A Two-Factor Thermal Screen Control Strategy for Chinese Solar Greenhouses in High-Latitude Areas

Round 1

Reviewer 1 Report

General comments

1) Line 128 : equation 4, what does mean Js and Jr

2) Line 130 : Ug not appear in the text , please check the nomenclature

3) Line 159 : delete this « is the » 

4) Line 168 : How authors can explain roof plastic  thermal inversion effect by night, which contribute to greenhouse air cooler

5) Line 234 : why authors chose two different period time (8-9 for suny ) ( 9*10 for cloudy)

6)Figure 4:

·         -What figure 4 represent, measured or calculated value

·        - Not appear in the text and not clear,

·         -How authors can explain that in one hour the low and high temperature difference can be change between -25 °C and 5 °C

·         -How authors can explain the increase of temperature in cloudy day compared to the sunny one which characterized by a high solar radiation (400 w/m²)

7) Figure 5

- Axis titlse not clear and different between figure a and b

- Figure description not clear, Is very difficult to understand what did means, authors should revise and check all this paragraph (272 to 287).

8) Same observations for Figures 6 7, 8 and 9 , paper need more explain and correlation between figure, results values and description

 

9) Generally, paper is very interesting, but is not well presented, especially theorical part, results description and figures presentation, which makes it very difficult to understand. So, the paper needs to be improved and  restructured  

Author Response

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Reviewer 2 Report

1. The abstract of the paper needs revision. It should reflect the relevance, the purpose of the study, the methods used to achieve it and the results of the study.

2. Chinese solar greenhouse is a brand and special greenhouse design that is developed and used only in China?

3. line 39 China must be capitalized .

4. line 94-95: it is not entirely clear if the mathematical models used are valid for all types of greenhouses or only for CSG? It is necessary to describe why these methods were chosen and what makes them special. Also provide references on them in the literature.

5. line 115: "..passive heat harvesting solar energy harvesting building.." probably missing an article, hard to understand.

6. Fig.7: the figure shows the dependence of solar radiation on temperature, but the caption of the figure refers to the difference between the external and internal temperatures. It is necessary to clarify what Figure 7 reflects 

7. It is necessary to make a comparison with the current practice of opening and closing greenhouses, which would reflect the novelty of the proposed approach.

8. It is also necessary to formulate and highlight the purpose of the study.

9. It is not entirely clear whether the presented experience can be extended to other types of greenhouses, and where else besides China such types of greenhouses are used.

10. The text of the article requires proofreading.

Author Response

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Reviewer 3 Report

Evaluation

 

Summary

In this study a control procedure for opening and closing the thermal screen of Chinese Solar Greenhouses (CSGs) is developed. Starting with two intuitive rules, one for opening and one for closing, which aim at maximizing the energy available to the greenhouse, an energy balance model of the greenhouse is used to find the relationships between the temperature rise (indoor temperature minus outdoor temperature) and solar (global) radiation which satisfy these control rules (Figs. 7 and 9). In application (Fig. 10), measured temperature rise is used to calculate the appropriate global radiation for screen opening and closing, which is compared with the actual (measured) global radiation. A decision of non-action or opening or closing is then taken.

 

Evaluation

While the general scheme seems plausible, the presentation of the material is difficult to follow and appreciate. My main critique is under ‘General comments’ below.

 

 

General comments

 

Editing

I found it rather difficult to follow the manuscript in terms of line-of-argument, description-of-model, English-wording, topped by careless presentation. I had to move up and down to make sure what was the general concept. Most figures require improvement, including size of font and headings. Of the many difficult points I encountered, I list only a few in the specific comments below.

 

Nomenclature

The symbols are not ordered alphabetically, nor grouped usefully otherwise. Many symbols are missing. Examples: (1) Is S ‘area’, as in Nomenclature, or ‘energy storage’ as in Eqs. 9-11? (2)

h is not Greek. (3) Qh and Qd  not in Nomenclature. (4) Is Qs ‘the heat lost when the greenhouse air reaches an ideal temperature’ as in Eq. 12, or ‘greenhouse storage energy’ as in Nomenclature? Etc…

 

Model

Performance criterion (objective function)

There is no specific mention of a performance criterion, except indirectly, via the two control rules. Presumably the goal is to maintain the highest possible mean air temperature in the greenhouse (lowest ‘heat load’?). The contribution of the environment (solar radiation) to production (photosynthesis) is not even mentioned, presumably because the greenhouse is treated as a housing structure. It is conceivable that opening time of the thermal screen would be advanced and closing would be delayed (to capture more light) if production would be considered.

