advanced technologies for appropriate control of heat and ... · protective slat-angle control of...

1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of the organizing committee of the SBE16 Tallinn and Helsinki Conference.doi: 10.1016/j.egypro.2016.09.092

Energy Procedia 96 ( 2016 ) 33 – 41

ScienceDirect

SBE16 Tallinn and Helsinki Conference; Build Green and Renovate Deep, 5-7 October 2016, Tallinn and Helsinki

Advanced technologies for appropriate control of heat and light at windows

Takashi Inouea,*, Masayuki Ichinoseb aTokyo university of science, 2641 yamazaki noda-shi chiba 278-8510, Japan

bTokyo metropolitan university, 1-1 minamiosawa hachioji-shi tokyo 192-0397, Japan

Abstract

Windows are thermally weak compared with external walls and roofs, and have a large effect on the indoor thermal and light environments, and the energy used for lighting and for heating, ventilation, and air-conditioning. Furthermore, it is important that the window system and blinds could be controlled appropriately according to the wishes of the occupants to ensure satisfactory thermal and light environment, and acceptable views from the windows. This paper reports the basic concepts and the advanced technologies and mechanisms of the windows for controlling heat and light, and their effects based on specific examples. © 2016 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of the SBE16 Tallinn and Helsinki Conference.

Keywords: window; solar-shading; daylighting; near-infrared range; retro-reflection; thermotropic glass

1. Introduction

Windows are the primary means for using sunlight, but they basically consist of thin panes of glass and have significantly reduced thermal insulation performance and solar-shading performance compared with other parts of the building envelope, such as the walls and the roof. As a result, windows tend to be a major weakness from the perspective of heating, ventilation, and air-conditioning (HVAC). In fact, the period immediately after the first oil crisis (1973) saw the construction of energy-saving office buildings in which the windows were made as small as

* Corresponding author. Tel.: +81-7-7124-1501 (ex.3504); fax: +81-4-7125-7533.

E-mail address: [email protected] (T. Inoue)

Available online at www.sciencedirect.com

© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of the organizing committee of the SBE16 Tallinn and Helsinki Conference.

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34 Takashi Inoue and Masayuki Ichinose / Energy Procedia 96 ( 2016 ) 33 – 41

Fig. 1. Effects of daylighting, blinds control, glazing on energy consumption in office [Appendix A].

possible in order to reduce HVAC load. However, taking into account that lighting consumes the next largest amount of energy after HVAC, energy-saving results may differ if the lighting can be turned off or controlled using the sunlight from the window. From this perspective, calculations were performed, adding a function that evaluates sunlight use with respect to the dynamic heat load simulations (HASP-L). The results indicated that windows should be somewhat larger on the assumption of that sunlight can be used for energy savings [1-3]. Essentially the same conclusions were obtained when attempting such simulations with the recently developed Building Energy Simulation Tool (BEST) program as shown in Fig. 1 [Appendix A].

2. Basic idea of controlling solar radiation through windows

If we consider the intensity of solar radiation, particularly direct solar radiation, which has a maximum strength of approximately 1 kW/m2, it is necessary to block solar radiation appropriately from the perspective of the thermal and light environment and the air-conditioning (cooling) load in offices and other buildings. Currently, the following procedure is thought to be effective: first, using high thermal performance window systems such as airflow windows, external shading, or a double skin; second, maintaining the outside view and scenery; third, using sunlight incident between the blind slats; and fourth, implementing lighting control, such as turning off or dimming the light.

With respect to the key point of demand to allow light inside while keeping out heat, the basic idea is to transmit as much visible light as possible while reflecting the near-infrared component to the outside. Although shading-type Low-E double glazing is very effective for this purpose, when variations in the strength of the direct component of the sunlight are considered, achieving this with glass alone is extremely difficult. It is essential to use this type of glass in combination with appropriately controlled blinds, specifically, blinds that block light at a slat angle and are sufficient for blocking the direct solar radiation component above a threshold value (Fig. 2) [3][4]. Furthermore, the near-infrared component of the solar radiation reflected outside by the window surface deteriorates the thermal environment of the city space, including in the surrounding neighborhood and street areas. To resolve this problem, a retro-reflective film that reflects only the near-infrared component upward has been proposed, and progress is being made applying it to buildings and verifying the effects.

