Harumi Fujimoto, Karen Kurisu*
Ritsumeikan High School
*Email:
Abstract
Global warming and the risks of nuclear power generation highlight the need for eco-friendly renewable energy. Wave power generation, if widely adopted, could significantly benefit Japan, an island nation surrounded by the sea. This study examines a pendulum-type wave power generation device known for its efficiency and environmental friendliness. Previous research indicated that conventional pendulums are typically straight, leading to the hypothesis that altering their shape could enhance wave energy conversion efficiency. To evaluate the effectiveness of various pendulum designs, a series of simulations and experimental tests were conducted. A force sensor measured the force exerted by the pendulum, while a voltage sensor recorded the generated voltage during movement. Results showed that a newly designed pendulum shape exerted the greatest force, while a right-sided curved design produced the highest voltage output. These findings confirm that changing the pendulum’s shape can lead to improved efficiency. Future research will focus on discovering even more efficient shapes and exploring the effects of varying wave heights on performance. This approach aims to optimize wave power generation for practical application in Japan, contributing to sustainable energy solutions.
Introduction
Amid global warming concerns and fossil fuel depletion, the use of renewable energy is becoming more widespread. However, in Japan 71.9 % of electricity generation in 2022 relied on fossil fuels, resulting in a significant burden on the environment. In contrast, the available wave energy along continental coastlines is approximately 29,500 TWh, surpassing the total global electricity consumption of 24,877 TWh. This study focuses on the design of a new pendulum-type wave power generation device that utilizes wave motion and evaluates its efficiency. The pendulum-type system is expected to be simple in design, highly efficient, and capable of low-cost production. The goal is to contribute to providing a sustainable energy supply in Japan.
Experiment 1
Aim: To find the optimal ratio between the weights of the top and bottom parts of the pendulum for effectively measuring force using a force sensor.
Method: The wave generation and dissipating devices were set up in a water tank with the simulated pendulum-type wave power generation device. Waves were created to make the pendulum move and the force was measured using a force sensor. Also, weight ratios of 1:1, 1:2, 2:3, 3:2, and 2:1 (top: bottom) were each tested three times and the data was analyzed.
Results and Discussion: Based on Figure 1, the weight ratio of 2:1 resulted in the highest average force. Therefore, the 2:1 weight ratio is considered the most effective for measuring force in this experiment. Consequently, the 2:1 ratio was used in Experiment 2.
Experiment 2
Aim: To determine which pendulum shape generates force the most efficiently.
Method: The wave generation and dissipating devices were set up in a water tank with the simulated pendulum type wave power generation device. Waves were created to make the pendulum move and the force was measured using a force sensor. The above steps were repeated for pendulum shapes a, b, c, d, e, f, and g.
Results and Discussion: The force sensor recorded the highest average force with shape d. Therefore, based on Experiment 2, shape d is considered to have the highest conversion efficiency for converting wave energy into force.
Experiment 3
Aim: To compare the rotation speed of the pendulum axis for each shape, the voltage generated by the motor connected to the axis was measured.
Method: The wave generation and dissipating devices were set up in a water tank with the simulated pendulum type wave power generation device. Waves were created to make the pendulum move, and the voltage created by the rotation was measured using a voltage sensor. The above steps were repeated for all the pendulums.
Results and Discussion: According to the results of Experiment 3, shape b generated the highest voltage. This suggests that the axis of shape b rotated the fastest. The other shapes produced relatively similar values. Moving forward, it will be necessary to investigate why the voltage was higher when testing shape b.
Experiment 4
Aim: To compare a new shape, which was designed based on the considerations from experiments 2 and 3, with the previously devised shapes (a, b, and d) in terms of both force and voltage. Shape a was chosen because it was from previous research, while b and d demonstrated the best performance.
Method: Synthetic sea salt was dissolved in the water tank to create artificial seawater. The wave generation and dissipating devices were set up in a water tank with the simulated pendulum-type wave power generation device. Waves were created to make the pendulum move, and force and voltage were measured using a force sensor and a voltage sensor. The above steps were repeated for the four pendulum shapes.
Results and Discussion: In the experiment with the force sensor, the measured force increased in the order of shapes a, b, d, and h, with shape h recording the highest force. In the experiment with the voltage sensor, the measured voltage increased in the order of shapes a, d, h, and b, with shape b recording the highest voltage.
Figure 7. Average force generated by pendulum shape. Error bars represent standard error. 
Figure 8. Average voltage generated by pendulum shape. Error bars represent standard error.
Summary
Based on experiment 2, it was found that Shape d has a high efficiency in converting wave energy into force. In the voltage measurement conducted in Experiment 3, Shape b exhibited a significantly higher rotation speed. Based on the experiment 4, Shape h was found to be more efficient in converting wave energy into force than the other previously devised shapes. However, a higher voltage was measured with shape b than with shape h.
Future Plans
Moving forward, the focus will be on investigating the differences between Shapes b, c, and d by comparing their performances in force and voltage tests in greater detail. Future research will attempt to isolate the reason why the single curve pendulum unexpectedly outperformed the double curved pendulum in terms of voltage. Experiments will be conducted by varying the wave height and the surrounding environment.
References
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https://doi.org/10.30967/IJCRSET/Diriba-Gonfa-Tolasa/168
