Performance Analysis of Piezoelectric Energy Harvesting System Under Varying Bluff Body Masses and Diameters—Experimental Study and Validation with 0–1 Test

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors This paper conducts a comprehensive and in-depth experimental study on the performance of piezoelectric energy harvesting systems under varying blunt body mass and diameter conditions, with rigorous research design and scientific methods. The author revealed the influence of blunt body geometry on energy harvesting efficiency through carefully designed experimental setups and systematic parameter changes. The paper innovatively applies 0-1 chaos testing as a diagnostic tool to analyze the dynamic characteristics of the system, providing a new perspective for understanding the complex behavior of energy harvesting systems. The research results have important guiding value for optimizing the design of piezoelectric energy harvesters, especially providing experimental basis for selecting blunt body geometric parameters. The paper has a clear structure, rich charts, professional data presentation, and in-depth analysis of the relationship between experimental results and theoretical expectations in the discussion section. The author team has extensive research experience in the field of piezoelectric energy harvesting, and the references comprehensively cover the latest developments in related fields.     1. It is recommended to add a description of experimental repeatability and error control in the "2. Research Object and Test rig" section, indicating the number of repetitions and measurement error range under each testing condition, in order to enhance the reliability of experimental results. At present, this part of the information is missing, making it difficult for readers to evaluate the statistical significance of the data. 2. The presentation of Figures 8 and 9 can be improved. It is recommended to integrate the results of different diameters into the same chart and display them in subgraph form for readers to intuitively compare the performance differences under different diameter conditions. The current scattered chart layout increases the difficulty for readers to compare across charts. 3. In the paper, the terms "bluff body" and "exceter" are used interchangeably to refer to the same object (such as in line 5 of the abstract and multiple places in the main text). It is recommended to unify the terminology to avoid confusion. At the first appearance, it should be clearly defined and consistent throughout the text. 4. In the Results and Discussion section, it is recommended to provide clearer definitions and differentiation criteria for "oscillatory response" and "transient response", preferably by providing quantitative indicator thresholds, rather than relying solely on illustrated case studies.

Author Response

Reviewer no. 1

 

All the authors of this manuscript are grateful to the reviewer not only for his/her positive and encouraging comments, but also for the constructive criticism that is intended to improve our work. Below please find the answers on given questions.

 

General comment: This paper conducts a comprehensive and in-depth experimental study on the performance of piezoelectric energy harvesting systems under varying blunt body mass and diameter conditions, with rigorous research design and scientific methods. The author revealed the influence of blunt body geometry on energy harvesting efficiency through carefully designed experimental setups and systematic parameter changes. The paper innovatively applies 0-1 chaos testing as a diagnostic tool to analyze the dynamic characteristics of the system, providing a new perspective for understanding the complex behavior of energy harvesting systems. The research results have important guiding value for optimizing the design of piezoelectric energy harvesters, especially providing experimental basis for selecting blunt body geometric parameters. The paper has a clear structure, rich charts, professional data presentation, and in-depth analysis of the relationship between experimental results and theoretical expectations in the discussion section. The author team has extensive research experience in the field of piezoelectric energy harvesting, and the references comprehensively cover the latest developments in related fields.  

 

Response: We sincerely thank the Reviewer for the thorough evaluation and encouraging remarks regarding our work. We are grateful for the recognition of our research design, experimental methodology, and the application of 0–1 chaos testing. We have carefully addressed all additional comments and suggestions to improve the clarity and consistency of the manuscript. We believe these revisions have further strengthened the quality of our paper.

 

Comment no. 1: It is recommended to add a description of experimental repeatability and error control in the "2. Research Object and Test rig" section, indicating the number of repetitions and measurement error range under each testing condition, in order to enhance the reliability of experimental results. At present, this part of the information is missing, making it difficult for readers to evaluate the statistical significance of the data.

