ITOMAN CITY HALL. Koui TSUKAMOTO 1 Manabu TOCHIGI 1

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1 1-8 The 25 World Sustainable Building Conference, Tokyo, September 25 (SB5Tokyo) ITOMAN CITY HALL Koui TSUKAMOTO 1 Manabu TOCHIGI 1 1 Environment & MEP Engineering Department of Nihonsekkei. INC., 29 th Fl., Shinjuku I-LAND Tower Nishi-shinjuku, Shinjuku, Tokyo , Japan, tsukamoto-k@nihonsekkei.co.jp / tochigim@nihonsekkei.co.jp Keywords: environment friendly building design, solar shading, photovoltaic power generation, natural ventilation, natural lighting, thermal storage system, rain water utilization system Summary Prior to the Itoman city hall development project, Itoman City had established Itoman new (alternative) energy vision in Itoman city expressed the concept to consider introduction of new energy system as one of the solution for global environmental problems in it. Reflecting the new energy vision, Itoman city hall had been designed as an environment friendly building with the integration of architectural design and building service engineering. Natural energy utilization, air conditioning load reduction and city-infrastructures load reduction are the major subjects in this project. With the external louvers which are surrounding the Itoman city hall, solar shading, photovoltaic power generation, natural ventilation and natural lighting are introduced as technologies for natural energy utilization and air conditioning load reduction. Thermal storage system and rain water utilization system are provided to the building in order to reduce the load of the power supply and city water supply infrastructures. The total reduction rate of the annual primary-energy consumption in Itoman city hall is estimated 22% compare to the standard office building in this region. 12% of annual power consumption was shifted from daytime to nighttime with the thermal storage system and 33% of annual water consumption was supplied by rain water utilization system. 1. Project Outline Itoman city is located on the southernmost tip of Okinawa Hontou (Main Island) at north latitude 26 8 and east longitude The Itoman city is 12 kilometers south of Okinawa s capital city Naha. The population of Itoman city is approximately 6,. The design competition held in After schematic design and design development work, the construction started in November 2 and completed in March 22. The administrative service is started in new city hall from May 22. Okinawa 旧庁舎 1.1 Site Plan Depend on the wide area and long term regional redevelopment plan in southern region of Okinawa Hontou, and in order to attain the improvement in service and in efficiency to cope with the increment of population, the relocation of the city administration and cultural facilities to the public building zone in Minamihama reclaimed land was decided. (Fig.1) Besides the new city hall, civic hall (theater), public health improvement center and civic square have been planned to construct in public building zone in future. The buildings in the public building zone will be connected each other and form the network of public services. (Fig.2) As development relief (mitigation) to reclamation development, planting with local vegetation is planned, Project Site Fig.1 Site Map Center for Public Health Seashore Recreation zone 国道 331 号線ハ イハ ス 糸満市庁舎 Minami-hama Reclaimed land Itoman city hall Civic Square Fig.2 Public Building Zone Block Plan Public Services Network Civic Hall

2 and the seashore recreation zone with environment friendly shore protection is constructed. The 25 World Sustainable Building Conference, Tokyo, September 25 (SB5Tokyo) 1.2 Building Plan The Itoman city hall is consisted with the main building and the water-board annex. The water-board annex has two (2) stories, water-board office is located at first floor, dinning-room and kitchen is located at second floor. From the marine gallery which is located on the roof of the annex, Kerama islands can be seen in the west. The main building is planned with east & west both-ends core. Office spaces are allotted in north and south wings. Each office space is approximately 9m 2 without internal pillars. Also the modulated ceiling and Fig3. Southern side external view of Itoman city hall raised floor are provided to have suitable flexibility as Table1. Building data sophisticated office space. Name Itoman city hall Site address Two courtyards are provided in center part of the main building to bring brightness and ventilation to the center portions of the main building. First floor and second floor which have the service reception counters, are planned with barrier-free (universal) design guide line which issued by Okinawa welfare office. The elevator which has enough Shiozaki tyou 1-1, Itoman City, Okinawa Site area 13,844.76m 2 Total floor area 15,434.75m 2 Structure RC with press-tress beam Stories 5 floor, penthouse dimensions for a wheelchair and stretcher, multiple-purpose rest room, and breast-feeding room are provided, and also voice guidance with the hearing aid system is installed in Itoman city hall. Itoman city hall has the particular space under the southern external louvers in order to connect the city hall and the civic square which will be the most important facility in the public building zone as a communication space for itoman citizen. Various events in itoman city such as traditional festival will be held at civic square. 