Comparative evaluation of the performance of an improved solar-biomass hybrid dryer

Abstract

A solar biomass hybrid dryer intially designed with a front pass flat plate solar air heater and a biomass heating stove was redesigned, reconstructed in order to minimize the excessive convective heat losses and its performance re-evaluated. Due to poor design and contruction of the biomass heating and solar collector sections, the efficiency of the initial design was low. It is believed that the drying efficiency of the dryer could be enhanced if a back pass solar collector and a biomass heating stove incorporated with a gas to gas heat exchanger to ensure that the hot air reaching the samples is clean, smokeless and ash free, substitute for the original solar collector and biomass unit respectively in the improved version. The system's drying performance was tested on both no load and full capacity load under different meteorological conditions within Nsukka (Lat. 7°N) for two weeks. The testing results showed that the incorporation of a new back pass solar collector and the heat exchanger enhanced the trays temperatures on no load test. Similarly, the efficiency of the dryer based on solar, biomass and solarbiomass heating in drying of fresh okra, fresh groundnut and fresh cassava chips increased from 5.19-16.04%, 0.23-3.34% and 1.636-8.96% respectively over the initial construction. This shows that the dryer can help improve the post-harvest processing and storage quality of farm produce by drying if further optimized.