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

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.

Development and Performance Evaluation of a Novel Solar Dryer Integrated with Thermal Energy Storage System for Drying of Agricultural Products

“…Active solar dyers are generally incorporated with active components such as a fan or heat pump to move the heated air from the collector to the drying chamber, hence suitable for large-scale drying operations . Active solar dryers require substantial capital investments and burn significant amounts of fossil fuel, making them unsuitable for rural areas, particularly in sub-Saharan Africa, where the electrification rate is low and financial resources are limited . Passive solar dryers use only solar energy and do not use any active components, making them ideal for small-scale holders and agro-processors with limited resources, such as those in rural sub-Saharan Africa, due to attributes such as low capital investment and maintenance costs. , The most significant drawback of passive solar dyers is their intermittent nature, as they rely totally on the availability of sun radiation .…”

“…Active solar dryers require substantial capital investments and burn significant amounts of fossil fuel, making them unsuitable for rural areas, particularly in sub-Saharan Africa, where the electrification rate is low and financial resources are limited . Passive solar dryers use only solar energy and do not use any active components, making them ideal for small-scale holders and agro-processors with limited resources, such as those in rural sub-Saharan Africa, due to attributes such as low capital investment and maintenance costs. , The most significant drawback of passive solar dyers is their intermittent nature, as they rely totally on the availability of sun radiation . Passive solar dryers are thus ineffective during cloudy days or nighttime, demanding alternative solutions to these limitations.…”

Simulation of mixed-mode solar dryer with vertical air distribution channel

“…Significant number of research has been done to improve solar dryer design and process. Common classification of solar dryers are based on solar radiation conversion mechanisms (direct, indirect and mixed) and driving forces of airflow (forced and natural) inside the dryer [ 8 ]. In mixed mode solar dryers the product temperature is raised by the air coming from solar collector and by direct absorption of solar radiation in the drying chamber [ 9 ].…”

Use of design thinking in the proposal of a multi-compound solar dryer applied to processes of traditional P'urhépecha Medicine

“…Therefore, the implementation of the passive indirect solar dryer is a viable alternative for drying medicinal plants, however, as commented by Matavel et al, 2021, the physical and thermal properties must be evaluated, as well as the use of an appropriate methodology to obtain results with greater certainty about the potential benefits of this type of alternative technologies so as not to generate economic losses and disuse due to technological innovation, which in the particular case, this proposal aims to complement traditional technological development schemes and promote eco-technological processes from a participatory approach.…”