Beyond Seasonal Arbitrage—Structured Review on Distributed Long Duration Energy Storage and Its Benefits to the Distribution Grid

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper focuses on the core contradiction of insufficient flexibility in the power system under the high proportion of variable renewable energy penetration. The core goal is to break through the single perspective of seasonal arbitrage and systematically explore the diverse value of distributed long-term energy storage on the distribution network. Through a systematic literature review and integration of academic and policy resources from 2015 to 2025, the paper comprehensively sorts out the underpaid value of distributed LDES in distribution network support, cost optimization, and resilience enhancement. Theoretical design combines methodological rigor with engineering practice orientation, and experimental verification covers multiple regional cases and multidimensional indicators. The conclusion has important academic and industrial value in promoting the transformation of distributed LDES from technological exploration to large-scale application, and has reached the level of journal publication as a whole. Specific evaluations are as follows:

(1) The paper focuses on the technical and economic benefits, but does not systematically evaluate the environmental costs of the entire lifecycle of distributed LDES. Hydrogen energy storage involves energy consumption in electrolytic cell manufacturing, electrolyte pollution risks in flow batteries, and the possibility of greenhouse gas leakage in thermal storage systems. Existing analysis may overestimate its environmental advantages. Suggest supplementing LCA analysis, comparing environmental indicators of different technologies, quantifying the impact of key links, proposing low-carbon optimization solutions, ensuring synchronous demonstration of environmental benefits and technical economy of distributed LDES, and avoiding sustainability deviations caused by prioritizing technology over environmental protection.

(2) This study did not involve the treatment strategies for the retirement stage of distributed LDES. Improper disposal of hydrogen storage tanks, electrode materials for flow batteries, insulation layers for thermal storage systems, etc. after retirement can result in environmental risks and resource waste. It is recommended to supplement retirement and cycling research, sort out the retirement years of main flow LDES technology, design retirement processes, analyze resource cycling efficiency, quantify retirement costs, propose policy recommendations, and fill the gap in the full life cycle research of distributed LDES.

(3) The paper defines LDES as the mainstream standard for discharge duration exceeding 10 hours, and mentions the classification difference between 4 hours and 20 hours, but does not explain why 10 hours has become the threshold for most studies from the perspective of energy system flexibility theory. The load fluctuation cycles of different power grids (such as intraday peak valley difference, seasonal supply-demand gap) have different demands for LDES duration, and a unified threshold may ignore system specificity. May I ask how to verify the universality of the 10 hour threshold through the correlation model of "grid load fluctuation characteristics - LDES duration demand". When the seasonal supply-demand gap in the power grid exceeds 30%, will the 10 hour threshold lead to insufficient LDES capacity, can the theoretical gap be quantified through the load storage balance formula, and will it increase the renewable energy curtailment rate by more than 5%.

(4) To make the introduction more comprehensive, it is recommended that the author refer to the following two papers on algorithms. 1)Towards visual interaction: hand segmentation by combining 3d graph deep learning and laser point cloud for intelligent rehabilitation. 2)Intelligent rehabilitation in an aging population: empowering human-machine interaction for hand function rehabilitation through 3d deep learning and point cloud.

(5) In the analysis of multi energy systems, the author did not clarify the priority of multi vector coupling of "electricity heat gas", assuming that each vector is equally important, but did not explain the rationality of thermal vector priority from the perspective of energy cascade utilization theory. The thermal load accounts for 40% -60% of the total load on the user side, and the cost of thermal energy storage is 30% lower than that of electrical energy storage. Prioritizing coupling thermal vectors can improve system economy. May I ask how to optimize the order of multi vector coupling through the "energy grade coupling priority" model. When the proportion of heat load exceeds 50%, can the theoretical gain of prioritizing the coupling of heat vectors for LDES cost optimization be calculated through the cascade utilization efficiency formula, and will it exceed 20%.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This study provided a review regarding distributed LDES and its bnefits to the distributed grid. The authors reviews large number of research articals to enhance the points. It is an useful research work, especially for the potential of distributed LDES in future energy systems. There are some issues to be addressed as follow:

1) Abstract must enhance the comprehensive review novelty and contribution.

2) All figs and tables are not mentioned in the context.

3) Part 2: It's two easy. The author should provide more detail of the method which you used through detailed flowchart.

4) What do you express your idea in table 2? I just find some litarature listed.

5) In 3.7 modeling: the authors do should provide their own perspective on modeling and it's limitation.

6) In 3.8 optimization: The author must provide mainstream optimization methods for presentation.

7)  The full text abbreviation list is incomplete, please double check.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents an interesting topic on energy storage. The manuscript showed strong potential with renewable energy integration and could contribute positively to the emerging importance of grid-level flexibility. However, it needs to be revised for improvement in quality. My comments for improvement are as follows:

1. Introduction: Authors are advised to discuss the difference between distributed LDES and other distributed storage systems, such as thermal, electrochemical, and mechanical storage etc.
2. Figure 1: Improve the quality of the figure
3. Table 1: Explain the key outcomes of Table 1.
4. Results: The author should provide a quantitative discussion in section 3. It is a big section with mostly qualitative information.
5. Section 3.8: Optimization; Authors should add some case studies to strengthen this section.
6. Compensation and Business Models: Authors should propose a scheme for a business model.
7. Condense the conclusion section and add only the key findings of the review

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The author has provided good answers to the questions raised by the reviewers, and this paper is acceptable.

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks for authors' revision. I'm satisfied with the response and revision. I reckon that the paper can be accepted in present form.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all the comments appropriately.