## 7 Supplying Power to a Real Vigilance Station  
In this last section the viability of supplying power to a real station is analyzed. Clearly, depending on the station under consideration, with its associated equipment, a different power supply will be necessary. Nonetheless, since one of the main advantages of thermoelectricity is its scalability, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Thermoelectric** & \multicolumn{2}{c}{**Total Time**} & \multicolumn{3}{c}{**Percentage of Time in Operation (\%)**} \\ \cline{3-6}
**Module** & **in Operation (h)** & **Average** & **Typical** & **Hot Days** & **Cold Days** \\ \hline M1 & 0 & 0\% & 0\% & 0\% & 0\% \\ M2 & 4441.4 & 86.2\% & 78.2\% & 87.6\% & 73.4\% \\ M3 & 269.1 & 5.2\% & 0\% & 16.8\% & 0\% \\ M4 & 0 & 0\% & 0\% & 0\% & 0\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Total hours in operation and percentage of time active of the four thermoelectric modules installed, considering the average between 19 December 2019 and 20 August 2020, as well as their behavior under typical conditions (Figure 11), hot days (Figure 12) and cold days (Figure 14). Figure 15: Power generated by M2 versus the temperature difference between their sides \(\Delta T=T_{H}-T_{C}\) between 19 December 2019 and 20 August. an increase in the generated power can be simply achieved by installing more thermoelectric modules (with their associated heat exchangers). This section considers as reference one of the vigilance stations located at Teide volcano. More specifically, the one located at \"La Fortaleza\" lookout, which is next to the installed prototype and belongs to the Volcanological Institute of the Canary Islands [69]. The station is composed of a seismograph, a WEST continuous monitoring flux unit that measures the concentration of several gases (CO\({}_{2}\), H\({}_{2}\)S, CH\({}_{4}\)), soil moisture and temperature, as well as various meteorological parameters [70], and a GSM router to emit the measured data to the control center. The power consumption of the station was monitored over two days. As a result, it was obtained that both the seismograph and the router present a practically uniform power consumption of 1.86 W and 3.77 W on average respectively. In contrast, the flux unit presents an average demand of 1.5 W that is not constant but with peaks of demand once an hour. Nowadays, this consumption is powered by means of a 175 W photovoltaic panel of dimensions 1306 \(\times\) 991 \(\times\) 40 mm\({}^{3}\). This panel is connected to a Victron BlueSolar MPPT 75[15][71], a charge controller that maximizes energy harvesting from the panel and stores it in a 1260 W lead-acid battery. The system is over-dimensioned in order to ensure the vigilance of the volcano despite snow periods up to 3.7 days. Nevertheless, it complicates maintenance due to its size and weight. The solution proposed in the present paper, based on a geothermal thermoelectric generator, permits a more uniform generation that even improves with adverse meteorological conditions. Therefore, it would be possible to reduce the energy storage requirements or replace it with other technologies such as supercapacitors. Nonetheless, in order to make it possible, it is desirable to reduce the power demand to a minimum due to the low efficiency of the thermoelectric modules. In the power measurements, the high power demand of the router stands out, which is two and three times the average consumption of the seismograph and the flux unit respectively, while being the least critical for the volcano vigilance and the easiest one to be modified. As explained in Section 5, LoRa is able to communicate wirelessly over a considerable distance with a minimal consumption of just 0.11 W, which supposes a reduction of 97 % in the power requirement of the communication system, leading to a reduced number of thermoelectric modules necessary in order to obtain a completely autonomous volcanic monitoring station.