Reduction of return temperatures in urban district heating systems by the implementation of energy-cascades

Exergy analysis of district energy systems and comparison of their exergetic, energetic and environmental performance

“…One focus of the investigation was the use of the return line of an existing DHN for supplying heat (i.e. cascaded use of heat) (Köfinger, et al, 2016). Here, some share of the flow in the return line is extracted and fed into the heating systems/substations of suitable buildings using a separate pipe.…”

Optimal operation model of integrated energy system for industrial plants considering cascade utilisation of heat energy

“…where constraints (23) and (24) specify the total input electrical power and the total output heat power of the IAC, respectively; the energy conversion model of chiller is shown as constraint (25); and the constraints (26) and (27) are the mathematical model of the ice tank; constraint (28) defines the initial energy level as well as constraint (29) ensures that the energy level of the first time period is the same of the last time period; constraint (30) gives the upper bound and lower bound of the energy level of the ice tank; constraint (31) specifies the start and end charging time of the ice tank; constraint (32) specifies the start and end discharging time; constraint (33) ensures the consistency of charging and discharging process; constraint (34) ensures that the ice tank cannot start and end charging energy as well as start and end discharging energy; constraint (35) defines the charging and discharging times and constraint (36) limits the charging and discharging times of the ice tank.…”

“…According to different heat load demand characteristics, energy cascade system supplies high-grade heat, medium-grade waste heat and low-grade waste heat to different types of end users separately [34,35]. Kofinger et al [36] focused on energy cascade of the return water system in urban district heating networks; the optimisation model was built to improve the performance of system operation via exploiting heat energy cascade potential between various kinds of buildings in a city. Han et al [37] proposed a compression refrigeration system depending on waste heat recycle.…”

Enhancement of a District Heating Substation as Part of a Low-Investment Optimization Strategy for District Heating Systems

“…Basciotti et al [6] investigated the influence of building renovation on the reduction of return temperatures. However, only a significant retrofitting rate (more than 80% of the 2 of 17 buildings in the studied area) helped to bring down return temperature in the DHN up to 1.2 • C. Köfinger et al [7] examined the reduction by supplying new consumers with low system temperatures from the return flow of existing consumers with high system temperatures. In that scenario, consumers with a total heat demand of 630 MWh were connected to an existing heating network with an annual demand of 2400 MWh.…”