Drying fish (Rastrineobola argentea) on the bank of Lake Victoria in a prototype solar-heated enclosure: Using renewable energy to reduce drying-time and improve product quality and value

Abstract

Silver cyprinids (Rastrineobola argentea) are small pelagic fish endemic to Lake Victoria. High-quality dried fish are an important protein-rich human food. This study was carried out to determine if it would be practical to use renewable energy to dry silver cyprinid. Drying is presently achieved by laying fish out in the sun on the ground or on racks. In the wet seasons, however, drying is compromised and much of the catch becomes fit only for animal consumption, or spoils. Lake Victoria’s surface waters are c. 25°C year-round. Its enormous volume of tropical water offers a source of thermal energy that could be used to dry fish. As a proof of concept, we used solar-generated electricity to drive a heat pump to harvest heat energy from water in a 10,000-L rainwater tank beside Lake Victoria, used the energy to heat air, and blew the air over fish in a tent-like enclosure. Fish in the enclosure dried in about 4 h versus about 7 h outside, were free from insects, and not at risk of theft by or defecation upon by birds. The drying processes inside and outside the enclosure were modelled. The model correctly reproduced observed drying times, and enabled exploration of options to improve drying performance. Up-scaling the prototype could provide year-round sustainable fish-drying capability, reduce waste, boost food security, and add value to the catch.