 

Response: Thank you for your valuable comment and suggestion regarding the experimental methodology. Due to the stable operating conditions of the test rig and the high repeatability observed during preliminary trials, each measurement condition was recorded once, following a sufficient flow stabilization period. To ensure consistency and minimize experimental uncertainty, the system was carefully reset before each test point. Additionally, continuous monitoring of the sensor calibration and signal integrity was conducted throughout the data acquisition process. The acquisition system used provides high resolution and accuracy, which ensured reliable and reproducible data collection under all tested conditions. In the revised version of the manuscript, we have expanded the description of our approach to data repeatability and sensors accuracy.

 

Comment no. 2: The presentation of Figures 8 and 9 can be improved. It is recommended to integrate the results of different diameters into the same chart and display them in subgraph form for readers to intuitively compare the performance differences under different diameter conditions. The current scattered chart layout increases the difficulty for readers to compare across charts.

 

Response: Thank you for the helpful suggestion. In response, we have aligned the axes across all subplots in Figure 8 to facilitate direct comparison of voltage values for different bluff body diameters. Additionally, we increased the font size to improve readability and visual consistency. For Figure 9, we increased the font size and marker size to improve visibility and clarity, while using thinner lines. These adjustments enhance the overall readability of the figure and support a more intuitive comparison of the results.

 

Comment no. 3: In the paper, the terms "bluff body" and "exceter" are used interchangeably to refer to the same object (such as in line 5 of the abstract and multiple places in the main text). It is recommended to unify the terminology to avoid confusion. At the first appearance, it should be clearly defined and consistent throughout the text.

 

Response: Thank you for your valuable comment. We agree that the term could be misleading, and therefore we have replaced all instances with the unified term “bluff body” throughout the manuscript. We appreciate your attention to detail.

 

Comment no. 4: In the Results and Discussion section, it is recommended to provide clearer definitions and differentiation criteria for "oscillatory response" and "transient response", preferably by providing quantitative indicator thresholds, rather than relying solely on illustrated case studies.

 

Response: Thank you for your insightful comment regarding the need for clearer definitions and differentiation criteria between the "oscillatory response" and the "transient response." In response, we have revised the Results and Discussion section to provide quantitative thresholds that objectively define the boundaries between these two dynamic regimes.

 

In particular, we now refer to the results of the 0-1 test for chaos, and we define the onset of transient or chaotic behavior as the point at which the K-value exceeds 0.4. This threshold applies to both variants of the test:

 

• K1 – calculated via the Mean Square Displacement (MSD) method,
• K2 – based on the Pearson correlation coefficient.

 

These threshold values are summarized in Table 3, which lists the airflow velocities at which this transition occurs for various mass–diameter configurations. This provides a reproducible, quantitative basis for distinguishing between regular (oscillatory) and chaotic (transient) behavior.

 

We have also revised the interpretation of Table 2, which originally indicated transition points based on visual analysis of signal patterns and peak-to-peak voltage (RMS) trends. While Table 2 reflects empirical observations and qualitative dynamics inferred from the voltage signal, Table 3 supports and extends these findings by offering a formal, numerical criterion grounded in nonlinear time-series analysis.

This combined approach ensures that the classification of system behavior is not solely reliant on illustrative examples, but rather supported by complementary indicators: energy-based (RMS) and chaos-based (K-value). We believe these revisions significantly improve the objectivity, transparency, and reproducibility of the presented results.

We again thank the Reviewer for the valuable feedback, which has led to meaningful improvements in the quality, scope, and clarity of our manuscript. We have made every effort to enhance the article in accordance with the recommendations and hope that the overall contribution of our work will be duly appreciated.

Reviewer 2 Report

Comments and Suggestions for Authors

Pawel reported Piezoelectric Energy Harvesting System and i carefully read the whole manuscript which written very well. I think this study can be accepted after revisions. 