2. Environment Friendly Building Design in Subtropical Climate Based on the Itoman new energy vision, natural energy utilization / air-conditioning load reduction and infrastructure load reduction were considered as the major theme in this project. In Itoman city hall, solar shading, photovoltaics, natural ventilation, and natural lighting were adopted as technical elements of natural energy utilization and airconditioning load reduction which suited in subtropical climate. (Fig.4) In Okinawa, the higher cost is required to maintain the sufficient capacity and reliability of city infrastructure because Okinawa is islands region geographically which is apart form mainland of Japan. In order to reduce load of the electric power infrastructure, the thermal storage system was provided, also to reduce load of city water infrastructure, the rain water utilization system was installed in Itoman city hall. Solar Shading South: Horizontal Louvers North: Vertical Louvers East: PC Screens West: PC Screens Roof: Horizontal Louvers Natural Lighting Lighting Controls With illumination Sensors At Northern Wing Water Board Annex Main Building North Wing ern Southern Wing Photovoltaic System Roof: Solar cell Shelter South: Solar cell Louvers Natural Ventilation Large opening at All external Walls Courtyards For Natural Ventilation And Natural Lighting In addition, valuable chilled water circulation system, air to air heat-exchanger and high frequency fluorescent light devices are adopted in building services to make higher efficiency of energy consumption. Fig.4 technical elements for natural energy utilization and air conditioning load reduction.

3 2.1 Solar Shading Fig. 5 shows the relationship between Perimeter zone Annual air conditioning Load (PAL) and total heat transfer rate of the building / total solar permeation rate of the building in Sapporo (cold climate), Tokyo and Naha (subtropical climate). The PAL values at Naha show that reducing total solar permeation rate is more effective to reduce PAL values than reducing total heat transfer rate in subtropical climate. In Itoman city hall, the shapes of external louvers are studied to cut solar radiation efficiently. The horizontal louvers are provided at southern wall of building, pre-cast concrete screens are provided eastern and western wall, the vertical louvers are provided to northern wall and horizontal louvers are provided at roof as a shelter. To evaluate PAL reduction effect of the external louvers, three (3) types of buildings shown in table 2 are compared. In the PAL evaluation, direct solar radiation, sky solar radiation, reflecting solar radiation and heat transfer through the widows and walls in the perimeter area are calculated. The external louvers provided to the Itoman city hall cut the solar radiation effectively especially when the solar altitude becomes low. The evaluated PAL of Itoman city hall is 1,39 [GJ/year]. It is 1,474 [GJ/year] smaller than Case1: No Louvers building, and 1,69 [GJ/year] smaller than Case2: Standard Lovers building. Total heat transfer rate Monthly 月積算外壁冷房負荷 Perimeter A/C GJ/ 月 Load ] Case1: No louvers Building PAL Total solar permeate rate The 25 World Sustainable Building Conference, Tokyo, September 25 (SB5Tokyo) Total heat transfer rate PAL Total solar permeate rate Sapporo Tokyo Naha 図 -6 Fig.5 PAL 曲線の地域的変化 PAL Value in three ( 日本建築学会 cities / 建物の省エネルギー計 in Japan Table2 Variation of external louvers Case2: Standard louvers (balcony) Building Total heat transfer rate PAL Total solar permeate rate Case3: Itoman city hall [GJ/Month] 4 35 Case1 3 Case2 25 Case 月 Fig.6 Monthly amount of Perimeter A/C Load 2.2 Photovoltaic Power Generation System Photovoltaic modules are installed on southern horizontal louvers and horizontal louvers of roof shelter. The total capacity of the photovoltaic modules is 195.6[kW]. In order to operate the photovoltaic system at high efficiency, the photovoltaic system was designed as the interactive system with power infrastructure which can reverse the power to Okinawa electric company. In the weekends and holidays, surplus of photovoltaic power over the electrical demand in the building is sold to Okinawa Power Company. The