Evaluation of reduced energy use resulting from a DHC network in the Shinjuku DHC area

Transcription

1 Evaluation of reduced energy use resulting from a DHC network in the Shinjuku DHC area Hashidate D 1 ; Nakajima Y 2 1 Graduate School Kogakuin University, Tokyo, Japan 2 Associate Professor Kogakuin University, Tokyo, Japan Reduced energy use and low carbon emissions by cities are important, and area-wide energy usage is an effective way to achieve these goals. District heating and cooling (DHC) is a typical form of area-wide energy usage. However, declining efficiency is a concern for heat source equipment that has been in operation for a long period of time. Therefore, facilities have to be updated or heat transfer has to be facilitated (connections to plants) in order to make an existing DHC network more efficient. This study analyzed and evaluated how effectively the DHC network between the Nishi- Shinjuku 1-chome area and the Shinjuku Shin-toshin area reduced energy use. This network began transferring chilled water between the 2 areas in Shinjuku Ward, Tokyo starting in 213. Results revealed that the DHC network resulted in about a 5 % reduction in the primary energy input per year in the area studied. Keywords: DHC, DHC network, heat transfer, reduced energy use, area-wide energy usage 1 Introduction In recent years, the use of area-wide energy has been promoted as a result of amendment of the Act concerning the Rational Use of Energy. District heating and cooling (DHC) is a typical form of area-wide energy usage. That said, declining efficiency is a concern for heat source equipment that has been in operation for a long period of time. Therefore, existing DHC networks have to be made more efficient. Heat transfer between DHC areas had previously been regulated but is now being considered as a result of measures to promote area-wide energy usage under the Kyoto Protocol Target Achievement Plan. Moreover, heat transfer started in 2 DHC areas in Shinjuku as an example of a DHC network following the creation of DHC areas around Nagoya Station. This study estimated the reduced energy use resulting from a DHC network between the Nishi-Shinjuku 1-chome area and the Shinjuku Shin-toshin area that started in Summary of the DHC areas studied The location of the DHC areas studied and the heat transfer pipe are shown in Fig. 1 and a summary of the DHC areas studied is shown in Table 1. The Nishi-Shinjuku 1-chome area has two plants, and it further reduces energy use by accepting exhaust heat from combined heat and power (CHP) generated for Mode Gakuen. The Shinjuku Shin-toshin area is one of the world's largest DHC areas that supplies heating and cooling to buildings with a total floor area of 2.2 million square meters. The Shinjuku Shin-toshin area supplies electric power to the Tokyo Metropolitan Government Building and the Shinjuku Park Tower via CHP. 1378

2 ISBN: Important aspects of the DHC network in the Shinjuku Shin-toshin area are that it supplies about 7.5 times the cooling and about 11 times the heating supplied by the Nishi-Shinjuku 1chome area throughout the year. There is a large difference in the heating demand of the 2 areas, and most of the heat source equipment in the Shinjuku Shin-toshin plant is more efficient than that in the Nishi-Shinjuku 1-chome plant. Furthermore, upgrading of some equipment in the Shinjuku Shin-toshin plant is planned. Having the Shinjuku Shin-toshin plant provide the amount of cooling required by both areas should reduce energy use in both areas as a whole when the cooling demand is low, such as at night or during the winter or during intervening periods [between seasons]. Fig. 1 Location of the DHC areas studied and the heat transfer pipe Table 1 Summary of the DHC areas studied Boiler Name Total Floor Area Nishi-Shinjuku 1-chome area About 357,88 Flue Fire Tube Boiler Once-Through Boiler Double Effect Absorption 9[t/h] 12[t/h] 18[t/h] 2[t/h] 6[RT] 9[RT] 1,1[RT] 1,3[RT] About 2,222, March 31 CHP Plant Equipment Shinjuku Shin-toshin area Water-Tube Boiler Condensing Turbine Centrifugal Back Pressure Turbine Centrifugal Double Effect Absorption Electric Turbine Turbo Gas Turbine CHP Waste Heat Boiler Gas Turbine CHP Waste Heat Boiler 3[t/h] 6[t/h] 3 3 5,[RT] 4 4,[kW] 7.2[t/h] 4,5[kW] 1.6[t/h] 4,[RT] 1,[RT] 2,[RT] 2,87[RT] 1,[RT] 2,65[RT] 2379

3 3 Evaluation of the DHC network 3.1 Summary of heat transfer between the Nishi-Shinjuku 1-chome area and the Shinjuku Shin-toshin area The DHC network in the Shinjuku DHC area was intended to help reduce energy use and lower carbon emissions by the city. A pipe connects the 2 areas. A diagram of the DHC network is shown in Fig. 2. The DHC network transfers up to 38 GJ (3,RT) of cooling produced in the Shinjuku Shin-toshin area to the Nishi-Shinjuku 1- chome area via 3 heat exchangers and 3 cold water pumps in the Nishi-Shinjuku 1-chome area. The Shinjuku Shin-toshin area supplies cooling of 4ºC and the Nishi-Shinjuku 1-chome area supplies cooling of 7ºC. Because the supplied temperature of cooling differs between the areas, heat is exchanged more efficiently. Customers Heat Transfer Pipe 4 3 Cold Water Pumps 7 13 Shinjuku Shintoshin area 12 3 Heat Exchangers Nishi-Shinjuku 1-chome area Fig. 2 DHC network 3.2 Study and analysis of heat transfer The amount of the daily cooling supply from April to November 213 in the Nishi-Shinjuku 1-chome area is shown in Fig. 3. Cooling transfer began in earnest in June. Cooling is produced in the Nishi-Shinjuku 1-chome area in the summer. However, most cooling that is required in the Nishi-Shinjuku 1-chome area can be supplemented by the DHC network because the cooling demand decreases after autumn. The amount of cooling supply by time during the week in which the largest amount of cooling was transferred is shown in Fig. 4. Because little cooling is needed in the middle of the night, the total cooling that was needed in the Nishi-Shinjuku 1-chome area was supplemented by transferring cooling. Maximum cooling is not transferred at peak times since the amount of cooling that can be transferred is limited by adjustments to equipment. A study indicated that there was no transfer on August 9 th at the behest of the Shinjuku Shin-toshin plant. 338

4 1, Transferred Cooling Cooling Needed in the Nishi-Shinjuku 1-chome Area Cooling Produced in the Nishi-Shinjuku 1-chome Area GJ/D] /1 7/1 8/1 9/1 1/1 11/1 Amount of Cold [ Fig. 3 Amount of daily cooling supply in the Nishi-Shinjuku 1-chome area GJ/h] 5 Amount of Cold [ Transferred Cooling Transferred Cooling(HEX3) Cooling Needed in the Nishi-Shinjuku 1-chome Area Transferred Cooling(HEX2) Cooling Produced in the Nishi-Shinjuku 1-chome Area Maximum Transferable Cold Heat 8/5 8/6 8/7 8/8 8/9 8/1 8/11 Fig. 4 Amount of hourly cooling supply in the Nishi-Shinjuku 1-chome area 3.3 Evaluation of reduced energy use resulting from the DHC network In order to evaluate the reduced energy use resulting from a DHC network, primary energy per unit of cold supply was estimated each year from 29 to 213. The data from June to November in those years were used in estimates because cooling was transferred in earnest over that period in 213. Moreover, primary energy input each year was compared. Results of the evaluation are shown in Fig. 5. In this figure, Gas for Cold Supply is the amount of gas consumed in the manufacture of steam to operate chillers. Transferred Cooling is the amount of gas and power consumption that were used to transfer cooling in the Shinjuku Shin-toshin area. Auxiliary Power is the sum of the total electrical energy of the primary cooling pump, cooling water pump, secondary cooling pump, cooling tower fan, and cooling pump for the DHC network, and the electrical energy of other equipment that was divided by the ratio of heating and cooling supplied. Calculations indicated that the primary energy input was about 5.6% less in 213 compared to the average primary energy input from 29 to 212. This indicates that gas for cold supply and auxiliary power were greatly reduced in the Nishi-Shinjuku 1-chome area. 4381

