## 2 Thematic Review and Analysis
### The Distribution Network
#### 2.1.3 Cascading Applications
Key aspects of the project include reducing the supply temperature required by buildings and improving cooling to lower return temperatures; categorizing buildings based on their temperature and flow requirements; assessing sub-networks according to these categories; and evaluating heat transmission and generation, with a focus on local heat pumps and micro-grids. The project identifies temperature levels of 90 \({}^{\circ}\)C, 50 \({}^{\circ}\)C, and 25 \({}^{\circ}\)C, demonstrating the ability of various sub-networks to support different return temperature levels across successive networks and consumer substations. [PERSON] et al. [81] conducted a comparative analysis of cascading strategies for supplying low-temperature consumers through various substation configurations. Two strategies were evaluated: (i) connecting the substation intake to the DH return line with an admixing bypass to increase the inlet temperature for domestic hot water units, and (ii) connecting one substation intake to the DH return line for space heating and another to the DH supply line for domestic hot water. Both strategies resulted in reduced return temperatures compared to a reference case with no low-temperature consumers. Winter simulations revealed return temperatures of approximately 46 \({}^{\circ}\)C and 42 \({}^{\circ}\)C for the first and second strategies, respectively, compared to 50 \({}^{\circ}\)C in the reference case. The study also compared excess flow requirements, noting an 18% increase in average flow rate for traditional substation connections, with cascading strategies showing increases of 18% and 8%. [PERSON] [82] analyzed a network cascading application for a low-temperature DH system in Neveshir, Turkije, using a low-grade geothermal well with a brine temperature of 65 \({}^{\circ}\)C and a flow capacity of 360 t/h, with a design outdoor temperature of \(-\)15 \({}^{\circ}\)C and an overall heat demand of 11.5 kWh per apartment. The study highlighted several constraints without network cascading:  
1. Designing home radiators without over-dimensioning necessitates a peak plant with a larger capacity to raise the supply temperature from 60 \({}^{\circ}\)C to 90 \({}^{\circ}\)C.
2. DH return temperatures exceeded 60 \({}^{\circ}\)C during cold spells below \(-\)7.5 \({}^{\circ}\)C, preventing effective supply from the geothermal well. 3. Radiators would need to be oversized by 160% to maintain a 60/30 \({}^{\circ}\)C operation scheme without a peak plant. 4. Economic optimization is achieved by using radiant panels alongside peak plant temperature boosting. To address these constraints, a cascading approach is proposed: a primary cascade level supplies homes with radiators, while a secondary level provides DH return to homes with radiant panels. The design includes  
1. A peak plant boosting the DH supply temperature to 75 \({}^{\circ}\)C.
2. Radiator-equipped homes, oversized by 46%, cooling to a return temperature of 50 \({}^{\circ}\)C.
3. Radiant panel-equipped homes, receiving a return temperature of approximately 35 \({}^{\circ}\)C from the return pipeline, which is then redirected. Expanding the proportion of homes with radiant panels from 40% to 60% can increase the DH capacity, accommodating up to 1900 apartments and increasing geothermal well capacity from 12.6 MWth to 13.4 MWth, while reducing peak plant capacity from 4.3 MWth to 3.4 MWth [82]. [PERSON] et al. [83] investigated the hydraulic interface between high-temperature DH networks and low-temperature sub-networks, focusing on area-substations configured with heat exchangers to separate the two systems. Direct connection methods, such as mixing shunts and 3-pipe connections, are briefly mentioned [84] (could not find this citation). Two indirect area-substation configurations were explored:  
1. The first option utilizes a heat exchanger with inlets from both the DH supply and return pipelines to boost temperature when return temperatures are low, maintaining the required supply temperature for the low-temperature sub-network. 2.