Topic A9: Indoor air acoustics and lighting EFFECT OF LIVING ROOM LED LIGHTING CONTROLLED BY OCCUPANTS ON CIRCADIAN RHYTHM AND ENERGY SAVING Tomoko TANIGUCHI*, Toshie IWATA and Mina WATANBE Department of Architecture and Building Engineering, Tokai University, Kanagawa, Japan *

Corresponding email: [email protected]

Keywords: Living room, LED lighting, CCT, Illuminance, Circadian rhythm, Energy saving SUMMARY The purpose of this study is to identify the effect of the task-based or mood-based luminous environment controlled by residents on their circadian rhythm and on the power consumption. In 10 living rooms, the existing luminaires were replaced by LED ceiling luminaire which can change CCT, total luminous flux and direction of light by remote controls. Before replacing the lights, vertical illuminance, spectral power distribution and luminance distribution were measured at the eye position of the residents, as a preliminary measurement. The result of preliminary measurements in 10 living rooms showed that 70% of living rooms have lights which suppress melatonin by more than 10% from 2:00 to 3:00 am. The measurement of lighting environment created by dimmable and color-changeable LED luminaire was carried out. The result showed a positive effect of the luminous environment controlled by residents on their circadian rhythm and on the power consumption. INTRODUCTION Lighting influences functional and emotional needs in indoor environments. It has become clear that light has an effect on human circadian rhythm which is sensitive to shortwavelength light. Recently in Japan, LED lighting has become popular for living room. LED ceiling light fixtures, which can change correlated colour temperature (CCT), total luminous flux and the direction of light, have been marketed. In Japan, living room is used as a multipurpose room, residents in living rooms usually control luminous environment to keep the visibility for their task or to create a comfortable atmosphere. The purpose of this study is to identify the effect of the task-based or mood-based luminous environment controlled by residents on their circadian rhythm and the electric consumption. LIGHT ENVIRONMENT EVALUATION BASED ON MELATONIN SUPPRESSION Action spectrum Figure 1 shows Action spectrum Vm(λ) and V(λ). The relative spectral power distribution for white LED is also shown in Figure 1. The action spectrum is a model by Gall (2002, 2004), which is based on Brainard’s (2002) action spectrum for melatonin. The Peak wavelength of V(λ) is 555 nm, while the peak wavelength of the action spectrum Vm(λ) is 460 nm. Since the peak wavelength of LED is about 460 nm, LED may cause a stronger effect on the circadian rhythm than other type of lamp.

Relative sensitivity to melatonin suppression Relative sensitivity [-]

1.0

V(λ)

0.5

White LED

0 380

580

780

Wavelength [nm]

Figure 1. Action spectrum Vm(λ) for nocturnal melatonin suppression in comparison to sensitivity for daylight vision V(λ). Suppression ratio of melatonin secretion Suppression ratio of melatonin secretion MS, which is calculated from vertical illuminance and Correlated Color Temperature (CCT) at the eye position, is proposed by Kubota (2005). The melatonin suppression flux of 460 nm monochromatic light per unit illuminance is calculated by Equation 1 and the melatonin suppression MS is calculated by Equation 2, q460/E =1.6*10-14 CCT 3-7.0*10-10CCT 2＋1.1*10-5CCT - 0.0133 ( 2000K ≦ CCT ≦ 10000K ) MS =

0 - 66.9 +66.9 1+(q460 / x50(460))1.27

(1)

(2)

where q460 is the melatonin suppression flux per unit area which corresponds to illuminance in photometry of 460nm monochromatic light [photon/cm2/s], E is the vertical illuminance at the eye position [lx], CCT is the color temperature [K], MS is plasma melatonin % change control-adjusted[%] (percent melatonin change score = 03:30 hr melatonin – 02:00 hr melatonin) / 02:00 melatonin) and x50(460) is photon density of 460nm monochromatic light for MS=50% (=4.96) [photon/cm2/s]. PRELIMINARY MEASUREMENT OF LIGHTING ENVIRONMENT IN LIVING ROOMS Method Preliminary measurements of light environment in living rooms were carried out in 10 residences from October 20 to November 30, 2013, after sunset. Types of existing luminaires and lamps were identified. Vertical illuminance, spectral power distribution and luminance distribution were measured at the eye position (0.75m to 1.1m from the floor) of the residents. Task illuminance was measured on the table in front of each seat. The luminance distribution of the visual field from each seat was measured by using CCD camera system. Also the rated power of living room lighting was determined from type of lamp of the luminaires.