0 20 40 60 80 1000

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High-reflective glazing Single glazing + inner blind

Low-E(Ag2) double glazing + outdoor blind

Single glazing

Low-E(Ag2) double glazing+ inner blind

Low-E(Ag2) double glazing

Single glazing without lighting control

Low-E(Ag2) double glazing without lighting control

South-perimeter zone

Window ratio (Window Area/Facade) [%]

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Takashi Inoue and Masayuki Ichinose / Energy Procedia 96 ( 2016 ) 33 – 41 35

Fig. 2. Protective slat-angle control of automatic blinds

3. Advanced technologies and their effects

3.1. Application to office buildings

High-performance window systems are effective when combined with automatic blinds that control vertical movement of slats and change slat angles based on the solar radiation conditions [2-4]; with glass or film that has suitable wavelength-selective and transmitted reflection-directive properties [5, 6]; and with lighting control that uses high-efficiency light sources. In some high-rise office building projects we have been involved with, we were able to achieve energy savings of 30–50% by adopting these measures (Figs. 3–5) [7].

(a) Façade (b) Cross-section of window

(c) Measured annual energy consumption

Fig. 3. Office building with shading type Low-E double glazing, airflow windows and automatic blinds

Protective angle

View

Daylight

Horizontalcanopy

Exhaust air duct

Solar-shading typeLow-E double glazing:8+A12+8mm

Automatic venetian blinds(bright color)

Laminar glass:5+5mm

Verticallouver

Air intake

Peri-counter

0

500

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2173 1823 1263

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Marunouchi-Park BuildingOffice

-

Average Large Buildingin Tokyo

Lighting

Entire city block

LightingOutlet

Air-conditioning transport

Heat sourceCold source

Other

Heat sourceCold source

Air conditioning transport

OutletTenant Power

Other

Prim

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gy c

onsu

mpt

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[MJ/

m2]


(a) Façade (b) Comparison of interior surface temperature of different type of building

Fig. 4. Office building with exterior blinds

(a) Façade (b) Cross-section of window

(c) Measurement of daylight at window (d) Blind control and measured upward/downward daylight

Fig. 5. Office building with airflow windows, double-skin and automatic blinds

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Exterior blinds(mediumcolored)

Conventional blinds (medium colored)

Conventional blinds (light colored)

Control slat angle to shade direct sunlight

Minimum angle for

protection

Slat angle : horizontal

[Clear weather] [Cloudy or rainy weather]

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Along with developing high-performance building envelopes that use multiple layers with linked sensor, communication, control, and drive technologies, we are also exploring passive techniques such as building skin facades of materials that selectively transmit, reflect, and absorb in the same manner as biological skin. This allows achieving internal comfort and energy-saving requirements by varying performance of envelopes autonomously in response to indoor and outdoor conditions.

In particular, we have experimented, in an actual research institute building (Fig.6), with solar shading and natural-light use through a responsive thermotropic glass that incorporates a polymer hydrogel. This window becomes translucent when the temperature rises above its phase-transition temperature due to factors such as solar radiation, and changes back to transparent when the temperature drops below the phase-transition temperature again [8]. In addition to saving energy, we also received fairly positive feedback from people working in the building.

Technologies, such as multi-layered shading-type Low-E double glazing, which transmits light and reflects the

near-infrared range of solar radiation, and film with similar wavelength characteristics, are now in general use, and we are conducting research on films with retro-reflective properties in only the near-infrared wavelength range. The films have been installed in high-rise buildings in Tokyo (Fig. 7). In conventional high-reflectivity techniques, specular near-infrared component reflections from the window surface fall directly on neighboring streets, which increases the equivalent temperature substantially. We expect that reflecting this radiation upward will improve the street-level thermal environment and mitigate the heat island phenomenon [10].

