Thammasat Int. J. Sc. Tech., Vol.6, No.3, September-December 2001
Energy Efficient Fenestration
for Daylighting Apptication in Thailand
S. Chungloo, B. Limmeechokchai and S. Chungpaibulpatana Sirindhorn International Institute of Technology, Thammasat University
P.O. Box.22 Thammasat Post Office, Pathumthani 12121, Thailand Abstract
Combinations of side-window parameters are proposed which produce less energy consumption in Thai commercial buildings. A generic reference building is generated by using DOE-2, a building energy simulation program,irsing Thailand's weather data. The base case of the office building model incliJes both the typical energy consumption characteristics and the daylight factor at various room depths. In the daylighting case, lighting integrated with stepped dimming devices is considered as an
"n.rgy saving option compared with the conventional lighting system. The daylighting application usin! steppeJ dimming devices is recommended to reduce artificial lighting energy and electricity
"on.Iu*piion of the Thammasat hospital building. Results of parameterization study and combinations of window properties, window-to-wall ratios, and external shadings give recommendations for energy efficient fenestration design. Finally, daylighting application in the Thammasat hospital can reduce annual electricity consumf,tion by i.Z"l"*i7t', a payback period of 2.82years and an internal rate of return of 43.8o/o,revealinga high potential for daylight utilization in Thailand'
Keywords: Daylighting, fenestration, lighting integration, generic reference buildings, building energy simulation.
1. Introduction
New office buildings in Thailand are constructed to comply with the 1992 Energy Conservation Promotion (ECP) Act t 1l Limitations of window height and low shading coefficient (SC) to meet the Overall Thermal Transfer Value (OTTV) result in high artificial lighting power density. There is abundant natural daylight in Thailand, the potential of which has been reported [2]' However, real application is often overlooked because the effect of the sun's radiant energy on cooling load of the air-conditioning system is still questionable.
The Lumen method is considered as a gooo daylighting calculation method [3]. Because of its manual calculation, detail analyses are often simplified. The daylight factor curves from DOE-2 daylight processor are used [4] for creating an energy efficient daylighting design of different LI/WRs, room types and orientations Most previous works focused on daylighting potential but energy efficient side-window design was rarely investigated'
This paper aims to assess and figure out parameters effecting energy consumption in buildings utilizing daylighting through a generic reference office building. Combinations of window glazing types, WWRs and external shading devices to achieve optimum energy consumption are proposed taking into account Thailand's weatlrer data [5]. A case study of Thammasat hospital to achieve daylighting utilization was investigated in the office zones o f t h e h o s p i t a l b u i l d i n g s .
2. The Generic Reference Building (GRB) The use of a generic reference building (GRB) is necessary in order to investigate the thermal effect of parameterization' A 20-storey office building of two daylit zones was modeled for DOE-2 simulation [6]. (see Fig' l). The b u i f d i n g d i m e n s i o n i s 2 4 . 5 m x 4 0 . 5 r n w i t h a 1 4 . 5 m x 1 4 . 5 m n o n - a i r - c o n d i t i o n e d s e r v i c e core. The floor-to-ceiling height is 2'5m with conventional concrete-block wall design. The fype of window is strip-window of aluminum frame without overhang with WWR of 0.42 and single tinted glazing with SC of 0.69. Uniform
2 7
electric lighting without daylighting is usually applied in Thai commercial buildings. Recessed fluorescent lamps with luminaires are typical characteristics. The average val-ue of lighting power density is 17.22 Wm'. The office equipment load is l6 W/m2 and the occupancy density is I I m'lperson. The air-conditioning system is a constant volume type with a set- point temperature of 24.5"C. Chillers are water- coofed centrifugal type with a COP of 3.22 and annual service hours of 2,772hrs.
Figure 1. Generic reference office building (a) Floor plan (b) 3D view.
Results of DOE-2 simulation agree rvith the audit reports of the Department of Energy Development and Prornotion [7] (DEDP) and give an energy consumption of 204,2 kWh/m'- yr (52o/" for air-conditioning system, 27Yo for equipment load, and 2lYo for lighting load). The GRB in the base case is simulated to reflect energy performance and daylighting potential of t h e c o m m e r c i a l b u i l d i n g s i n T h a i l a n d [ 8 ] .
