IMPROVEMENT IN THE EFFICIENCY OF DISTRICT HEATING AND COOLING (DHC) WITH A REGIONAL STEAM NETWORK OF CHPs AND MUNICIPAL INCINERATION PLANTS IN TOKYO

Transcription

1 IMPROVEMENT IN THE EFFICIENCY OF DISTRICT HEATING AND COOLING (DHC) WITH A REGIONAL STEAM NETWORK OF CHPs AND MUNICIPAL INCINERATION PLANTS IN TOKYO Wataru Fujisaki, Toru Ichikawa,3, Eisuke Hori 2, Mingfeng Cao 2 and Toshio Ojima 2,3 Energy sales and planning department, Tokyo Gas Co., Ltd. Shinjuku Park Tower, 3-7- Nishishinjuku, Shinjuku-ku, Tokyo 63-59, Japan 2 Department of Architecture, Science and Engineering, Waseda University, 3 Asia Institute of Urban Environment ABSTRACT District Heating and Cooling system (DHC) is an efficient energy system as they can supply chilled and heating water/steam effectively by integrating heating and cooling demand of neighboring buildings. However, there is possibility for further improvement of energy efficiency by integrated operation of adjacent DHC and utilizing waste heat from municipal incinerators and CHPs. In this study, the effect of such flexible use of heat and electricity in integrated DHC systems is examined. The main object is to raise total thermal efficiency and reduce CO 2 emission. The results of the study showed significant reduction of primary energy consumption and CO 2 emission by 2 to 36%. In addition, various side contributions to urban environment and city function were suggested such as mitigation of urban heat island, improvement of business continuity plan (BCP), electric-load leveling and improvement of city landscape. KEYWORDS District Hating and Cooling, CHP, Integrated energy use, Steam network, CO 2 INTRODUCTION The Kyoto Protocol, which became effective in 5, requires Japan to reduce greenhouse gas (GHG) emissions by 6% from 99 levels during the primary due period of However, CO 2 emissions in Japan in the end of 2, increased by % in the industry sector, 22% in the transportation sector and 28% in the residential and commercial sector from 99 levels. Among those the CO 2 emissions from the residential and commercial sector increased significantly, suggesting that the reduction of CO 2 by energy saving is getting more important especially in urban areas, which have the most concentrated energy demand. Integrated energy utilization of buildings, which include District Heating and Cooling (DHC) systems, has been discussed as one of the energy conservation measures in urban areas, as well as upgrading individual building facilities to energy efficient models. Concerning the difficulties to improve the efficiency of all buildings facilities to energy efficient models, integrated energy utilization of buildings is more effective to improve energy efficiency and reduce CO 2 emission from urban areas. Based on these circumstances, establishing highly efficient integrated energy utilization models, which utilize unused energy and natural energy, is required. Also the Urban Rejuvenation Project by the Urban Renaissance Headquarters promotes, with the slogan of Against global warming and heat island through urban renaissance projects, the measure for environmental loads reduction in combination with regional development, including rational use of Corresponding Author: Tel: , Fax: address: wfuji@tokyo-gas.co.jp

