What is a sub-zero cold storage?

A sub-zero cold storage is a facility in which the temperature is maintained between 18 to 20 degrees Celsius. By using special refrigerants and two-stage compressors, the temperature can be lowered to as low as minus 40 degrees Celsius. This type of cold storage is used for freezing various fruits, vegetables, and food items.

History of Sub-Zero Cold Storage:

The history of cold storage in Iran dates back to the preservation of food in caves. With the advancement of Iranian architecture, icehouses became the best places for preserving food. In the past, they would pour water that had frozen overnight into ice pits, filling the space between the ice with water to freeze it again and make it thicker, ensuring it wouldn’t melt easily. Then, they would cover it with soil and soft straw for use in the summer. In 1290, the first cold storage was established in Iran by the Russians for the storage of seafood from the north. With this development, cold storages have evolved into their present form. The history of cold storage in Iran spans approximately 280 years, and this progress continues with the production of sub-zero and above-zero cold storages.

Types of Sub-Zero Cold Storage:

• Small Sub-Zero Cold Room: This type is suitable for stores and hypermarkets for the storage and distribution of food and protein.
• Containerized Cold Storage: This type is used for long-term storage of food items and is primarily used on ships and oil platforms. These cold storages are produced in two sizes: 20 and 40 feet.
• Industrial Sub-Zero Cold Storage: This type of cold storage is built for the long-term storage of products and food items in large sizes. Items such as meat, fish, shrimp, dried fruits, and fruits are stored in it.
• Mobile Sub-Zero Cold Storage: This type is suitable for transporting frozen food items.

Technical Specifications of Sub-Zero Cold Storage:

Sub-zero cold storage is built with a capacity of 20 to 80 horsepower. Depending on the type of application, equipment within its capacity range is used. Sub-zero cold storages are divided into two categories based on the refrigerant gas used:

Freon Sub-Zero Cold Storage:

Advantages include non-flammability, non-toxicity, and lower maintenance costs compared to ammonia cold storage. For this reason, it has many enthusiasts. Freon cold storage is used in cases where a small cold storage is needed.

Ammonia Sub-Zero Cold Storage :

This type of cold storage is highly desirable for storing food items. Its advantages include the highest cooling effect among refrigerants, cost-effectiveness, and the strong odor of the refrigerant (which is crucial in case of a leak in the cold storage). These cold storages are more suitable for installation in factories.

Sub-Zero Cold Storage Flooring:

To cover the floor of a sub-zero cold storage, polyurethane and epoxy floorings are used.
Epoxy flooring is durable up to minus 4 degrees Celsius, and polyurethane flooring is suitable for temperatures down to minus 30 degrees Celsius. Temperatures above 30 degrees can damage polyurethane flooring, so it is reinforced with concrete and hard layers underneath. Heaters and heating pipes are usually used in the lower layers of the cold storage to protect the floor coverings for longer durability.

Sub-Zero Cold Storage Flooring:

• Extends the shelf life of products
• Stores food items like meat, chicken, fish, and shrimp.
• Rapidly freezes food items.

Disadvantages of Sub-Zero Cold Storage:

• Food items should be replaced with fresh ones after 14 days.

Applications of Sub-Zero Cold Storage:

In the pharmaceutical industry, sub-zero cold storage is used in pharmacies, drug production and distribution companies, and hospitals.
In the food industry, it is used in stores, hypermarkets, warehouses, food production factories, meat and poultry slaughterhouses, restaurants, dining halls, and greenhouses.
In the chemical industry, these cold storages are used in companies producing and distributing chemicals.

Constructing a Sub-Zero Cold Storage:

One of the most important issues facing those in this field is the construction of a sub-zero cold storage and the costs of equipping and preparing it. The main expenses for building a sub-zero cold storage and preparing it include: the dimensions of the cold storage, electrical plans, electrical panels, motor (compressor), operator, sandwich panels, valves, and control equipment (such as Castel or Danfoss).