Improving the Energy Efficiency of Cooling Systems

Crunching the Numbers

The efficiency of a refrigeration system has a direct effect on a business’ environmental and financial performance. This should be in every end-user’s mind when selecting and operating cooling equipment.

There are a various ways of reducing energy consumption through a number of approaches that require little to no monetary investment. The first one is a reduction in heat load. The more the load is reduced the lesser the cooling required both in terms of capacity and duration. Many refrigeration systems are running at lower temperatures than actually required which increases energy consumption. Selection of the most suitable components for a given application along with measuring and analysis of the system are  important to ensure that over years of operation, a refrigeration system is running as efficiently as when it was first commissioned.

Approximately 80% of the energy used in an industrial refrigeration system is accounted for by the compressor. Most industrial cooling, HVAC and heating systems can typically make a 10% reduction in energy by making small changes and it could be paid back within a year. This short payback period should be palatable for any forward thinking business but surprisingly few chose to act.

Reducing Heat Load

Good dock seal and door management prevents air ingress into temperature controlled chambers from the ambient and adjacent, higher temperature rooms. Warm air entering into chill and cold rooms adds both heat load and moisture. The refrigeration plant draws extra electricity to maintain the room temperature and moisture can pool on floors causing a slip hazard. The example below demonstrates that for every cubic meter per second of air entering into a +2°C chill room, the extra energy consumption could be £10,000 per year just from having a small gap by the door.

Reducing the electrical load of components such as lighting and fans in a temperature controlled facility delivers a double benefit.

Lighting is a continuous load for many buildings including offices and warehouses.  The heat emitted by lighting enters the room and it is then extracted by the cooling equipment.  This is a double penalty as you are not only paying for the lighting electricity but also the refrigeration or air conditioning power to remove the heat. Switching to LED lights has a number of benefits, including intelligent control sensors which will result in significant energy savings.

The development of LED lighting and intelligent control began in offices, homes and other ambient temperature facilities, reducing lighting load through lower energy bulbs but also the use of intelligent lighting control which switches lights off when areas are unoccupied.

More recently, this technology has been implemented in temperature controlled warehouses, particularly cold storage facilities.  Following below there is an early example of such a facility where a trial was undertaken to demonstrate the benefit of LED lighting. The seven existing sodium based lights consumed 250W each and had to be left on 24/7 due to the time taken to warm up again if switched off.  They were replaced by 7 off 48W LEDs.  This immediately reduced lighting power by more than 80% and with intelligent control, the annual saving is between 85% and 90% based on aisle usage.  The reduction in energy has the added benefit of lowering load on the refrigeration plant.  For a typical cold store, every 2kW saving in lighting energy reduces the refrigeration plant power consumption by 1kW.

Additionally, electrical usage can be reduced by experimenting with switching off booster fans. If you switch them off and there is no immediate effect on temperature control, you have an immediate saving. This action requires no capital investment and will result in lower energy consumption.