## 3 Results
### Evaluation of Environmental Factors in the Field
#### 3.3.2 Temperature  
Figure 7 shows the average horary temperature recorded inside each greenhouse and outside for September, October and November.  
\begin{table}
\begin{tabular}{c c c} \hline
**EPC** & **PAR (\(\mu\)mol m\({}^{-2}\) s\({}^{-1}\))** & **Transmittance (\%)** \\ \hline Blue & 319.51 & 22.91 \\ Grey & 710.28 & 50.93 \\ Yellow & 997.08 & 71.50 \\ Colorless & 1075.6 & 77.13 \\ \hline \end{tabular}
\end{table}
Table 10: Integral daily PAR radiation transmitted through the EPCs installed in the pilot greenhouses and its percentage related to outdoor PAR (1394.56 \(\mu\)mol m\({}^{-2}\) s\({}^{-1}\)). Measurements on 25 September 2019 between 6:00 h and 18:00 h (solar time).  
Figure 6: Incident PAR radiation in \(\mu\)mol m\({}^{-2}\) s\({}^{-1}\) from the outdoor side and that transmitted through the EPCs, as measured on 25 September 2019 between 6:00 h and 18:00 h (solar time).  
Considering the poor ventilation, low air volume and lack of humidity in the greenhouses, very high maximum temperatures were reached. The blue EPC and grey EPC were the ones that registered much smaller differences in terms of the maximum temperatures, which was due to their lower PAR and NIR transmission percentages compared to the yellow and colorless EPCs.  
During the night, the temperatures in the pilot greenhouses were around 3 \({}^{\circ}\)C higher than the outdoor temperatures in September and October. Nevertheless, in November, a  
Figure 7: Average horary temperature recorded inside each greenhouse and outside for **(a)** September, **(b)** October and **(c)** November.  
thermal inversion phenomenon was observed from 11:00 p.m. to 7:00 a.m. for the pilot greenhouses with the yellow EPC and colorless EPC. In the grey EPC, it rose above this temperature starting at 8.00 a.m.; however, the blue, yellow and colorless EPCs rose above this temperature starting at 10.00 a.m. The blue EPC roses 10 \({}^{\circ}\)C from 1.00 to 5.00 p.m., and the grey EPC rose to 15 \({}^{\circ}\)C during the same period. However, the yellow and colorless EPCs increased above the outdoor temperature up to 20 \({}^{\circ}\)C in the same period.  
Table 12 shows the difference in the average, minimum and maximum temperatures (\({}^{\circ}\)C) recorded inside each greenhouse with respect to outside. The average temperatures reached inside the pilot greenhouses were in the range of from 3.5 to 4.5 \({}^{\circ}\)C higher than those outside. The minimum temperatures were similar to those outside (\(\pm\)1 \({}^{\circ}\)C), with a thermal inversion effect being observed in the yellow and colorless EPCs in November. In relation to the maximum temperatures, the best performance was found in the blue EPC with an average increase of 10 \({}^{\circ}\)C, an intermediate performance was found in the grey EPC with an increase of 12 \({}^{\circ}\)C and an inadequate and excessive performance was found for the yellow and colorless EPCs.  
Figure 8 shows the correlation between the NIR (%) and maximum temperature (\({}^{\circ}\)C) inside the pilot greenhouses. In the trial conditions, a strong correlation between the NIR received inside the pilot greenhouses and the maximum temperatures reached was observed.