(a) Façade (b) Floor plan

(c) Thermotropic glass window

Fig. 6. National institute building with thermotropic glass

AHU for east block

AHU for west block

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AHU for east block

AHU for west blockAHU for west block

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Thermotropicglass

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Thermotropicglass



Thermotropic glass

Gel

Air gap

Low-E


(a) Façade (b) Detail of window with retro-reflective film

(c) Result of comparison experiment (d) Effects of retro-reflective windows on thermal environment in street

Fig. 7. Building with retro-reflective film

3.2. Daylight film

Daylight film has also been developed that works in conjunction with blind control and effectively admits sunlight to the interior of the room when attached to the upper part of the window surface. The contribution of this film to energy savings through using solar radiation and controlling lighting has been confirmed in experiments and in offices [11].

Fig.8. Room with daylight film and automatic blinds

Outer glass:FL12mm

Near-infrared retro-reflective film

Light colored blinds

Air inlet

Guide rail(ceiling surface)

Double sliding ty

Both sides of blinds are white

(laboratory rooms, etc.)

Controlpanel forblinds

Manually opened/closednatural air circulation port

Both sides of blinds are black

(for use as blackout curtain in classrooms)

with Retro-reflective film

Retro-reflective

UV+V

NIR

Conventional Retro-reflective

Daylight film


3.3. Near-infrared reflective blinds for direct gain passive solar house

Direct solar gain systems that obtain solar heat directly from the windows are often installed in passive solar houses. For the system to work well, the amount of solar heat gain and effectiveness of the thermal mass must match. We proposed a combination of blinds that reflect only near-infrared solar radiation upward to the ceiling and the PCM (Phase Change Material) in the ceiling. The system distributed and absorbed solar heat adequately. We evaluated the direct gain system experimentally and with a simulation. The system could improve indoor thermal environment and contribute to energy saving [12].

(a) Conventional direct gain system

(b) Near-infrared reflective blinds (c) Proposed direct gain system

Fig. 9. Improvement of thermal storage by near-infrared reflective blinds

(a) Without blinds Jan. / 2016 (b) Near-infrared reflective blinds Jan. / 2016

Fig. 10. Effect of near-infrared reflective blinds on ceiling

overheat in the daytimenighttime chill

Thermal storage material

High thermal insulation

carpet and furniture disturb thermal storage

Near-infrared Reflective filmr

Visible imageNear-infrared image Near-infrared image Visible image


4. Conclusions

Control of both the heat and light of solar radiation incident on the glass surface is extremely important in terms energy savings and the indoor thermal and light environment, but it is possible to greatly increase energy savings and improve the office work environment by appropriate design and control of the characteristics of the windows. During the process of adopting the use of sunlight, however, the illuminance of desktop surfaces—an indicator of the visual and light environment in modern offices—is insufficient. We believe that it is necessary to give full consideration to goals such as ensuring a natural view, providing a feeling of openness, preventing glare, imparting a feeling of brightness, and reflecting natural changes of season, time, and weather in the room. Furthermore, if we can increase efficiency to the next level by using high-efficiency lighting such as LEDs, the effect of reducing the lighting power consumption by appropriately adjusting the lighting and the effect of reducing the cooling load by reducing the heat generated by the lighting, would become smaller. Thus, we can change to an emphasis on people with respect to the use of solar radiation.

Furthermore, daylighting films that obtain a large sunlight utilization effect when affixed to windows and retro-reflective films that reduce both the cooling load and the adverse effects on the surrounding neighborhood by maintaining transparency in the visible light region while reflecting the near-infrared component of the solar radiation upwards are among the technologies that have reached the stage of practical application. With the development and spread of new technologies, we can expect to take a step toward reducing the environmental load and improving comfort.

