1. Introduction
Preservation of agricultural produce is one of the central problems facing developing countries. Owing to the lack or inadequacy of preservation methods, large quantities of urgently needed food spoil there. And as time goes on, these problems will be aggravated by the growing dietary needs of these countries burgeoning populations.
In Morocco this problem exists with many fruit and vegetable varieties, which cannot be marketed fast enough owing to their limited keep-ability. Large quantities of apricots, grapes, and tomatoes spoil owing to inadequate infrastructure, insufficient processing capacities, and growing marketing difficulties caused by intensifying competition and protectionism in the world's agricultural markets. Drying these products can help solve these problems, while also making an important contribution to improving the population's income and supply situation.
However, traditional sun drying methods often yield poor quality, since the produce is not protected against dust, rain and wind, or even against insects, birds, rodents and domestic animals while drying. Soiling, contamination with microorganisms, formation of mycotoxins, and infection with disease-causing germs are the result. The drying equipment used in industrialized countries overcomes all of these problems, but unfortunately is not very well-suited for use in Morocco because it requires substantial investments and a well-developed infrastructure.
Solar drying facilities combine the advantages of traditional and industrial methods, namely low investment costs and high product quality. Based upon this realization, the "Special Energy Program Morocco (SEP)" of the Deutsche Gesellschaft fhnische Zusammenarbeit (GTZ) GmbH provided the framework for an effort to develop a solar dryer that is appropriate to the climatic and structural conditions prevailing in Morocco. This work was conducted in cooperation with the Office Regional de Mise en Valeur Agricole du Haonz (ORMVAH) in Marrakech, the Institut Agronomique et Vrinaire Hassan II (IAV) in Rabat, the Centre de Dloppement des Energies Renouvelables (CER) in Marrakech and the Institute for Agricultural Engineering in the Tropics and Subtropics of the University of Hohenheim (UK) in Stuttgart, Germany.
The first phase (1989-1990) of the project section "Solar Drying" was devoted to developing a dryer for fruits and vegetables that could be constructed using locally available materials only. In the second phase (1991-1993), this solar dryer served as the basis for devising a batch dryer for medicinal and spice plants to diversify the product palette. Parallel to this, market analyses were carried out for the dried products and the economic efficiency of the solar dryer was calculated. In the ongoing third phase (1994-1996), additional demonstration facilities are being installed to support dissemination of the solar dryer.
