Greenhouse drying shows a significant role in the bulk level of drying. In the present setup, a greenhouse dryer operating under natural convection mode was designed and fabricated. The sensible heat storage concept was applied to the bed of the drying chamber. Four different beds, namely, gravel bed, ground bed, concrete bed, and black painted gravel bed was being selected for the comparative heat transfer analyses of the proposed setup. The maximum heat gain takes place at the black painted gravel bed conditions, i.e., 53%, while for concrete bed, gravel bed, and ground bed, it is 33%, 49%, and 29%, respectively. Hence, black painted gravel bed condition is strongly recommended for maximum heat storage. The proposed setup was used for drying of tomato flakes in black painted gravel bed condition. It has been found that the moisture content in the tomato flakes has been removed from 96% to 9.10% in 13 h. The average drying efficiency of the proposed greenhouse dryer is found to be 23.49%. The comparative analysis of the performance evaluation has been done with other investigators, and it was found that the drying rate of the proposed setup shows superior performance as compared with others. The design of the proposed greenhouse setup with black painted gravel bed condition is strongly recommended for small-scale industries and farmers.

Solar stills represent a crucial technology in the quest to provide clean and accessible water, particularly in regions facing water scarcity and limited energy resources. This study investigates various solar still designs, exploring their advantages and limitations in water purification. Through an analysis of the current global landscape of solar still usage and ongoing research endeavors, this study aims to highlight the potential of solar stills and propose modifications to enhance their efficiency. The study also investigates various extensive analysis of diverse solar still designs and their performance metrics, including factors like reflectors, wick materials, absorber plates, and air velocity, this study elucidates key strategies to augment water output and energy utilization. Reflectors and pebbles, variations in wick materials, and modifications in absorber plate design have shown promising results in increasing productivity. Additionally, insights into the impact of environmental variables such as solar radiation, wind velocity, and ambient temperature on solar still performance are provided, informing the design optimization process. Through an analysis of global usage patterns and ongoing research efforts, this study highlights the untapped potential of solar stills and proposes strategies to enhance their performance. Furthermore, it suggests avenues for future research, including the integration of heat storage materials and the development of advanced modeling and control algorithms, to further enhance the performance of solar stills. Through these efforts, solar stills can emerge as a sustainable and reliable solution for water purification, contributing significantly to global efforts to combat water scarcity.

Drying via solar energy is an environmentally friendly and inexpensive process. For controlled and bulk level drying, a greenhouse solar dryer is the most suitable controlled level solar dryer. The efficiency of a solar greenhouse dryer can be increased by using thermal storage. The agricultural products dried in greenhouses are reported to be of a higher quality than those dried in the sun because they are shielded from dust, rain, insects, birds, and animals. The heat storage-based greenhouse was found to be superior for drying of all types of crops in comparison to a normal greenhouse dryer, as it provides constant heat throughout the drying process. Hence, this can be used in rural areas by farmers and small-scale industrialists, and with minor modifications, it can be used anywhere in the world. This article provides a comprehensive analysis of the development of solar greenhouse dryers for drying various agricultural products, including their design, thermal modelling methods, cost, energy, and environmental implications. Furthermore, the choice and application of solar photovoltaic panels and thermal energy storage units in the solar greenhouse dryers are examined in detail, with a view to achieving continuous and grid-independent drying. The energy requirements of various greenhouse dryer configurations/shapes are compared. Thermodynamic and thermal modelling research that reported on the performance prediction of solar greenhouse dryers, and drying kinetics studies on various agricultural products, has been compiled in this study.

This communication focuses on the experimental investigation of mixed heat storage based hybrid greenhouse dryer. The proposed system is a combination of a solar air heater and greenhouse dryer. The mixed heat storage material is applied on the bed of the dryer, which is a combination of paraffin wax and black painted gravel. The tomato flakes were selected for drying in both hybrid system and natural sun drying. Tomato flakes were rehydrated up to 1.29% and 10.10% under hybrid and open modes. The daily drying efficiency for drying tomato flakes in the proposed dryer was 50.18%, while it was 30.02% for open mode. The effective moisture diffusivity was 0.8666 × 1010 m2/s and 11.650 × 10¹⁰ m²/s for open and hybrid modes. The embodied energy of the novel hybrid greenhouse dryer was evalauted as 1591.07 kWh, and the cost was calculated as 22664.30, while CO₂ emission/year of the system was found to be 33.86 kg. The payback time of the proposed system was found to be 1.87 year; hence the amount invested in the manufacturing of the dryer can be recovered in a shorter period, with higher profit.