References

[1] Takashi INOUE, et.al, Lighting Control and Energy Conservation in Office Building, Flat Glass Manufacturers Association of Japan; 2007 March

[2] Takashi INOUE, Masayuki ICHINOSE, Effects of automatically controlled blinds on visual environment and energy consumption in office buildings, Proceedings of CISBAT 2009

[3] Planning manual of automatic blind system for environment-conscious buildings, SHASE-M1008-2009 [4] Ryo AKAIKE, Takashi INOUE, Masayuki ICHINOSE, et.al., Combination control of blinds and lighting to reflect changes in natural light

environment, J.Illum.Engng. Inst,Jpn.Vol.98 No5(2014) 218-223 [5] Sho FUJITA, Takashi INOUE, Masayuki ICHINOSE, Tsutomu NAGAHAMA, Improvement of outdoor radiative environment by high-

reflective façade –Effect of heat-shielding film with retro-reflective property in near infrared band-, J.Environ.ENg.,AIJ,Vol.79 No696,(2014),167-172

[6] Takashi INOUE, Masayuki ICHINOSE, Tsutomu NAGAHAMA, Retro-reflecting film with wavelength-selective properties against near-infrared solar radiation and improving effects of indoor/outdoor thermal environment, Proceedings of CISBAT 2013

[7] Marunouchi Park Building –Example of a low-carbon building located Tokyo-, Tokyo Initiative & Low Emission Building TOP 30,(2011),p20 [8] Takashi INOUE, Solar shading and daylighting by means of autonomous responsive dimming glass -practical application-, Energy and Building,

35, (2003) , 463-471 [9] Paul Baker, Dirk Saelens, Matt Grace, Takashi Inoue, Advanced Envelopes, IEA Annex32, Vol.3, (2000), ISBN 90 75 741 07 3 [10] Takashi INOUE, Masayuki ICHINOSE, Tsutomu NAGAHAMA, Improvement of outdoor thermal radiation environment in urban areas using

wavelength-selective retro-reflective film, proceeding PLEA 2015, (2015), 48 [11] Takuma Ban, Takashi Inoue, Nozomu Yoshizawa, et.al., Evaluation of lighting energy consumption and lighting environment by using daylight

in Japanese office building, Proceedings of 28th CIE Session 2015, (2015), 1927-1936 [12] Yoshiki Shimada, Maya Ishiwata, Takashi Inoue, et.al., Study on Direct Solar Gain System Controlling Near-Infrared Range, AIJ Journal of

Environmental Engineering,AIJ,vol22 No51,(2016),603-607


Appendix A

Table A-1. Simulation model

Table A-2. Glass spec

Fig. A-1 Simulation model

Perimeter zone:5,000

Without control

Item Configuration Location Tokyo (36 N,140 E) South Perimeter

Outer wall U-value 1.16[W/ /K] Inner wall 1.97[W/ /K]

Ceiling 1.57[W/ /K] Lighting High frequency Fluorescent lamp

12.5[W/ ] 100[lm/W] 750[lx]

Occupant 0.1[Person/ ]

Office

equipment 10[W/ ]

Schedule

Preset Summer:26.0[ ]

air-temp. Intermidiate:24.0[ ] Winter:22.0[ ]

Preset humidity

40-60[%]

Glass Type Pane τV ρV τ ρ U-value SHGC Clear 1 0.88 0.08 0.77 0.07 4.6 0.83

2 0.79 0.15 0.66 0.12 2.6 0.74 High performance heat-reflective 1 0.08 0.41 0.06 0.34 3.8 0.22

2 0.07 0.42 0.05 0.36 2.1 0.14 Low-E (One Ag2 layer) 2 0.75 0.12 0.50 0.20 1.7 0.57 Low-E (Two Ag2 layer) 2 0.67 0.12 0.33 0.32 1.5 0.39 Clear + inner blind 1 0.88 0.08 0.77 0.07 4.6 0.44 Low-E (One Ag2 layer) + inner blind

2 0.75 0.12 0.50 0.20 1.7 0.36

Low-E (Two Ag2 layer) + inner blind

2 0.67 0.12 0.33 0.32 1.5 0.32

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