Optimising Operations: The World of Industrial Refrigeration
Refrigeration, at its core, is the mechanical process of reducing or maintaining the temperature of a given space, product, or industrial process. In the industrial sector, its applications primarily revolve around two key areas:
- Preserving Food Products: This includes cooling, freezing, and precise temperature management throughout the storage, transportation, and distribution phases of food items.
- Air Conditioning Systems: Large-scale climate control for industrial facilities.
Beyond these main uses, industrial refrigeration is vital in diverse fields like chemical plants, various manufacturing and construction processes, facilities for ice and snow sports, and environmental test chambers. Notably, in sectors such as food and drink, as well as chemicals, refrigeration can represent a substantial portion of a site’s overall energy expenditure.
The Energy Technology List (ETL) categorizes industrial refrigeration into eight core sub-technologies:
- Absorption & Other Heat-Driven Cooling & Heating Equipment
- Air-Cooled Condensing Units
- Automatic Permanent Refrigerant Leak Detection
- Refrigeration System Controls
- Evaporative Condensers
- Packaged Chillers
- Refrigeration Compressors
- Air Blast Coolers
Diving Deeper into Industrial Refrigeration Technologies
Absorption and Other Heat-Driven Cooling & Heating Equipment
This specific category on the ETL is limited to products integrated into a Combined Heat and Power (CHP) scheme that holds a certificate from the CHP Quality Assurance (CHPQA) programme. Essentially, the cooling effect generated by an absorption chiller must be powered by heat directly from the CHP plant. The performance of this absorption plant is evaluated alongside the CHP plant under the CHPQA programme. These absorption coolers (chillers) are unique because they use heat, rather than electricity, to cool industrial processes or products.
Air-Cooled Condensing Units
An air-cooled condensing unit is a pre-assembled, factory-wired system comprising a compressor and an air-cooled condenser, along with various essential supporting components. These can include a liquid receiver, shut-off valves, filter dryer, sight glass, and control mechanisms. This integrated unit offers a convenient way to power cold rooms or other cooling apparatus. Within the unit, refrigerant vapour from the evaporator is compressed and then condensed into a high-pressure liquid, which is subsequently returned to the evaporator via an expansion valve.
These units are widely employed for the storage of both frozen and chilled food products, with medium and low-temperature applications. Typical evaporating temperatures are around -35°C for frozen goods and -10°C for chilled items. Meanwhile, high-temperature units are specifically designed for air conditioning applications.
Automatic Permanent Refrigerant Leak Detection
Automatic permanent refrigerant leak detection systems are designed to continuously monitor the air surrounding refrigeration equipment. Should refrigerant be detected, these systems immediately trigger an alarm. This functionality is crucial for boosting the energy efficiency of refrigeration systems and for cutting down on carbon emissions and other greenhouse gases. Most industrial refrigeration systems currently rely on either HCFC or HFC refrigerants. While some systems use ammonia, ammonia detection devices are not currently within the ETL’s scope.
Refrigeration System Controls
The capabilities and complexity of refrigeration system controllers vary immensely. The most basic form is a simple thermostat that regulates the temperature of the cooled space. However, more intricate refrigeration systems, particularly those with multiple compressors, demand more advanced control. When correctly implemented, these controls can significantly reduce a refrigeration system’s energy consumption.
The ETL currently features:
- System management units or packages: These consist of one or more control units or modules engineered to optimize an entire refrigeration system.
- ‘Add-on’ controllers: These are designed to work in conjunction with a specific system management unit or package, enabling the optimization of additional refrigeration compressors, evaporators, and condensers.
For an industrial site operating eight evaporators and one cold room, selecting ETL-listed refrigeration system controls could lead to significant annual savings, estimated at:
- £2,900
- 26,200 kWh
- 9.2 tonnes CO2
Evaporative Condensers
In a refrigeration system, condensers are responsible for liquefying the refrigerant gas discharged by the compressor. In an evaporative condenser, the gas undergoing condensation flows through a coil that is continuously wetted on the outside by recirculated water. Air is then drawn over this coil, causing some of the water to evaporate.
Evaporative condensers offer two distinct advantages over air-cooled types:
- Water evaporation is a more efficient method of heat removal than relying solely on dry air.
- Heat is rejected against the wet bulb ambient temperature rather than the dry bulb temperature. The wet bulb temperature can be up to 8°C lower than the dry bulb in hot weather, leading to more efficient heat rejection.
Packaged Chillers
Packaged chillers are factory-assembled refrigeration units designed to cool liquid through a self-contained, electrically-driven mechanical vapour compression system. A packaged chiller typically integrates the refrigeration compressor(s), controls, and the evaporator into a single unit. The condenser can either be built-in or a remote component.
The ETL classifies packaged chillers into four product categories:
- Air-cooled packaged chillers providing cooling only.
- Air-cooled, reverse cycle, packaged chillers offering both heating and cooling.
- Water-cooled packaged chillers providing cooling only.
- Water-cooled, reverse cycle, packaged chillers offering both heating and cooling.
By choosing an ETL-listed 400kW air-cooled packaged chiller instead of a non-compliant alternative, the potential annual savings are calculated as:
- £4,600
- 41,800 kWh
- 14.7 tonnes CO2
Refrigeration Compressors
The compressor is a fundamental component of any refrigeration system. Its function is to compress the refrigerant gas from the evaporator’s low pressure to a higher pressure. This increased pressure allows the gas to condense in the condenser, thereby releasing heat to the ambient air or water.