2 energy, reduction of waste heat and utilization of new energies at the city level. In this study, the effects of energy saving and CO 2 reduction about several DHC in central Tokyo are examined when their energy infrastructure are restructured. In addition, urban energy systems for further energy saving and CO 2 reduction are discussed when DHC systems are connected to a high-temperature steam network which utilizes steam from CHPs and waste heat from municipal incinerators. TARGETED DISTRICTS FOR ENERGY INFRASTRUCTURE RESTRUCTURING AND THE CONCEPT OF PHASED INTRODUCTION Restructuring energy infrastructure in districts with higher energy load density will be more effective in energy saving and CO 2 reduction in the city. Eight districts in the Tokyo metropolitan area were selected as model districts with high energy load density in the previous investigation (). Among those Shibuya District, Kasumigaseki & Toranomon District, Akasaka District and Ginza & Nihonbashi District are selected this time. Practically the integrated energy utilization system cannot be constructed at a time but will be constructed in phases. This study assumes that regional heat source network will be developed through the following phases. Phase : Conventional DHC systems supplying chilled and heating water/steam Phase : Expansion of supply of heating/chilled water to the neighboring large buildings around the DHC area. Phase 2: Connect heating and chilled water/steam pipes and electric cable of neighboring DHC each other. Operate integrally both DHC systems. Introduce high efficiency CHPs to DHC and utilize waste heat to produce heating and chilled water. Phase 3: Connect DHC system to the regional steam network and utilize waste heat from municipal incinerators and CHPs. OUTLINE OF GINZA & NIHONBASHI DISTRICT In this study, four districts are examined respectively. The result of Ginza & Nihonbashi District is described as the representative example in the following sections. Fig. shows the targeted districts and their heat load density. The targeted district is divided into five areas from to, and the DHC system restructuring is examined for each area. At first, the characteristics of buildings in each targeted area are surveyed, and the loads of electricity, cooling, heating and hot water demand (hereinafter referred to as various loads ) are calculated. The Tokyo geographic information system and Zmap-town II for 2, an electronic house map from Zenrin Co., Ltd., are used for understanding the characteristics of buildings in each area. The categorization of building use is decided based on the Tokyo geographic information system. The total floor area is produced simply by multiplying the building area by the floor count. Fig. 2 shows the total floor areas of buildings in each area and Fig. 3 shows the building use ratios in each area. The loads are calculated separately for DHC applied and unapplied buildings. Buildings with total floor area of 2,m 2 or more are classified as DHC applied, and with total floor area of 2,m 2 or less are classified as DHC unapplied. The heat loads of DHC applied buildings are the values of heat sales volume listed in the Handbook of Heat Service Utilities. The heat loads of DHC unapplied buildings are produced by calculating various energy consumptions based on the energy consumption ratio, selecting a heat source equipment for each building based on the implementation ratio of each heat source equipment by total floor area and by building use, and multiplying the COP set for each heat source equipment by the various energy consumptions. Fig. 4 shows the electricity, cooling, heating and hot water loads in a year and Fig. 5 shows the cumulative loads by hour.

3 The result indicates that the targeted area has a high heat loads density, which is suitable for DHC to be implemented as regional level. However, the building use ratio of offices is high, and as the result there is a high cooling loads compared to heating loads. Next which DHC system is the best to be implemented in the targeted district is examined based on the identified loads. Total energy utilization efficiency in the district is used as the indicator. The definition of total energy utilization efficiency is shown below: Total energy utilization efficiency = (Cooling heat supply + Heating heat supply + Steam supplied heat + Heat generated from CHPs) / (Gas input to CHPs + received steam x conversion rate) (TJ/year),6,4,, Cooling Heating Hot water Figure 4, cooling, heating and hot water load in a year Table Generation capacity of each area [TJ/ha 年] ~5 [TJ/ha 年] 5~ [TJ/ha 年] ~ [TJ/ha 年] 5~ [TJ/ha 年] 2~ [TJ/ha 年] 25~ [TJ/ha 年] 3~ [TJ/ha 年] Figure Targeted districts and heat load density Total Total output of generator kw 65, 52, 45, 52, 68, 282, Total refrigerating capacityrt 25, 8, 6, 2, 4, 85, Hot water absorption chiller 3, 2, 2, 2, 3, 2, Steam absorption chiller 22, 6, 4,,, 73, (MWh/h) Total floor area (m2),6,,4,,,,, 8, 6, 4,, Floor area over m2 Floor area under m2 (GJ/h) (GJ/h) load curve Cooling load curve Figure 2 Total floor areas of buildings in each Heating load curve 3% 7% 2% 3% 2% 3% 2% 3% 3% 2% 4% 5% 3% (GJ/h) % 2 76% 85% 93% 73% 58% Office Commercial buildings Hotel Public buildings School Hall, theater Amusement park House Other Figure 3 Building use ratios in each area Hot water load curve Figure 5 Cumulative loads by hour