3. The GRB's Daylighting Reference Case Without daylighting the Lumen method gives the average illuminance of electric lighting on work plane of 546 to'/64 lux. According to Illumination Engineering Society [9] (IES).
standards the space illuminances comply with the standards. When daylight is allowed to enter the space, DOE-Z daylighting program will calculate hourly daylight illuminance taking into account the current sun-position and cloud cover presented in the weather file. Figure 2 shows results of simulation of the base case in which electric lighting is unnecessary in the da),lighting reference case at a distance less than 10.5 m from windows, but glare is too high especially for a few meters from the window. In case of controlling glare, the interior movable- shading device is set to automatically deploy window shading devices to satisfy the maximum specified glare index.
4 . 5 6 7 . 5 9
D i s t s n e f r o m w i n d o w ( m )
(a)
l
(a) 7,000
^ 6,000
3 s.ooo
.E.,*
! r,ooo
:
$ z.ooo
o t.000 0
3 r+,ooo
.t 12,000
! ro.ooo E s.ooo
=
! 6,000
.ED->
4.000
- z,ooo 0 r8,o0o.].
t6,000 J ] t f
- e t " " " i o . * + W a o n c l 0 r . n
* F E z o n € 2 p . m + W z o t e 2 p . m : - . n - - E e n . 4 p m
-*-*wzone 4 pm
1 5 3 4 5 6 ' 1
5 9 1 0 . 5 Distarce frem wlndow (m)
(b)
Figure 2. Daylight illurninance at dtstances from window (a) April (b) November.
To simulate the energy saving fiom daylighting the DOE-2 program requires input data for B U I L D I N G - L O C A T I O N , W I N D O W S a n d S P A C E - CONDITION commands as shown in Table l. For an urban area and tropical climate location of the
unice Z o n e 2 i
I Ofiice
i Zo.e1
2 8
building, recommended by the DOE-2 manual, the value of moisture and particulate pollutant indices are 1.3 and 0.12 respectively. The tinted glass with a SC value of 0.69 in the GRB is converted to a GLASS- TYPE-CODE (G-T-C) value of 1205. In the SPACE- CONDITIONS variable, the three-stepped light dimming system is chosen. Maximum glare index is 22, recommended by the DOE-2 for general office work. ln addition, the depth and the target lux level must be soecified.
Daylight sensors
Figure 3. Location ofdaylight sensors.
Figure 2 shows that at 10 to 10.5m from window, daylight alone provides illuminance of 200 to 600 lux. The values suggest that electric light should be integrated to daylight and daylight sensors are placed at this depth. The daylit fraction of the space is about 70% and daylight sensors are placed at x :12.3 m, y ( d e p t h ) : 1 0 m a n d z ( h e i g h t a b o v e f l o o r ) : 0 . 7 5 m in office zones from the 2no -19"' floors as s h o w n i n F i g . 3 .
4. Daylighting Application 4.1 Window-to-Wall Ratio (WWR)
Tall and narrow windows give a deeper daylighting zone and a better open view but high glare if they face south, east or west and are more likely to create lighVdark contrast [10]' For the same window area, a wider window at a h i g h e r l e v e l p r o v i d e s m o r e d a y l i g h t i l l u m i n a t i o n and high level of mitrimum daylight factor.
Building designers often recommend the latter because of less glare and preference of the occupant for a wider window. Figure 4 ilf ustrates parameterization of WWR values and the clrange of energy consumption of the building run by DOE-2. The higher tlte WWR,
Thammasat lnt. J. Sc. Tech., Vol.6, No.3, September-December 2001
the more is the electric-lighting saving from daylighting. For the generic reference building with a IIITR of 0.43, 30yo of electric lighting, 4.3oh of electric cooling, and 7.6oh of total electricity consumption are saved annually from the daylighting appl ication.
Table L Description of keyword values for DOE-2 simulation.
D a v l i e h t i n e c o m m a n d s K e v w o r d v a l u e s B u i l d i n g l o c a t i o n
Atmospheric moisture Atmosnheric turbidity
L 3 0 0 . 1 2 G l a s s ty p e
G l a s s t v n e c o d e l 205
S p a c e c o n d i t i o n s D a y l i g h t i n g Target lux S e n s o r l o c a t i o n Lighting control system Lighting control steps M a x i m u m g l a r e in d e x R a t i o o f d i m m i n g a r e a
Y E S 500 ( 1 2 . 3 . 1 0 , 0 . 7 5 )