Commercial & Retail Refrigeration Solutions
Refrigeration involves the mechanical process of cooling or reducing the temperature of a given space, product, or ongoing process. In the commercial sector, its primary applications are two-fold:
- Food and Drink Preservation: Cooling, freezing, and maintaining optimal temperatures for food and beverage products during storage.
- Air Conditioning Systems: Providing climate control for commercial and retail spaces.
The Energy Technology List (ETL) divides commercial refrigeration technology into six key sub-technologies:
- Cellar Cooling Equipment
- Professional Refrigerated Storage Cabinets
- Refrigerated Display Cabinets
- Curtains, Blinds, Doors, and Covers for Refrigerated Display Cabinets
- Refrigeration Compressors
- Refrigeration System Controls
Exploring Commercial Refrigeration Technologies
Cellar Cooling Systems
Cellar cooling systems are designed to maintain indoor environments, typically cellars in pubs, restaurants, and hotels, at a consistent 10-12°C, which is ideal for storing chilled beverages.
There are three types of cellar cooling systems eligible for inclusion on the ETL:
- Split systems: These are the most common type, featuring an evaporator located inside the cellar and a condensing unit positioned externally (usually outdoors).
- Dual split systems: Comprising two evaporators connected to a single condensing unit.
- Free cooling units: These systems offer “free cooling” by using a fan to draw in cooler outdoor air when the ambient temperature is sufficiently low.
Example: Installing an ETL-listed 7.3kW cellar cooling system instead of a non-listed system of the same size could yield the following potential annual savings:
- £540
- 4,900 kWh
- 1.7 tonnes CO2
Professional Refrigerated Storage Cabinets (PRSCs)
Professional refrigerated storage cabinets (PRSCs) are appliances, typically featuring one or two solid doors, widely used for storing food and beverages in commercial kitchens. They are designed to hold chilled food between -1°C and 5°C, and frozen food between -18°C and -15°C.
The ETL lists PRSCs with single and double doors, including larder and chest types, as well as counter and under-counter models for both chilled and frozen food storage. Importantly, PRSCs are equipped with solid-faced lids, doors, or drawers and are not used for displaying food (for display options, refer to the refrigerated display cabinets section).
Refrigerated Display Cabinets
Refrigerated display cabinets are utilized by food retailers to showcase food and beverages. These cabinets incorporate one or more evaporator/expansion devices that use liquid refrigerant, supplied by either an integral condensing unit or a remote system.
All common types of display cabinets are listed on the ETL, including multi-decks, chest freezers, upright freezers with glass doors, and serve-over cabinets. They accommodate a broad spectrum of storage temperatures, from -18°C for frozen food to 5°C and 10°C for chilled food.
Example: By installing an ETL-listed 2.5m open-fronted chilled food cabinet instead of a non-listed system of equivalent size, the potential annual savings are estimated as:
- £220
- 2,000 kWh
- 0.7 tonnes CO2
Curtains, Blinds, Doors, and Covers for Refrigerated Display Cases
Many refrigerated display cases are designed with an open front, which significantly increases the heat load on the refrigeration system. Fortunately, various add-on components are available to mitigate this heat load and enhance energy efficiency. These include:
- Strip curtains: Overlapping, transparent plastic strips that permanently fit the open front of display cases.
- Doors: Sliding or hinged transparent doors that permanently enclose the open front of display cases.
- Covers (bubble lids): Rigid plastic covers that permanently fit over the top of open freezers.
- Blinds: Roller-type blinds fitted to the front of cabinets, sometimes incorporating a motorized control system.
- Enhanced air flow management devices: These systems are designed to guide cold air more efficiently down the front of open fridge cabinets.
For these components to effectively reduce heat load and improve energy efficiency, proper installation is paramount.
Refrigeration Compressors
The compressor is an integral part of any refrigeration system. It functions by compressing the refrigerant gas from a lower pressure to a higher pressure. Subsequently, the gas condenses, releasing heat to either ambient air or water in the condenser. The ETL covers the following specific types of refrigeration compressors:
- High temperature with HFC or HC refrigerant.
- Medium temperature with HFC or HC refrigerant.
- Low temperature with HFC or HC refrigerant.
- Medium temperature transcritical/subcritical with R744 refrigerant.
- Low temperature transcritical/subcritical with R744 refrigerant.
- Low temperature subcritical cascade with R744 refrigerant.
By installing an ETL-listed compressor instead of a typical market-average unit, the potential annual savings are calculated as:
- £330
- 2,970 kWh
- 1,040 kg CO2
Refrigeration System Controls
The functionality and complexity of refrigeration system controllers vary widely. The simplest form is a basic thermostat that merely regulates the temperature of the cooled space. However, more sophisticated refrigeration systems, particularly those with multiple compressors, ideally require more advanced control. When correctly deployed, these controls can significantly reduce the energy consumed by a refrigeration system.
The ETL currently includes:
- System management units: These are designed to optimize an entire refrigeration system, encompassing the operation of refrigeration compressor(s), evaporator(s), and condenser(s).
- ‘Add-on’ controllers: These are intended for use in conjunction with a specific system management unit, enabling the optimization of additional refrigeration compressors, evaporators, and condensers.
Do you have any specific questions about these refrigeration technologies or their applications?