COLD STORES


rooms can be included: stand-alone units and remote condensing units. There are different alternatives worth analysing in detail, considering that the choice of the refrigerant will determine the design of the unit, especially if the selection is R744 (CO2


).


Moreover, energy efficiency regulations aim to optimise the use of the systems and consequently reduce electricity consumption. One example involves the energy conservation standards imposed by the Department of Energy (DOE) in United States for walk-in coolers and freezers. The deadline for the regulation was reached


last June, and a new rule has been already published, coming into force on 8 September 2017. It should be noted that the limits have the same values as the Max-Tech ones, which means that the best technology available should be used to comply with the rules. In Europe, the regulations for condensing


units are included in ENTR Lot 1, with coefficient of performance (COP) values for low capacities and seasonal energy performance ratio (SEPR) for high capacities, with the first tier in July 2016 and the second in July 2018. SEPR takes into account variations in temperature during the year, which makes it especially important to manage the variations of load precisely. According to one of the statements in the ENTR Lot 1 regulations, a specific regulation for walk-in cold rooms is expected to be published in the next year. In this context, technological advances have mainly been focused on increasing the efficiency of devices. Recently, a new concept has emerged: the Internet of Things (IoT). WithIn the field of refrigeration, interconnection will allow systems to be optimised by improving control through utilising knowledge of historical data. The objective is to increase the efficiency of equipment to the highest level. The first steps have already been taken, whereas


implementation and dissemination are expected to begin soon.


Trends and benefits Selection of the most appropriate technology for cold rooms not only allows the limits set by the regulations to be met, but also guarantees that the stored products will retain their quality, as well as ensuring the reliability, safety and flexibility of the system. First, it is important to provide an efficient control system with optimised and advanced control algorithms. This ensures a constant temperature and humidity in the cold room, parameters that are essential for maintaining the quality of stored food products. An optimised control system also has benefits in terms of energy efficiency, with a consequent reduction in environmental impact. Obviously, the reliability and safety of the


cold room are also increased by precise control of the unit. Furthermore, configurability is highly desirable, as this allows greater flexibility by giving users the possibility to select the operating conditions. Closely related to control are alarms and supervision systems, essential in optimising energy performance and maximising savings, thus maintaining the quality of the stored products as well as ensuring operator safety. In this regard, development of the IoT will definitively bring additional benefits. Moreover, DC technology allows compressor speed and consequently unit cooling capacity to be modulated, with precise load management and constant control of the compressor envelope. This makes significant increases in unit COP possible during operation at part load, giving a higher SEPR. Clearly, it also helps to maintain the quality of the stored products by keeping a constant temperature. Installation of a humidifier in the cold room with a corresponding advanced control system


is highly recommended, as this ensures the minimum level of humidity required (90%) to optimise food preservation while maintaining the appearance and freshness of the produce. Evaporative pre-cooling of the condenser


units or dry and gas coolers can be applied to cut power consumption during periods of peak temperatures.


Evaporative cooling exploits the natural evaporation of water, which occurs both in the intake air flow and on the coils, using the renewable heat of the outside air. This additional, sustainable cooling enhances equipment heat rejection and thus dramatically reduces power consumption. It should be noted that evaporative cooling


does not add any direct global warming potential because it uses water as the coolant. Regarding its indirect effect, this is very low due to the low power consumption of the evaporative cooler. In some cases, this can be fully offset or even exceeded by the associated decrease in energy consumption of the dry/gas cooler condenser. Another important component is the expansion valve. In particular, the use of electronic expansion valves allows adaptive adjustment of the control characteristics during operation, as well as operation with a lower pressure difference, meaning a more radical decrease in condensing temperature. This increases both system energy efficiency and reliability. Last but not least, the choice of a low GWP refrigerant with high performance meets the challenge to reduce environmental impact while increasing energy efficiency. Available technology allows for the development of highly efficient refrigeration systems for cold rooms, with essential features that meet market requirements and ensure both the quality of the stored products and reliable, flexible operation, while also being environmentally friendly.


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