STEPPED 3 2 2 0 . 8 I n t e r i o r v i s i b l e li g h t r e f l e c t a n c e
F lo o r W a l l C e i l i n g
0 . 2 0 . 5 0 . 7
] . 5 0 0
3 , 0 0 0
y ' . l o i I 9 6 \ ' 2 i 4 8 8 l R r - I 0 0
a l . t u u E' 2 0 0 0
; r 5 0 0
a
. 1 0 0 0
1 0 0
0 L - - - - . . . . - - . - - .
0 0 0 l 0 ? 0 l 0 4 0 5 0 6 0 7
r elecl - "'*f,#t* rotal
+ e l o C L ( N o D L ) * e l c l i g h ( N o D L ) ' t o t a l ( N o D t ' )
Figure 4. Annual electric consumption at various window-to-wal I ratios.
4.2 Window Glazing
The DOE-2 program contains a window library covering common glazings, which are available in the market as well as experimental ef ectroclrromic (EC) glazing. In this stLrdy pararneterizations are perforrned by varying one- by-one the glazing type covering 28 single-pane g l a z i n g s i n c l e a r . ti n t e d . re f l e c t i v e . l o w - e a n d
EC types, as shown in Table 2. The glazing properties such as 7lu,r. ffu'r. I,o1. RFro1. Ur and SC are important parameters in daylighting design [1 l]. For instance high I"'' glazings are fypically appropriate in daylighting design but if Zu;, is too high the SC value must be high and allow high solar cooling load.
Table 2. Summary of DOE-2 glazing properties.
G-T-C W i n d o w t l o e ^tc I ' i . R e m a r k l 0xx" C lc a r 1 . 0 t ) . 8 9
I 2 x x T i n t e d 0 . 1 1 0 . 5 7 I { 0 0 Rell ecti ve 0 2 3 0 0 8 l . l l 8 R e t l e c t i v e 0 5 8 0 . 3 3 I 4xx' Reflective 0 . 1 5 0 1 6
602 Low-e 0.84 0 . 8 1
800 Absorbed EC 0 . 9 8 0 . 8 5 Bleached 8 0 1 Absorbed EC 0 . 3 6 0 1 3 Colored
802 Reflective EC 0 . 8 5 0 8 2 Bleached
803 Reflective EC 0 . 3 4 0 t 6 Colored
N o t e : a , , . c r e p r e s e n t l 0 0 l - 1 0 0 3 , l 2 0 l - 1 2 0 1 a n d 1 4 0 0 - 1 4 1 8 respectively.
. l 4 i l
- . . t 4 t ?
ll lfirr t 2 0 l
+ & f g c --+--- l2nt
Figure 5. Annual electric lighting saving of different glazings.
Table 3. Summary of electric lighting savings.
Simulation results show that the daylighting application saves the largest electric lighting in the case of clear glazings followed by EC, tinted and reflective glazings respectively (see Fig. 5) and Table 3.
. Bas case (No Daylight) - + B a s e c a s e ( D a y l i g h t ) , '
5
. 9
E
BE
g
g a E
3 , 1 0 0 3,000 2,900 2,800 2,100 2,600 2,500 2,400 2,300
=
= -
-
2
O . 9
t j , r 0 0 1,000 2,900 2,800 2,780 2,600 2.500 2,400 2.300
3 , 1 0 0 3.000 2,900 2,800 2,100 2,600 2,500 2,400 2,300
WWR ( c ) 3 , 1 0 0
3 , 0 0 0 2.900 2.800 2 , 7 0 0 2.600 2 . 5 0 0 2,400 2 . 3 0 0
0 0 . i 5 0 . 3 0 4 5 0 . 6 0 . 7 s w w R
( d )
Figure 6. Annual electricity consumption of different glazings.
a 1 6 0 2 a . 1 8 0 0 -x 1802
B6e Cas {No Daylight) r''
+ B6e cse (Daylight) ..J
"
a l 2 0 l , . . , '
o t 2 o 3 ' * A
a t z o 6 . ' * g $ "
t + A o
, . + ' a , o
. 1+ 1 6 o
t ' j $ 8 r o o
" o a o
" -"^---ii-l . Base cM (Nc daylight) r i
wwR Electric
l i o h f i n o s r v i n q Glazing type G-T.C
> 0 . 5 0 > 50Yo C l e a r . E C . [-ow-e
0 0 1 , 8 0 1 . 1 6 0 2
> 0 . 5 0 40-5jYo Tinted 2 0 1 . t 2 0 3 . 206
> 0.50 < 400h Retlectiv€ 4 0 0 - t 4 l 8
< 0 . 5 0 30-50v' Clear, EC.
Low-e, tinted 0 0 1 , 80 1 ,1 602, 203
3 0
Thammasat Int. J. Sc. Tech., Vol.6, No.3, September-December 2001
However, total electricity consumption reduction from daylighting application is shown in Fig. 6 where the penalty of using too high WWR and too high SC glazing is pointed out.
Figure 6 illustrates that the reflective EC glazing ofcode#1802 shows the largest savings for each value of IlWRs. At I/WR<0.5, electric saving of EC glazing is larger than low-e, tinted, clear and reflective glazings. \Nhen WWR>0.5, electric saving of EC glazing is larger than reflective, tinted, low-e and clear glazings. It is clearly shown that, at llWR less than 0.5, high l""i' glazings increase energy savings, but for the l(IlR greater than 0.5, the SC value must be paid more attention tlran the 2",,. The saving in the base case having LVWR of 0.43 is increased by 4% if 2",, increases from 0.43 to 0'75, i.e.
changed from gray tinted glazing ofcode#1205 to green tinted glazing ofcode#1203.
4.3 The External Shading
Simulation results of the daylighting case with overhangs in the south windows and setbacks in the east and west windows are shown in Fig. 7. It shows parameterization of shading devices with depth to window height (D/II') ratios of 0.2,0.4,0.6, 0.8, 1.0 for glazings o f G - T - C c o d e # 1 0 0 1 , # 1 0 0 3 , # 1 2 0 1 , # 1 2 0 3 ,
# 1 2 0 5 , # 1 2 0 6 , # 1 4 0 0 , # 1 4 1 8 , # 1 6 0 2 , # 1 8 0 0 a n d
#1802. It reveals that external shading devices reduce solar cooling load by 2-18% depending on WWRs and glazing materials.
l 8 t 6 t 4 1 2 t 0
8 6 2 0
q , n't o q
0 . 4 WW iir. . 1003
(a)
1 r . * ' F ' + ' S . - ] ' t F ' l F ' I
Off:o 4
r - " l . - E - - l - ' ] ' l - " l t - ' * ' f , m'0.2
- . c - . 1 2 0 1 * . r : 1 - -
0 . 4 0 . 6 0 . 8
wwn
1 2 0 3 - ' a - - 1 2 0 5 - " x - - 1 2 0 6
(b)
l 6 t 2 l 0
I 6
2 0
0 . 0 0 . 2 0 . 4 0 . 6 0 . 8
wwn
. - - o - - - 1 4 0 0 - . + . " . 1 4 l 8
0 . 4 wwR
" . . x - . . 1 8 0 0 " ' e ) 1 8 0 2
( d )
Figure 7. Percentage of decrease in solar load with shadings for various WIlRs, glazings and D/Hs.
However. the percentage decreases in solar load for EC glazing decrease sharply bv 1-l0o%
with increasing shading depth. Because Iu1, property of the EC glazing is set to adjust as close as possible to the illuminance set point,
= l 0
i r
a
. 2 6
E ,
g r
s
g
s
9 8 7 ,
! e
, ]
E t
S l
0
0 . 2 0 . 0
0.2
I
:r
s<ffi;,
g - & ' l - * * . f , l : t ; , ,
o - - o . - ^ ' - . . * - * . + . j
_ _ . o . . ; . . B : : 6 ; , f , i i
X..9.
: T ; t * * n ' f l ' . r . ] ' * " *
" ' F .? _ i $
o . . . l 0 0 i r . 1 6 0 2
3 l
increasing D/H ratio changes EC glazing from a colored state to a bleached state for more Zvi,.
The percentage difference of electric liehtine.. AElect;"t,. describes the effect of external shading devices on the electric lighting reduction in the daylighting application. A high /E/ecrinr,, value means hiqh eft
on the electric lighting i.e. more electric light to substitute for the obstructed natural da),light.
The percentage difference between electric lighting with external shading and electric lighting without shading devices is determined from the following equation.
