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Listed below are several energy reduction and performance improvement methods that can often be employed with any refrigerant and in both new and existing systems. Since equipment design changes are commonly done when there is a change of refrigerant, this might be a good opportunity to use one or more of the following methods to improve the new system’s performance. The methods to improve energy efficiency listed below are not meant to be a complete and exhaustive list and as a general rule, could all be used in centralised systems and condensing units and to a lesser degree in stand-alone equipment. Component level efficiency improvement such as variable capacity or variable speed compression to match load, electronically commutated motors (ECM) for fans etc. are all well established and important and are not discussed here. System vs Component efficiency In commercial refrigeration, more than in most other types of applications, it is important to take a holistic system approach to defining energy efficiency. In the case of stand-alone equipment, this is often the case; for condensing units, there are some countries that have established a whole system efficiency measure (AHRI 1250 2014). However, for centralised systems in supermarkets, system efficiency measures are rare. Because of this, performance of components such as compressors are used to define the whole system efficiency. Taking a component or a sub-system approach to efficiency, when the outdoor ambient, the cooling load, and all components of a system affect the performance, leaves many energy savings opportunities unaddressed (Minetto, 2018). Some of these measures, that can only be realised through a whole system approach, are described below. Floating head pressure or low condensing operation When air cooled condensers are used, the condensing temperature or pressure of a system tracks the ambient air temperature. It is common practice to restrict the condensing temperature from going too low in order to allow the expansion devices and compressors to work optimally. With improvements in these component technologies and the widespread use of electronics, it is possible to allow this minimum condensing temperature to be much lower. The advantage of doing this is that as the condensing temperature decreases, power consumption decreases, thus increasing the energy efficiency. By calculating the system efficiency for a whole year of operation, as opposed to just one “standard” condition, the value of this “floating head pressure” operation can be measured and accounted for. Adiabatic condensing /Evaporative condensing This is a method to lower the temperature of the air cooling in the condenser coil by adding moisture to the (dry) air stream. This type of condenser has been shown to be quite effective in dry warm climates for improving the efficiency of R-744 centralised systems, though this method of efficiency improvement is applicable to all refrigerants. Availability of water may however be a challenge in some areas. Heat recovery and system integration This has always been one of the more popular forms of system efficiency improvement and has found an increasing number of applications with the growth of R-744 as a refrigerant. The heat from the condenser/gas-cooler of the refrigeration system – especially in a centralised system – can be recovered and used to heat or preheat water, indoor air heating in the winter, and even snow melting systems buried in sidewalks at the entrance to buildings. Utilisation of heat recovery contributes to improve the overall efficiency of the entire refrigeration system beyond what is found by the traditional method of calculating performance. When describing R-744 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 89PDF Image | Heat Pumps Technical Options
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