## 3 Results and Analyses
### Analyses between the Photovoltaic Greenhouse and the Contrast Greenhouse  
Zigzag-film greenhouses and sunsheleters are widely applied in tropical areas. This study made a parallel comparison on the illuminance and temperature and humidity between a photovoltaic greenhouse, a zigzag-film greenhouse, and a sunsheller. Results are shown in Figure 7 and Table 5. During the comparison, the compound mean values of the collection sites were used for the photovoltaic greenhouse data, while the measured values of the collection sites were used for the zigzag-film greenhouse and sunsheller data. The test time was 9 May 2015. The weather was cloudy. The roof shelter of the zigzag-film greenhouse was kept open during the test, and the plastic film covered on its roof and wall had been used for four years, which had the problem of stains, aging and reduced light transmittance, etc. The photovoltaic greenhouse and the sunsheller were newly built and had been used for less than one year.  
Figure 6: Temperature and humidity changes inside and outside the photovoltaic greenhouse in summer: (**a**) indoor and outdoor temperatures; (**b**) indoor and outdoor humidity values.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**29 July** & **Outdoor** & **Site A** & **Site B** & **Site C** & **Site D** & **Site E** & **Site F** & **Site G** &
\begin{tabular}{c} **Indoor** \\ **Average** \\ \end{tabular} \\ \hline Highest temperature (\({}^{\circ}\)C) & 33.5 & 35.2 & 35.5 & 37.4 & 35.0 & 38.0 & 36.0 & 36.3 & 36.2 \\ Lowest temperature (\({}^{\circ}\)C) & 26.1 & 26.3 & 26.0 & 26.5 & 25.6 & 26.6 & 26.2 & 26.4 & 26.2 \\ Highest relative humidity (\%) & 88 & 91 & 94 & 88 & 93 & 88 & 89 & 87 & 90.3 \\ Lowest relative humidity (\%) & 55 & 55 & 52 & 49 & 54 & 46 & 49 & 51 & 50.9 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Temperature and humidity extremum values inside and outside the photovoltaic greenhouse in summer.  
Figure 7: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**5 January 2016** & **Outdoor** & **Site A** & **Site B** & **Site C** & **Site D** & **Site E** & **Site F** & **Site G** &
\begin{tabular}{c} **Indoor** \\ **Average** \\ \end{tabular} \\ \hline Highest temperature (\({}^{\circ}\)C) & 29.2 & 29.3 & 27.2 & 28.9 & 28.0 & 29.0 & 27.6 & 28.5 & 28.4 \\ Lowest temperature (\({}^{\circ}\)C) & 22.3 & 22.1 & 22.3 & 22.2 & 22.3 & 22.4 & 22.2 & 22.2 & 22.2 \\ Highest relative humidity (\%) & 95 & 96 & 96 & 97 & 97 & 94 & 96 & 95 & 95.8 \\ Lowest relative humidity (\%) & 66 & 65 & 71 & 69 & 70 & 67 & 72 & 68 & 68.8 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Temperature and humidity extremum values inside and outside the photovoltaic greenhouse in winter.  
According to Figure 7 and Table 5, for the average illumination were shown in descending order: the photovoltaic greenhouse > the zigzag-film greenhouse > the sunshelter; the outdoor temperatures were between 30.7 and 33.5 \({}^{\circ}\)C, and the relative humidity values were between 66% and 76%. For the average temperatures were shown in descending order: the zigzag-film greenhouse (34.4 \({}^{\circ}\)C) > the photovoltaic greenhouse (33.3 \({}^{\circ}\)C) > the sunshelter (32.8 \({}^{\circ}\)C). The difference was not significant, and the temperature and humidity environment of the photovoltaic greenhouse was close to that of a normal greenhouse. The zigzag-film greenhouse had a relatively high temperature, because it was covered with films (some roll-film is open) and had poorer venting compared with the photovoltaic greenhouse and the shelter which were covered with a sunshade net.