Commercial preservation of agro-produce by solar drying entails using large-scale dryer units that are generally not affordable by potential users in a rural setting. The objective of this study was to design a photo-voltaic greenhouse solar drying unit with air convection powered by a photovoltaic system as part of a research study to develop a cost-effective commercial solar dryer for the preservation of tomatoes in a rural setting. The design methodology involved. First, the determination of thermophysical properties of local tomatoes and predicting its drying model. Second, determination of design parameters; design equations, design conditions and assumptions, and psychrometric analysis. Third, application of the design parameters under the climatic conditions of Botswana to produce the embodiment of design with the drawings and specifications for a solar hot air dryer unit of 2000 kg batch-load of wet tomatoes. This drying unit is integrated into a solar collector with a cost-friendly thermal energy storage system to store solar energy during the day for use after sunset for better performance.