0.4
. - o - - - l 0 0 l
w w R [ J . . . 100]
(a) 30
2 5
AEI ect"x' (/ol- ( E'ntat - E*ro't'uo" ) x I 00
E u l o shade
0 . 6
r 1602
0 0 0 2 0 4 0 6 0 8
wrvR
- - + - . l 2 0 l * . i . i - . 1 2 0 3 - . & - 1 2 0 5 - . x - . 1 2 0 6
W H " 1 A .,, / . a \ = a a a'? ? \i
' a r N H = 0 6 - f
! / u
E t 5
d r 0F
.*
5
l 8
l 4
i r z
6
6 '
< 6 2 0
0 , 8
( l )
Where AElecl;r1,1 is the Percentage difference of electric lighting between building with external shading and without external shading, 8.6"6" is electric lighting with external shading devices, and E*ro ,1,u6. is electric lighting without external shading devices.
Results of the study shows that there are four consequences of external shading devices obstructing the daylight (see Fig. 8). The p"rameterization results of I I representative glazings in the range of 0.14<l(WR<0.71 and 0.2<D/H<1.0 are as follows:
(l) Increasingin WII'Rs decreases the effect of external shadings. External shadings for h i g h S C g l a z i n g s c o d e # 1 0 0 1 , # 1 0 0 3 a n d
#1602 reduce lighting savings by 2-25%
compared to the case without shadings, see Fig. 8a.
(2) External shadings have small effect on lighting savings. External shadings for tinted glazings such as code# 1201, #1203, #1205 and #1206 have less effect on lighting savings, about 1-67o saving changes (see Fig 8b).
(3) External shadings have high effects on electric lighting saving. The reflective
glazing code#1400 is highly affected by external shadings as savings reduce rapidly from 0-16% without daylight recovering from increasi ng LVllRs (see Fig. 8c).
(4) External shadings reduce lighting savings.
Lighting savings from EC glazings are independent of IIWRs but are decreased with high-depth external shadings from 1-
1 3 % (s e e F i g . 8 d ) .
3 + o
' i
! 3 0
t 0 0 . 0
(b)
o . 2 0 4 w w R o - - - 1 4 0 0 . +
(cJ
0 . 6
t 4 t E
, * 9 i & " + * ! h . *
32
X6 }6 X+ *X6 -9 .)6 .tF .X "-o' X- .X- -X" X"XitX"X .XD/s:o'2 0 0 0 2
* o i *
0 6 0 . 8
. . . x . . - l E 0 0 " . - o - - . l E 0 2
(d)
Figure 8. Percentage difference between electric lighting with external shading and without shading devices.
The percentage difference of annual electricity consumption of the GRB building with external shadings and without external shadings is determined from the following equation.
AElec ,or^1 1o/o1 - ( 6tor. shud. - Eror. ",o shud. ) " I 00 6tot. w/o shade
Where AElec torar is the percentage difference of annual electricity consumption between buildings with external shadings and without external shadings, 4ot, sLad" is the annual electricity consumption with external
shadings, and do,, w/o shade iS the annual electricity consumption without external shadings.
Figure 9. Percentage difference ofannual electricity consumption between buildings with external shading and
Thammasat Int. J. Sc. Tech., Vol.6, No.3, September-December 2001
without shading.
Equation (2) suggests that when AElec66) 0, external shadings reduce annual electricity consumption, i.e. promoting energy savings.
When AElectotat : 0, external shadings do not affect the annual electricity consumption and when AElecrotur ( 0 external shadings increase the total electricity consumption.
Increasing the D/H ratio for clear ( c o d e # 1 0 0 1 a n d # 1 0 0 3 ) , l o w - e (c o d e # 1 6 0 2 ) a n d EC (code#1800 and #1802) glazings results in significant reductions in annual electricity consumption (see Fig. 9). In clear, low-e and absorbed EC glazing, the electricity saving with external shading starts at a WI{R value between 0.3 and 0.4. The low SC reflective (code#1400) and tinted glazings code#1201, #1203, #1205 and #1206 do not affect electricity consumption with increasing WWR: or D/H ratios. The high SC reflective glazing, i.e. code#1418, increases annual electricity consumption at any WWR and D/H ratios, because its low Zvis_i!-itEellsilivele increasing IZZR (see Fig. 8c) and its high SC value is sensitive to solar load (see Fig. 7c) and ,I/WR.
