19 July 2016
By Alan Jackson and Stewart Bonner, BJA Refrigeration Consultants
Refrigeration system energy consumption typically accounts for 50-70% of operators' running costs. Through good practice and taking advantage of available technology, you can reduce the operating costs associated with refrigeration through:
- Retailer operation
- Service and maintenance
- Store Refitting
By following the correct disciplines, you, as an operator, can improve efficiency:
- Optimise air flows by eliminating obstructions. e.g. ensure products do not cover the 'display case air return grilles'.
- Don't compromise a manufacturer's maximum fill line. Overloading a display case will restrict air flow.
- Switching lights off when there is no requirement to illuminate product.
- Keeping cold room doors closed.
- Use night blinds correctly.
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Service and maintenance
Maintenance can play a significant role in increasing efficiency during routine maintenance visits. Examples include:
- Ensure you maintain evaporation set points at the manufacturer's recommended conditions.
- Optimise and maintain compressor set points by ensuring the suction pressure is only as low as it needs to be. Adjust the discharge pressure as low as possible.
- Ensure that condensers are clean and have free air flow to them. Blocked condenser fins will result in higher condensing temperatures, and for each 1°C, the power used by the compressor will increase by c. 2-4%.
- Perform system leak checks; alongside the environmental impact, leaking refrigeration systems can also increase energy consumption.
Refitting presents a significant opportunity to improve efficiency. The following examples of investment are worth considering:
Installing doors to display cases will significantly reduce energy consumption and load. A new initiative that will reduce power consumption to open fronted display cases is to install them with Aerofoil Energy technology.
Aerofoils are patented shaped strips fixed to the ends of display case shelves and positioned to sit on the outer edge of the air curtain. Aerofoils reduce energy costs and air curtain spillage through improving the direction of airflow.
N.B. If you reduce the cooling load on an existing refrigeration system, give care and consideration to the effects the load reduction might have on the system reliability:
- A reduced load means the plant may now be too large and cause short-cycling of the compressors
- Reduced load also means reduced mass flow in the piped services, and this could cause problems with oil return
- Replace traditional lighting fixtures in display cases and cold rooms with LED lights.
- Replace thermostatic expansion valves with electronic expansion valves.
- Maintain air tightness and thermal integrity by repairing any fabric leaks in cold rooms.
- Replace condenser fan motors with EC fan technology.
- Installation of inverter control technology to compressor packs will optimise compressor operation through ensuring that staging is ‘smooth’ as the system load demand changes. The inverter control technology will minimise compressor starts and reduce energy consumption.
- Investing in condenser fin corrosion protection extends the life of a condenser while also presenting energy savings.
- Replace pipework insulation that is damaged or has broken down over time will prevent unnecessary heat gain.
This article identifies steps that can be made to improve energy efficiency, whether through daily operation, service and maintenance, retrofitting or replacement. The suggestions connected with retrofitting and replacement have different capital cost. However, when considered in the life cycle of a system's operation, these improvements will provide a return on investment through reduced energy consumption.