Title: Exergetic optimisation of a solar-biomass hybrid greenhouse dryer in drying banana slices

Authors: Florence G. Kiburi; Erick K. Ronoh; Christopher L. Kanali; Gareth M. Kituu; Patrick O. Ajwang

Addresses: Agricultural and Biosystems Engineering Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya ' Agricultural and Biosystems Engineering Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya ' Agricultural and Biosystems Engineering Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya ' Agricultural and Biosystems Engineering Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya ' Agricultural and Biosystems Engineering Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya

Abstract: In this study, an elitist non-dominated sorting genetic algorithm was applied in exergetic optimisation of a solar-biomass hybrid greenhouse dryer in drying banana slices. To develop comprehensive relationships for objective functions under each drying mode (solar, biomass, and solar-biomass), the system was linearised around drying and exit air temperatures. The objective functions involved maximising exergy efficiency and drying air temperature of the system. The trade-offs showed that solar and solar-biomass modes required the same airflow rate (0.05 kg/s) indicating that at these combinations the dryer received almost equal energy input. Biomass mode trade-offs indicated that a lower flow rate (0.01 kg/s) was required for drying. Further, both solar-biomass and biomass modes must maintain a fuel feed rate of 0.001 kg/s for maximum exergy efficiency (solar-biomass: 80.21% ± 14.26%; biomass: 79.28% ± 10.38%) and drying air temperature of 333 K. Performance evaluation of the optimised system demonstrated its superiority compared to the unoptimised system.

Keywords: exergy; hybrid greenhouse dryer; solar-biomass; energy mode; optimisation; genetic algorithm; efficiency; drying temperature; performance evaluation; banana slices.

DOI: 10.1504/IJEX.2023.130940

International Journal of Exergy, 2023 Vol.41 No.1, pp.41 - 59

Received: 11 Feb 2022
Received in revised form: 17 Nov 2022
Accepted: 19 Nov 2022
Published online: 14 May 2023 *

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