## 6 Conclusions  
* In this case study, where the temperature at 3 m depth is 13 \({}^{\circ}\)C, the vertical spiral tube is the shape of the EAHE system with a length of 29 m, the size of the greenhouse is 2 \(\times\) 1.4 \(\times\) 1.4 m\({}^{3}\), February is the month of experience with specific variations in ambient temperature (from 29.5 to 4 \({}^{\circ}\)C) and ambient humidity (from 88.5 to 11.5%), the conclusion can be formulated as follows. * The GH + EAHE open loop is the better option in heating mode. In cooling mode, the closed-loop is better. * In this case study, the EAHE system reduced energy consumption for maintaining the temperature of the microclimate in the GH + EAHE by more than 40%. Gas emissions were also reduced by more than 10%. * It is better to use a lower temperature difference between the set temperature in the heater and the outlet air temperature of the EAHE system, to avoid the EAHE system doing the opposite of what we used it for, resulting in higher energy consumption and more CO2 emissions. * On cold days, the heater operating time is more than 19 h, for example, B3. For this reason, the use of the EAHE system is recommended in terms of reducing energy consumption and CO2 emissions. Although the EAHE system reduces the heating energy consumption, the humidity measurements for GH + EAHE are higher than for GH. Further research is needed to control relative humidity. In future work, a dehumidification (DH) system will be installed in the EAHE system entrance, and the results of this study will be used to conduct the new research. Based on the GH models, the effects of EAHE + DH performance on temperature and humidity distribution in GHs will be studied. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **[PERSON] et al.** & **[PERSON] et al. [24]** & **[PERSON]** & **[PERSON] [30]** & **Current Study** \\ \hline Location, Climate & Izmir, Turkey & Iran & Loughborough, UK & Elazig, Turkey & Covilhá, Portugal \\ GH size (m\({}^{3}\)) & - & 1600 & 142.87 & 150 & 5 \\ EAHE Length (m) & 47 Horizontal & 40 Horizontal & 60 Vertical & 246 & 29 Vertical \\  & Closed loop & Open loop & serpentine & serpentine & spiral \\ Soil temperature (\({}^{\circ}\)C) & 25 & 21 & 17 & 12 & 13 \\ COPCooling or & 10 & - & 1.2 & [2.9, 3.5] & [0.5, 7.3] \\ COPheating or & 6.3 & - & 2.1 & [0, 3.4] \\ Heating supply (M/m\({}^{2}\)) & - & 119 & 44 & - & - & - \\ Cooling supply (M/m\({}^{2}\)) & - & 212 & 160 & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Parameter from literature. **Author Contributions:** Conceptualization, L.C.C.P. and P.D.S. ; methodology, L.C.C.P. and P.D.S. ; validation, L.C.C.P. and P.D.S. ; formal analysis, S.H., L.C.C.P. and P.D.S. ; investigation, S.H. ; resources, L.C.C.P. and P.D.S. ; data curation, S.H. ; writing--original draft preparation, S.H. ; writing--review and editing, P.D.G., L.C.C.P. and P.D.S. ; supervision, L.C.C.P. and P.D.S. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Data Availability Statement:** The authors confirm that the data supporting the findings of this study are available within the article. **Acknowledgments:** This work was supported in part by the Fundacao para a Ciencia e Tecnologia (FCT) and C-MAST (Centre for Mechanical and Aerospace Science and Technologies), under project UIDB/00151/2020. **Conflicts of Interest:** The authors declare no conflict of interest. **Nomenclature**  
Amb Ambient  
C\({}_{\rm P}\) Specific heat capacity of air (J.kg\({}^{-1}\).K\({}^{-1}\))  
CFD Computational Fluid Dynamic  
COP Coefficient of Performance  
\(D\) Dimension  
EAHE Earth-to-air heat exchanger  
GH Greenhouse  
\(I\) Electrical current used by the fan (A).