solar fruit drying

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Effects - Sean Currans – AG 21 August 2013

SOLAR FRUIT DRYING

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Value Adding

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Aftabi Raisins

Grower price Aftabi

$0.50 to $2.00/kg

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Kishmish Raisins

Grower price = $2.00 to $5.00 / kg

Premium 25mm Shundukhani kishmish

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Kishmish Khana Tradition

Large 30 meter long Kishmish Khana• Estimate $12,000 cost to build• 13,500kg fresh Shundukhani yield 3,300kg kishmish

• 13,500 x $0.30/kg = $4,050 cost of grapes• 3,300 x $2.00/kg = $6,600 gross• 3,300 x $5.00/kg = $16,500 gross• Gross kishmish revenue - cost of grapes = added value

• $6,600 - $4,050 = $2,550 added value• $16,500 - $4,050 = $12,450 added value

• 30 days to dry grapes and traditionally one batch per season

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Improved Direct Solar Drying

• More sanitary• Faster drying• More productive

• “Direct” Solar• Maybe Kishmish if use p.metabisulfite?

• “Batch” process

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Critical Kishmish Parameters

What makes Kishmish raisins?

• Shundukhani grapes• Shade

– minimal Ultraviolet light

• Lower temperatures– Probably no higher than 38 Celsius

Should experiment with potassium carbonate and potassium metabisulfite

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Raisin Production• Drying grapes

– Heat– Air flow– Relative Humidity– Time

• Drying can be faster, if:– Higher temperatures are maintained 24/7– More airflow– Grapes are spread in thin layers– Some grape treatments are used

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Kishmish Khana / Kishmish Konex™?

Is Kishmish Khana necessary ?

Perhaps containers will be better?

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Break & Questions

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Technical Raisin Questions

Kishmish Raisin Quality1. If constant 38 Celsius temperature, will quality be

same?

2. If raisins are dried faster with more airflow, will quality be same?

3. If grapes are pre-treated to speed drying, will quality be the same?

• Potassium carbonate• Blanch hot water• Other

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Conventional Dryer with Gas Heat

‘McKenzie’ Dryer• 1860kg fresh grape• 465kg Kishmish• $930-$2325 per load Kishmish• Guessing 48 hr per load at 38 Celsius

Estimate Cost to run• Electric fan = $1.00/hr• Gas heat= $5.00/hr

$6/hr x 48 hr = $288

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Indirect Solar Drying

Containers• Inexpensive• Protects fruit from sun• Easy sanitation• Easy to modify to create indirect solar dryer

65 Celsius

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Solar Container Dryer Estimates

Rough estimate:• 9,525kg fresh Shundukhani grapes = 2,116kg kishmish

• With high airflow only perhaps dry in 8 days

• With high airflow and solar collector with heat storage, perhaps dry in 4 days.

• 2,100 kg Kishmish x $2/kg = $4,200 in 8 days?

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Experiment Proposed

• Thin layer grapes• 80mm tray spacing• High speed fan airflow• container with solar collector or without

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Small Scale Experiment Proposed

Small test box could make from wood• Thin layer grapes on mesh trays• 80mm tray spacing• High speed fan airflow• Keep grapes in dark• ensure fresh ambient airflow

How many hours to dry grapes into Kishmish raisins?

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Break & Questions

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Solar Dryer - only ambient heat

Insulated ducting

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What is a Solar Collector?

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Solar dryer -with collector only

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What is Heat Storage?

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Solar Collector and Heat Storage

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Solar Dryer Workflow

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Solar Container Dryer Estimates

Rough estimate:• 9,525kg fresh Shundukhani grapes = 2,116kg kishmish

• With high airflow only perhaps dry in 8 days

• With high airflow and solar collector with heat storage, perhaps dry in 4 days.

• 2,100 kg Kishmish x $2/kg = $4,200 in 8 days?

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Questions

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Summary

1. Anybody want to learn more?

2. Shall we build a small test dryer box?

3. Shall we build a pilot Kishmish Konex™?

solar fruit drying

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