How calculate refrigeration capacity for potatoes?

[Aik]

There is a problem: I need to calculate capacity for refrigerating unit and I don't how to calculate...
There is a potatoes depository in which storage potatoes which keeps in clamps. And there is ventilation in ducts (below floor).
In many literature sourses I red that cooling potatoes should realize by ventilation and the refrigeration unit should use only for maintenance temperature on later spring and summer.
Cuold anybody tell at what period (cooling, saving or both) the refrigeration unit must be used?
Where is evaporators can situated in room (depository)? Does refrigeration unit work at the same time with ventilation?

[nike123]

Check this pages:
http://oregonstate.edu/potatoes/
http://www.gov.mb.ca/agriculture/cro.../bda04s06.html

[Aik]

Check this pages:
http://oregonstate.edu/potatoes/
http://www.gov.mb.ca/agriculture/cro.../bda04s06.html

Thanks, nike.
In the first link:

Most of the crop is held in non- refrigerated, common, air ventilated farm storages.

My customer want to storage potatoes until june. At later spring and summer ventilation couldn't provide temperature conditions.
Ventilation eqipment has already install and I want to install air evaporators on the ceiling of depository.
If I understand correctly, ventilation must provide chilling and storage potatoes since harvest to beginning of may. Thus, air evaporators must work only in may and june (Am I righ?)
I want to placed air evaporators near the wall, opposite ventilation entrance. And suppose that ventilation must work on recirculation when air evaporators would work.
Could anybody tell remarks about my consideration? Maybe I have mistake in my conclusion?