## 2 Materials and Methods
### The Problem of Reducing Power Peaks  
There are at least several solutions to the presented problem, which can be divided into hardware and software solutions. By hardware solutions, we mean all those activities that require modifications to the existing infrastructure. Software solutions will be based solely on software modifications in PLC controllers installed in the laboratory. Mixed solutions can also be used. One example is the replacement of relay output controllers with continuous output controllers, where interference with the software of the programmable controllers is required, as well as the replacement of hardware components: cards with digital outputs by cards with analogue outputs and SSR electronic relays by analogue signal power amplifiers.  
The hardware solutions for reducing power peaks also include reducing the power rating of the heaters. Due to the limitations of the furnace design, this cannot be completed by increasing the resistance of the heaters. Instead, the voltage supplied to the heater can be reduced, which simultaneously involves a power reduction. Reducing twice the voltage of a heater will result in a fourfold reduction in its power. This solution requires the use of transformers, which would incur high costs, require a space to be arranged for their installation, as well as the switching off of the power supply and the interruption of ongoing tests. Another solution could be to replace the existing power generator with another one with a much higher nominal power. Apart from the economic aspect, it should be noted that diesel generators should not be operated at low loads in relation to their nominal power [36]. A solution to filter power peaks at the power source side is the use of local energy storage, e.g., in the form of capacitor banks [37; 38]. This solution is commonly used, for example, in electronic equipment, where a small capacitor is placed near the power supply of a digital chip to provide a source of energy for the large current peaks occurring when the digital gate transistors switch. Not placing capacitors near the power supply connection to digital chips results in destabilisation of the source seen from the side of that chip manifested by large voltage fluctuations [39].  
Due to the need not to interrupt ongoing tests and, prospectively, to be able to adapt the laboratory for efficient use of energy from photovoltaic panels, it was decided to conduct research on software solutions. As creep tests are conducted in the laboratory, it is not possible to research power peak limiting algorithms in this environment. Therefore, it was decided to conduct research in the MATLAB Simulink simulation environment using the developed model of the laboratory [40]. The Creep Test Laboratory model was built based on models of creep test machine furnaces and control systems. The creep test machine furnace's models were developed by identification. An active identification experiment was conducted to collect the required data, which were used to develop a linear model, then completed with a static non-linearity correction [41]. The laboratory model was extended with a data exchange mechanism between the functions operating as the master controller and the functions processing the outputs of the temperature controllers. These are the equivalent of data exchange between programmable controllers on a Profibus network.