Passive solar dryers as sustainable alternatives for drying agricultural produce in sub-Saharan Africa: advances and challenges

Abstract

Abstract The lack of adequate techniques for food processing is among the reasons underlying food losses and high levels of hunger in Sub-Saharan Africa; the application of solar energy to dry agricultural products is one potential solution. However, the total replacement of traditional uses of solar energy is still far from reality. Therefore, in this study, we systematically review the academic literature testing passive solar drying systems in order to assess their performance. Then the main limitations and challenges for passive solar dryers developed in Sub-Saharan Africa are derived. The literature search reveals very limited research and a lack of standardized methods to assess solar dryer performance. Studies mainly report parameters related to dryers’ thermal performance and physical features, thus neglecting parameters related to the quality of dried products and economics. Standardized and robust methodologies are urgently needed for more accurate conclusions and comparability of study results. Moreover, successfully applying passive solar dryers as an alternative to the traditional use of solar energy requires overcoming challenges such as time consumption, limited quantities of dried products, and the periodic nature of solar radiation. Thus, given its ability to significantly improve the self-life of food and overcome the current limitations for effective utilization of solar dryers in SSA, the use of mixed mode passive greenhouse dryers is proposed.

The lack of adequate techniques for food processing is among the reasons underlying food losses and high levels of hunger in Sub-Saharan Africa; the application of solar energy to dry agricultural products is one potential solution. However, the total replacement of traditional uses of solar energy is still far from reality. Therefore, in this study, we systematically review the academic literature testing passive solar drying systems in order to assess their performance. Then the main limitations and challenges for passive solar dryers developed in Sub-Saharan Africa are derived. The literature search reveals very limited research and a lack of standardized methods to assess solar dryer performance. Studies mainly report parameters related to dryers’ thermal performance and physical features, thus neglecting parameters related to the quality of dried products and economics. Standardized and robust methodologies are urgently needed for more accurate conclusions and comparability of study results. Moreover, successfully applying passive solar dryers as an alternative to the traditional use of solar energy requires overcoming challenges such as time consumption, limited quantities of dried products, and the periodic nature of solar radiation. Thus, given its ability to significantly improve the self-life of food and overcome the current limitations for effective utilization of solar dryers in SSA, the use of mixed mode passive greenhouse dryers is proposed.