Cold storage for fresh fruit and vegetables

A cold-storage warehouse for a fruit and vegetable storage facility in Aussenkehr, Namibia, designed to store products such as grapes, melons, dates and tomatoes operates using a design from GEA Refrigeration Africa. Installed on behalf of the Dutch company Cool Fresh International BV, the storage complex comprises four halls, where produce cultivated by the Orange River Irrigation Project of the Namibia Agricultural Ministry and marketed by Cool Fresh are received, sorted and consigned through a cooling tunnel.

Loek Schoenmaker, Cool Fresh CFO, said, “We awarded the contract to GEA because this company – like our firm – operates in accordance with international standards.”

In this case, one GEA Grasso G3.10 and two GEA Grasso G4.10 ammonia piston compressors provide the refrigeration requirements for the halls. The compressors here operate in single-stage mode to cool the halls to the required temperature of approx 0°C to a maximum of 12°C.  At hall temperatures of around 8°C, they offer cooling duty up to 180 kW (G3.10) and 240 kW (G4.10). Zinc-plated evaporators cool the halls via airflow.

During design work, the GEA project team took into account that the humidity in the hall would remain high enough to prevent drying of the fruit and vegetables.

Storage of the dates, which are harvested from February to April, required a special solution to enable them to be frozen in one of the halls until export. The refrigeration system operates in two stages (-28°C/0°C and 0°C/+35°C) to achieve the required temperature of -20°C in the hall. Special valve units enable switchover between the two-stage mode for freezing and the single-stage cooling mode.
Immediately after the warehouse complex was commissioned in September of 2011, it was required to prove its effectiveness in the African summer. The concept has proven effective and met expectations for energy efficiency. Partly responsible for these results is the natural refrigerant ammonia, which enables great efficiency in the central refrigeration complex. In addition, ammonia is climate-friendly – since any ammonia leaks will not contribute either to the greenhouse effect or to depletion of the ozone layer.