Tuesday, 22 May 2018

 

What factors can help improve storage conditions and reducing loss as much as possible? Potato Business Digital spoke with specialists from Tolsma and Agrovent to find out. 

The Tolsma-Grisnich Method

When designing a new cold storage one should think about the following things, Jan van Maldegem, marketing manager at Tolsma-Grisnich, explains:

1. Different varieties with different storage temperatures (for example creating independent climate zones depending on the susceptibility of varieties for sugar accumulation or different respiration levels);

2.Logistics (limiting fork lift traffic so this will improve efficiency and limit the labor and heat production of the fork lift in the cold storage. Also easy access to different crops without taking out many others is a thing to think about.);

3. Intake of the product (How much product at one time will come into the storage and has to be cooled down simultaneously. This strongly influences the necessary installed cooling capacity);

4. Sales schedule (another thing to think about in advance is the schedule which the product will be taken out of the storage. Maybe not always the same cooling capacity is required when half of the storage is filled in the warmer months of spring and summer).

The calculation of physical storage capacity and volume is more or less like this:

Bulk storage: the weight of potatoes in bulk is about 650 kg/m3. Also 1000 tons of potatoes take a volume of 1538 m3. As a maximum height for “healthy potatoes” is more or less 4m this will result in an area of about 384m2. With bulk storage the maximum length of the ventilation ducts is about 25m, so the width will be15 m.

Box storage: the typical Dutch potato box contains about 2 m3 of potatoes being 1,300 kg. Usual stacking height is 6 so one pile (covering 1,2 x 1,6 = 1,92 m2) contains 6 x 1,300 = 7,800 kg.  

Depending on the system of ventilation (space ventilation, airbag system or letter box) the distance between the rows is about 20 – 50 cm.

The Agrovent Method

First you have to decide your storage method: in bulk, in boxes or otherwise. This choice can be affected by the product type, storage amount, mixed varieties and/or qualities in one storage and logistical considerations, Huub Kasius, managing director at Agrovent BV, explains.

In general, the higher the product value, the more inclined you will be to opt for a higher storage method (boxes vs bulk) in smaller quantities per room. 

Secondly, depending on the soil type and climate, one has to choose between the available storage methods. If you have a light soil and relatively dry product, a simple ventilation will do. If you need extensive drying, we will have to use a system with a pressure wall and forced ventilation.

With these choices made, we can start designing a storage room. Select the proper size that fits your logistical capacities. It does not make sense having one storage room of 2000 tons if you harvesting capacity means it would take weeks to fill up one room. In general we see room sizes between 200 and 1000 tons for boxes, and between 500 and 2500 tons for bulk storages

The type of cooling unit is also determined by the storage method. If you take a box storage with lower ventilation capacity (dry product), the ventilation and cooling equipment are usually combined in one single unit (Compact cooler, or Combivent). This unit also contains an inlet and air-mixing hatch to provide air refreshment and the use of suitable outside air for cooling.

In bulk storages, or all other systems with forced ventilation, a normal cooling unit with evaporators above the potatoes will be sufficient.

The complete version of this article can be read in our digital magazine which can be accessed free on tablet or mobile: 

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