Development of intelligent farm product storage and preservation system: (case study: Yam tuber)

Abstract

Based on FAO/World Bank report, the value of post-harvest food losses in sub-Saharan Africa is around $4 billion a year and this is mainly due to poor storage condition of the farm products. Yam tuber is one of the most commonly available farm products in West African and it belongs to one of the food items which suffer losses due to poor storage system. Presently, yam tubers are stored via the use of yam barn (of different construction and shapes), delayed harvesting (yams deliberately left in the ground), underground pits and raised huts. Unfortunately, all these storage systems produce unsatisfactory results as the yams are exposed to an uncontrollable environment (temperature, humidity, aeration, insects, rodents etc), thereby causing the tubers to lose its quality as well as to get rotten. Recent advancement in technology can be harnessed to improve the condition of traditional yam storage system. Consequently, this thesis examines simple but effective procedures in alleviating problems associated with traditional yam storage system through: (i) proper choice of construction materials, (ii) proper design of storage system (iii) effective method of ventilating the storage system and (iv) intelligent control of temperature and air flow within the storage system. The effect of outdoor temperature on the indoor temperature was first investigated under the influence of heat of respiration of yam tubers and changing properties of building materials. The timber material was found to have high resistance to outdoor temperature as compared to concrete and brick materials. The ventilation rate for yam storage system has been investigated for single span with single longitudinal roof opening and with both longitudinal roof and vertical side wall openings. The result shows an increase in ventilation rate with increase in window opening angle and temperature difference. The development of Computational Fluid Dynamics (CFD) as a powerful tool for prediction of air-flow around building are presented in this research, COMSOL Multiphysics was used to predict the air-flow distribution in a proposed yam storage system and results have shown acceptable ventilation rates that can be achieved through a cross-ventilation which is capable of removing heat of respiration of yam tuber. Finally, an intelligent control technique for yam storage system based on fuzzy logic controller was developed. The controller was simulated and later validated on the proposed yam storage prototype for different typical levels of input parameters. The results show that, the proposed controller is capable of responding to the changes in temperature conditions by adjusting the window opening angle to keep the internal temperature within acceptable range (13oC-17oC). The controller also satisfies safety requirements due to sudden changes in wind velocity and presence of rain fall.