# Model-Based Assessment of Energy Efficiency in Industrial Pump Systems: A Case Study Approach
## 6 Results
### System Efficiency Maps  
The generated system efficiency maps are shown in Figures 15-17 for all variants listed in Table 4. The dark red boundary indicates the operating plane of the pump, while the blue and red curves mark the operating limits of the motor when the TR is not utilised and when it is utilised, respectively. In addition, an annual dataset of OPs is added to each map, which will (later) be used as a criterion for predicting energy consumption. Table 5 summarises the main statistics for each variant in terms of average and peak efficiency. The average efficiency is calculated for three Q-\(H\) regions: (1) complete pump operating plane (dark red), (2) pump operating plane limited to the utilised motor TR (blue curve), and (3) pump operating plane limited to the unutilised motor TR (red curve). In the case of the 237 pump (Figure 15), the use of an SRM instead of an IM offers two significant advantages: The maximum system efficiency is 2 percentage points higher, reaching 77.63%, and the motor with a thermal reserve (TR) can cover almost the entire operating level of the pump (blue line). The efficiency curve is similarly steep for both motors, although the IM has a more pronounced peak. The average efficiency within the operating plane of the pump is 63.57% for 237-IE3 and 65.59% for 237-IE5. However, if the operating limits of the motor, such as the utilisation of the TR, are taken into account, the difference in average efficiency increases to 2.6%. Similar conclusions can be drawn when analysing the system with the 252 pump (Figures 16 and 17a). The maximum efficiency is significantly higher when using the SRM  
Figure 17: System efficiency map for (**a**) the 252-IE5 and (**b**) the equivalent to the existing 258-IE1 pump and drive combinations. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**System** & \multicolumn{3}{c}{**Average Efficiency (\%)**} & \multicolumn{2}{c}{**Max Efficiency (\%)**} \\ \hline  & **Complete Pump** & **Limited to Utilised** & **Limited to Unutilised** & \\  & **Operating Plane** & **Motor TR** & **Motor TR** & \\ \hline
237-IE3 & 63.58 & 62.86 & 61.72 & 75.90 (at 240 m\({}^{3}\)/h and 10.32 m) \\
237-IE5 & 65.59 & 65.50 & 64.14 & 77.63 (at 283 m\({}^{3}\)/h and 14.04 m) \\
252-IE3 & 64.76 & 63.77 & 62.80 & 77.41 (at 320 m\({}^{3}\)/h and 12.08 m) \\
252-IE4 & 67.56 & 67.30 & 66.20 & 80.67 (at 395 m\({}^{3}\)/h and 19.24 m) \\
252-IE5 & 68.59 & 68.59 & 68.27 & 80.71 (at 395 m\({}^{3}\)/h and 19.24 m) \\
258-IE1 & 62.93 & N/A & 60.96 & 76.79 (at 425 m\({}^{3}\)/h and 15.84 m) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: System efficiency statistics. type (252-IE4 and 252-IE5), up to 3.2 percentage points higher than in the system with an IM (252-IE3). In terms of average efficiency, the 252-IE5 outperforms the 252-IE4 by around 1 percentage point, regardless of the application of the motor limit. However, both SRM systems have a significant advantage over the 252-IE3, with efficiency differences reaching up to 5.5 percentage points when the TR is not utilised. It is also worth noting that the efficiency maps for the 252 pump do not show a pronounced peak area on the right-hand side of the operating plane. The use of the motor TR increases the permissible operating range of the VSDP. This is particularly true for SRMs, where the nominal temperature rise is lower than for IMs (252-IE5 in Figure 17a) have particularly large reserves). The disadvantage of using TR is a slight reduction in efficiency in this area. However, as the hydraulic losses dominate the system efficiency, the overall reduction is only about 1 percentage point. Nevertheless, the utilisation of this extended range in variable pump operation is advantageous. The system efficiency map for the existing system equivalent, 258-IE1, is shown in Figure 17b. Despite the use of a higher rated motor and pump, the efficiency is quite poor by today's standards. The average efficiency considering the motor limits (no TR is available for the IE1 motor) reaches only 61%, with a maximum efficiency of 76.8%.