## 2 Improve of Regulation Capacity in Refrigeration Compressors. Case Study  
The company studied is a large industry located in the Valencian Community in Spain, where it has a complex consisting of a beef processing centre surrounded by the attached facilities necessary for the proper functioning of the main activity. In this factory, two work shifts of 8 hours each are executed daily, plus a third cleaning shift. This factory was designed to operate with the greatest respect for the environment, as well as to achieve the highest efficiency ratios in operation, having obtained important national and international awards. Electric energy consumption can be seen in the graphs in Figures 1 and 2, where the electricity consumption profile for different times of the year is observed. Within the electrical energy consumption of the factory, the refrigeration systems account for a percentage of 44.1% of the total (Figure 3). The factory's refrigeration plant (Figures 4 and 5) is made up of nine screw-type refrigeration compressors that use ammonia (NH\({}_{3}\)) as a refrigerant, which is distributed through three main lines (Figure 4). Line N\({}^{\circ}\)1 at \(-\)40 \({}^{\circ}\)C of evaporation is associated with the freezing tunnels, line N\({}^{\circ}\)2 at \(-\)33 \({}^{\circ}\)C of evaporation is for the meat treatment processes and freezing chambers, and Line N\({}^{\circ}\)3 at \(-\)15 \({}^{\circ}\)C of evaporation is for chambers and the heated meat processing areas (Figures 4 and 5). The compressors used in the industrial refrigeration system have the technical characteristics of the equipment for the specific operating data of the different operating refrigeration circuits, as described in Table 1.  
Figure 1: Electricity consumption profile during average week in the factory. Figure 3: Sectorization of electricity consumption by main facilities. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Designation (ID)**} & \multirow{2}{*}{**Line**} & \multirow{2}{*}{**Nominal Cold**} & \multicolumn{2}{c}{**Nominal Cold**} & \multicolumn{2}{c}{**Nominal Absorbed**} & \multirow{2}{*}{**Cos \(\blacklozenge\)**} & \multirow{2}{*}{**V**} & \multicolumn{2}{c}{**Average**} & \multicolumn{1}{c}{**Annual**} \\  & & **Power (Kw)** & & & & **Annual** & & **Working** \\  & & & & **Power (Kw)** & & & **Capacity (\%)** & & **Hours (h)** \\ \hline A9/C9 & & 347.2 & 394.3 & 0.84 & 408 & & 74.9 & 4.318 \\ A1/C1 & NH3 & 227.8 & 268.5 & 0.91 & 408 & 82 & 85 & 8.428 \\ A2/C2 & \(-40\,^{\circ}\)C & 227.8 & 268.5 & 0.91 & 408 & & 84.5 & 1.931 \\ \hline A3/C3 & NH3 & 110.4 & 88.6 & 0.77 & 408 & 75.9 & 77.5 & 3.630 \\ A4/C4 & \(-33\,^{\circ}\)C & 110.4 & 88.6 & 0.77 & 408 & & 74 & 3.062 \\ \hline A5/C5 & & 1108.9 & 336 & 0.9 & 408 & & 70.8 & 5.634 \\ A6/C6 & NH3 & 1108.9 & 336 & 0.89 & 408 & & 62.92 & 61.3 & 3.342 \\ A7/C7 & \(-15\,^{\circ}\)C & 1108.9 & 336 & 0.89 & 408 & & 55.8 & 3.254 \\ A8/C8 & & 1108.9 & 336 & 0.89 & 408 & & 52.2 & 1.478 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technical and operational characteristics of refrigeration equipment. Figure 2: Electricity consumption profile in the factory during four periods. The automatic regulation of the capacity of the refrigeration compressors is carried out by means of an integrated PID (proportional, integral, derivative) function that modifies the location of the mechanical slide integrated in the compressor to adapt the volumetric com  
Figure 4: Refrigeration system main diagram. Figure 5: View of industrial refrigeration compressor room under study. pression ratio (Vi) to the existing working conditions (thermal load), that are determined from the variation of the suction pressure (evaporation pressure) of the compressors. With the variation of the slide, the quantity of refrigerant gas driven is directly affected by the recirculating part of the refrigerant sucked in before being compressed, thereby significantly reducing the associated energy consumption.