## 3 Results and Discussion  
Using 3 solar batteries with a total power of 870 W, a solar power plant was installed on the flat roof of a building. The modules of the solar power plant were oriented towards the south at an angle of 35 degrees (such installation conditions are recommended according to the area). Since it is well known that the power of solar power plants depends on the temperature of the environment and the batteries, the temperature of the surface of each module was monitored in order to evaluate its influence on the generated electricity power. 15 August 2022, was chosen to monitor the parameters of the solar power plant because it is one of the hottest days of the year according to meteorological observations. Such a day was chosen so that there would be as large a temperature difference between the light and dark time of the day as possible, in order to assess the influence of the ambient temperature on the operation of the solar power plant as accurately as possible. A hybrid data transmission network consisting of various data transmission chains was created for data transmission and processing. The concept of the hybrid data transmission network is presented in Figure 1. RS 485 modules with an interface to the main controller board were used to transmit the information of the surface temperature of the batteries and sensors. A simple shielded cable directly connected to the main controller board was used to transmit the electrical parameters of the solar modules. The processing of received data and formation of information packets was carried out using a PIC series microcontroller on the main controller board. An RF module capable of transmitting and receiving information using radio communication was used to transmit information packets to the data server. The use of RF modules allows stable transmission of digital information packets regardless of the stability of the external internet connection. Using the GSM network, the information related to the parameters of the solar power plant can be transferred from the central server to the mobile device used by the system operator, who evaluates the system (solar power plant) operation based on the received data and makes decisions as needed. A one-month hybrid data network speed measurement was performed, the results of which are presented in Figure 2. Network speed fluctuations are partly caused by the fact that the monitoring system was in different parts of the building on different days of the month. As we can see, the data network speed is slightly different, within the range 15.5-16 Mbps. Such a data network is fully sufficient to transmit data from various sensors to a central server. With the already mentioned data rate, it is possible to transmit the operating parameters of each solar panel (obtained from voltage, current and other sensors) to the data server. When designing the network, it is possible to create a separate data transmission channel from each solar module with a data rate of approximately 16 Mbps. It is worth noting that the speed of the data network is greatly influenced by the technical characteristics of the RF modules and the specific choice according to the needs. Figure 1: Block diagram of a hybrid data transmission network. A central controller was developed using a PIC series microcontroller to monitor solar electrical parameters and surface temperature. The algorithm scheme of program code (using the C programming language) which was created to analyze and evaluate information and to form information packets is presented in Figure 3. The program starts by booting the microcontroller. Figure 3: Algorithm scheme of the program code for the central controller to monitor and transmit the parameters of the solar power plant and the environment. Figure 2: Hybrid data network speed. Temperature values are obtained from the temperature sensors located on the surface of the solar batteries. Next, the voltage and current measurements of the solar batteries are performed and transmitted to the central controller.