## 1 Introduction  
This work shows the potential opportunities for energy saving in a large industry in its installations of industrial refrigeration, through combining the use of speed regulation of the compressors with the slide control in big refrigerators' compressors. For this purpose, refrigeration production has been studied, considering a large factory in the meat industry situated in the Valencian Community (Spain) [1], analysing electric energy consumption, suggesting the actions to be carried out and executing the necessary measures to achieve maximum efficiency in the production of industrial refrigeration.  
The energy consumption is considerable for this type of consumer, and the meat industry has been identified as one of the most suitable segments for the implementation of actions to improve energy demand [2, 3]. Heat, ventilation, and refrigeration are among the largest amounts of energy consumed in processes in the meat industry [4]. Electricity consumption is mainly used for cooling and ventilation, while fossil fuels such as natural gas or diesel are generally used for process heating. In the meat industry, refrigeration production and distribution constitute between 45% and 55% of the total final electricity consumption on weekdays [4], making this process more energy intensive for most consumers in this segment. In the meat industries, the energy demand to produce industrial refrigeration can represent a very important percentage of the energy consumption, generally higher than 50%. There are studies that have been carried out [5, 6, 7] to evaluate the response of the demand of different sectors (mainly for commercial and industrial sectors), where flexibility has traditionally been related to the capacity of a system to adapt itself to production changes [8, 9] or it can absorb these changes depending on any of the system entities or the external environment [10]. Optimizing and improving energy demand in refrigeration can be an important point to achieve in this type of industry.  
Improving the energy efficiency of industrial refrigeration systems in the meat industry has been analysed from different aspects [11, 12, 13, 14, 15]. In this work, the results of the improvement of a large industrial refrigeration system will be seen, describing a practical case where measures have been implemented for the energy improvement of this system by regulating the speed of electric motors in combination with the variation of the volumetric compression ratio by the physical regulation of the mechanical slide integrated in the compressors, allowing one to evaluate the effectiveness of this technique in such a promising sector as the meat industry.  
This article analyses the study of a real case in a first level meat industry located in Spain, where energy consumption in industrial refrigeration is 44.1% of the total. The work is organized as follows: Section 2 describes the main characteristics of the company's industrial refrigeration system. Later (Section 3) the measurements, carried out to establish the improvement process by combining the speed regulation with the mechanical slide regulation of the compressors to adapt the system capacity, are exposed. Once the capacity of the different refrigeration lines has been analysed, Section 4 shows the measures adopted and the results obtained, which show significant energy savings in the refrigeration plant, close to 400 MWh per year.