Solar dryers have always been criticized for their lower performances. There are numerous ways to define the performance of a solar drying system such as thermal performance, drying kinetics, environmental aspects, economic evaluations, and quality of the dried product. Different modeling techniques have also been developed to design and analyze solar dryers and drying processes. This article presents a systematic, comprehensive, and state-of-the-art overview of various performance indicators and modeling techniques used for the evaluation and analysis of solar dryers, especially domestic and low cost solar dryers. Environmental analysis has severe global implications, and product quality is one of the biggest concerns of consumers. But the environmental impact and product quality assessments for domestic solar dryers are observed to be rarely reported in the literature. The use of modeling techniques in solar drying has changed the way of analyzing any thermal system. Here, an attempt is made to establish an overall assessment criterion for domestic solar dryers and to give a one-stop solution for researchers and users around the world.
This work explores the effect of latent heat storage on the performance of a passive‐type mixed‐mode greenhouse dryer for groundnuts drying. Experiments were conducted for mixed‐mode greenhouse groundnuts drying (MMGGD), modified mixed‐mode greenhouse groundnuts drying (MMMGGD), and open sun groundnuts drying (OSGD) under the climate of Hisar (India). Average convective heat transfer coefficients for MMGGD, MMMGGD, and OSGD were 0.738, 0.607, and 0.555 W/m2 °C, respectively, and the respective average evaporative heat transfer coefficients were 113.304, 41.483, and 14.266 W/m2 °C. Energy and exergy efficiencies were found higher for MMMGGD, whereas the specific energy consumption was found lower as compared to MMGGD. Statistical analysis has shown the appropriateness of the page model for predicting the thin‐layer drying behavior of groundnuts for MMGGD, MMMGGD, and OSGD. The lower value of energy payback time (4.47 years) and the higher value of CO2 mitigation (953.299 tons) for MMMGGD show the environmental suitability as compared to MMGGD.
Practical applications
The present study focuses on the development of drying systems to prevent post‐harvest losses in groundnuts due to moisture and uncontrolled weather conditions. The temperature range of the proposed modified mixed‐mode greenhouse dryer is suitable for drying for most of the agricultural commodities. This drying system can be used for a range of food crops in different small and medium industries. Due to electrical independence, the proposed system seems best suited for small farms and farmers in remote and rural areas. The modified mixed‐mode greenhouse may also be used as a field‐based storage house for grains and freshly harvested crops.
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