## 3 Discussion
Annual inspections of substation cooling performance are necessary, either if substations are owned by the DH company or if mandated by law. Pressure-independent thermostatic radiator valves offer a solution for maintaining hydraulic balance, thereby mitigating thermal discomfort and inadequate cooling at end-user stations. In contrast, decentralizing demand-driven pumps at end-user locations provides an alternative to traditional DH system configurations. This approach eliminates the need for a central primary pump station and hydraulic control valves, thereby effectively maintaining the required flow rate at all end-user stations according to demand and generally reducing excessive return temperatures. Although not commonly emphasized, the addition of additives to the heat carrier medium or other make-up fluids could be considered to reduce return temperatures. Another innovative approach involves configuring a large-scale, centralized heat pump unit that utilizes DH return medium as a heat source. Modern DH systems, equipped with smart heat meters and robust IT communication infrastructure, are capable of monitoring end-user stations. It is recommended to extend this application for continuous evaluation of substation performance (cooling capacity), even though it is primarily used for heat metering. A comprehensive overview of the key technical, operational, and economic considerations that influence return temperature reduction in DH systems is shown in Table 2. These factors collectively contribute to optimizing system efficiency, minimizing energy losses, and enhancing the economic viability of DH networks. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **Consideration** & **Description** \\ \hline \multirow{5}{*}{Cascading Applications} & \multirow{2}{*}{Hydraulic Balancing} & Ensures even heat distribution and prevents return temperature spikes. \\ \cline{3-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \hline \multirow{5}{*}{Heat Storage Systems} & \multirow{2}{*}{Thermal storage solutions to stabilize temperature variations and improve efficiency.} \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \hline \multirow{5}{*}{Bypass Regulation} & \multirow{2}{*}{Hinimizing unnecessary bypass flows that elevate return temperatures and impact efficiency.} \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \hline \multirow{5}{*}{Cascading and Awareness} & \multirow{2}{*}{Thermal storage solutions to stabilize temperature variations and improve efficiency.} \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \hline \multirow{5}{*}{Cascading and Awareness} & \multirow{2}{*}{Thermal storage solutions to stabilize temperature variations and improve efficiency.} \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \cline{2-3}  & & \\ \hline \end{tabular}
\end{table} 
Table 2: Technical, operational, and economic factors essential for return temperature reduction in DH systems. A holistic approach in DH efficiency improvement necessitates the simultaneous consideration of multiple interdependent system components rather than optimizing each in isolation. Correct operation of the DH network, particularly its design and control strategies, plays a pivotal role in ensuring system-wide efficiency, with a major cumulative impact on overall performance. This interconnection extends to heat source efficiency, system-level optimization, and the integration of novel concepts and implementation strategies, all of which are necessary to achieve long-term sustainability and enhanced energy performance.