1. As i found that introduction section doesn’t clearly provide sufficient research gap and novelty.
2. Authors are suggested to provide more details for experimental methodology such as data repeatability and sensor accuracy.
3. Figures quality should be improved. 
4. Please include quantitative statistical analysis for the results.
5. Discussion is not sufficient for system’s long-term durability and its environmental effects. Please elaborate in details. 
6. Please include recent references such as 2025 to support the claimed results.
7. Please check grammatical errors and typos errors. 
8. Chellanges and limitation can be added in conclusion section. 

Author Response

Reviewer no. 2

 

All the authors of this manuscript are grateful to the reviewer not only for his/her positive and encouraging comments, but also for the constructive criticism that is intended to improve our work. Below please find the answers on given questions.

 

Comment no. 1: As i found that introduction section doesn’t clearly provide sufficient research gap and novelty.

 

Response: Thank you for your insightful comment. In response, we have revised the Introduction to more clearly articulate the research gap and the novelty of our work. Specifically, we now emphasize that, unlike previous studies (e.g., by Zeng), which focused on flow control techniques and surface modifications of bluff bodies, our study investigates the influence of mass and velocity of a cylindrical bluff body on the performance of a piezoelectric energy harvester. This aspect has not been addressed in prior literature. Additionally, we highlight our use of the 0–1 test as a novel approach to characterize energy harvester’s dynamics. These clarifications have been added to strengthen the motivation and originality of the study.

 

Comment no. 2: Authors are suggested to provide more details for experimental methodology such as data repeatability and sensor accuracy.

 

Response: Thank you for your valuable comment and suggestion regarding the experimental methodology. Due to the stable operating conditions of the test rig and the high repeatability observed during preliminary trials, each measurement condition was recorded once, following a sufficient flow stabilization period. To ensure consistency and minimize experimental uncertainty, the system was carefully reset before each test point. Additionally, continuous monitoring of the sensor calibration and signal integrity was conducted throughout the data acquisition process. The acquisition system used provides high resolution and accuracy, which ensured reliable and reproducible data collection under all tested conditions. In the revised version of the manuscript, we have expanded the description of our approach to data repeatability and sensors accuracy.

 

Comment no. 3: Figures quality should be improved. 

 

Response: Thank you for your comment. The issue with figure quality likely occurred during the automatic compression of the DOCX file to PDF within the submission system. Unfortunately, this process is beyond our control. However, to support the editorial process, we will provide a separate file containing all figures in high resolution along with our response to the reviewers.

 

Comment no. 4: Please include quantitative statistical analysis for the results.

 

Response: Thank you for your suggestion. A quantitative statistical analysis has been added to the revised manuscript. For considered cases, the mean and standard deviation of the peak-to-peak voltage were calculated, along with the number of peaks considered. These values provide a clearer understanding of signal variability across different dynamic regimes and are supported by corresponding histograms.

 

Comment no. 5: Discussion is not sufficient for system’s long-term durability and its environmental effects. Please elaborate in details.

 

Response: Thank you for pointing this out. We have expanded the discussion in the revised manuscript to address the system’s long-term durability and environmental effects in more detail.

 

As shown in Table 1, the M2807-P1 piezoelectric sensor used in the energy harvesting system is engineered for high durability. It offers a typical lifetime of up to 10¹¹ cycles under moderate strain conditions (<400 ppm), making it well-suited for long-term operation in dynamic environments. The sensor also supports a wide operating voltage range (-500 V to +1500 V) and can function at frequencies below 1 MHz, which ensures stable performance over prolonged usage without material fatigue or degradation under normal working conditions.

 

Regarding environmental effects, the piezoelectric element used is based on solid-state materials and does not require external power to generate voltage from mechanical vibrations, making it an energy-efficient and low-emission solution. Furthermore, its compact form factor (300 µm thickness) and long operational life reduce the need for frequent replacement, thereby minimizing material waste and the environmental impact associated with maintenance or disposal.

 

These characteristics contribute to both the sustainability and reliability of the proposed system in long-term, vibration-based energy harvesting applications.

