It is estimated that, through energy consumption, cold storage rooms are responsible for the world’s 2.5% greenhouse gas emissions. A survey by the Market Transformation Programme shows that 50% of energy is used for retail and commercial refrigeration and 50% of energy for storage, freezing and chilling. Overall figures indicate that refrigeration consumes 40% to 70% of energy in cold storage. The rest of energy consumption goes to lighting, battery charging, dock and freezer doors, office equipment, office HVAC and electric defrost.
There is a lack of surveys demonstrating the performance of a large number of temperature controlled warehouses. In 2006, Werner et al carried out a survey, which compared the performance of 34 cold stores. The results indicate that 15% to 26% energy savings could be achieved by applying energy-efficient practices. Surveys focusing on a small number of cold storage warehouses show that businesses can save 30% to 40% energy if they repair and/or upgrade the equipment and optimise the utilisation of the warehouse.
Energy efficiency benchmarking
Benchmarking is essential in order to understand energy consumption of the existing facilities and components in cold storage rooms. You can use a SCADA system to analyse whether the investments of energy retrofits will pay off in the long run. You can benchmark energy efficiency of your facility against the Energy Efficiency Benchmarking Survey conducted by the Refrigerated Warehouse and Transport Association of Australia.
The energy use of the refrigeration system can be optimized by applying control strategies, reducing compressor, evaporator and condenser energy use. As far as control systems are concerned, choose localized programmable logic controllers, which allow you to optimize the energy efficiency of the individual parts of the refrigeration system. In contrast, opt for a centralized control system to regulate the energy use of the entire refrigeration system.
Compressors are components consuming the most energy in cold storage, so try maximizing the suction pressure and minimizing the head pressure, which will reduce the compression ratio. When it comes to evaporators, you can install EC fan motors, add sensor control, VFD control, or upgrade the existing evaporators with the ones defrosting with hot gas, or water. Finally, choose control systems for the floating head pressure, retrofit from an evaporative condenser to an air-cooled condenser, or install an over-sized condenser.
NH3/CO2 refrigeration systems
Unlike ammonia systems, carbon dioxide/ammonia systems use two refrigerants. The main function of the additional component is to cool down the first one. The energy consumption is decreased considerably as the electricity consumption is reduced. In addition, this system can operate on the agro-fuel and the bio-mass. If you use the carbon dioxide/ammonia system, you need smaller pipes, pumps and less insulation. In addition, carbon dioxide is safer than ammonia. It is non-toxic, non-inflammable and odourless. With NH3/CO2 refrigeration systems, ammonia is not in direct contact with the cold storage.
Pallet racking for temperature-controlled storage rooms
State-of-the art pallet racking and shelving solutions allow you to maximize storage density and move products efficiently. For example, a mobile pallet racking solution can save up to 40% of the space and increase storage capacity by 80%, while operating only one aisle. The combination of a pallet shuttle system and drive-in/deepstore is suitable for cold rooms with low levels of SKU. Finally, a pallet flow racking is ideal for storage rooms with a high rate of turnover.
Improving door openings
Warm and humid air from the outside can contribute to daily defrosts. The first solution includes decreasing the number and the size of doors in the warehouse. To limit the infiltration of the outside air into the cold storage, install airlocks on all (PA) doors and forklift ramps. You can also replace the existing doors on loading docks with high-speed doors. Opt for insulated finger-docks.
Lighting can consume 10% to 12% of energy in cold rooms. LED lights are the best solution for cold storage rooms. They are highly efficient and require minimal heat generation. In addition, LED lights are not sensitive to cold temperatures. They work well with switches and sensors. Switches can be turned on and off as many times as required. You can also consider high-bay linear fluorescent lights instead of high intensity discharge lighting. Occupancy sensors and photo sensors can additionally save energy use. The latest technological advances have introduced the application of optical fiber based lighting systems, as well.
Batteries can pose a serious problem in cold environments as their life cycle and the rate of charging can decrease compared to batteries working in ambient warehouses. Opt for fast-charging battery systems. Not only are they energy efficient because they reduce charging time, but they are a good space-saving option, as well. Finally, consider automated lift trucks.
These energy efficient upgrades take both time and money. Before you consider them, benchmarking and energy audits conducted by professionals can help you understand the advantages and disadvantages of specific methods you want to apply in your warehouse.