Improving Thermal Performance of Solar Heating Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper addresses a topic that falls within the scope of the journal. The abstract, in its current form, is not sufficiently informative and should be revised. Since the authors aim to discuss how to improve the thermal performance of solar heating systems, the abstract should begin with a general overview of this topic rather than focusing solely on heat accumulation during the summer months.

In the introduction, the authors should provide a concise overview of solar thermal heating systems in the built environment. This should include domestic solar hot water systems before moving on to space heating applications. Given that the majority of solar thermal systems are used for domestic hot water production, a short summary of their current status, supported by relevant references, is recommended.

The following references are suggested as indicative starting points:

• 10.1016/j.enbuild.2025.116011

• 10.1016/j.est.2024.114700

• 10.1016/j.applthermaleng.2022.119630

Section 2 should be omitted, as it provides background information already familiar to solar energy practitioners.

In Section 3, the rationale for using the degree-day methodology must be explained, especially since more accurate methods are available. Furthermore, the solar system itself is not adequately described, which makes it unclear why the simultaneous heating of a swimming pool and space heating was assumed to be impossible.

Finally, the authors state that calculations were performed using a modified algorithm described in one of their previous papers. A brief overview of this algorithm should be included, along with details of the modifications made and evidence of validation.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Overall, the research work lacks sufficient novelty. It strongly recommend that the authors clearly highlight the novelty of this research work at the end of introduction. My comments are:

1. Overall, English needs to improve over the whole manuscript.
2. Introduction. The introduction is too long and can be condensed. Furthermore, the literature should focus on the research work related to the current study reflecting the status and gas of the current study. The overall logic of the introduction needs to improve.
3. Figure 1 is not clear; it is recommended to use different color for different circulation loop.
4. it is suggested to add a simulation flow chart to describe the system simulation procedure.
5. Please explain why Tt during the summer period is lower than the following seasons in Figure 11.
6. The actual benefit of the use of solar heating for swimming pool should be discussed and evaluated. Furthermore, it needs to clearly specify the scale of the use of swimming pool in the country. This will highlight the importance of the research work.

Comments on the Quality of English Language

The English should be improved. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents a numerical study of a solar heating system for a residential building, with emphasis on mitigating summer excess heat by redirecting it to an outdoor swimming pool. The approach is analyzed using the concept of solar utilizability and a modified algorithm that accounts for dynamic heat balances in collectors, tanks, building loads, and pool heating. The study provides useful insights, but the manuscript requires improvements in clarity, validation, and discussion to meet publication standards.

1. An experimental validation, if possible, would strengthen the paper.
2. Results such as predicted pool water temperatures remain below typical comfort levels of approx. 25-30 °C. A critical discussion is advised.
3. Can you estimate and discuss the impact of used simplifications, such as well-mixed pool water, constant wall mass, daily timestep etc. on transient behavior?
4. What is the reasoning behind the assumption that pool and space heating cannot operate simultaneously? Some real systems do allow parallel heat distribution.
5. A comparison of other methods of handling summer excess heat, such as seasonal borehole storage, PCM storage, dry coolers etc. would be useful.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors should provide more information on the  calculation algorithm  presented in a block diagram (Fig. 3) which is also provided in https://doi.org/10.1016/j.solener.2025.113789.

Although the algorithm was validated by comparison with the results obtained from the TRNSYS application, which was described in detail in the authors' publication https://doi.org/10.1016/j.solener.2025.113789, a brief description of the algorithm should be provided, along with the key differences between the current and the previous work. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf