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The mass flow rate requirement per the end-user (Gunique) and the overall DH volumetric flow rate (Vp); and the pump model appointed [45], as obtained for the scenarios. * The pump models were selected from the Grundfos product centre [45].

Table 10 The mass flow rate requirement per the end-user (Gunique) and the overall DH volumetric flow rate (Vp); and the pump model appointed [45], as obtained for the scenarios. * The pump models were selected from the Grundfos product centre [45].

Related Figures (31)

The grade (absolute of the slope) values of the weather- compensation curves as designated for various heat emit- ter types, calculation based on temperature values at [°C] as converted from the raw data taken from [14].
The grade (absolute of the slope) values of the weather- compensation curves as designated for various heat emit- ter types, calculation based on temperature values at [°C] as converted from the raw data taken from [14].
Fig. 1. The simplified block (signal flow) diagrams of the controllers; (a) the traditional weather-compensation based control and (b) the new demand- responsive control strategy.
Fig. 1. The simplified block (signal flow) diagrams of the controllers; (a) the traditional weather-compensation based control and (b) the new demand- responsive control strategy.
Fig. 2. Soil temperature variation through the heating season (depth at 1 m), as ordered according to the load duration curve.
Fig. 2. Soil temperature variation through the heating season (depth at 1 m), as ordered according to the load duration curve.
Regression coefficients for the sinusoidal regression equation given in Eq. (3) fitted for a depth of 1 m, the reference raw data for interpolation taken from [56].
Regression coefficients for the sinusoidal regression equation given in Eq. (3) fitted for a depth of 1 m, the reference raw data for interpolation taken from [56].
Materials and thermal conductivity of the pipe layers assumed in this current study [50,52]. Table 2
Materials and thermal conductivity of the pipe layers assumed in this current study [50,52]. Table 2
The regression coefficients as obtained for traditional sin- gle pipes (insulation Series 1) for a nominal diameter range between 20 and 250 mm [50].
The regression coefficients as obtained for traditional sin- gle pipes (insulation Series 1) for a nominal diameter range between 20 and 250 mm [50].
The regression coefficients as obtained for the weather- compensation curves as given for the direct and the in- direct substation configurations (the labels/slopes to be selected between 1 and 40 with an interval of 1) [61,62].
The regression coefficients as obtained for the weather- compensation curves as given for the direct and the in- direct substation configurations (the labels/slopes to be selected between 1 and 40 with an interval of 1) [61,62].
The regression coefficients as obtained for the weather- compensation curve at DH level, raw data taken from (the labels/slopes to be selected between 0.25 and 4 with an interval of 0.25) [63].
The regression coefficients as obtained for the weather- compensation curve at DH level, raw data taken from (the labels/slopes to be selected between 0.25 and 4 with an interval of 0.25) [63].
Fig. 6. Illustration for the Simulation 2, with interactions of models considered. Fig. 5. Illustration for the Simulation 1, with interactions of models considered.
Fig. 6. Illustration for the Simulation 2, with interactions of models considered. Fig. 5. Illustration for the Simulation 1, with interactions of models considered.
Fig. 7. Illustrations of the configurations for the direct substation type, (a) with a direct connection without substation controller unit, (b) with the patent idea and (b) with the substation controller using the Weather Compensation (WC).
Fig. 7. Illustrations of the configurations for the direct substation type, (a) with a direct connection without substation controller unit, (b) with the patent idea and (b) with the substation controller using the Weather Compensation (WC).
Fig. 8. Illustrations of the configurations for the indirect substation type, (a) with the substation controller using weather-compensation, (b) with the con- troller maximising the supply-return temperature difference (AT) at the substa- tion level, and (c) having the same controller described in (b) but together with the new DH control unit.
Fig. 8. Illustrations of the configurations for the indirect substation type, (a) with the substation controller using weather-compensation, (b) with the con- troller maximising the supply-return temperature difference (AT) at the substa- tion level, and (c) having the same controller described in (b) but together with the new DH control unit.
* ‘NC’, as the abbreviation of ‘No Control’, refers to the direct connection without alteration (or change) of the inlet temperature to the radiator unit. + ‘WC’ refers to the Weather Compensation (as dependent where it is indicated — i.e. at the substation level or at the DH level). * ‘AT’ refers to the substation controller for indirect type, which keeps the supply-return temperature difference at the primary side maximum - e.g. by Gustafsson et al. [7] (Please see Section 2.1 for the details of this approach). 8 ‘FT’, the abbreviation of the ‘Fixed Temperature’ refers to the temperature strategy of keeping the supply tempera- ture as constant through the whole heating periods, in this simulation as fixed at 90 °C. | ‘Patent’ refers to the novel temperature strategy enclosed within this current study (Please see Section 3.1.2), as enclosed in [16]. Description of cases, details given about the substation types together with the control strategies at the radiator, the substation, and the DH level.
* ‘NC’, as the abbreviation of ‘No Control’, refers to the direct connection without alteration (or change) of the inlet temperature to the radiator unit. + ‘WC’ refers to the Weather Compensation (as dependent where it is indicated — i.e. at the substation level or at the DH level). * ‘AT’ refers to the substation controller for indirect type, which keeps the supply-return temperature difference at the primary side maximum - e.g. by Gustafsson et al. [7] (Please see Section 2.1 for the details of this approach). 8 ‘FT’, the abbreviation of the ‘Fixed Temperature’ refers to the temperature strategy of keeping the supply tempera- ture as constant through the whole heating periods, in this simulation as fixed at 90 °C. | ‘Patent’ refers to the novel temperature strategy enclosed within this current study (Please see Section 3.1.2), as enclosed in [16]. Description of cases, details given about the substation types together with the control strategies at the radiator, the substation, and the DH level.
