Design and construction of a solar powered silver fish dryer.

Abstract

Silver fish is one of the protein foods we have in Uganda and the world at large. It is consumed in a dried form most especially by middle income people across East Africa and other countries and mainly caught between January and May. After harvest, silverfish is highly perishable due to its high moisture content (73%) and therefore this moisture content has to be reduced up to 5% for a long shelf life in order for it to be used for either consumption or the animal feeds industry. Dried silverfish essential in brain development to children and helps pregnant women against the coronary heart diseases as a result of concentration of the unsaturated fatty acids caused by the drying effect. Silver fish is mainly consumed in a dried form by the usage of solar energy. The common forms of drying include the use of open air sun drying and the use of improved raised racks which have drawbacks such as extended drying hours due to uncontrolled drying conditions and high postharvest losses such as contamination from dust, animal droppings, and subjection to pests. This research report therefore provides for utilization of the renewable solar energy, optimization of the drying conditions with emphasis on temperature and humidity, and providing a hygienic and enclosed drying environment to minimize the post-harvest losses. A solar powered silverfish drier was designed and fabricated through the methodology, data was collected which involved literature reviews, designing the system components, constructing the prototype which was tested and the results analyzed. In this research project, thermometer readings gave a maximum temperature of 43°C recorded at 2:00pm being the peak sun hour of maximum insolation from the ambient temperature of 25°C; the transparent glazing was used a solar concentrator with a concentration ration of 1 to about 337W/m 2/day. A solar collector of 1.25 m 2 with a working principle of a black body radiation was used. Drying temperatures inside the dryer were monitored using a thermometer and records were made at hourly intervals records. Any further increase in temperature beyond 43°C, a solar powered sanction fan with a power rating of 15W and a speed of O.76ms1 was used to cause a temperature drop thus restoring the temperature inside the drier to ambient temperature. After achieving this temperature, temperature build is the allowed to continue as a result of the greenhouse effect created by the black body or the solar collector. However, testing the solar powered drier was not effective due to unfavorable weather conditions such as rainy and cloudy hours of the day. Further work such as measuring the air temperature at the fan exit, was done in order to evaluate the effectiveness of the sanction fan. Since most of the fish landing sites lack electricity, the adoption of this environmentally and ecologically sustainable drier will help improve the standards of living and preservation of the silverfish. Lastly, for purposes of further research, the solar angle of tilt sensors, temperature sensors connected to the fan has to be incorporated in order to automate the optimization process of the drying conditions inside the drier.