4.4 f,lectric Energy Savings and f,conomic Analysis
" l 0 . 3 8 d
s 4
,,}f
*\*-X=*",=',
;{IT*e6*ooo'''o'
{ " t ) F * ) F , y € , r ( . x } , = 0 6
(2)
J00,000
2 5 0 , 0 0 0
200,000
| 50,000
I 00.000
50.000
0
t . 4 0 0 1 . 3 5 0 t . ) 0 0 r , 2 5 0 '€ r - z o o E
1 , 1 5 0 t t l 0 0 ? t . 0 5 0 1 , 0 0 0
a
.9
.I ' ' . r . - - E n e r g c o n m p l i o n ( l ( w h )
+ Elcctrrc demand (kw)
r 2 0
,;
f , , r o
.2.0
- & 0
,e Fcb m{ Apr May Js Jul AB Sept Oct Nov D*
Figure 10. Energy consumption of the GRB.
According to electric tariffs in Thailand, electricity bills differ from types and sizes of businesses. Because the generic reference office building shows a minimum l5-minute integrated demand of 1000-1200 kW and the energy demand of 3 consecutive months less than 250,000 kWh (see Fig. l0), it is categorized as a medium enterorise consumer.
3 3
The stepped dimming method of fluorescent lamps (FLs) is to completely turn off a portion of lamps when the level of daylight exceeds a pre-defined limit. The 3-stepped- dimming lighting system consists of three components: l) the photo sensor, 2) electronic controller and 3) FLs. When the existing FLs and luminaire arrangement in Fig. l1 is used, 13 5 lamps are dimmed (70%" of the office area x 64 luminaires x 3 lamps per luminaire).
Typically, an electronic controller is able to support 1000W, thus 5 controllers are required in each zone (Philips Electronics, 2000). Table 4 provides estimated investment costs of 3- stepped dimming devices and Table 5 is the estimated costs of fenestration materials for five different LVWRs.
Table 5.Investment costs of glazing materials.
Note: The l2xx stands for code#1201. #1203,fl1205 and l8xx stands for code # I 800 and # I 802.
Results ofenergy saving analysis show that daylighting application can save 10-15% of annual efectric energy when proper glazings are installed on a building of ltWR > 0.50. In the same case, if there are external shading devices of any depth attached to the window, annual electric energy savings increase about 1-6%
compared to the case without shading.
Therefore, economic analyses of the five best glazing options from Table 5 with external shading devices for WWRs of 0.43, 0.50, 0.57, 0.64 and 0.71 are studied to determine economic attractiveness of each option. The average simple payback periods and internal rates of return (lRRs) of five WWRs for eight glazing materials are shown in Fis. 12.
r 0 0 1 l 2 0 t 1 2 0 3 1 2 0 5 1 4 0 0 1 6 0 2 r 8 0 0 l t t 2 Glsing type
I Paybmk pqiod (y@) + lntmal rate of rerutD (%)
Figure 12. Simple payback periods and IRRs of window glazings.
From the economic point of view, the two best options are glazing using code#1203 and
#1400 with payback periods of 5.3 and 5.4 years and IRRs of 13.3 and 13.2o/o respectively. For all
F E E
- -
-
l.$l
a '
1 9
lio
, *
n 9 2 5 0
Figure I l. Plan view of uniform arrangement of recessed fluorescent lamps in the office GRB.
Table 4. Costs of 3-stepped dimming devices.
20
'? rz
€ d
20
1 6 s
E
8 E
) =
0
G-T-C I 0 0 1 I 2 x x I 400 1602 I 8xx
Cost(BahUm') t97 1 0 5 t.047 2t9'7 2600
Cost 0" Baht
WWR=0.43 0 . 5 4 0 . 8 4 2.89 6.06 6.89 wwR:O.50 0.64 0.98 3 . 3 7 7.07 8.04 WWR=0.57 0.73 t . t 2 3 . 8 5 8 , 0 8 9 . 1 9 wwR-0.64 0.82 | . l o 4 . 3 3 9.09 1 0 . 4
wwR-0.71 0.9 r L 4 0 4 . 8 2 t0.2 r 1.5
ltem Quantity
used
Cost/unit ( B a h r )
Total cost ( B a h t )
Controller 1 9 0 10,400 1.976.000
Photo sensor 3 8 2.630 99,940
S e n s o r c a b l e 3 0 0 500 1 5 , 0 0 0
I n s t a l l a t i o n 5 . | ] 0 40 Balit/lamp 205.200
Total investment 2,386, I 40
Source ctronrcs hailand) t,td
3 4
glazingtypes, an increase in IIWR decreases the payback periods.
