# Influence of the Parameters of an Agricultural Biogas Plant on the Amount of Power Generated
## 3 Results  
### Recorded Parameters for the Biogas Plant under Study  
The first parameter measured in the agricultural biogas plant studied was the temperature of the digestion mass--Figure 2. According to the technical specifications of the biogas plant, the digestion process should be carried out at 42 \({}^{\circ}\)C.  
As can be seen from Figure 1, the average temperature of the fermentation mass was 36 \({}^{\circ}\)C during the measurements, with a maximum deviation of \(\pm 1\)\({}^{\circ}\)C. It is an average temperature of 6 \({}^{\circ}\)C lower than the value reported in the catalogue data. Nevertheless, it is more similar to the values attributed in the literature [22; 23] for mesophilic fermentations (35 \({}^{\circ}\)C). Consequently, we assert that the fermenter temperature value presented in the technical documentation appears inaccurate and necessitates significant rectification.  
The slurry flow (Figure 3) and the height of the digester mass (Figure 4) were also measured to determine the slurry used for biogas production.  
The mean recorded slurry flow was 57.5 m\({}^{3}\), with a standard deviation of 10 m\({}^{3}\). The maximum slurry flow rate during the recording period was 76 m\({}^{3}\), with a minimum of 24 m\({}^{3}\). Despite this significant variation in the amount of slurry pumped into the digester, the digester mass level averaged 1.65 m throughout the recording period, with a standard deviation of 0.06 m (extreme values were 1.55 and 1.75 m, respectively). This is mainly because the digester mass was topped up with fresh slurry, according to the scheme described in the technical data of the biogas plant.  
The anaerobic digestion process in the digester produced biogas, which was collected in the tank dome. The recorded amount of biogas described by the height of the dome is shown in Figure 5.  
Figure 2: The course of the temperature variation of the digestion mass in the agricultural biogas plant under study.  
Figure 4: Fermenter mass height recorded at the agricultural biogas plant under study.  
Figure 5: Biogas level recorded at the agricultural biogas plant under study.  
Figure 3: Slurry flow recorded at the agricultural biogas plant under study.  
The level of biogas accumulated in the digester was also not constant and varied from 2.08 to 3.74 m (the average biogas volume at the time of recording was 2.95 m). The recorded changes in the amount of biogas and the digester mass level may be due to using a pressure sensor in the digester. Perhaps a better solution would be to use a height sensor (digester mass level) for this purpose.  
The biogas produced was burned in internal combustion engines installed in the biogas container. The amount of active power P and reactive power Q fed into the electricity grid, minus the biogas plant's own needs, is shown in Figure 6.  
From an analysis of the waveforms shown in Figure 6, several relationships can be seen:  
* The agricultural biogas plant studied never reached its rated output (40 kW); the highest recorded active power value was 38.3 kW, 96% of the rated power; this was most likely due to the energy consumption of the individual electrical appliances of the biogas plant (the plant's own needs) and the power losses occurring in their current paths;
* The minimum active power value recorded during the tests was only 17.8 kW, resulting from the operation of the mixers (rated at 2 \(\times\) 9 kW) installed in the digester; the actual power consumed by the substrate mixers was lower, at around 14.2 kW;
* The reactive power produced in the biogas plant was inductive and took values of 9.8 kvar to 23.6 kvar; during regular system operation, the reactive power took on lower values, while switching on the substrate mixers increased it by an average of 6.6 kvar.