5 Auxiliary Power Primary Energy per Unit of the Cold Supply GJ/GJ] [.8.6 Transferred Cooling Gas and Power consumption in the Shinjuku Shintoshin area.4 Gas for Cold Supply Average 213 Fig. 5 Primary energy per unit of cold supply by year 4 Discussion based on simulations Because there were times when cooling transfer was not utilized as a result of adjustments to equipment, a simulation was performed assuming there were no limits on cooling transfer. The anticipated reduction in energy use resulting from the DHC network was estimated. The software "SPREEM-UD [1][2] " was used for simulations. Entering the heating and cooling supply per hour, COP, and partial load characteristics of each piece of equipment in the Nishi- Shinjuku 1-chome area allowed calculation of the amount of gas that each boiler consumes, the amount of steam that each boiler produces and that each chiller consumes, and the amount of cooling that each chiller produces per hour based on data provided by Energy Advance Co., Ltd. Simulations were performed using 3 scenarios with different amounts of cooling transferred, and the data from June to November (4,392 hours) were used in the simulations. [Regular Transfer]: Scenario where the amount of transferred cooling is similar to the results in 213. [Limited Transfer]: Scenario where the amount of transferred cooling is limited to 6% when the amount of power received by the Shinjuku Shin-toshin plant exceeded 9 MWh/h. [Ideal Transfer]: Scenario where all transferable cooling is transferred. Limited Transfer is explained here. When the amount of power received by the Shinjuku Shin-toshin plant exceeds 9 MWh/h, less cooling tends to be transferred than usual. Therefore, transferred cooling is presumably limited in accordance with the amount of power received by the Shinjuku Shin-toshin plant. The amount of transferred cooling and the amount of the cooling supply in the Nishi-Shinjuku 1-chome area in each scenario is shown in Fig. 6. In the figure, ideal transferred cold is the amount of the cooling supply in the Ideal Transfer scenario, and limited transferred cold is the 5382

6 amount of the cooling supply in the Limited Transfer scenario. An increase in the amount of cooling transferred in these scenarios is apparent in comparison to the cooling transferred in the Regular Transfer scenario. Based on the total amount of cooling transferred from June to November, the amount of cooling actually transferred was only approximately 67% of the amount of ideally transferred cooling. After the intervening period [between seasons], almost the entire amount of cooling needed in the Nishi-Shinjuku 1-chome area was covered by the amount of actually transferred cooling regardless of the scenario. Results of each scenario are shown in Fig.7. A Limited Transfer resulted in about a.4 % reduction in primary energy input and an Ideal Transfer resulted in about a 5.7 % reduction in primary energy input compared to a Regular Transfer. Moreover, the Limited Transfer was predicted to reduce primary energy input about 6. % and the Ideal Transfer was predicted to reduce primary energy input about 11.3 % in comparison to primary energy input prior to establishment of the DHC network. TJ] Cooling Supply Actual Transferred Cooling Jun. Jul. Aug. Sep. Oct. Nov. Amount of Cooling [ Ideal Transferred Cooling TJ] Total Fig. 6 Amount of cooling consumption and transferred cooling (June - November) Amount of Cooling [ Auxiliary Power 8 Primary Energy TJ] 6 [ 4 Transferred cooling Gas and Power Consumption in the Shinjuku Shin-toshin area Gas for Cold Supply 2 Regular Transfer Limited Transfer Ideal Transfer Fig. 7 Amount of total primary energy from June to November 6383

7 5 Conclusion This study estimated the reduced energy use resulted from a DHC network between the Nishi- Shinjuku 1-chome area and the Shinjuku Shin-toshin area that began operating in 213. As evidence of reduced energy use resulting from the DHC network, primary energy input was reduced about 5.6 % in comparison to primary energy input prior to establishment of the DHC network. In addition, a simulation revealed that primary energy input should be reduced about.4 % except when cooling transfer is limited as a result of adjustments to equipment. Primary energy input should be reduced about 5.7 % when all transferable cooling is transferred from the Shinjuku Shin-toshin area to the Nishi-Shinjuku 1-chome area. Limits on transferable cooling due to adjustments to equipment should decrease in the future. Further studies will analyze and evaluate reduced energy use in DHC networks and a model of a DHC network will be created in the future. Acknowledgment The authors wish to thank Energy Advance Co., Ltd. for the data and suggestions regarding data processing that the firm provided. References [1] Hayashi et al. Development of an energy and carbon emissions simulator for urban design (Parts 1 and 2). Technical Papers from the Annual Meeting of the Society of Heating, Air-Conditioning, and Sanitary Engineers of Japan, 29 [2] Sugihara et al. Development of technology to optimize smart energy networks (Optimization of the configuration of a DHC and optimization of its operation). The 27th Conference on Energy Systems, the Economy, and the Environment,