TABLE 1. The drying of green mango slices and diced sweet potatoes in a solar cabinet dryer. DAY TIME DRYING DRYING MOISTURE DRYING TIME (hr) TEMP.(C) CONTENT (%) EFFICIENCY (Z) Mangoes 1 11.00 0 43 87 - 1 13.00 2 47 83 57 1 15.00 4 48 77 50 1 17.00 6 37 74 39 2 8.00 9 37 68 31 2 11.00 12 55 55 28 2 14.00 15 50 40 25 2 17.00 18 36 29 22 3 9.00 22 60 23 18 3 11.00 24 66 12 17 Sweet Potatoes 1 11.00 0 50 67 - 1 13.00 2 53 47 83 1 15.00 4 56 22 65 1 17.00 6 41 13 46 2 8.00 9 47 10 40 2 11.00 12 45 5 31 TABLE 2. The drying of sorrel and hot peppers in a solar cabinet dryer. DAY TIME DRYING DRYING MOISTURE DRYING TIME (hr) TEMP. (C) CONTENT (%) EFFICIENCY (%) Sorrel 1 10.30 0 51 88 - 1 13.00 2.5 52 80 59 1 16.00 5.5 47 68 43 2 8.30 10.0 37 53 28 2 11.00 12.5 60 32 24 2 13.00 14.5 55 21 22 Hot Pepper 1 10.00 0 53 87 - 1 13.00 3.0 57 81 66 1 14.30 4.5 52 77 59 2 9.00 11.0 37 66 34 2 11.00 13.0 49 53 33 2 13.00 15.0 47 31 32 TABLE 3. Solar cabinet drying systems for small farms ranging from 0.125 1.0 ha in size. FARM SIZE (ha) 0.125 0.250 0.500 1.00 Quantity of crop to be dried per annum, (kg) 750 1500 3000 6000 Dryer batch size, (kg) 17.8 35.7 71.4 142.8 Dryer cover area, (m2) 3.8 7.7 15.4 30.8 Estimated dryer initial cost, ($US) 75 150 300 600 Based on an annual yield of 12,000 kg/ha for sorrel and assuming 50% sold on the fresh market dried. With simple woodframe construction and plastic sheeting, it is felt that the minimum initial cost/m2 of dryer area is approx- imately US$20.00. With these parameters, for farms ranging in size from 0.125 1 ha, the dryer capacity using Equation [3], the dryer cover area us- ing Equation [5] and the dryer initial cost using Equation [6], may all be established. These calculated results are shown in Table 3. For the small Caribbean farmer, these initial costs, although significant, may be acceptable. However, for larger acreages, the initial costs associated with solar drying may be pro- hibitive, despite benefits of reduced labour requirements and im- proved crop quality as compared to open sun drying. It should be noted that to obtain rapid drying of perishables, the approximate loading density of the crop in the solar cabinet dryer should be less than 5 kg/m2. Higher loading densities will require stirring of the crop in the trays to ensure uniformity in drying and to pre- vent possible deterioration. CONCLUSIONS Perishable crops such as sweet potatoes, sorrel, hot peppers and green mangoes can be safely dried in a simple solar cabinet dryer. With loading densities of less than 5 kg/m2 of drying tray area, drying can be completed in two days of fair weather. The drying efficiency is dependent upon the crop characteristics, and as dry- ing proceeds and the drying rate reduces, the drying efficiency correspondingly declines. For the multi-rack cabinet dryer tested, an average drying efficiency of 25% in the complete drying cycle can be expected for crops such as de-seeded sorrel, cut hot pep- pers and sliced green mangoes. The simple solar cabinet drying system appears suitable for use by small farmers desirous of drying a portion of their annual crops. Such a system can reduce the labour requirements associated with open sun drying and may also improve the quality of the crop. For the small Caribbean farmers, with farm sizes of 0.125 1 ha, the initial costs of such systems are significant, but not prohibitive. Acknowledgements The author would like to thank Mr. Milton Edwards (Dominica), Mr. Gene Knight (St. Kitts) and Mr. Ivan Rodriques (Antigua) for their contributions to this study. References 1. Headley, 0. and Singh, U. 1979. Solar drying of crops. Proceedings of the Symposium on Technology Applied to Solar Energy Systems, University of Mexico, pp. 237-246. 2. Lawand, T.A. 1966. A solar cabinet dryer. Sol. Energy 10:158-164. 3. Lof, G.O.G. 1962. Solar energy for the drying of solids. Sol. Energy 6:122-128. 4. Pande, P.C., K.P. Thanvi, N.M. Nahar, B.V. Ramana Rao. 1981. A multipurpose device. Sunworld 5:141-143. 5. Sandhu, B.S., K.D. Mannan, G.S. Dhillon, L.S. Cheema. 1979. Design development and performance of multi-rack natural convection dryer. Proceedings of the International Solar Energy Society Silver Jubilee Congress. 1:25-28. 6. Smith, G.W.R. 1967. Solar radiation measurements at St. Augustine, Trinidad: An interim report. University of the West Indies, St. Augustine, Trinidad. 7. Szulmayer, W. 1971. From sundrying to solar dehydration. I. Methods and equipment. Fd. Technol. Aust. 23:440-443. 8. Umarov, G.G., and Z. Tairov. 1982. A combination solar unit for drying fruit and grapes. Geliotekhnika 18:61-63. PROCEEDINGS of the CARIBBEAN FOOD CROPS SOCIETY-VOL. XX 266