# Thermal Evaluation of a Hybrid Dryer with Solar and Geothermal Energy for Agroindustry Application
## 4 Discussion and Conclusions  
Ambient temperature and irradiation is one of the factors that can drastically affect the operation of a solar dryer. When analyzing the drying chamber without a heat dissipation medium, it was observed that on very bad days, the maximum internal temperature increase of the reached chamber was 10 \({}^{\circ}\)C. Therefore, adapting another energy source that compensated for the design temperature was justified to maintain the kinetics of the constant drying of the product. The stability time of the experimental prototype was 40 min for the solar dryer and hybrid solar-system. As expected in a solar dryer, running only as a greenhouse effect means that the stability time of the chamber is longer. Furthermore, we checked the good thermal resistance of the materials used in the structure of the drying chamber. In the case of adapting a low enthalpy horizontal geothermal system in the prototype, it was determined that in the hours of low irradiation, the energy input will depend mainly on the aerothermal system. However, in the hours of increased irradiation, the dominant factor will be the solar collector. Testing on the models determined that the best results were obtained in hybrid mode with an aerothermal system where an efficiency of 60% to 70% was observed. Moreover, it was determined that the efficiency of the solar dryer with the collector was 30 to 60%. The proposed photovoltaic installation allowed us to meet the energy demand of the 95 Wp electrical system in total by keeping a fan and the control system on. The energy consumption of the auxiliary system on days with clear sky will be minimal, therefore operating the dryer most of the time only with the contribution of solar radiation. However, it is evident that the constant use of the power source on very bad days, on the other hand, where energy savings in electricity consumption between 3 to 5 kW/day were achieved. Regarding the soil profile (geothermal energy), our results indicate that the temperature remained stable at a depth of 70 cm, with an increase of 5 \({}^{\circ}\)C more in reference to the ambient temperature at night, while during the day, the temperature increase of the air was 10 to 14 \({}^{\circ}\)C. The soil temperature had a sinusoidal tendency or behavior, and its amplitude decreased depending on the depth, with the exception of the surface temperature. The change in the energy matrix of Ecuador promotes the implementation of renewable energy in the framework of distributed energy systems as a mechanism to achieve sustainable development and an important alternative with impacts in the social and economic development of the Ecuador population. The dryer built in this study meets these requirements, and could be considered as an alternative solution for local development to be used by small and medium industries that need to dry their products  
E.D.-P. and J.P.-J. methodology, design, analyses, and interpretation of data, writing--original draft preparation; J.R.-T. measurements; M.Q. and M.P. investigation; A.A. simulation and analysis; M.A. and O.G. measurements; B.V.-M. formal analysis and review. This research was funded by SENESCYT \"National Secretary of Higher Education, Science and Technology\". **Acknowledgments:** (Risiged) Iberoamerica network of hybrid systems of distributed generation. Cited. **Conflicts of Interest:** The authors declare no conflict of interest. * [PERSON] (2010) [PERSON] _Diseho Concurrent de una Secadora Vertical Intermittente Para Arroz_, 1 st ed. ; Editor ESPOCH: Chimborazo, Ecuador, 2010; Volume 1, pp. 25-30. * [PERSON] and [PERSON] (2018) [PERSON]; [PERSON] Assessment of drying technology for rice, corn and cocoa products in Guayas and Los Rios province. Magazine Engineering, ICT's and industrial processes. In Proceedings of the REDU Congress VI, Ibarra, Ecuador, 14 November 2018; pp. 664-676. * [PERSON] (2015) [PERSON] _Diseho, Modelo Matematico Y Construccion de un Secadero Optimizado Con Energias Limpias_, 1 st ed.