Results Table 1 shows types of luminaire, types of lamps and their rated power of living room lighting. Eighty percent of living rooms use fluorescent lamps and 20% use LED lamps. Table 2 shows the results of the measurements. Figure 2 shows the image of the luminance distribution in living rooms using the cool white lamp and the warm white lamp, as examples. Table 1. The type of lamps and rated power of the existing luminaire used. Floor area of living rooms Types of luminaires [m2]

Residence

Types of lamps (number of lamps)

Rated power [W]

A

19

Chandelier

Circular fluorescent lamps (2)

80

B

12

Pendant light

Circular fluorescent lamps (2)

61

C

19

Ceiling luminaire

Circular fluorescent lamps (2)

72

D

12

Pendant light

LED lamps (2)

17.2

E

19

Pendant light

Circular fluorescent lamps (2)

75

F

12

Down light

LED lamp(4)

17.2

G

19

Chandelier

Fluorescent bulbs (6)

72

H

10

Ceiling luminaire

Fluorescent tubes (8)

72

I

12

Chandelier

Fluorescent bulbs (4)

72

J

10

Ceiling luminaire

Circular fluorescent lamps (2)

72

Table 2. Illuminance, CCT, peak wavelength and Maximum luminance. Residence

Average vertical illuminance[lx]

Average CCT [K]

Average task Peak illuminance[lx] wavelength [nm]

A

413

4800

649

545

B

117

4300

217

545

C

74

3900

192

545

D

58

2400

56

623

E

150

2600

189

612

F

63

2700

92

610

G

123

2500

217

612

H

170

5100

214

545

I

59

2700

123

780

J

49

5000

69

544

CCT : 5300 K

CCT : 2400 K 50000

50000

1 [cd/m2] Residence D used the warm white lump

1 [cd/m2] Residence A used the cool white lump

Figure 2. The image of luminance distribution of the visual field.

Figure 3 shows horizontal illuminance, vertical illuminance and CCT of the living rooms. The comfort zone proposed by Kruithof (1941) and melatonin suppression contour are also drawn in Figure 3. The comfort zone is determined by combination of horizontal illuminance and CCT. Although 40% of living rooms are within the comfort zone, 70% of living rooms have light which suppress melatonin by more than 10% from 2:00 to 3:00 am. Kruithof’s comfort zone

Brainard’s melatonin suppression

Illuminance [lx]

1000

Holizontal illuminance

30% 20%

100

Vertical illuminance at the eye position

10%

5% 1%

8000

7000

6000

5000

4000

3000

2000

10

CCT [K]

Figure 3. Illuminance and CCT in living rooms. LIGHTING ENVIRONMENT CONTROLLED BY LED LUMINAIRE Method Light environments controlled by residents by using a dimmable and color-changeable LED luminaire were measured. The measurements were carried out from December 1 to December 30, 2013. Before the measurements, the residents had used LED luminaires for 2 weeks to get used to controlling them. Residents controlled LED luminaire in which RGB sensors were installed depending on task performed or the mood.

Dimmable and color-changeable LED luminaire The LED ceiling luminaires (Panasonic LGBZ3104) shown in Figure 4 were used in these measurements. They can change CCT, total luminous flux and the direction of light. Luminous intensity distributions of the luminaire and the RGB sensors’ positions are shown in Figure 5. The modes of the LED luminaire are shown in Table 3. Data logger

No.3 No.2

No.1

: RGB sensor

Indirect light

Indirect light ϕ705mm

General light Figure 4. LED ceiling luminaire.

Center light

Figure 5. Luminous intensity distributions of the ceiling luminaire and the setting position of RGB sensors.

The luminous intensity distributions are 3 types: the direct light illuminating the entire rooms, the center light illuminating the table and the indirect light illuminating the walls of the living rooms. The LED luminaire also has 4 modes (Relaxation mode, Cool mode, Theater mode and Study mode) as shown in Table 3. The dimmable range is 5% to 100% and the colorchangeable range is cool white to warm white. There are 450 combinations in total. Table 3. Mode of LED luminaire. Mode Amount of light Light color Amount of light Light color Amount of light Cool mode Light color Amount of light Theater mode Light color Amount of light Study mode Light color Normal mode Relaxation mode

Luminous intensity distributions

General light

Center light Indirect light 100% ~ 5 % Cool white ～Warm white 100% or 0% 100% ~ 5% Warm white Orange light 100% ~ 5% or 0% 100% Cool white Blue light 100% or 0% Warm white 100% ~ 5% 35% ~ 5% Cool white 90% + Warm white 10%

RGB sensors with Data loggers Three RGB sensors with a data logger were set to LED ceiling luminaire as shown in Figure 5 to measure and record a change in light from the luminaire. Figure 6 shows RGB sensor (HAMAMATSU S9706) and the data logger (ARDUINO UNO3) which includes a clock. A calibration was conducted to determine vertical illuminance and CCT at the eye level from the signals from the RGB sensors. Figure 7 shows the flow chart to determine vertical illuminance and CCT at the eye level. Regression equations are shown in Equation 3 to 8. Correlation coefficients of these equations range from 0.82 to 1.00.

START Signals from RGB sensors G2＜150 and B2