photovoltaic system is consisted with power conditioners, power collectors and multi-crystalline silicon solar cells. An auxiliary 2[Ah] battery is installed in the system to operate during the power failure in case of disaster. (Fig.8) As the Itoman city hall is located in the littoral district, consideration on the prevention of the damage caused by briny air had been taken. The solar cells are protected with two sheets of tempered glass provided on both of front and back side to have self-purification effect by rainwater. (Fig.9) The amount of power generated by photovoltaic system and reduced CO 2 weight by the power generation are indicated on the monitoring system display installed in citizen hall on the first floor of the Itoman city hall. The monitoring system gives information people to raise awareness on the environment problem and energy problem. Briny wind Battery Panel Battery Junction Fig.7 Itoman city hall from bird s eye view 5kW Power Collector Junction Junction PV Modules x 5 Sets On Southern Louvers Solar radiation Power Interactive Point (6.6kV) Display Monitoring System 1kW Power Power Interaction Panel Collector 1kW Power Thermostat Heliograph 1kW Power PV Modules x 14 Sets On Roof Shelter Fig.8 Photovoltaic system diagram Standard PV Module Strengthening With frame Salt Briny wind Self purification by rainwater Solar radiation Fig.9 Details of photovoltaic modules Itoman PV Module Strengthening With tempered glass

4 Monthly amount of power generation by photovoltaic system are shown in Fig.1. In 23, the annual amount of power generation by photovoltaic system is 213,34[kWh/year].It corresponds to 12% of the total annual power consumption of Itoman city hall. Photovoltaic system is introduced with subsidy of New Energy and Industrial Technology Development Organization (NEDO). Monthly 発電電力量 Power [kwh/ Generation 月 ] The 25 World Sustainable Building Conference, Tokyo, September 25 (SB5Tokyo) 3, [kwh/month] Sep.22-Aug.23 H14.9~H , Sep.23-Aug.24 H15.9~H16.8 2, 15, 1, 5, 月 Fig.1 Monthly amount of measured power generation 2.3 Natural Ventilation In Itoman city hall building, spring, autumn and winter (from November to May next year), the air conditioning system is stopped. The natural ventilation is planned to maintain the indoor thermal environment in acceptable condition during the air condition system are stopped. By the external louvers which cut solar radiation effectively, the large windows could be provided all external walls for the natural ventilation without air-conditioning load increment. The natural ventilation route in Itoman city hall is formed with the sliding windows on the external walls, and sliding doors and extrusion windows facing to two courtyards which are provided in centre of the building. (Fig.11) The ventilation rate by the natural ventilation is estimated with ventilation network calculation. When there is 1. m/s external wind, the ventilation rate in major rooms in Itoman city hall was presumed to be 12-4 [times/hour] as shown Table3. During the season which air-conditioning system is stopped, indoor thermal environment is moderately maintained acceptably by natural ventilation. The amount of annual air conditioning load removed by natural ventilation is presumed to be 398 [GJ/year]. (Fig.12) 2.4 Natural Lighting The sky light with little unpleasant glare is taken in Itoman city hall as a lighting source by cutting direct solar rays with the external louvers. And two courtyards are provided to introduce natural light into the central part of Itoman city hall. Automatic lighting controls with illumination sensors are provided at perimeter area of office spaces in northern wings. The reduced annual total power consumption of lighting by natural lighting is presumed to be 12,944[kWh/year]. (Fig.13) 2.5 The Effect of Natural Energy Utilization and Air- primary-energy conditioning Load Reduction The reduction rate of annual consumption by the natural energy utilization and airconditioning load reduction are evaluated as 22%. The primary-energy consumption per unit area based on the measure value in 23 is 1,111 [MJ/m 2 year]. (Fig.14) Wind 5th FL 4th FL 3rd FL Direction Verocity Monthly 冷房負荷 Air conditioning [GJ/ 月 ] Load 2nd FL 1st FL North South North South North South North South North South Wing Wing Wing Wing Wing Wing Wing Wing Wing Wing N E S W Monthly power consumption for lighting 照明電力量 in northern [kwh/ 月 ] wing [GJ/Month] 8 A/C Load removed by 自然換気の効果 7 Natural Ventilation 市庁舎空調負荷 6 A/C Load of City Hall Fig.12 Estimated A/C load removed 月 by natural ventilation [kwh/month] 7, 6, 5, 4, 3, 2, 1, 月 Fig.13 Estimated power consumption reduced by natural lighting 照明使用電力量自動調光設備による削減量 [MJ/m 2 year] 16 昼光利用 22% 22% reduction Natural Lighting 削減 14 自然換気太陽光発電 Natural Ventilation 12 日射遮蔽受電電力 PV Power Generation 1 フ ロハ ンカ ス Solar Shading 8 Power Consumption 6 LPG Consumption 4 Primary-energy consumption 年間一次エネルギー消費単位量 per unit area [ MJ/ m2 年 ] Fig.11 Section of Itoman city hall Table3 Ventilation rate [times/hour] 2 Reduced Power Consumption by Natural Lighting Power Consumption for Lighting in North Wing Standard building Itoman city hall 基準庁舎糸満市庁舎 Fig.14 Prim ary-energy conservation with Natural energy utilization and air-conditioning load reduction technologies