5. The Case Study of Thammasat Hospital
Lighting power density reduction can be achieved through reducing the number of lamps per Iuminaire, and using the low-loss and electronic ballasts. The daylighting application is a good option for electric lighting reduction.
This study analyses daylighting application in the office areas through the existing fenestration design of the treatment & accident building on the 3'd-6'h floors where the annual working hours are 2.380 hours per year. The building's LltllR is 0.38 and the fenestration is tinted glazing with SC of 0.75, I,i. of 0.60 and a U-value of 5.2 Wm2oC. There are external shading devices of D/H=| .33 and internal venetian blind (see Fig.
13). It is assumed that occupants adjust the venetian blinds to reduce the window SC value to (0.6) x (0.75) : 0.45 and a visible transmittance reduce Zri, to (0.6) x (0.35) : 0.21 (recommended by DOE-2 program for diffusive white translucent drape). The study of Thammasat hospital is focused on daylighting application in office zones using 3-stepped dimmine devices at the target lux of 430.
l--tffi*l nFlcl
Figure 13. The fenestration of the office floors of treatment & accident buildine.
5.1 The Existing Electric Lighting System of the Daylit Zones
The present electric lighting specification effects the capability of daylighting application' To determine the existing lux level, trial measurements of electric lux level in perimeter zones are conducted. Table 6 shows lighting power intensity and illumination. The illumination of specific daylit zones are shown i n F i g . 1 4 .
The shading areas in Fig. 14 indicate the daylit zones for daylighting application. It
Thammasat lnt. J..Sc. Tech., Vol.6, No.3, September-December 2001
illustrates that some perimeter zones are divided into small rooms and the interior partitions obstruct the natural daylight (see daylit zone 2 of floor#4, #5 and #6). However in the daylighting simulation, these partitions are removed to leave empty space between windows and the daylighting sensors.
5.2 Daylighting Simulation
At the present time, occupants in the treatment & accident building utilize interior venetian blinds as a glare-controlling tool and as another direct daylight protection device.
However, interior shading devices obstruct daylight. To investigate the significant of the interior-shading device, energy savings from daylighting application in the present-window case, utilizing interior shading devices, and in the bare-window case are simulated by DOE-2 as shown in Table 7.
Table 6. The lighting power intensity.
| 3 . 2 4 . 5 m . l
D$'lit dc3
S n
F l o o # Wim' I l l u m i n a t i o n ( l u x
3 5 . 1 8 300-700
4 1 . 6 3 250-700
5 5 . 3 0 550-650
6 7 . 4 4 550-650
Average 4.90 367 -67 s
t
t 2 . h l
3 5
Deylghr sosor
D o h / o r u | I i' - : It t i
Enersv savins ll2.'7 to 121.9
Results of simulation shown in Table 7, are e n e r g y s a v i n g s o f t h e 3 - s t e p p e d d i m m i n g lighting system in office zones on lhe 3'd. 4"'. 5"' and 6'" floors. The daylighting commands and keyword values are similar to that shown in Table I except the specific'properlies of glazing and target lux of430. The positions ofreference
p o i n t s a r e s h o w n a s d a y l i g h t s e n s o r s i n F i g . 1 4 . For daylighting case. the bare-window application does not have shading devices to obstruct any da),light but in the present window application. the existing SC and Z* are reduced by 60% and 35%. respectively. To solve glare- problem in the bare-window, daylighting performance in the specific zones was investigated and it was found that daylit zone#2 of the 3'd, 4'r', 5tr' and 6tr' floors had high glare index. The percentage of hours with too high glare is greater than l0% of total annual working hours, i.e. 238 hours/year. By using interior shading devices only in the daylit zone#2, annual energy consumption is 5,280.2 M W h a n d e n e r g y s a v i n g i n c r e a s e s u p t o 1 2 1 . 9 MWh per year (see the glare-control case in Table 7). The electric lighting savings, average daylight illuminance, average glare index, and percentages of hours with too high glare are shown in Table 8.
Thus total annual electricity saving from daylighting application in this building is 121 ,900 kWh/year which accounts for 2.3%o of the total electricity consumption. For the area utilizing daylighting, electric saving is 24.42 kWh/m2'year ( 121,900 kWhlyearl4,gg l .52 m2).
From Table 9 the electricity consumption in the b a s e c a s e i s 2 2 7 , 1 4 8 k W h p e r y e a r o r 2 2 7 , 1 4 8 kWhl4,9g1 .52 rn' = 45.51 kWh/m2.year.
