*2.3. Energy Consumption in Manufacturing Companies*

The study of energy consumption in manufacturing companies focuses on identifying and analyzing the elements that contribute to power consumption. Each element is characterized by a different energy consumption profile. In a manufacturing company, the number of elements to be surveyed is significantly high, therefore, depending on the purpose of the survey, it is necessary to divide the company into smaller elements, for which the survey is simpler.

It is possible to study individual elements, with their impact on the examined area, and then add/sum up other elements, thus extending the scope of the research, the examined energy consumption. In the literature, these ranges are called levels of energy testing. The most common is the division into three to six levels. Research in this range has been conducted, for example, by [3,4,41].

Based on these, four levels of energy consumption testing have been identified:


• Multi-factory level—differentiated manufacturing companies that are in a relationship with each other due to the joint performance of activities, generating synergy effects are subject to examination.

Determining the energy consumption levels is easiest to study for the lowest level (machine level), and at subsequent levels, add energy consumption profiles for additional resources included in the analysis. For example, examining energy consumption at the multi-machine level would consist of overlaying the energy consumption profiles of each machine and adding up the results for each moment/period of analysis [42–44]. Testing the energy consumption of a single machine is a complex task [45–47] and requires the definition of a consumption profile for each machine. The consumption profile is closely linked to the various states that the machine can be in (process operation state, standby state, etc.). In each of these states, the power consumption of the machine is different and the total energy consumption depends on the duration of each state. Research on the identification of possible states to be reached by machines has been the subject of many publications, for example, [41,45,48], especially in the engineering industry. Based on the research presented, nine states were identified: Power off, Shut down, Warm-up, Power on, Start-up, Stand by, Production, Maintenance, Failure. The publications by [1,48,49] identified the status/characteristics of the values taken in each state by defining them as constant or stochastic (or variable). This aspect is important for the detailed analysis of power consumption at a given time and the study of parameters, conditioning the power consumption.
