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Operating Conditions;

The crop is placed in drying trays. If it is in large pieces like yam or potato, it should be sliced or chopped. Cassava and sweet potato have been chopped into small chunks, 1 cm3 and smaller before drying. Yam has been sliced into thin strips 1 to 3 mm thick before drying.

Economic Details:

19 sheets, 0,457 galvanized steel 50.35

22,5 Kg, 50/50 tin-lead solder 87.50

3 tubes silicone sealant 13.50 2k vcr styrotex beads 6.90

1 Kg vermiculite .50

5 m, 6,35 mm mesh galvanized wire 3.12

4 hinges, rivets and paint 4.10

TOTAL COST of materials: 191.17

Labour, 120 man hours 96.00

TOTAL COST (1971) 287.17

Annual Operating Expenditure:

On the average, the unit will dry 11 Kg in about 10 hours and 22 Kg in about 15 hours since the lower trays dry more slowly. About 30 minutes per day is required for filling and charging trays. Operating costs are therefore about 1 person-hour of labour per 22 Kg load.

Capital costs, depreciation and interest rates will have to be calculated for each locality and will vary.

In Trinidad, capital charges are about 38.00 $U.S. per year, assuming an interest rate of 10%, an insurance cost of 5.00 $U.S. and a life expectancy of 10 years. At 1 100 Kg per year (assuming 100 days of drying) operating costs are 75.00 $U.S. Hence drying cost about 10.3 $ per Kg. This is for a seasonal crop where the load factor is about 30%; with higher load factors, costswill be lower.

Balance of money for the production of dried sorrel, under Trinidad conditions

Expenditures: cost in U.S. $

50 Kg of fresh sorrel 12.00

removal of seeds (about 50% of total weight) 4.00

transport, storage, etc. (2,5 Kg at 10ji per Kg) 0.25

incomes:

Sales during the off-peak season

net profit 8.67

i.e., it is possible to obtain a profit of nearly 50% on sorrel if it is dried, stored and then sold during the season when it is scarce.

Estimated Life of the Dryer; 8 to 10 years

Comments on the Dryer;

Construction problems are mostly technical; they require the use of a reasonably good sheet metal workshop, if however, the unit is built with wood, then construction is simple.

This unit is experimental and it is too expensive to be built on a large scale.

Principal investigator(s);

Headiey, Oliver Springer, Basil

University of West indies St. Augustine, Trinidad West Indies

No. 1 Dryer

No. 1 Dryer

Figure 2. Section View Through Solar Dryer
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