## 4 Results and Discussion  
### Performance of the SUS and SDS in Each Configuration  
Tables 3 and 4 show the most important operation conditions for both substations in each configuration. In the SUS unit (Table 3) using a DAHT, it is possible to obtain higher temperatures in the heat transport network (\(T_{t,s}\)) and temperature lift (\(\Delta T_{lift}\)) in the SUS, but at the expense of a higher consumption of waste heat and lower COP. For the other cases, the configurations providing the highest transport temperature and temperature lift are configurations (b) and (c) that use a cooling tower for the rejection of heat in the condenser, which allow rejection of heat at lower temperatures. This is a typical behavior in heat transformers. The lower the rejection temperature, the higher the output temperature is. As expected, with respect to the SDS (Table 4), the best performance for cooling (COP\({}_{\text{C}}\)) is provided by the configuration using the double effect unit but at the same time provides the lowest efficiency for heating. The configurations with double lift absorption units provide the highest temperatures for the local heat distribution network. Configuration (b) can offer quite acceptable performances for heating and cooling, but in that case, a cooling tower would be necessary for the SUS. These tables also show the required change in the solution concentration and required operation pressures. All of them are in a feasible range for the present absorption technology.  
In order to check the feasibility of absorption systems to provide heating and cooling simultaneously at the required conditions, Figure 6 shows the PTX diagram for the step-down thermal substation (SDS) in each system configuration. For the case of the SE + 2 xSE/H&C configuration, the two SDS cycles are represented in the same diagram. These diagrams show the performance operation conditions of each configuration. Double-lift AHPs achieve higher heating temperatures than single-effect heat pumps, with the possibility of producing hot and chilled water simultaneously in a single unit and for the same driving temperature. According to Figure 6, it is concluded that all the absorption systems of the SDS operate in a feasible field of temperatures, pressures, and concentrations.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Configuration** & \begin{tabular}{c} **Type of** \\ **AHT** \\ \end{tabular} & \(T_{t,\text{S}}\) (\({}^{\text{C}}\)**C)** & \(\Delta T_{lift}\) (\({}^{\text{C}}\)**C)** & \(p_{h}\)/\(p_{1}\) (kPa)** & \(\dot{m}_{WH}\) (kg/s) & \(\dot{m}_{CT}\) (kg/s) & \(\Delta_{x}\) (\({}^{\text{e}}\)) (\%) & \begin{tabular}{c} **COP** \\ **(W/W)** \\ \end{tabular} \\ \hline (a) SE + SE/H & SEAHT & 82.9 & 12.9 & 23.9/5.9 & 12.6 & - & 6.4 & 0.482 \\ \hline (b) SE + SE/H\& SEAHT (\({}^{\text{(CT)}}\)) & 94.7 & 24.7 & 23.9/4.5 & 19.5 & 6.8 & 2.9 & 0.431 \\ \hline (c) SE + DL/H\& SEAHT (\({}^{\text{(CT)}}\)) & 94.7 & 24.7 & 23.9/4.5 & 17.5 & 7.8 & 2.9 & 0.431 \\ \hline (d) SE + 2 xSE/H\& SEAHT & 82.4 & 12.4 & 23.9/7.8 & 11.5 & - & 4.1 & 0.473 \\ \hline (e) DA + DE/H\& \
\begin{tabular}{c} DAHT Type \\ 3 (\({}^{\text{(CT)}}\)) \\ \end{tabular} & 118.8 & 48.8 & 59.6/4.5 & 45.0 & 27.5 & 3.1 & 0.267 \\ \hline (f) DA + DL/H\&
\begin{tabular}{c} DAHT Type \\ 3 (\({}^{\text{(CT)}}\)) \\ \end{tabular} & 118.8 & 48.8 & 59.6/4.5 & 41.1 & 27.5 & 3.1 & 0.267 \\ \hline \hline \end{tabular} \({}^{\text{(*)}}\)\(\Delta x=x_{max}-x_{min}\), (\({}^{\text{(CT)}}\) With a cooling tower.  
\end{table}
Table 3: Performance analysis of the absorption heat transformers used as SUS (Step-Up Substation) in each system configuration.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  
\({}^{(\circ)}\)\(\Delta x=x_{\text{max}}-x_{\text{min}}\), (\({}^{\text{