NRS Process Systems details assessment framework and eight efficiency measures for cold storage

Soon Jin Chew, technical director at NRS Process Systems, has outlined a structured approach to assessing and improving energy efficiency in medium-to-large cold storage facilities serving cold chain logistics centres in Southeast Asia. The work generates baseline data that the company uses to benchmark efficiency gains on subsequent projects.

How energy performance is assessed

Because property size and layout differ from site to site, direct comparisons between facilities are difficult. Chew assesses performance through three parameters: load calculations, refrigeration plant design, and operation.

Load calculations are the first step in determining the overall cooling load and selecting equipment. They cover four components: insulation, air infiltration, product load, and miscellaneous load. Insulation and miscellaneous loads are relatively stable and can be determined accurately. Air infiltration rates, which depend on door-opening frequency and duration, and product throughput are typically conservative estimates unless the client supplies more detailed input.

Once the total cooling load for each room is computed, the overall system design is defined. The design engineer balances energy efficiency against cost, and the facility layout often constrains the refrigeration plant configuration. The chosen design can affect day-to-day operations, so compromises are common when available space and customer requirements are the deciding factors. Operation of the refrigerated facility is identified as a further key element in keeping power consumption low.

Eight measures to improve overall efficiency

Chew lists the following actions:

• Review the design cooling-load calculations, particularly daily product throughput, to ensure they match actual conditions and minimise the overall cooling load.
• Where room temperature is stable, raise it from −20 °C to −18 °C to improve compressor efficiency by roughly 5 to 8 %.
• Optimise product racks and storage systems to achieve a better kWh-to-stored-pallet ratio.
• Analyse traffic flows and door design or arrangement for different space types to reduce warm, moist-air infiltration into cool or cold rooms and minimise wet floors, walls, or ceilings.
• Use high-efficiency compressors, oil separators, and motors.
• Ensure good air distribution within the room geometry in relation to storage racks.
• Use electronics to collect data, trend key parameters, and analyse results to drive further efficiency gains.
• Assign experienced or trained personnel to operate, maintain, and service the facility, including safety, to keep efficiency levels high.

Chew notes that coordinating and maintaining these key areas helps ensure the right equipment is in place and that the facility operates at its optimum efficiency.

NRS Process Systems is a member of the publication; Chew's work focuses on customers in cold chain logistics centres and on identifying how optimum energy efficiency can be achieved in medium-to-large cold storage facilities in Southeast Asia.