Heat load

The greenhouse model is a mystery to me. The heat load, a central concept in this manuscript (Fig. 11), is defined in Eq. (12) as “Qh = Qs + Qd  , where Qs is the heat lost when the greenhouse air reaches an ideal temperature, and Qd is the heat gain energy by the greenhouse.” It is not explained how Qs and Qd are defined (calculated), what is an ‘ideal’ temperature, nor how all the previous equations relate to Eq. (12). Possibly, ‘SketchUp’ and ‘EnergyPlus’, mentioned in Section 2.4 but not available to the reader, have the answer. The only useful information regarding the greenhouse model is Fig. 3, where an excellent agreement between calculated and measured indoor air temperature for 4 sunny days is presented. No check for cloudy days is given. The roles of transpiration and CO₂ concentration are obscure.

 

 

Specific comments (Jotted as I was reading)

 

1. Introduction

L39: “in the china”

L64; “Wang et al. (2014) HAVE shown…”

Fig. 1: (1) No need for fractions of hectare. (2) What is hm²?

L95: “calculatION model” example

 

2. Materials and Methods

 

2.1. Energy balance calculation

Start by telling what will be available to the grower in the foreseeable future. Solar radiation and temperature measurements? Computer?. What is the goal function?

L111: “the thermal screen should be opened, when the front roof can compensate for the heat lost from the greenhouse. At night, thermal screen is turned off when the greenhouse accumulator stores the most heat.” These must be the two intuitive control rules.

L127: “Jn is the amount of direct solar radiation through the atmosphere” On the horizontal plane? If so, I expect that two angles are required to determine Jh.

Eq. (4): I could not find Jr and Js in nomenclature. S is curved area? Much later you explain.

L135: “The loss of greenhouse energy IS another”

L138: “U3 is the heat consumption by plants due to water evaporation in the greenhouse,” Do you assume that none of the vapor condenses again. Does infiltration and ventilation involve just sensible heat? How are the U’s calculated?

Fig. 2: Should be presented first in the Introduction, 2^nd paragraph.

 

2.2. Reference greenhouse

 

2.3 Experimental arrangement

L191: “compare the real hourly temperature with the measured temperature” What is ‘real’ compared to ‘measured’?

 

2.4 Calculation model

L205: “the thermal simulation was carried out by EnergyPlus” I am not familiar with its capabilities. Adapting a building thermal environment simulator to greenhouses, where the dominant processes (including plant growth and transpiration) are different, may not be a good idea.

Fig. 3: Font too small.

Eq. (13): In Nomenclature you define IA as ‘rate of deviation’.

L239: “the MODEL is proved to be completely consistent with the MODEL” ??

Fig. 4: Where in the text do you refer to this figure?

 

3. Results

 

3.1 Calculation of opening time

L251: “the thermal screen should be opened rapidly, when the energy gained by the FRONT ROOF of greenhouse is greater than the energy lost by it. “ Why not the greenhouse as a whole? This is a repetition.

L301: “under this condition” Which condition?

L306: “can be used to predict the opening time of the thermal screen” How? You only explain this with Fig. 10.

 

3.2 Calculation of closing time

L316: “the thermal screen should be closed when the greenhouse has the most heat reserves.” This is a repeat of the closing rule.

L363: “In this paper, the traditional control method of thermal screen HAS NO FIXED METHOD.” ?? The reference (conventional, traditional) method of Fig. 11 was not  clearly specified. For instance, how does the ‘cooling point’ enter the control decisions?

Author Response

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Round 2

Reviewer 1 Report

·         Please review the line 16 an 17 in the abstract, the sentence not correct

·         Figure 3 is better to change the title « comparison between simulated and measured temperature »

also use the following axis title  temperature instead simulation temperature

·         Figure 4 : The weather condition (a) typical sunny weather and  (b) typical  cloudy weather

·         Figure 5 : Front roof energy balance under different external temperatures  (a) sunny day and  (b) cloudy day .

·         Figure 8 : Greenhouse heat storage under different external temperatures  (a) sunny day and (b) cloudy day

Author Response

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