Integration of Photovoltaic Cells in Solar Drying Systems

Abstract

Photovoltaic (PV) cells have not been sufficiently used in drying processes in the past, particularly for solar drying, due to their high price and low efficiency. This is now changing due to the important scientific and technological recent developments in the PV field. An increase in the number of published scientific works related to the integration of PV cells is clearly visible. It is revealed that PV cells are integrated in drying systems for two essential reasons. The first relates to their use as a part of the solar collector (generally solar air collector), which permits an improvement of their low efficiency. As a result, and in most of the studied cases, the total solar collector efficiency has reached 70%. The second reason relates to the recycling of the electrical energy consumed by other drying system components such as fans. The recycled electrical energy was directly used for instant energy consumption or stored in batteries. The main application of PV cells is their use in direct- and indirect-type forced convection dryers, generally for food and herb drying. In a study case, an economic analysis has shown that payback is dependent on the ratio of the PV cell surface to the total solar collector surface, with the possibility of an optimum payback in less than one year. In another study case, an additional heat pump significantly improved the performance of the photovoltaic–thermal (PV/T) solar dryer, reaching an efficiency of 70%. A proper design of solar drying plays an important role in attaining optimum results. In this case, particular care is given to the design of solar dryers with a detailed presentation of the influence of the different parameters such as the surface of the PV cell, geographical location, and materials used. For most of the presented systems, efficiency is calculated after application of the heat and mass balance for each solar dryer compound.

Keywords:

• Convective dryer
• Design
• Efficiency
• Electrical energy
• Greenhouse dryer
• Thermal energy

ACKNOWLEDGMENTS

The author is grateful to the National Fund of Scientific Research of Belgium for the funding of his Foreign Postdoctoral Fellowship. He is also grateful to Mohammed Bennamoun, professor at Western University (Perth, Australia), for his careful revision of the article.