Environmental and economic analysis of a photovoltaic assisted mixed mode solar dryer with thermal energy storage and exhaust air recirculation

The cost effectiveness and the drying quality are the most common challenges for solar drying applications. The expensive kinetic and drying temperature sensing and control systems add to the cost in one hand, and the heat losses and the intermittent heat supplied result in poor drying quality in the other hand. In order to overcome these limitations for local farmers, a novel greenhouse cabinet solar dryer operating in mixed mode for household applications is fabricated with cost-effective and locally available materials. The environmental and economic performance of the proposed dryer is then compared with that of the conventional open sun drying. The proposed solar dryer includes a thermal energy storage system using paraffin wax and exhaust air recirculation to enhance the drying performance. The overall drying efficiency of the system is found to be 18.6% and 10.8% with and without the thermal storage, respectively. From environmental and economic perspective, the proposed dryer with thermal storage resulted in an energy payback time of 1.91 years and a discounted payback period of 0.8 years which is much lower than the dryer life making it both environmentally and economically sustainable.

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