Dependence of PV Module Temperature on Incident Time-Dependent Solar Spectrum

Round 1

Reviewer 1 Report

The manuscript describes the energy balance method for estimating the temperature of photovoltaic (PV) cells. It is more accurate than the rough estimation based on simple NOCT formula and STC method in the past. The result also shows an overestimation of PV temperature using simple but popular NOCT method. This is a piece of good engineering work with more sophisticated parameters putting in, therefore the new result is in better accuracy. However, there are little new physics inside, neither highly impact on the solar energy society. For the Applied Science, it seems lack of general interest for the readers. Maybe another engineering journal with more specified topics on solar energy engineering is better suited for this manuscript.

More information should be provided in Equation (1-5) for reader for easier to understand, although they are already cited in the references provided. For example, the G in equation (2), what is the G? What is STC should be written it up; the unit of each equation should be specified because the equations involve empirical numbers. There are also typos in the pdf file need corrections. For examples, line 185 of page 7: then10; line 197 of page 7: literature should be literatures…..

Author Response

Units in equations added.

Typos corrected.

Author Response File: Author Response.pdf

Reviewer 2 Report

This article reports a theoretical model to estimate the PV module temperature under various solar spectra irradiance conditions using energy balance equations. The resulted temperatures for different PV modules, c-Si, a-Si/u-Si, CdTe and CIGS, are close to the manufacturers’ NOCT temperatures, and this method might give a promising tool for PV community. Therefore, I think this article is worth publishing from Applied Sciences.

Author Response

No comments

Reviewer 3 Report

In this manuscript, the authors reported a theoretical study on the temperature-dependent photovoltaic conversion processes. By changing the materials type in the PV modules, different performances have been obtained for c-Si, a-Si/ c-Si, CdTe and CIGS respectively. The newly proposed model for the temperature effect calculation is based on the combination of the Nominal Operating Cell Temperature (NOCT) and the energy balance equation, which determined the PV module temperature through energy balance and the solar irradiance. These simulation results were matched well with the data from the manufacturers' NOCT temperatures. This work looks interesting and promising for the photovoltaic applications. Thus, I recommend the paper for publishing in this journal after the below concerns have been addressed:

Comments:

1. In Page 1, the introduction section, the authors mentioned that “Many expressions for the operating temperature have been proposed in the literature, some are simplified working equation as NOCT (Nominal Operating Cell Temperature), others are based on energy balance equations, and many more on combinations of the energy balance equation and NOCT model [1]- [8]. Expressions for the operating temperature of the PV modules are either explicit forms giving directly the temperature, or are implicit forms involving variables which themselves depend on the temperature [3], [7].” However, they did not mention the advantage of their combination method presented here with both energy balance equation and NOCT method compared to the references 1-8. What is the major difference? And what is the most improved part in comparison to the results and models in current literatures.

2. In Page 4, Figure, 1, the authors have shown “External quantum efficiency of four module technologies.” for four types of PV elements, i.e., c-Si, a-Si/ c-Si, CdTe and CIGS. However, they did not mention why they chose these four types of materials for the model verification. And will the other materials exhibit the different operation temperature trend with the current model?

3. In Page 6, Table 3, the authors have listed their calculation results with the measurement data from the manufacturer. There is some temperature difference between the calculation and the manufacture data. And some of the PV element had a larger temperature deviation, some had a smaller one which is more close to the calculation? Does it mean the modeling is more suitable for the CdTe ones? What is the tolerance for the model? How many percentage?

4. In Page 7, Figure 4, it is shown that “Figure 4. Variation of c-Si module temperature at noon on the 21st of month, Dec.-June.” In general, the NOCT results are overall much higher than the Spectra-based method. The authors should explain why this phenomenon was obtained and what is the key factor for these results. And are there another standard results that can be used as the bench mark for the calculations?

Author Response

As stated in the manuscript “One must be careful in applying a particular expression for the operating temperature of the PV module because the expressions have been developed for particular deployments of the PV system. For that reason, one cannot compare methods and results of the operating temperature for different types of PV systems and at different locations”. Therefore, the manuscript did not mention the advantage of the proposed method in comparison to the references in 1-8. The purpose of the present study is to offer a new approach (model) for the determination of the operating temperature of PV modules which is different from models in the current literatures. The simulation results are close to the manufacturers' NOCT temperatures, thus verifying, by simulation, the validity of the new spectrum approach.  Still, the new approach justifies further studies. The four PV cell types studied in the article are cells representing different common technologies, covering a wide range of spectral response, see Fig. 1. Other cells types may behave similarly. Difference in the operating temperature using different models, at different locations and different in the module deployment in the field may result in more than 5 degrees. The tolerance for the model therefore depends on the variation of many factors including also on the day and time. The results for CdTe does not mean that the proposed method is more suitable for this type of cells. The calculated module temperaturesin Table-3 are average maximum values based on the solar spectrum model at the particular site. The proposed and NOCT are totally different methods. The proposed method is based heat transfer mechanism and solar radiation spectrum, i.e., on materials, location and time of the day whereas the NOCT method is a general method dependent only on the solar radiation and the ambient temperature. The results show that NOCT overestimates the operating temperature, again at the specific site and time of the day.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

no further query.

Reviewer 3 Report

The manuscript has been improved after revisions according to the reviewers' comments. I recommend the paper to be published in the present form.