A Comprehensive State-of-the-Art Review on the Recent Developments in Greenhouse Drying

Abstract

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.

Review of recent advancement in performance, and thermal energy storage studies on indirect solar dryers for agricultural products.

“…Air that has been heated by the solar is forced through the drying chamber by air pressure, buoyancy forces, or a combination of both. Moist air is evacuated through a chimney or an exit at the top of the dryer [38], [39]. These dryers can be used to preserve fish, vegetables, and fruits at home by drying modest quantities of agricultural items at temperatures between 40°C and 50°C.…”

Novel design and performance evaluation of an indirectly forced convection desiccant integrated solar dryer for drying tomatoes in Pakistan

“…Moreover, the ancient food was dried directly from the sun and breeze. More evidence of the former cultures has been found, each would have approaches and materials that would replicate their sources of sustenance, such as domestic animals and fish etc [ 3 , 4 ]. Vegetables & Fruits have also been preserved thro drying since ancient periods [ 5 ].…”

Development of Finite‐Element Model for Drying of Tomato Flakes under Passive Greenhouse Dryer: Experimental Validation and Optimization Potential

“…The primary objective of drying is to reduce the product's moisture content to a level that ensures safe storage for a specific period. [ 2 ] Greenhouse solar dryers are currently outperforming conventional solar dryers in terms of efficiency, as shown by Ahmad et al [ 3 ] Numerous studies have explored the use of passive greenhouse solar dryers for drying tomato flakes. A medium‐sized, natural convection (passive) solar dryer was built using affordable local materials and a thin polythene sheet.…”