Fig. 9. Return temperature and required mass flow rate as to changing heat demand rates at various levels of the supply temperature based on a design condition of 90|70|20 °C at q,= 9 kw [16].
Fig. 9. Return temperature and required mass flow rate as to changing heat demand rates at various levels of the supply temperature based on a design condition of 90|70|20 °C at q,= 9 kw [16].
The heat loss in thermal energy [GWh,,] as obtained for the scenarios in question.
The heat loss in thermal energy [GWh,,] as obtained for the scenarios in question.
Fig. 10. Return temperature and required mass flow rate at the primary side (of the heat exchanger) as to changing heat demand rates at various levels of the DI supply temperature based on a design condition given at the introduction of Section 3.3.
Fig. 10. Return temperature and required mass flow rate at the primary side (of the heat exchanger) as to changing heat demand rates at various levels of the DI supply temperature based on a design condition given at the introduction of Section 3.3.
Fig. 11. Supply temperature (solid lines) and consequent return temperature degrees (dashed lines —- same colour as the supply for each scenario), as obtained fot the scenarios of Simulation 1.
Fig. 11. Supply temperature (solid lines) and consequent return temperature degrees (dashed lines —- same colour as the supply for each scenario), as obtained fot the scenarios of Simulation 1.
Fig. 12. z-Factor ratios as obtained for each period of the whole heating season based on the temperature degrees by the scenarios (shown in Fig. 11- same colour scheme kept for the scenarios).
Fig. 12. z-Factor ratios as obtained for each period of the whole heating season based on the temperature degrees by the scenarios (shown in Fig. 11- same colour scheme kept for the scenarios).
Labels for sensitivity cases as based on the length multiplier and the consumer number serviced per each node. pipes, again by use of the ‘Maximum Pressure Gradient (Target Pres- sure Loss)’ dimensioning method. The design condition was considered to be with Sc2, the operational strategy being based on the weather- compensation curve (other strategies were formed to use the same pipe dimensions). The total lengths found for each of the nominal diameters are given in Table 14.
Labels for sensitivity cases as based on the length multiplier and the consumer number serviced per each node. pipes, again by use of the ‘Maximum Pressure Gradient (Target Pres- sure Loss)’ dimensioning method. The design condition was considered to be with Sc2, the operational strategy being based on the weather- compensation curve (other strategies were formed to use the same pipe dimensions). The total lengths found for each of the nominal diameters are given in Table 14.
The length of the pipe diameters (traditional steel pipes — insulation level 1 [50]) as obtained by use of the ‘Maximum Pressure Gradient (Target Pressure Loss)’ method for each of the scenarios (Sc3 and Sc3r makes use of the same diameter by Sc2). Table 12
The length of the pipe diameters (traditional steel pipes — insulation level 1 [50]) as obtained by use of the ‘Maximum Pressure Gradient (Target Pressure Loss)’ method for each of the scenarios (Sc3 and Sc3r makes use of the same diameter by Sc2). Table 12
Fig. 13. Overall annual electricity cost [GWh,,] as obtained considering the pump consumption and the loss of electricity at the cogeneration plant as a consequenc by the generation of the heat load and the heat loss.
Fig. 13. Overall annual electricity cost [GWh,,] as obtained considering the pump consumption and the loss of electricity at the cogeneration plant as a consequenc by the generation of the heat load and the heat loss.
Length of nominal pipe diameters, as obtained for each of the sensitivity cases. Table 14
Length of nominal pipe diameters, as obtained for each of the sensitivity cases. Table 14
Fig. 14. Linear heat density and relevant weighted average diameter as a function of the DH overall network length and the DH heat load, as obtained for the case network.
Fig. 14. Linear heat density and relevant weighted average diameter as a function of the DH overall network length and the DH heat load, as obtained for the case network.
Fig. 16. Temperature drop as a function of the flow rate as found for different inlet temperature levels for a pipe segment of DN50 at a length of 1 km. Fig. 15. Overall annual electricity cost [GWh,,] as obtained for each of the sensitivity cases. 4. Discussion
Fig. 16. Temperature drop as a function of the flow rate as found for different inlet temperature levels for a pipe segment of DN50 at a length of 1 km. Fig. 15. Overall annual electricity cost [GWh,,] as obtained for each of the sensitivity cases. 4. Discussion
Fig. 17. Temperature alteration in the DH system for the direct substation configuration considering various cases of operational control strategies at the substation and DH level.
Fig. 17. Temperature alteration in the DH system for the direct substation configuration considering various cases of operational control strategies at the substation and DH level.
Fig. 18. Temperature alteration in the DH system for the indirect substation configuration considering various cases of operational control strategies at the substation and DH level.
Fig. 18. Temperature alteration in the DH system for the indirect substation configuration considering various cases of operational control strategies at the substation and DH level.
Fig. 19. Return temperature as obtained by the case studies based on direct substation configuration.
Fig. 19. Return temperature as obtained by the case studies based on direct substation configuration.
Fig. 20. Return temperature as obtained by the case studies based on indirect substation configuration.
Fig. 20. Return temperature as obtained by the case studies based on indirect substation configuration.
Related topics:
Renewable EnergySubstation automationDistrict HeatingLow Temperature District Heating
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