Assessment of thermal and environmental benchmarking of a solar dryer as a pilot zero-emission drying technology

Abstract

Food drying is a highly energy intensive process and therefore significantly contribute to carbon emission. Although solar air dryers are considered renewable, they are not fully emission free as conventional energy from grid is required to run the fan or blower. The solar air efficiency as well as fan power requirements are influenced by the mass flow rate of air, and therefore flow rate is essential parameter for evaluating solar air dryer performance in terms of thermal, drying and environmental parameters. It is essential to develop a framework to evaluate critical mass flow rate by considering the optimum thermal, drying, and environmental performance for benchmarking of zero-emission solar air dryer. However, such a framework is currently lacking. To address this issue, a novel study was conducted using V-groove double pass solar air heater (SAH) to experimentally analyse thermal, drying and environmental parameters to develop a methodology for zero emission solar air dryers based on critical flow rate for fan power consumption. The experiments were conducted at five different flow rates (0.021, 0.031, 0.041, 0.051, and 0.061 kgs−1). The maximum thermal efficiency achieved was 74.89% at 0.061 kgs−1. However, the average COP, average exergy efficiency, moisture ratio, and CO2 mitigation had optimum results at 0.041 kg/s mass flow rate as fan power consumption was reduced by 16% compared to 0.061 kgs−1. The critical flow rate evaluation is useful for predicting and minimising power consumption and progress towards zero emission system by using photovoltaics in future systems. The successful implementation of the proposed method can substantially contribute to the industrialisation and cutting of emissions of solar air heaters for drying applications.