Photo: Overall view of the R&D Centre (seen from the north).

The centre comprises two main buildings. The research building (11 stories above ground and one below, with a total floor area of 27,360 m²) lies at the centre of the site (around 46,000 m²), with a welfare/conference building (three stories above ground and one below, around 9,911 m²) on the northern border. An entrance lobby (1,121 m²) connects the two buildings.

A typical floor of the research building is 64 m long in an east-west direction and 28.8 m wide in a north-south direction. To minimise the heat load, the windows are arranged on the north- and south-facing walls. The east and west sides of the building form the core sections, where machine/electric rooms and common facilities, such as lifts and lavatories, are located. The rectangular working space (51.2 m by 28.8 m) is divided into a northern laboratory area and a southern open plan study room without partition walls, where booths separated by low partitions provide privacy for each researcher. The outside balconies on the north and south sides provide emergency escape routes.

2.  Architectural Features

The Laboratory Block No.1 and Conference Room Block, both of which have windows mainly on the north and south side in consideration of energy-saving. Rows of round columns standing in the entrance lobby of this building forcefully indicate the directions of the circulating paths connecting the lobby with Laboratory Block No.1 and Conference Room Block. In the morning and at the sunset, the colonnade receives soft sunlight and casts its shadow on the lobby. With the evolution of the season and the time of the day, the sunlight thus creates diversified silhouettes and pleasing sensations in this architectural space. The lobby ceiling is composed of perforated metal sheets made to form a gentle curve, and the sheets are finished with metal paint to add to the said directional feature and delicate light variation. Through the skylight which forms a part of this ceiling continuity, the sunlight softened by the perforated metal ceiling is cast on the stairs below it. Perforated metal ceiling of the hall. Perforated metal ceiling can be seen through the stairwell.

Entrance Lobby

2.1 Photo Gallery
 

Facade facing south (installed with PV panels): --> (the rows in dark blue)	tepco01.jpg 85.22 Kb	tepco02.jpg 94.88 Kb	tepco03.jpg 64.47 Kb	tepco04.jpg 101.44 Kb	tepco05.jpg 96.97 Kb
Facade facing north (without PV panels): -->	tepco06.jpg 84.52 Kb	tepco07.jpg 84.90 Kb	tepco08.jpg 89.25 Kb	tepco09.jpg 96.23 Kb

3.  Energy Saving Design

(a)  Control of Heat and Light in the Research Building
To deal properly with the demands for both heat and light, it is essential that offices are shaded appropriately against insolation. However, it is also possible to significantly reduce the energy consumption for lighting, and thus the cooling load caused by lighting, by using incoming sunlight as a light source and controlling artificial lighting in accordance with incoming daylight levels. In order to balance these needs, the south side of the research building was fitted with ventilation windows with integral automatic control blinds. A lighting control system was also installed, which was capable of continuously dimming artificial lighting near the windows over a wide dimming range (Figure 1).
 

	Figure 1: Ventilation window and daylight-compensation lighting control system (south side).

(b)  Ventilation Window System
The ventilation window is a double window with an integral venetian blind between the two panes. Indoor air passing between the panes cools the slats of the blind and removes the solar heat. This air then exits through an outlet at the top of the window (Figure 1). In this way, the window reduces the solar heat gain and the overall heat transfer coefficient to between 1/3 and 1/2 that of ordinary windows. The ventilation window thus not only considerably reduces the cooling load caused by excessive solar radiation, but also eliminates the need for perimeter air-conditioning units.
 

In order to reduce the perimeter cooling/heating load , the room air flows upwards through the panes, and is exhausted outdoors as ventilation. Effects of the system are as follows: The passing air picks up solar heat which warms the blinds.  The temperature difference between the passing air and the room air narrows, and overall heat transfer is reduced.  As the surface temperature of the inner pane is close to the room temperature, people in the room feel more satisfied from the viewpoint of personal thermal comfort.  To make the thermal insulation and shielding intended for the purpose of energy-saving compatible with see-through visibility that enhances the esthetical expression, heat mirror glass composed of laminated double glass with a special film membrane inserted between two glass sheets are used for the east and west glass curtain walls. This specific heat mirror glass has a heat insulating ability equal to 400% of ordinary sheet glass. In addition, the building's west facade is provided with brise-soleils whose slat angles are automatically adjustable according to the sun's position while the east side space is provided with interior roll blinds.

(c) Automatic Blind Control System
By automatically controlling the angle of the slats, the blind stops direct solar radiation over a certain intensity from penetrating the room beyond a given distance from the window. This prevents incoming sunlight from adversely affecting thermal comfort and increasing the cooling load. If there is no sunlight, the slats are flat or raised, providing an outside view and improving the amenity's psychological aspects (Figure 2).
 

Figure 2: Blind control.