5 The 25 World Sustainable Building Conference, Tokyo, September 25 (SB5Tokyo) 3. Reduction on the Reduction of the Infrastructure Load 3.1 Thermal Storage System Okinawa Electric Power Company is separated from the wide area power supply network which is consisted with nine (9) electric power companies in mainland of Japan. To maintain the sufficient capacity and reliability of power supply, much cost is required for electric power supply infrastructure in Okinawa. Shifting the power consumption from daytime to nighttime by thermal storage system is not only to reduce the operation cost but to contribute control of the increment of the maximum power demand of power infrastructure and effective operation of power infrastructure. Fig.15 Thermal storage system diagram The thermal storage system was constituted combining the stratification type chilled water thermal storage system which has sufficient operation efficiency and the ice-thermal-storage system which has sufficient space efficiency. (Fig.15) The chilled water thermal storage system is consisted with pre-insulated panel tanks. The thermal storage system is divided into two tanks, and installed in the machine room on the first floor of the water board annex. Two thermal storage tanks are connected with interconnecting pipe and these tanks are functioning as one stratification type thermal storage tank. The ice-thermal-storage units are installed on the flat roof. The amount of the power shifted from daytime to night time is 1,576,24 [kwh/year]. And it is corresponding to 11.9% of the annual total power consumption in Itoman city hall. (Fig.16) [kwh/month] 25, Nighttime Power Consumption 2, Daytime Power Consumption Monthly power 使用電力量 consumption [kwh/ 月 in ] building 15, 1, 5, Ice thermal storage unit with air cooled chillers Stratification chilled water thermal storage tank 1 月 2 月 3 月 4 月 5 月 6 月 7 月 8 月 9 月 1 月 11 月 12 月 Fig.16 Power consumption 月 shifted from daytime to nighttime by thermal storage system RD 雨水集水面積 Roof 2,43 2,4m 2 m2 RD 3.2 Rain Water Utilization System Reduction of the load to city water supply infrastructure is important although annual precipitation in Okinawa is large, since that there is no big river and precipitation is concentrating in the rainy season and typhoon season. In Itoman city hall, the rainfall on the roofs is collected in the foundation-pits and treated with the sand filtration system. The treated water is stored in service water tank which is also installed in the foundation-pits and supplied as flashing water for toilets and irrigation water for plantings. (Fig.17) The annual total water volume supplied by rain water utilization system is 2,16m 3. It is corresponding to 28% of water consumption in Itoman city hall building. (Fig.18) on 雑用水揚水ホ ンフ Monthly Water consumpti 使用量 in building [m 3 / 月 ] Water treatment system and supply pumps 雑用水高置水槽へ 雑用水槽 Service 原水槽 33m water 3 tank 1m 3 砂ろ過装置 8.m 3 /h N 排水管へ雨水遮断弁 沈砂槽 Raw water 雨水貯留槽 tank 28m3 28m 3 雨水遮断弁排水管へ Discharge pipe Fig.18 上水使用量 Monthly 雨水使用量 water consumption 月 and treated water volume N Sedimentation 沈砂槽 Pit Fig.17 Rain water utilization system diagram [m 3 /month] Water Volume Supplied by Rain Water Utilization System Water Volume Supplied by City Water Infrastructure

6 The 25 World Sustainable Building Conference, Tokyo, September 25 (SB5Tokyo) 4. Closing Remarks Since the Itoman city hall opened in May 22, many visitors not only Itoman city residents but also many people from other prefectures such as the construction-administrative officers and students on school excursion visit Itoman city hall. These are considered good opportunities to deepen understanding on the global environmental problems and energy problems. It becomes more important to consider the integration of architectural design and building service engineering to fit the building with the local climate at building site in order to get higher basic performance of the building. References Koui, TSUKAMOTO and Manabu TOCHIGI 24, Case study on the buildings in Okinawa No.1: Itoman city hall, Society of Heating, Air-conditioning & Sanitary Engineers of Japan (SHASE) transaction, September 24. Hiromasa, KATSURAGI and Manabu TOCHIGI 24, the new environment friendly buildings, Case study on Itoman city hall, Architectural Institute of Japan (AIJ) magazine, March, 24.