Drying performance and economic analysis of novel hybrid passive-mode and active-mode solar dryers for drying fruits in East Africa

Abstract

In East Africa, post-harvest loss of fresh perishable fruits is enormous, causing recurrent seasonal deficits. In response, a modified passive-mode hybrid solar dryer hereafter called; ‘an Improved Solar Dryer (ISD)’, was developed as a potential low-cost technology alternative for drying fruits in Uganda. An improved PV-assisted hot air dryer using active-mode hybrid solar dryer hereafter called; ‘Solar Photovoltaic and Electric (SPE)’ was also fabricated. The ISD dryer utilises freely-available solar energy to dry the produce. In contrast, the SPE dryer uses both solar photovoltaic and electricity sources. In this study, the drying performance of the ISD and SPE dryers were performed and compared to that of the traditional open sun drying (OSD) method. Relative to the OSD method, the economic performance of the ISD and SPE dryers was analysed. The drying performance results show that the mean drying air temperatures achieved by the ISD and SPE dryers were 31.9 and 41.1 °C respectively; relative to the 27.6 °C for the OSD method. On average, the thermal energy attained by the ISD and SPE dryers were 3551 and 5757 Watts (W) respectively, as compared to 2952 (W) obtained for the OSD method. It took the ISD and SPE dryers 10 and 18 h to effectively dry the fruit (pineapple) products, respectively as opposed to the 30 h taken by the OSD method. The results confirm the superior performance of the ISD and SPE dryers than the OSD method. Results for the economic performance analysis show more reduced costs of drying the products using the ISD than the SPE dryer. Similarly, the pay-back period for the ISD was 2.4 times shorter than that of the SPE dryer. Joint results for economic analysis and drying performance confirm the ISD as a better drying technology than the SPE dryer in the context of the resource-constrained farmers/agro-processors without electricity in Uganda and East Africa.