# Sustainable Modularity Approach to Facilities Development Based on Geothermal Energy Potential
## 3 Results and Discussion
### Available Thermal Power and Potential Balneological Utilization  
#### 3.1.1 The Site of Ljuba  
The yield of geothermal waters at the discharge site is changeable, and its average value equals Q = 4.5 L/s. Geothermal resources at the site of Ljuba can be classified as sub-geothermal [43] since the temperature is 20.5 \({}^{\circ}\)C. According to their chemical composition, groundwater belongs to the HCO\({}_{3}\)-Ca water type with low mineralization.  
Table 5 shows basic physical-chemical values of the analyzed geothermal phenomenon. Taking into account the complex geological composition of the terrain and its active tectonics, what was carried out is the classification of geothermal water using the method of D'Amore's genetic parameters. According to the calculations of genetic parameters, geothermal water on the Ljuba site belong to the carbonated type, and this confirmed that the primary geothermal reservoir was formed in the Triassic rocks of the basin bedrock (Figure 9).  
Available thermal power from the geothermal resource at the Ljuba site is calculated for the following scenario:  
* open-loop geothermal heat pump system
* covering peak-load demands
* first cascade stage (temperature reduction for heating)
* second cascade stage (balleological purposes but not bathing)
* temperature reduction, \(\Delta\)T = 16 \({}^{\circ}\)C. This temperature reduction, which we obtained from the resource temperature of 20.5 \({}^{\circ}\)C, was taken to calculate the total available thermal power on the site. In that case, the leaving water temperature was near 4 \({}^{\circ}\)C, reaching the highest liquid density.  
In accordance with Equation (1) the available thermal power was:  
\[\mathrm{E}=4.2\ \mathrm{kJ}/\mathrm{kg}/^{\circ}\mathrm{C}4.5\ \mathrm{l}/ \mathrm{s}\times 16^{\circ}\mathrm{C}\]  
which generates around 300 kW of thermal power available for use.  
Geothermal waters on the Ljuba site, apart from their energy significance, also possess a healing importance, so they can be used for balleological purposes as well. On the basis of their physical-chemical characteristics, these are characterized as natural, hypothermal, arsenic oligomineral waters, which can be used for health purposes under medical surveillance.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**T** & **Conductivity** & **pH** & **Na** & **K** & **Ca** & **Mg** & **HCO3** & **SO4** \\ \hline (\({}^{\circ}\)C) & (\(\mu\)S/cm) & & mg/L & mg/L & mg/1 & mg/L & mg/L & mg/L \\
20.5 & 850 & 7.2 & 20.5 & 2.7 & 102.9 & 39.9 & 495.8 & 26.5 \\ \hline
**Cl** & **Fe** & **Mn** & **F** & **AI** & **As** & **Cu** & **Zn** & **Cr** \\ \hline mg/L & mg/L & mg/L & mg/L & mg/L & mg/L & mg/L & mg/L & mg/L \\
14.4 & \textless{}0.1 & \textless{}0.02 & 0.276 & \textless{}0.05 & 47.6 & \textless{}0.05 & \textless{}0.03 & \textless{}0.01 \\ \hline
**Cd** & **Ni** & **Pb** & **Se** & **Si** & **Hg** & **Sr** & **Li** & **H2 SiO3** \\ \hline mg/L & mg/L & mg/L & mg/L & mg/L & mg/L & mg/L & mg/L & mg/L \\ \textless{}0.002 & \textless{}0.02 & \textless{}0.01 & \textless{}0.002 & 5.6 & \textless{}0.5 & 0.77 & \textless{}0.04 & 15.6 \\ \hline \hline \end{tabular} Legend for Figure 9a: A \(-\)indicates that geothermal waters had circulated through a calcareous terrains rather than an evaporative one; B \(-\)indicates that the geothermal water is enriched by sodium and may come from sedimentary terrains; C \(-\)is low, which excludes water deriving from a flysch, volcanic or schistose basement; D \(-\)indicates water circulation through dolomite; E \(-\) indicates that geothermal water had circulated in a carbonated reservoir rather than in a sulfated one; F \(-\)no indication in growth of potassium content, which excludes possible circulation in granitic field.  
\end{table}
Table 5: Physical-chemical features of geothermal waters on the site of Ljuba.