How to future-proof your potato cooling system

A well-designed cooling system is vital for minimising storage losses and maintaining produce quality. However, the challenge lies in doing so sustainably and energy-efficiently.

Additionally, the extreme weather patterns and harvest variations we’ve seen in recent years significantly impact the storage process. So, how can you ensure your cooling system is built to withstand these challenges?

Three questions to determine the right cooling capacity

To determine the appropriate capacity and setup for a cooling system, it’s essential to answer these three questions:

1. What cooling capacity do your potatoes require?

Consider when and for how long you intend to store your potatoes, how quickly the temperature needs to decrease and the conditions under which you want to store the produce for a specific period.

This requires performing a cooling load calculation.

Depending on the variety of potato, the cooling capacity ranges from between 60–140 watts per tonne of stored produce.

2. Do your storage cells need to be cooled simultaneously, and when?

Create a cooling schedule to determine which rooms will be cooled simultaneously.

For example, if you have three rooms with a total cooling capacity of 100kW, but plan to use only two rooms at full capacity simultaneously, the simultaneity factor would be 2/3, or 67%.

In this case, your cooling system would only need to provide 200kW of cooling.

3. At what temperatures will the cooling take place?

Establish the maximum outdoor temperature and the minimum room temperature.

With this information, you can determine the condensation temperature and the evaporation temperature of your system.

The condensation temperature is typically 10°C higher than the maximum outdoor temperature, and the evaporation temperature is typically 7°C lower than the minimum room temperature. These values are crucial for determining your system’s effective cooling capacity.

Choose a cooling system that meets your needs

Two types of cooling systems are commonly used for storing potatoes. A direct cooling system (often referred to as DX or Direct Expansion) and an indirect cooling system.

In a direct system, a refrigerant evaporates in the cooling coils of the system, cooling the air in the storage rooms.

The compressor compresses the gas, raising its temperature, and this hot gas then condenses in the condenser, releasing heat to the outside air.

An indirect system can also be used, where the cold air is not directly released into the storage rooms, but instead it circulates through an intermediary system that uses a mixture of water and glycol.

A direct cooling system is typically more cost-effective in terms of initial investment and generally consumes less energy compared to an indirect system.

On the other hand, an indirect cooling system allows for more precise control of the temperature in the coolers in each storage room individually.

This helps tailor the cooling process more precisely to your potatoes and minimises the risk of dehydration.

Use of efficient natural refrigerants

Cooling with natural refrigerants is not only more environmentally friendly than synthetic alternatives but can also help reduce energy consumption.

Depending on your situation, natural refrigerants can reduce energy consumption by around 15–30%.

The most used natural refrigerants are propane, CO₂ and ammonia.

Generally, propane is ideal for smaller cooling capacities up to around 75kW, CO₂ for capacities up to around 300kW and ammonia is best for larger capacities.

The efficiency of natural refrigerants depends on factors such as variety, outdoor temperature, the storage room temperature and whether a direct or indirect cooling system is used.

Consulting with an expert is recommended for guidance.

Continuous monitoring of storage conditions

Use a storage management system that monitors real-time conditions of your produce 24/7.

This system automatically adjusts the cooling system, hatches and air circulation to maintain the desired conditions in your storage.

By properly setting up automation, you can reduce manual workload and ensure your potatoes stay at the perfect temperature.

Now’s the perfect time to review your storage

Learn what you can improve in your storage and make sure changes are implemented before your next harvest.

Contact Omnivent’s UK representative Ronnie Laing for a no-obligation storage consult.

Visit omnivent.com/consult or call 0794 006 7458.

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