4 Best mixed utilization of gas, electricity and heat in the district is effective to improve the total energy utilization efficiency. In addition the introduction of wind or biomass power generation will contribute to the government policy for promoting new energy utilization. The heat and electricity demands of commercial buildings fluctuate wildly, which sometimes makes it difficult to operate CHPs constantly at a high total efficiency. However, our model resolves this problem by integrating heat and electricity demands of the whole district. Based on examinations, this study chooses a solution that multiple large scale gas engines with high generation efficiency are introduced in the areas as CHPs to supply electricity and heat to buildings in the areas. SIMULATION RESULTS OF DHC SYSTEM AFTER RESTRUCTURING Outlines of proposed system The size of CHPs is set to the level with which all the electricity demands in each area can be supplied. The DHC system is also connected with a large scale heat source network to utilize waste energy of high-temperature steam from municipal incinerators and other CHPs. Fig, 6 shows the outline of proposed plant. The electricity generated from the gas engine preferentially supplies the electricity demands within the plant, and then supplies the electricity demands of buildings in each area. Also the collected heat from gas engines supplies steam for heating load and chilled water for cooling road by using absorption refrigerators to buildings of 2,m 2 or more. Heat pump with high COP (coefficient of performance) is used as the heat source equipment for buildings under 2,m 2. To address the heat island issue or other related problems, waste heat from plant refrigerators is processed using river water or municipal discharge. ) Setting conditions for plant simulation Based on the loads in each area calculated in Section 3, the capacities of CHPs and refrigerators are decided. The capacity of CHP is set to 45kWh as the general electricity consumption within the plant with transmission loss of 5% against the maximum electricity load. The heat loss of % during transportation is allowed to refrigerators. Table shows the decided capacities of equipments. Total capacity of generators required for each area is 45,kW to 68,kW, and 282,kW for the whole targeted district. Total capacity of refrigerators is 85,RT. The CHPs are operated constantly based on the assumption that the waste heat from CHPs and the steam from a high-temperature steam network will be interchanged. CHP plant Buildings Floor area under m2 In-plant electricity Heat pump Cooling Heating Hot water Floor area over m2 Gas Steam network Generator Gas engine Hot water Hot water Heat exchanger absorption chiller Exhaust gas boiler Steam absorption chiller Accumulator Steam header Chilled water Chilled water header Steam Heat exchanger Heat exchanger Storage tank Cooling Heating Hot water Efficiency(%) Figure 6 Outline of proposed plant 5 (%) 4 Steam(%) Hot water(%) Load(%) Figure 7 Characteristics of gas engine Table 2 COPs of refrigerators Equipm ent Hot water absorption chiller Steam absorption chiller COP.65.4 Cooling 2.5 H eat pum p Heating 3. Hot water 3.

5 Next the order of heat utilization is set. Gas engines generate hot water from the jacket cooling water and steam from exhaust gas boiler. Since the proposed systems do not supply hot water, all the collected hot water was supplied to hot water absorption refrigerators to generate chilled water. Next the collected steam was supplied to steam absorption refrigerators to generate chilled water, not directly supply for heating. If there is any surplus in chilled water supply, the surplus steam is used for heating. Conversely if the steam collected from the CHP is larger than the steam required within the plant, the steam surplus is provided to a high-temperature steam network, to be used in other plants as unutilized energy. The assumed gas engine is 6kW class high efficient gas engines and their part-load efficiencies are considered in the simulation. Fig. 7 shows the partial load efficiencies of gas engines and Table 2 shows the COPs of refrigerators. Plant simulation results Figure 8 to 3 shows the results of plant operation simulation for. Figure 8 shows the electricity demand and supply at typical one day of each month. The electricity consumption in summer season is higher than that of other month. Most of the electricity is supplied from CHP. Figure 9 shows the chilled water demand and supply at typical one day of each month. The most of chilled water demands can be covered by absorption chiller which utilize the hot water from CHPs throughout a year, but has a shortage in some periods mainly during summer. Figure shows the steam demand and supply at typical one day of each month. There is little steam demand in summer season. The steam demand in winter season is covered from the steam from CHP. The results of to show similar trends with. 2) (G J/h ) 5 S team (G J/h) generated by C H P Electrisity dem and In -p lant electricity Steam used fro m the regionalsteam network Chilled w a te r (G J/h ) Figure 8 demand and supply Chiled water dem and Hotwater absorption chiler Steam absorption chiler Figure 9 Chilled water demand and supply Steam (G J/h) Figure Steam comes from the regional steam network Steam provided to the regionalsteam network Figure 2 Steam provided to the regional steam network S team (G J/h) 5 5 S team (G J/h) Steam fro m gas engine Steam dem and Figure Steam demand and supply Steam produced in Ootemachi,M arunouchiand Y urakucho area Steam provided to the regionalsteam network Figure 3 Detail of steam amount in the Otemachi, Marunouchi & Yurakucho District