(d) Intelligent Lighting Control Systems

Daylight-compensation lighting control system
This control system calculates the level of daylight in a room according to the state of the blind. It then uses this information to dim or turn off the lights in a particular order, up to the second row from the window (Figure 1). The luminaire selected to prevent this lighting control from causing discomfort to the occupants in the room is an HF type 1 with an electronic high-frequency ballast using an inverter. This luminaire can be dimmed from 0-100%.

Combined with indirect light from the windows, the two rows of illumination fixtures near the windows provide continuous controlled lighting at a level of 750 lux above office workers' desks, reducing the energy used to provide the illumination and the cooling load required to handle the heat generated in the interior of the rooms. Building and building equipment integration of this kind improves the heat and illumination environment of the interior rooms at the same time as it reduces energy consumption.

Optimum light control
Luminaires factor in light depreciation by the degradation of lamps with the passage of time and light loss resulting from dirt build-up on their surface. The light from a luminaire immediately after installation or cleaning is therefore around 40% higher than the design value. To prevent excessive illumination, the light output is automatically tuned once a month, at night, using the inverters in the electronic ballasts.

Time scheduling
Timers automatically switch off all lights in the research building between 12:00 - 13:00, and 19:00 - 22:00. Occupants requiring light during these times can manually switch lights on themselves. This control can reduce lighting power consumption by 10%.

The integrated application of these lighting controls halves the power used for lighting and reduces the cooling load from lighting by about 10%.

(e) Control of Heat and Light in the Entrance Lobby
Entrance lobbies are generally required to be large, bright and open spaces. However, this creates problems when the aim is to maintain a good thermal environment and save energy. The entrance lobby of the R&D Centre is also large. Connecting the research building to the south with the welfare/conference building to the north, the lobby is 55 m long (north-south direction), 15 m wide and 8 m high. It has large glazed areas on the east and west sides (Figure 3). To create a comfortable and energy-efficient space in this lobby, automatically-controlled exterior blinds and double glazing with integral low-emissivity (low-e) film were installed.
 

Figure 3: Cross-section of entrance lobby.

Automatically-controlled exterior blinds
The automatic exterior blinds adjust the angle of their slats, raising or lowering them in the same manner as the automatic blinds in the research building. This prevents direct solar radiation above a certain intensity from entering the lobby, whilst allowing an outside view as much as possible. If the wind blows with a velocity exceeding 5 m/sec, the exterior blinds are automatically rolled up to prevent damage. A study based on a simulation showed that the blinds reduced the cooling load to just 1/5 that of interior blinds with the same solar shading characteristics. During the winter months the blinds are raised to allow insolation in the lobby, and thus lessen the heating load.

Double glazing with integral low-e film
This double glazing improves heat insulation and solar shading, whilst allowing visible rays to pass through largely unimpeded. This is achieved by using a low-e film, selected for its particular wavelength characteristics, in the gap between the two panes. A simulation to assess the effectiveness of this double glazing in winter indicated that it reduced the amount of heat dissipation to between 1/6 and 1/4 that of single glazing alone, or single glazing and interior blinds.

As shown in Figure 3, the entrance lobby is supplied with conditioned air through a ceiling outlet in summer and through a floor outlet in winter. The aforementioned measures, applied in combination with this inlet/outlet switching system, help reduce the thermal energy used by the air-conditioning unit to a maximum of 548.3 kJ (152.3 Whth)/m² per hour in summer and 364.1 kJ (101.1 Whth)/m² per hour in winter. These levels are very low for such a glazed area. In addition to the energy savings, the measures help to maintain thermal comfort.

(f)  Photovoltaic Power Generation System
21.1 kW solar modules are installed vertically on building balconies facing south, and 18kW modules on building roof tops. This system generates about 28,500kWh a year, which is equivalent to annual power comsumption of 10 families.

(g)  Ice storage HVAC system
TEPCO supplied 58.65GW as a peak load in 1995. On the peak day, over a third of this peak demand consisted of the load for air conditioning systems.  The minimum demand at night was 40% of the peak load. As this gap increased, the load factor decreased to approximately 55%.  Large scale buildings in Japan are characterized by footings composed of small spaces which have double floor structures to make buildings resistant to earthquakes.  Sections from these spaces can be inexpensively converted into thermal storage tanks.  However, these spaces are not large enough for chilled water storage tanks in this center. So, we have used an ice-on-coil type ice storage system that we have studied for more than a decade.  The system here consists of two brine chillers (three in future), an ice storage tank of 680m³ and ice making heat exchangers with a total length of 26,957m (40,435m in future). 

(h)  Low-temperature Cold-air Air Conditioning System

Conventional difuser    Newly developed type

(i)  Other energy technologies adopted in the building

• Fuel cell power generation

 

References:

• Homepage of Tokyo Electric Power Company's R&D Centre.
• Sustainable Design Guide vol.2, Japan Institute of Architects.
• CADDET Energy Efficiency Newsletter issue 4/98.
• Green Building Challenge 2000 Japan Case Study