*2.4. Energy Management Systems*

Another important issue in the context of this research is the systems supporting the managemen<sup>t</sup> of energy consumption by enterprises. An energy managemen<sup>t</sup> system is an interconnected set of elements, devices, and tools (hardware and software) used for monitoring, predicting, controlling, and optimizing energy consumption. Such systems have so far been mainly used by large enterprises, but with the development of modern technologies, digital twins, and the concept of Industry 4.0, they will become and are becoming much more accessible to smaller companies [50–52].

The whole system consists of several layers, the number of which varies according to the detail of the view of the issue. The first layer consists of the end devices (machines, equipment, but also energy sources), where the energy consumption data are collected [53,54]. The second layer is the communication and integration layer and is used to send data from devices in the first layer and to transmit commands from higher layers in the direction of the end devices [53,54]. The third layer consists of a server with a database and possibly other tools (machine learning, prediction engine, etc.) or a cloud environment [51,53,55]. The fourth layer is then functional (information and control), and consists of either specialized energy managemen<sup>t</sup> software (Siemens Simatic, Wattics, EnergyCAP, ProntoForms) or other less sophisticated tools for prediction and data visualization such as Python and Microsoft Power BI [51,53,55]. Within the previous two layers, they can be integrated with other enterprise systems designed for production managemen<sup>t</sup> such as the ERP, MES, APS, or simulation tools [55,56]. The fifth layer is the control logic itself in the form of objectives, strategies, and rules to ensure energy-efficient operation, respectively, the optimization of energy consumption, respecting production requirements and various other constraints [56–58].

Depending on the specific solution, specialized energy managemen<sup>t</sup> software can have different functions [59–61]. Key functions include [62–65].



However, to effectively manage energy consumption, respectively, ensure energyefficient operation of production using energy managemen<sup>t</sup> software, it is necessary to understand the optimal rules and strategies for the managemen<sup>t</sup> itself, taking into account different conditions (available energy, energy prices, etc.). Despite the relatively broad functionality, energy managemen<sup>t</sup> systems do not allow for the testing of various scenarios of future events related to energy limitations and the selection of the solution best suited to the needs of enterprises. Simulation modeling offers such possibilities.
