Quantifying the Shading Effects of a Small-Scale Rooftop-Installed Linear Fresnel Reflector in Cyprus
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors1. The introduction must be supplemented with a review of similar papers on taking into account shading and reducing the level of incoming solar radiation.
2. It is necessary to verify the received data to confirm its accuracy.
3. Ground-based measurement data for 4 years was used as actinometric information. Why exactly this data was used? they are averaged or modeling was carried out for each year.
4. Why are satellite measurement databases not used, where the data is processed and averaged over 25 years, which makes it possible to predict the intensity of solar radiation with a higher level of accuracy?
The scientific novelty of the paper is not clear, since there is no background review. The reliability of the results obtained is also unclear, since there is no comparison with experimental studies or similar results in other works.
Author Response
Dear reviewer, we thank you for your time in reading the paper and for your comments for improvement. Please find our answers to your comments here below.
Comments 1: The introduction must be supplemented with a review of similar papers on taking into account shading and reducing the level of incoming solar radiation.
Answer: We acknowledge the lack of similar references for the present study. However, this is explained as regarding Linear Fresnel Collectors as well as for any other solar concentration technologies, the enterprise of quantifying the shading effect has never been done before. Such work has been done for static PV collectors for instance and this is mentioned in the manuscript (references 22 and 23). But for LFRs this has never done: this is the novelty of the manuscript.
Comments 2: It is necessary to verify the received data to confirm its accuracy.
Answer: Could you be more precise? The pyrheliometer in use is the LP Pyrhe 16 AC, which a class A pyrheliometer (according to the ISO 9060, which is the best class possible of pyrheliometer). The data are available and free of access on Zenodo for further check (Reference 29 of the paper).
Comments 3: Ground-based measurement data for 4 years was used as actinometric information. Why exactly this data was used? they are averaged or modeling was carried out for each year.
The data are available on Zenodo for cross-check as stated before. The data used are in-situ data. The pyrheliometer is indeed located on an adjacent roof of the collector (less than 30 meters far from the collector). It is very hard to have more precise data with such interval of time, meaning with a record of every second for 4 years representing 126 x 10e6 samples. This is unique for such type of collector to collect data in real-time, with a class A pyrheliometer. For each second of the 4 years, ray-tracing is applied for the 340 squares with 10,000 rays per square. The shading ratio is multiplied by the DNI value every second for 4 years. As a matter of display, the values are shown as averaged per month (Figures 13, 14 and 15) as it would make no sense to have it represented for every second of the 4 years.
Comments 4: Why are satellite measurement databases not used, where the data is processed and averaged over 25 years, which makes it possible to predict the intensity of solar radiation with a higher level of accuracy?
The paper deals with real in situ data, that are not averaged. The DNI was recorded for 4 years every second. So this is much more precise for the following reasons:
- The satellites data have resolution of 250 m at best (NASA's Moderate-resolution Imaging Spectroradiometer) and 1 km for SolarGis (https://solargis.com/docs/methodology/meteo-data) while the pyrheliometer is only 30 m distant from the collector.
- The time resolution is up to 15 minutes for SolarGis, while for MODIS it of daily range
- The satellite data are measured from space, while pyhreliometers are in situ, capturing the final radiation actually reaching the level of the collector, with higher precision than the a remote satellite.
- Pyrheliometers are used to calibre satellite measurements, and not the other way round.
Comments 5: The scientific novelty of the paper is not clear, since there is no background review. The reliability of the results obtained is also unclear, since there is no comparison with experimental studies or similar results in other works.
For the Linear reflector field, meaning rotational collector type of CSP, the work has not been done before up to the best knowledge of the authors. This is the novelty, thus cannot be compared to similar works. This is a ray-tracing based study involving geometrical considerations, this is the experiment itself.
We tried to reformulate the novelty in a clearer manner in blue colour (line 53).
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript discusses a study that examines the shading effects of a linear fresnel reflector installed on a roof in Cyprus. The study uses numerical analysis software to assess the impact of shading on the roof surface throughout the year at various system heights, including the current height. The authors conduct a comprehensive literature review, providing detailed insights into each work's contribution to the study. Initially, the authors optimize the analysis method to minimize errors and then proceed to evaluate the irradiation distribution. They analyze the impact of the fresnel system at different heights for each month of the year.
Next, here are a couple of recommendations for improvement:
- Line 34: It would be beneficial if the authors could define the acronym U-LEAF.
- Line 240: Clarification on why the ratio is zero at 4 m is needed.
Author Response
Dear reviewer, we thank you for your time in reviewing the paper. We appreciate your well detailed summary that acknowledges your understanding of the followed methodology from the ray-tracing study set-up up to the final monthly energy assessment. We respond to the 2 comments hereafter.
Comments 1: Line 34: It would be beneficial if the authors could define the acronym U-LEAF.
This has been done (text in red colour). Thanks for noticing it.
Comments 2: Line 240: Clarification on why the ratio is zero at 4 m is needed.
We have added an explaining sentence (text in red colour).
Author Response File: Author Response.pdf