 

Comment no. 6: Please include recent references such as 2025 to support the claimed results.

 

Response: In the revised version of the paper, the Introduction and Discussion sections have been augmented with 13 recent references from 2024 and 2025. These newly added works focus on research into flow-induced vibrations (FIV), including vortex-induced vibrations (VIV), as mechanisms for energy harvesting, particularly wind energy. These studies explore various bluff body shapes and their spatial arrangements to enhance energy conversion efficiency and extend the operating range of such systems. To comprehend the complex fluid-structure interactions and validate the performance of these novel solutions, the authors of the cited works employed a wide array of research methodologies, including wind tunnel experiments, computational fluid dynamics (CFD) simulations, and advanced theoretical models.

 

Comment no. 7: Please check grammatical errors and typos errors. 

 

Response: After implementing the modifications, the entire work underwent a linguistic review to check for errors.

 

Comment no. 8: Chellanges and limitation can be added in conclusion section.

 

Response: Thank you for your suggestion. We have revised the conclusion section to explicitly include the key challenges and limitations of the system, such as its strong dependence on wind speed, sensitivity to bluff body mass and geometry, potential chaotic behavior, and the long-term durability of piezoelectric materials. These additions provide a clearer perspective on the current limitations and outline directions for future research.

 

We again thank the Reviewer for the valuable feedback, which has led to meaningful improvements in the quality, scope, and clarity of our manuscript. We have made every effort to enhance the article in accordance with the recommendations and hope that the overall contribution of our work will be duly appreciated.

 

Reviewer 3 Report

Comments and Suggestions for Authors

In this review manuscript, the authors present an experimental study on the performance of a piezoelectric energy harvesting system under varying bluff body masses and diameters. The study provides valuable insights into the impact of these parameters on energy harvesting efficiency. However, there are several areas where the manuscript could be improved to enhance its depth, clarity, and overall impact. Below are some specific questions and suggestions:

1. While the manuscript provides a comprehensive overview of the experimental setup and results, it could benefit from a more detailed discussion on the specific mechanisms by which the mass and diameter of the bluff body influence the piezoelectric energy harvesting efficiency. For example, a deeper dive into the role of bluff body orientation and its interaction with airflow would be valuable. Additionally, the manuscript could elaborate on how the distribution of mass along the bluff body affects the vibration modes and, consequently, the energy harvesting performance.
2. There are instances where terminology is used inconsistently throughout the manuscript. For example, the terms "bluff body mass" and "system mass" are used interchangeably, which can cause confusion. It would be beneficial to standardize the terminology to ensure clarity and avoid ambiguity.
3. The manuscript lists several challenges faced by the piezoelectric energy harvesting system, such as the system becoming trapped in a potential well and the limited range of effective operation. However, the discussion could be more in-depth. For instance, what are the underlying causes of these challenges, and how do they affect the long-term stability and performance of the energy harvester? A detailed analysis of these challenges would provide a better understanding of the limitations and potential improvements.
4. While PZT is a well-established material for piezoelectric applications, recent advancements in piezoelectric materials, such as novel polymers (eg. piezo-ionic-electric polymers, DOI: 10.1038/s41467-024-55177-y) and polymers with different morphologies, could offer advantages in terms of flexibility, lightweight structures, and improved performance under dynamic conditions. A brief discussion on the potential impact of these alternative materials on the energy harvesting efficiency and system dynamics would provide a broader perspective and highlight potential future directions for improving the system's performance.
5. The manuscript mentions various configurations of bluff bodies (e.g., different diameters and masses). Could the authors elaborate on the specific advantages and disadvantages of each configuration in the context of piezoelectric energy harvesting applications? For example, are there particular configurations that are more suitable for certain wind speed ranges due to their unique properties?

Author Response

Reviewer no. 3

 

All the authors of this manuscript are grateful to the reviewer not only for his/her positive and encouraging comments, but also for the constructive criticism that is intended to improve our work. Below please find the answers on given questions.

 

General comment: In this review manuscript, the authors present an experimental study on the performance of a piezoelectric energy harvesting system under varying bluff body masses and diameters. The study provides valuable insights into the impact of these parameters on energy harvesting efficiency. However, there are several areas where the manuscript could be improved to enhance its depth, clarity, and overall impact. Below are some specific questions and suggestions:

 

Response: We sincerely thank the Reviewer for the constructive feedback and for recognizing the relevance of our experimental study. We appreciate the thoughtful suggestions and specific questions, which have helped us to improve the clarity, depth, and overall quality of the manuscript. In response, we have carefully revised the text, addressed each comment in detail, and made corresponding changes to enhance the scientific rigor and presentation of our work.

 

Comment no. 1: While the manuscript provides a comprehensive overview of the experimental setup and results, it could benefit from a more detailed discussion on the specific mechanisms by which the mass and diameter of the bluff body influence the piezoelectric energy harvesting efficiency. For example, a deeper dive into the role of bluff body orientation and its interaction with airflow would be valuable. Additionally, the manuscript could elaborate on how the distribution of mass along the bluff body affects the vibration modes and, consequently, the energy harvesting performance.

 

Response: In the Results and Discussion section, information regarding the influence of mass and diameter on system efficiency has been added. Furthermore, a discussion was conducted concerning the bluff body's orientation and its interaction with the airflow.

 

Comment no. 2: There are instances where terminology is used inconsistently throughout the manuscript. For example, the terms "bluff body mass" and "system mass" are used interchangeably, which can cause confusion. It would be beneficial to standardize the terminology to ensure clarity and avoid ambiguity.

 

Response: Thank you very much for your valuable suggestion. We have carefully reviewed the manuscript and replaced the term “system mass” with “bluff body mass” where appropriate to ensure consistency. In our terminology, “bluff body” refers specifically to the oscillating mass mounted at the free end of the beam, while “system” refers to the complete setup, including the cantilever beam, support, springs, piezoelectric sensor, and the bluff body itself. These distinctions have now been clarified in the revised manuscript to avoid ambiguity.

 

Comment no. 3: The manuscript lists several challenges faced by the piezoelectric energy harvesting system, such as the system becoming trapped in a potential well and the limited range of effective operation. However, the discussion could be more in-depth. For instance, what are the underlying causes of these challenges, and how do they affect the long-term stability and performance of the energy harvester? A detailed analysis of these challenges would provide a better understanding of the limitations and potential improvements.

 

Response: In the Results and Discussion section, an analysis of the challenges encountered and their impact on the long-term stability and performance of the energy harvester has been incorporated. Additionally, the Conclusions section now characterizes future research challenges.

 

Comment no. 4: While PZT is a well-established material for piezoelectric applications, recent advancements in piezoelectric materials, such as novel polymers (eg. piezo-ionic-electric polymers, DOI: 10.1038/s41467-024-55177-y) and polymers with different morphologies, could offer advantages in terms of flexibility, lightweight structures, and improved performance under dynamic conditions. A brief discussion on the potential impact of these alternative materials on the energy harvesting efficiency and system dynamics would provide a broader perspective and highlight potential future directions for improving the system's performance.

 

Response: Thank you for the suggestion regarding new types of materials. This helped us to update the state of knowledge on recent advancements in piezoelectric materials. We've added information about this type of material to the Introduction section.

 

Comment no. 5: The manuscript mentions various configurations of bluff bodies (e.g., different diameters and masses). Could the authors elaborate on the specific advantages and disadvantages of each configuration in the context of piezoelectric energy harvesting applications? For example, are there particular configurations that are more suitable for certain wind speed ranges due to their unique properties?

 

Response: In the Results and Discussion section, an analysis of the influence of velocity and diameter on system performance has been added. Additionally, the Conclusions section has been supplemented with the most significant observations from the conducted research in this context.

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The author's revision is satisfactory. It can be accepted now for the publication.