.1016/j.rser.2010.06.016 Small-scale Hydrokinetic System Application  The development of hydrokinetic systems in the Philippines is currently in an exploratory and developmental phase, with multiple pilot projects and research initiatives underway to evaluate their feasibility and effectiveness. The Department of Science and Technology (DOST) has conducted studies indicating the significant potential of hydrokinetic turbines to generate power even in the low-flow conditions typical of many Philippine rivers (DOST, 2020). Furthermore, local universities and research institutions, such as the University of the Philippines, are actively engaged in developing and testing prototypes specifically designed for the unique hydrological and environmental conditions of the country (Aquino, Reyes, & Villafuerte, 2021). These efforts underscore the promise of hydrokinetic systems to substantially contribute to the nation’s renewable energy landscape, particularly in providing sustainable power to off-grid and rural communities. The geographic and demographic context of the Philippines further highlights the suitability and necessity of focusing on small-scale hydrokinetic systems. As an archipelagic nation comprising over 7,600 islands, the Philippines is composed of numerous rivers that offer consistent water flow, making them ideal for hydrokinetic energy generation (Philippine Statistics Authority, 2020). Many rural and remote communities, home to approximately 10 million people, are situated near these rivers and often lack access to the national power grid (National Electrification Administration, 2021). Small-scale hydrokinetic systems are particularly well-suited for these areas due to their capacity to generate continuous and reliable power, addressing the intermittency limitations of other renewable sources such as solar and wind, which are dependent on weather conditions (Asian Development Bank, 2018). Emphasizing small-scale hydrokinetic systems is crucial for several reasons. Firstly, these systems can be deployed with relatively low initial costs and maintenance requirements, making them accessible to remote and economically disadvantaged communities. Secondly, they can operate efficiently in the variable flow conditions of small rivers, providing a stable energy source that can enhance the energy security and economic development of these areas. Finally, the environmental impact of small-scale systems is minimal, making them a sustainable choice for local energy needs. Even though the output capacity is small, capacity can be increased by an array or modular installation (Alvarez et al., 2018, Shafei M.A.R et al., 2015). In addition, the system is easy to transport and relocate due to the small size of the plant. Moreover, the system can be installed along the riverside either mooring to a fixed structure or on a floating pontoon (Anyi and Kirke, 2010). The Savonius hydrokinetic turbine is particularly suitable for small-scale river applications due to its simple design, cost-effectiveness, and ability to operate efficiently in low-velocity water flows. Unlike other turbine types, the Savonius turbine's vertical axis design allows it to capture kinetic energy from water flowing in any direction, making it highly adaptable to the variable conditions often found in small rivers (Kishore et al., 2018). Additionally, the construction and maintenance costs of Savonius turbines are relatively low, which is advantageous for small-scale installations where budget constraints are significant (Bahaj et al., 2019). Their ability to start rotating at low water speeds enhances their utility in small rivers where water flow may not be consistently strong (Saha et al., 2020). This combination of simplicity, low cost, and efficiency in low-velocity conditions makes the Savonius hydrokinetic turbine an ideal choice for harnessing renewable energy in small-scale river applications. Savonius Hydrokinetic Turbines  This section discusses the operational and performance properties of Savonius hydrokinetic turbines (SHT). Its results on the literature findings on design parameters such as the blade placement and blade arc angles, number of blades, aspect ratio and operational parameters that affects the performance of a Savonius turbine. Hydrokinetic turbines can vary depending on the scale and intended purpose. With regards to wind turbine systems there are two primary modes: horizontal-axis or vertical-axis rotors. The former is typically used for larger scale ocean current application, whereas the latter is more suitable for cost-effective current applications. Among the various vertical-axis hydrokinetic turbines, the Savonius turbine is suitable for river current applications to deliver a sustainable electrical power supply. The primary reason for employing this turbine lies in its simpler system design, which consequently results in lower development costs compared to other vertical-axis turbines (Salleh et al., 2019). In a recent study conducted by Abeniso et al. (2023), it showed that by using a bed array system with a four-blade turbine results to an average output value of 0.024370889 watts with the parameters set to a velocity of 0.7401 m/s with a duration of 30 seconds. This study was conducted as a field experiment, showcasing the performance characteristics of a Savonius hydrokinetic turbine (SHT), emphasizing on various geometrical and operational parameters. While a separate study conducted by Wu et al. (2022), demonstrates the performance of SHT, highlighting the number of blades, blade arc angles, and blade placement angle, as factors affecting the efficiency of the system. The researchers tested different types of blade parameters, having 2, 4, 6, and 8 bladed turbines. The study was conducted in a controlled environment with three-dimensional CFD simulations with Re = 6.72 x 105, matching the experimental conditions. It revealed that having a six bladed turbine with an arc angle of 135° and placement angle of 0° yields a higher torque and better power performance. It also showed that having a lower aspect ratio (AR