# Influence of the Parameters of an Agricultural Biogas Plant on the Amount of Power Generated
## 3 Results
### Statistical Analysis of the Results Obtained  
Correlations between these quantities were determined to determine the influence of the basic parameters of the biogas plant on the amount of power generated in the agricultural biogas plant under study (Table 2). From the analysis of the values presented in Table 2, it can be seen that, in the case of the height of the substrate in the digester, no significant correlation was observed with the other parameters recorded. The other correlations tested, although mathematically significant, are much smaller than 1 (the highest calculated value is 0.26). Figure 6: The course of active power P and reactive power Q variation was recorded at the agricultural biogas plant under study. Figure 7 shows a scatter plot of the recorded active power values P as a function of the height of the substrate in the digester. From the measurement points presented there, it appears that the amount of power generated in an agricultural biogas plant does not depend on the height of the digestate in the digester. Assuming that the level of the digestion mass in the fermenter changes due to the action of the pumps supplying new substrate and pumping out the digestate, no closer correlation between the substrate level and the power fed into the electricity grid was observed. A similar relationship emerged between the amount of power generated and the slurry supplied to the digester (Figure 8). In this case, however, it can be seen that, as the amount of slurry pumped into the digester increases, there is a noticeable, slight decrease in the generated power sent to the electricity grid. This is most likely related to the increased power consumption of the pumps pumping the slurry into the chamber (the  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Variable**} & \multirow{2}{*}{**Average**} & \multirow{2}{*}{**Standard**} & \multicolumn{5}{c}{**Correlations**} \\ \cline{3-8}  & & **Deviation** & **h** & **d** & **t** & **b** & **P** \\ \hline h [m] & 1.6487 & 0.06039 & 1 & -0.025200 & -0.049520 & -0.096868 & -0.024616 \\ d [m\({}^{3}\)] &  
increased power demand from these pumps causes a decrease in the power injected into the electricity grid). An analogous relationship can be observed between power and biogas levels (Figure 9). Although, according to the adopted approximation, the amount of power decreases slightly as the amount of biogas increases, this change is negligible and does not exceed 2 kW over the entire recording period. As can be seen from the distribution of values shown in Figure 10, an increase in the amount of slurry pumped into the biogas plant has a positive effect on the amount of biogas produced. This is most likely the result of supplying the digester with large amounts of new 'fuel' from which the methane bacteria can produce methane much more quickly. At the same time, it is worth noting that injecting a new substrate (with a temperature lower than the temperature prevailing in the fermenter) does not significantly affect the temperature of the entire fermentation mass (Figure 10). Although the correlation shown in Figure 11 is positive, due to the low value of the correlation coefficient (r = 0.175), it can be concluded that the observed increase in temperature with increasing flow is negligibly slight and is due to a measurement error (the measured temperature was rounded to the nearest whole degree Celsius). An analogous lack of correlation can be seen when comparing the amount of biogas with the temperature prevailing in the fermenter (Figure 12). In this case, the correlation is positive, as in the flow case, but this cannot be considered a reliable relationship due to the low correlation coefficient value (r = 0.114). Figure 8: Scatter plot of the recorded values of the slurry flow (d) into the digester [m\({}^{3}\)] and the active power (P) [kW]. To check the correlation between the amount of biogas in the biogas plant and the slurry flow into the digester, a correlation of these values was drawn up (Figure 10).