Environmental Sustainability Analysis of a Hybrid Heat Source Dryer

Abstract

This paper presents the energy and exergy-based environmental sustainability analyses of a developed solar dryer equipped with electric heater as supplementary heat. The experimental study was applied for drying a local variety of red pepper (Shombo) near a coastal region of eastern Nigeria. The objectives of the study were to assess the suitability and overall performances of the hybrid solar dryer in this area. Results obtained indicate that the solar collector contributed about 39.4 to 48.5% of the total drying air temperature required for drying operation. The energy efficiency of the hybrid solar dryer ranged between 13.2 to 35.6%, whereas the specific energy requirements varied between 7.24 kJkg− 1 to 63.5 kJkg− 1. The percent solar energy contribution to the total energy requirement ranged between 28.8–52.68% at varying air temperatures (50, 60, and 70oC) and air velocities (1.14, 2.29, and 3.43 ms− 1). The drying time varied between 75 ± 5 to 180 ± 24 min. The energy and exergy efficiencies varied between 13.2–35.6% and 35.8 to 92.3%, respectively. The exergy-based sustainability indicators which take into account the ratio of waste exergy, sustainability index, and improvement capacity of the hybrid heat source dryer were found to be 0.11–0.167, 1.14–6.12, and 0.099–0.289 kJs− 1, respectively. Comparison between a CI-engine powered dryer reveals that the use of a hybrid solar-electric dryer can prevent emission of 398.86 to 3872.7 tons of CO2 into the environment per annum. Recommendation for future studies was suggested.