6 Then the steam requirement of each DHC plant from the regional steam network throughout a year is calculated. Conversely, the surplus amounts of steam which can be provided to the regional steam network are calculated. Fig. shows the steam used from the regional steam network and Fig. 2 shows the steam which can be provided to the regional steam network. Fig. and Fig. 2 indicate that there is little period in a year when all areas use the steam from the regional steam network, while there is a lot of steam which can be provided to the regional steam network. These results suggest that the key should be how to use these steams in terms of comprehensive energy utilization. The next section we discuss the effect of the steam which utilized in the Otemachi, Marunouchi & Urakucho DHC plant, the neighboring district of the Ginza & Nihonbashi District. Effective use of surplus steam There are four DHC plants in the Otemachi, Marunouchi & Yurakucho Distric. In these plants, steam was generated by gas boiler and this steam was supplied to steam absorption chiller to produce heating and chilled water. The total steam generated in the four DHC plants and the steam can be provided to the regional steam network from Ginza & Nihonbashi District are compared. The amount of steam reduction in four DHC plants by introducing steam from the regional steam network is calculated. The amount of primary energy reduction is calculated. The amount of steam produced in the four plants was the value of 4. Figure 3 shows the detail of steam amounts. The result of Fig. 3 indicates that the steam amount which can be provided to the regional steam network accounts for 75% of the steam generated in the four plants and is approximately 697 [TJ] per year. It is estimated that if the steam is generated by boilers of COP.85, about 82[TJ] of the primary energy needs per year. Assessment of the proposed systems The effect of systems proposed above is assessed in two aspects: energy saving (reduction of primary energy input) and environmental aspect (CO 2 and NO x reduction). The left bar shows baseline and right bar shows the proposed system.fig. 4 shows the effect of the primary energy input reduction. The primary energy inputs are reduced by 29% in, 28% in, 26% in, 29% in and 29% in. Fig. 5 shows the comparison of CO 2 emissions. CO 2 emissions are reduced to,t- CO 2 CO 2 in, 8,t- CO 2 in, 69,t- CO 2 in, 76,t- CO 2 in and 8,t- CO 2 in when comparing conventional thermal plant. Fig. 6 shows the comparison of NO x emissions. prim ary energy consum ption (TJ/year) 3,5 3, 2,5 2,,5, 5 29% 2,783,983 28% 2,2,593 26%,854,365 29% 2,96,49 29% 2,957 2,2 NOx em ission (ton/year) % % % % % 5 A re a D A re a E A rea A A rea B A rea C A rea D A rea E Figure 4 Primary energy input reduction Figure 6 NO x emissions 25 Table 3 Various specific consumptions CO2 em ission (x^3 ton/year) % 85 43% % % % 97 8 CO 2 NO X SO X.69 kg-c O 2 /kw h Gas 2.2kg-C O 2 /N m 3.8 g-n O x/kw h Gas(Boiler).68 g-n O x/n m 3 Gas(DHC).2 g-nox/nm3 Gas(CGS).95g-NOx/Nm3.4 g-so x/kw h Gas.8g-SOx/Nm3 A rea A A rea B A rea C A rea D A rea E Figure 5 CO 2 emissions

