EFFECT OF LIVING ROOM LED LIGHTING CONTROLLED BY OCCUPANTS ON CIRCADIAN RHYTHM AND ENERGY SAVING

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1 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 tommy.je.suis.heureuse@gmail.com 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.

2 Relative sensitivity [-] Relative sensitivity to melatonin suppression V(λ) White LED 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, q 460 /E =1.6*10-14 CCT 3-7.0*10-10 CCT *10-5 CCT (1) ( 2000K CCT 10000K ) MS = (2) 1+(q 460 / x 50 (460)) 1.27 where q 460 is the melatonin suppression flux per unit area which corresponds to illuminance in photometry of 460nm monochromatic light [photon/cm 2 /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 x 50 (460) is photon density of 460nm monochromatic light for MS=50% (=4.96) [photon/cm 2 /s]. PRELIMINARY MEASUREMENT OF LIGHTING ENVIRONMENT IN LIVING ROOMS Method Wavelength [nm] 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.

3 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. Residence Floor area of living rooms [m 2 ] Types of luminaires 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 illuminance[lx] Peak wavelength [nm] A B C D E F G H I J

4 CCT : 5300 K CCT : 2400 K Residence A used the cool white lump [cd/m 2 ] 1 [cd/m 2 ] Residence D used the warm 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. Brainard s melatonin suppression 1000 Kruithof s comfort zone Illuminance [lx] 100 5% 30% 20% 10% Holizontal illuminance Vertical illuminance at the eye position 10 1% 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, 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.

5 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 ϕ705mm Indirect light Indirect light General light Center light Figure 4. LED ceiling luminaire. 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 Luminous intensity distributions General light Center light Indirect light Normal Amount of light 100% ~ 5 % mode Light color Cool white ~Warm white Relaxation Amount of light 100% or 0% 100% ~ 5% mode Light color Warm white Orange light Cool mode Amount of light 100% ~ 5% or 0% 100% Light color Cool white Blue light Theater Amount of light 100% or 0% mode Light color Warm white Study mode Amount of light 100% ~ 5% 35% ~ 5% Light color 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.

6 START Signals from RGB sensors RGB sensors Data logger G 2 <150 and B 2 <70 No Yes B 3 >4000 and Yes R 3 <1500 No Normal mode or Study mode Relaxation mode or Theater mode E RT and CCT RT calculated by Equations 3 and 4 Cool mode E C and CCT C calculated by Equations 5 and 6 E NS and CCT NS calculated by Equations 6 and 7 Figure 6. RGB sensors and Data logger. Figure 7. RGB sensors and Data logger. E RT = f 1 (R 2 ) (3) CCT RT = f 3 (B 2 ) (4) E C = f 2 (R 2 ) (5) CCT C = f 4 (R 1, B 1 ) (6) E NS = f 5 (R 1, G 1, R 2, G 2, B 2, R 3 ) (7) CCT NS = f 6 (R 1, B 1, R 2, R 3 ) (8) R, G and B are the signals from the RGB sensors and the subscripts 1,2 and 3 are the sensor numbers(1=no.1, 2=No.2, 3=No.3), shown in Figure 5. Figure 8 shows the relationship between horizontal illuminance and CCT under the same power consumption. Illuminance decreases with CCT when the power of LED luminaire is constant. The power consumption is estimated from Equation 10, where E h is horizontal illuminance[lx], P is power consumption the LED luminaire. Illuminance [lx] W E h = f(p)*ln(cct) + g(p) (9) W 16W 7.2W CCT[K] g 1 (P) = a*p + b, g 2 (P) = c*p + d. (a=4.87, b= -9.25, c= -31.1, d=72.3) P = (10) E h -{b*ln(cct) + d} a*ln(cct) + c Figure 8. Relationship between horizontal illuminance and CCT under the same power consumption.

7 Results Figure 9 shows change in illuminance and CCT at the eye position in Residence E, as an example. Figure 10 shows illuminance and CCT before and after luminaire in living room was replaced by the LED luminaire in Residence A, B and E, as examples. The CCT and iiluminance just before bed was used for the LED luminaire. MS defined in Equation 2 decreased in all living rooms as shown in Figure 10. Table 4 shows power consumption for living room lights which is calculated by Equation CCT [K] 4000 Vertical illuminance CCT Time [hr] Illuminance [lx] Figure 9. Vertical illuminance and CCT at the eye level (Residence E). Brainard s melatonin suppression 1000 Controlable range of LED luminaire Illuminance [lx] 100 1% E % A 50% H 40% 30% 20% 10% Before with existing luminaire After with LED luminaire CCT [K] Figure 10. Melatonin suppressions controlled by LED luminaires (Residence A, E and H).

8 Table 4. Power consumption in living room lights s (Residence A,B and E). A E H Residence Before with existing After with LED luminaire luminaire E v [lx] CCT [K] Power consumption[w] E v [lx] CCT [K] Power consumption[w] E v [lx] CCT [K] Power consumption[w] CONCLUSIONS The result of preliminary measurements in 10 living rooms showed that 40% of living rooms are within the comfort zone proposed by Kruithof and 70% of living rooms 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 task-based or moodbased luminous environment controlled by residents on their circadian rhythm and on the power consumption. ACKNOWLEDGEMENT This work was supported by JSPS KAKENHI Grant-in-Aid for Scientific Research (A) (No ) and Tokai University support group. Authors acknowledge Mr.W.Iwai (Panasonic Co., Ltd) for his helpful advice to install RGB sensors with data logger. REFERENCES Brainard G C et al. (2002) Action spectrum for melatonin regulation in humans, evidence for a novel circadian photoreceptor. J Neurosci., 21(16), pp Gall D (2002) Circadiane Licht-größen und deren messtechnische Ermittlung, LICHT V54, pp Gall D (2004) Die Messung circadianer Strahlungsgrößen. Proc. 4. Symposium Licht und Gesundheit, Berlin, pp Kruithof,A.A.(1941) Tubular luminance lamps for general illuminance, Philips Tech Review,Vol.6, pp Kubota M, Iwata T (2005) Study on Evaluation of Light Environment Considering Biological Rhythms, Lux Europa 2005, Proceedings, pp.33-34