Design and 3D Manufacturing of an Improved Heliostatic Illuminator

Round 1

Reviewer 1 Report

Dear authors, thank you for submitting your manuscript to inventions. The manuscript is comprehensively written and shows a thorough effort to improve a design and its manufacturing, promising to overcome barriers for its implementation. Please consider my following comments, that I hope may be helpful mainly to support the reader and to distinguish your contribution from previous work.

Abstract:

The abstract might better introduce the reader if it was more specific. The first two sentences are very general, the third does not make it clear that the manuscript presents an engineering solution for a previously presented heliostat.

1. Introduction:

I consider the formulation of the first sentence problematic. The phrase "almost consensus" is taken from an article discussing the general societal perception - here it reads as if there was a significant disagreement among scientists on the subject.

I propose to rebalance the entire state of research, giving up general passages in favour of an in-depth report of the technique you want to improve. You are presenting engineering solutions for very particular heliostat design (as comprehensively stated on lines 165-166). Since heliostats and light guides for daylighting are a well researched field, as a reader I would appreciate to have not more but a minimal general background presented. Discussing light shelves, light pipes etc. in depth may be not helpful for the understanding of your work. Please consider a thorough report on the state of research of tracking daylighting devices instead, leading to a clear statement of the research problem, and the objectives of your work. This would allow the reader to immediatly identify the novelty and relevance of the presented work. Unfortunately, this important passage about the state of research with regards to heliostats for daylighting is currently very brief (lines 146-163) before it leads to the discussion of the authors prior work that the presented research shall improve. Detail: Please correct the reference to the work by Whang et al. here (currently leading to Gibson et al. [45]).

2. Fundamentals of Heliostat Operation

The manuscript presents an improvement of a device that has been described in previous publications (e.g. Torres-Roldan et al. (2015), Design of an innovative and simplified polar heliostat for integration in buildings and urban environments). All the fundamentals that have already been described do not have to be replicated in 2.1 and 2.2 but could be referenced (side-note, I could not find A' in the figures of the section). Shortening this to a very brief summary of the previous publications would not only make the novel contribution of this manuscript more visible, but provide additional space for a more in-depth discussion of the problems addressed by the proposed improvement.

3. Heliostat 3D manufacturing

The first two paragraphs of this section report the state of research in addaptive manufacturing and could be considered part of the introduction. Rather than reporting manufacturer and model (which may be valuable as footnotes), please consider to report the printing technology (as far as I know the device extrudes a filament) and any parameters (speed, filament / nozzle, temperature,...) that may impact the result. I was wondering what additional information Table 1 with its unitless numbers transmits since none of the listed materials was tested, or if it could be omitted.

4. Results

4.1.1 mentions that parts of the polygon are 3D printed as described in 3, while others are made of alumimum. Given that manufacturing forms one major part of the presented research, it would worth to distinguish these two materials and manufacturing techniques in the illustration (e.g. by different levels of green). Detail: The threaded tube T is mentioned several times in the text, but not labeled in Figure 8.

5. Conclusions

Please avoid any recapitulation of the introduction, as well as summaries of what has already been described in the method and result sections (e.g. lines 466-480). The conclusions section offers the unique opportunity to distill your main findings - e.g. the potential of the evaluated improvement to the device and the presented manufacturing technique, the limitations of the device and manufacturing technique as well as the research, new research problems that were identified etc. How to understand the stated reduction of mass (line 491) - does one tracker get 5kg lighter due to additive manufacturing, is the presented tracker's weight 5kg (so what would be a tracker with conventional assembly?)? Do the authors expect the durability of the 3D printed PETG (not PTEG) to be comparable to aluminum? Are there other findings from the practical application of the manufacturing technique during prototyping an accurate heliostat? Since this research is presented as an improvement of the previously described heliostat, please also discuss the resulting 10mrad pointing error (that appears to be slightly larger than the previous 9mrad).

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

the paper presents an improved version for a heliostatic illuminator based on 3D printing. The title is a little bit redundant, as heliostats are used only for urban applications.

There is a very long introduction about climate change and New Green Deal and little about the advantage of using heliostats - that can reduce lighting energy consumption with x % and little about problems arising with them - glare or the lack of view out etc.

The paper presents the result of an interdisciplinary team, that involved lighting specialist, mechanical and 3D printing engineers. it is not clear if the heliostat was produced as a result of the research and no data about real results and users  feedback.

In the abstract it is mentioned that the result is 'easily commercially available illuminator' but nowhere in the text is a mention how the authors intend to sell this solution: as a product or a solution freely available, where you can buy the 3D printing file etc.

But despite this unsolved issues it is an interesting paper for an improved illuminator

Small remarks:

Line 100: 'creases[29,30]' missing space 'creases [29,30]'

References 30 and 31 does not follow the same rules as the others

Author Response

Please see the attachment

Author Response File: Author Response.pdf