7 The NO x emissions are reduced to 48,t- NO x in, 38,t- NO x in, 33,t- NO x in, 36,t- NO x in and 5,t- NO x in compared to the average power generation plant. CONCLUSION OF GINZA & NIHONBASHI DISTRICT Following conclusion is found from the study on the DHC systems aiming at energy saving by integrated energy utilization in the Ginza & Nihonbashi District. ) If CHPs are installed to supply all the electricity demands in the Ginza & Nihonbashi District, their total generation capacity required in the whole district is approximately 282MW. 2) If the CHPs are introduced, primary energy inputs can be reduced by 28%, and CO 2 emissions by 36,t- CO 2 from current levels. 3) Total energy utilization efficiency was significantly increased from. to 2. by integrated energy utilization. CONCLUSION OF OTHER DISTRICTS Results from the similar investigation on Shibuya District, Kasumigaseki & Toranomon District and Akasaka District are shown in Table 4 and Fig.7. In the investigation of Shibuya District, the assessment is described using the primary energy consumption per capita and CO 2 emission per capita based on the assumption that total floor areas increase as the phase increments. The CO 2 reduction effect is larger than primary energy, and CO 2 can be reduced by 2 to 9% if shifting from Phase to Phase 3. 3) Totalfloor area P rim ary energy CO2 em ission P rim ary energy S pecific CO2 (m 2 ) consum ption (ton-c O 2/year) specific consum ption em ission (TJ/year) (M J/m 2/year) (kg-c O 2/m 2/year) Phase Phase 3 Phase Phase 3 Phase Phase 3 Phase Phase 3 Phase Phase 3 K asum igaseki, Toranom on Area 8,525,258 8,525,258 6,46 4,42 689, 67,,882, Akasaka Area 855, ,669 3,6 2,44 24,48 79,32 3,53 2, Shibuya Area 39,6 899, ,857 22,87 6,35 3,854 3, Table 4 Results of investigation on other districts Figure 7 Primary energy consumption per capita and CO 2 emission per capita (MJ/m2/year) Prim ary energy specific concum ption 4,5 4, Phase 3,5 Phase 3 3, 2,5 2,,5, 5 Kasum igaseki, Toranom on Area Akasaka Area Shibuya Area (kg-co2/m2/year) Kasum igaseki, Toranom on Area Specific C O 2 em ission Phase Phase 3 Akasaka Area Shibuya Area In this study, we showed the primary energy reduction potential and CO 2 emission reduction potential in DHC systems when they introduce high efficiency cogeneration system and connected to the regional

8 steam network. The results showed the large CO 2 reduction potential and significantly increase of total energy utilization efficiency. In the future, we are going to continue these studies on integrated energy utilization not only for individual districts but also for more expanded regions. We would like to propose more energy efficient infrastructures for the future metropolises. : Ikebukuro : Shinjuku : Shibuya : Shinagaw a : Kasum igaseki, T o ra n o m o n Area F : Iidabashi, Bunkyo -ku A re a G : O o te m a c h i, M arunouchi A re a H : G inza, N ihonbashi Legend symbol Study area DHC plant DHC area Municipal incinerator Sewage plant Steam Chilled water Hot water Future plan of regionaldhc high-tem perature steam netw ork in Tokyo area Figure 8 Future plan of regional DHC high-temperature steam network in Tokyo area ACKNOWLEDGEMENTS This study was supported by City and Regional Development Bureau, Ministry of Land, Infrastructure and Transport, Japan. REFERENCES ) Y. Ashie, M. Tanaka, T. Yamamoto and A. Taguchi(2) Study on regional heat volume from HVAC system and related equipment when concerning the cooling/heating device introduction ratio, Proceedings of the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan, Vol. 86, ) Japan District Heating and Cooling Association: Project 2, (995) Survey study of possibility to introduce district heating and cooling system in Japan, Japan District Heating and Cooling Association. 3) City and Regional Development Bureau, Ministry of Land, Infrastructure and Transport, Japan, (6) Study on effective utilization of energy in existent city area