Energy Efficiency

Energia Home > Energy Efficiency Service > Energy efficiency advice & tips

Energy efficiency advice & tips

Refrigeration

Refrigeration systems in commercial and public applications (e.g. retail outlets, restaurants, canteens) often represent a sizeable fraction of the electric load at the facilities.

Proper management of refrigeration systems can:

  • Save energy
  • Reduce maintenance
  • Decrease downtime
  • Increase production throughput
  • Improve product quality
  • Prolong shelf life

Electrical savings are generally achieved in one of four ways:

Anti-sweat heater controls
Refrigerated display cases use heaters to prevent condensation and frost build-up on glass doors. These anti-sweat heaters also add heat into the refrigerated case, which must then be removed by the refrigeration system. They often operate continuously.
Energy savings range from about 6% for shop display cases to 14% for reach-in freezers and 20% for reach-in refrigerators.
Demand defrost
This action involves installing new controls or modifying existing defrost controls so that the refrigeration system operates more efficiently and uses less energy for a given refrigeration load.

Moisture in the air accumulates on evaporator coils as frost. This ice layer reduces the heat transfer efficiency of the coil by insulating it and obstructing air flow across the coil.

To maintain efficiency this ice is removed periodically, it involves stopping the flow of refrigerant and applying heat to the inside or outside of the evaporator coil to melt the frost.

Demand control defrost controls often reduce defrost cycles by 20%, reducing the energy required for defrost by 20%. Estimated energy savings are 1–6% of refrigeration system energy use.
Improve case lighting efficiency
Lit refrigerated cases are used throughout the retail sector for displaying refrigerated or frozen foods for sale. The heat produced by the lights adds to the load on the refrigeration system. More efficient lighting reduces energy use d by the lamps and ballasts, the refrigeration costs are reduced due to lower heat output from the higher efficiency lighting.

Lighting energy savings are 15–50%. The actual savings are proportional to the difference between input wattages and operating hours compared with the previous T12 configuration.
Refrigeration controls
A refrigeration system that is well controlled, based on an optimum system set up will operate more efficiently and hence use less energy for a given load. This can be done by optimising settings/operating strategies of existing controls or installing new controls.

There are a number of possible control improvements that can be made to improve overall efficiency. The many different refrigerants, system configurations and applications mean that options must be assessed on a case-by-case basis. The following table gives an idea of the potential savings:

Raise the evaporator temperature: 1–2% power reduction per °C rise
Reduce the condenser temperature: 1–3% power reduction per °C drop in temp
Variable speed control of evaporative: 20–30 % of fan energy, 2–3% of refrigeration condenser or cooling tower fans system energy
Variable speed control of evaporator fans: 20–40 % of fan energy 0.5–1% of refrigeration system energy
Control evaporator fans based on coil: < 0.5% of refrigeration system energy temperature
Increase liquid refrigerant sub cooling: 2–10% of system energy
Defrost control: 0.5–2% of refrigeration use
Appurtenance control: 0.5–2% of refrigeration use
Central computer control: 0.5–5% of total refrigeration energy
Liquid Pump Refrigerant
Installing a centrifugal pump on the liquid refrigerant pumping system gives refrigeration systems capacity boosts while saving electrical energy of up to 30%.
The pump will:
  1. Reduce energy costs because pumping liquid refrigerant is up to 40 times more efficient than using head pressure from the compressor to do the same work.
  2. Eliminate liquid line flashing by overcoming line pressure losses
  3. Increase Evaporator capacity and improve refrigeration effect.
  4. Lower compression ratios and increase compressor life

Other Energy Efficiency Advice and Tips: