Summary

The agricultural and the food and beverage industries are increasingly using energy for cooling and freezing. TNO (Netherlands Organisation for Applied Scientific Research) has recently examined the possibility of producing a design guide for engineers and suppliers, known as Energy Monitor Refrigeration and Freezing. The Monitor provides guidelines for the design of energy-efficient refrigerating and freezing plants for almost all operational conditions.

The Monitor is now complete. TNO's preliminary study produced a basis for a design strategy for energy-efficient refrigeration and freezing. The strategy consists of four stages: determining the energy class, energy demand, cold store design and the installation concept.

The first priority in designing an energy-efficient cold store is to determine the energy class the owner requires. There are three classes: A (highly efficient), B (efficient) and C (moderately efficient). When that has been decided, the engineering stage starts.
First, the designer assesses the minimum refrigerating capacity. This depends on, among other things, the product metabolism, the heat output of the equipment installed in the cold store, the production volume and the requisite cooling-down time.

The effects of the various construction methods on energy demand (transmission losses) can then be assessed. At this stage, the designer chooses the wall materials, insulation and doorways. Opportunities for heat recovery are also ascertained at this point.

Finally, the results of the previous stages are processed into an installation concept. Choices are made between direct and indirect cooling and between centralised and decentralised refrigeration. The control method is also decided at this point.