Ambient ventilation cools a potato store with outside air whenever that air is colder than the crop; refrigeration cools it when outside air cannot. Many stores use both, with a Cropscan controller choosing between them automatically. This guide explains how each works and what decides the right mix for your store.
Potatoes in store need to be cooled and then kept at a steady temperature. There are two ways to do it. Ambient ventilation blows outside air through the crop when that air is colder than the potatoes. Refrigeration cools the store air mechanically, so it works whatever the weather is doing. We firmly believe in the benefits of combining the two, and most of the stores we equip use both.
A packaged ambient unit (PAU) is a free-standing mixer box with an axial fan, an ambient air intake louvre and a recirculation louvre, a wall intake section and a pest guard. When the outside air is cool enough, the fan draws it in and pushes it through the store; between cooling periods the recirculation louvre lets the fan keep the store air moving. Ducting on top of the unit carries the air to the top of the building, and a hood directs it over the boxes.
Cropscan’s airmix control works on duct temperature, so it can use outside air that is cooler than the crop without over-cooling it, and the operator sets maximum and minimum limits. Packaged ambient units give a cost-effective and efficient way to ventilate and control temperature, and they are especially suited to box stores and potato chitting stores. The fans are selected individually for each store.
When outside air is not cold enough, refrigeration takes over. A packaged refrigeration unit (PRU) holds the whole refrigeration system in one fully galvanised casing. It is fabricated and tested in the factory before despatch, and on site it only needs a three-phase mains connection. Because it is a self-contained package, it can be moved to another building later, or even sold as a working unit.
Other stores use split refrigeration units, with a remote condenser outside, or free-standing evaporator coils, which are mostly used in bulk stores and can be retrofitted to existing ambient stores. From the Tolsma-Grisnich Group we also supply climate units, the Quadro Compact Cooler and GCU cooling systems: see our refrigeration range.
An ambient-only store can only cool when the outside air is colder than the crop. A store that relies on refrigeration alone runs its compressor even when cold air is available outside for free. Combining them gives you cooling from outside air whenever it is available, and refrigeration to hold the temperature when it is not.
If you start with ambient ventilation, refrigeration can follow: a PAU stand can be lengthened to fit over existing solid walls, which also lets a fridge unit be added later. Motorised louvres give positive air control in both modes with minimal air leakage. Layout 1 on our potato storage page shows a box store with a packaged ambient unit, a packaged refrigeration unit, motorised louvres, a suction wall and air bags working together.
The Cropscan controller scans crop temperature continuously and selects refrigeration or ambient ventilation automatically, depending on the temperature differential. You can control on the highest or the average crop temperature, set limits to prevent over- or under-cooling, and set timed recirculation to keep air moving between cooling periods. A timed CO₂ purge clears carbon dioxide build-up. Connected to the internet, a Cropscan can be viewed and adjusted from a phone or tablet app, and it can email you about faults. On larger sites, the Vision Control climate computer’s Weather in Control module uses a 10-day forecast to decide when to ventilate with outside air and when to refrigerate.
Whichever way you cool, the air has to reach the crop evenly. In box stores, a timber suction wall at the same end as the air handling units evens out the air pattern, and air bags between the rows force air through the boxes. Fans matter too: EC fans use around 20% less power than AC fans, and less than half the power at 80% speed. A product humidity sensor helps keep unnecessary weight loss down, and the Fresh Box refreshes store air to remove CO₂ with minimal energy.
It depends on your tonnage, whether you store in boxes or bulk, and your building. Our technical sales team uses 3D and 2D design software to work through your requirements and specify the most efficient way to store your crop, in a new building or an existing one.
It cools the crop whenever outside air is colder than the potatoes. When it is not, the store needs refrigeration to hold the temperature, which is why many stores combine a packaged ambient unit with a refrigeration unit.
Yes. A PAU stand can be lengthened to fit over existing solid walls, which also lets a fridge unit be added later, and evaporator coils can be retrofitted to existing ambient stores.
The Cropscan controller. It scans crop temperature continuously and selects ambient ventilation or refrigeration automatically, depending on the temperature difference.
EC fans use around 20% less power than AC fans, and less than half the power at 80% speed.
Tell us your tonnage, whether you store in boxes or bulk, and your building through our contact page, and our design team will work out the airflow and refrigeration duty. Or see six typical layouts on our potato storage page first.
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