Techno-economic analysis of a hybrid solar-electric dryer

The technical performance and economic analysis of a developed hybrid solar-electric dryer (HSED) were investigated in this research work with respect to energy, exergy, and environmental sustainability. Experimental investigations were performed with and without load during the rainy season, in which the sunshine periods were affected by intertropical discontinuity, prompted by cold-prevalent wind interference from the Atlantic Ocean and regional water catchment. Thermal characteristics and drying efficiency of the hybrid dryer, as well as the effect of different drying temperatures (50, 60, and 70 degrees C), air velocities (0.5, 1.0, and 1.5 ms(-1)), and sample thicknesses (10, 15, and 20 mm) on the overall and specific energy usage for 1,500 g batch size of fresh sliced tomato samples, were investigated. The percent energy contributions of the solar and electric heat units at varying air velocities were also determined. Results obtained indicate that the mean solar collector efficiencies during sunshine hours ranged between 24.6 and 70.3%. The total and specific energy consumption of tomato slices (Lycopersicon esculentum) varied between 5.61-120.31 kJh and 5.18-167.59 kJhg(-1), respectively. Analysis of variance results show that drying air temperature, sample thickness, and velocity of air were significant atP> 0.05. The percent energy contribution by solar and electric heat units varied between 44.57-56.24% and 43.76-55.43%, respectively. Drying time and drying efficiency ranged between 130 +/- 7 and 330 +/- 5 min and 4.33-36.38%, respectively. The average energy efficiency of the hybrid system increased from 15.67 to 38.17%, whereas the mean exergy efficiency varied between 32.2 and 87.9%. The sustainability indicators such as ratio of waste exergy, sustainability index, and improvement potential of the HSED ranged from 0.083 to 0.158, 1.93-6.77, and 0.099-0.289 kJs(-1), respectively. Optimum drying conditions for improved final quality were given. The economic analysis established that the HSED could save up to $1,490.33 per annum with a low payback period (0.72 years), thus making the dryer cost effective and economically viable. Prospects for improvement and future works were highlighted.