Therefore, the daylighting application can save 53.1%o of electric energy in the office zones.
The number of 40-W lamos on the 3'o floor i s ( 6 1 0 . 5 5 m 2 x | 5 . | 8 W / r n 2 ) / ( 4 0 W / l a m p ) : 2 3 I lamps, on the 4th floor is 195 lamps, on the 5'h floor is 373 lamps, and on the 6'" floor is 425 lamps. Since the electronic controller is able to support up to 1000W, the required equipmenl quantity and the total cost are calculated and s h o w n i n T a b l e 1 0 .
ln 2001. a non-profit organization like Thammasat hospital. falls into schedule 6 of the electric tariff of Thailand where the norninal rate o f e n e r g y c h a r g e u s e d in t h i s s t u d y is 2 . 1 4 1 2 Baht /kWh. By assurning a nominal interest rate of l20k and a life-span of 10 years, a payback period of 2.82 years and the IRR of 43.8%o are determined indicating a highly attractive economic option.
' - . ' ' i
llsllrr uocd-l
I 1il1
t,
s m i
I
j - - - '
j * - k - r
j l l 5 n L l d l
(b) 4"'floor.
l)+\,r! /ste l
S r
D$ llgh ${nst}r
@ : Daylight sensor
No daylighting Dayllghting case Glare-control case
5 , l 4 l 0 5.092 2
5.402.1 5.289 4 5.280.2 4 8 8
; * , $ r
i silr Ihtll ?osc l
Dqlllght stnld
(c) 5'l'and 6th floor
Figure 14. The daylit zones and window system.
Table 7. Energy savings from daylighting applications.
E n e r g v c o n s u m o t i o n ( M W h ) Present window Bare-window
application application
3 6
Table 8. The results of daylighting application in the bare-window case.
Table 9. Annual electriciW consumption for the 3'd. 4'l'. 5'l' and 6'i floors.
Table 10. Total investment costs.
6. Conclusions
Daylighting application has high potential in Thailand. The utilization of energy efficient fenestration in the generic reference building results in electric lighting saving up to 50% and total electric energy saving up to 15Yo. From the economic point of view, green-colored tinted glazing of high I",. and SC of 0.71 is the best glazing option, followed by the reflective glazing of the lowest SC, and the bronze-colored
Thammasat Int. J. Sc. Tech., Vol.6, No.3, September-December 2001
tinted glazing having Z"i, of 0.53 and SC of 0.71.
The two best glazing options with LVWR>O.S and external shading ofany depth can save l5- 20o/o of electric energy with payback periods of 5.3 to 5.4 years and IRRs of 13.2to 13.3%.
A case study of daylighting applications in Thammasat hospital on the office floors of the treatment & accident building shows that daylighting has a high potential in total electric savings. The modification of internal partitions in perimeter zones and proper utilization of interior shading devices can reduce total electric consumption by 2.3% with an attractive IRR of 43.8Yo and a payback period of 2.82 years.
However. this study assumes. at the indicated position ofthe reference points. daylighting area is 80-1000% of the total daylit area. Increasing or decreasing in daylighting area can effect the total energy savings.
7. Acknowledgment
The authors would like to thank the National Energy Policy Office (NEPO) for providing research funds for this study.
8. Nomenclature AElecl,ryl
AElec61u1 COP
DEDP D/H EC
Percentage difference of electric l i g h t i n g
Percentage difference of total electricity
Coeffi cient of performance Department of Energy Development and Promotion Overhang depth to window height ratio
Electrochromic, a coating that makes the glazing more absorbing or more reflecting as the voltage applied to glazing changes.
Energy Conservation Promotion Fluorescent lamps
Generic Reference Buildins Glass Type Code
I l l u m i n a t i o n E n g i n e e r i n g S o c i e t y Internal rate of return (o4) National Energy Policy Office Overall Thermal Transfer Value (W/m2)
Payback period (years) Solar reflectance Visible I ight refl ectance Shadins coefficient
P h i l i p s ECP
FLs GRB G-T-C I E S IRR NEPO OTTV PBP
R-Fro1 ffui,
,SC
Daylit zone
% Lighting reduclion
Avg.
daylight l l l u m .
( l u x )
Avg.
glare index
%" Hour with too
h io h slare Floor
DL zone I 6 1 3 429.0 10.2 0
DL zone 2 54.2 328.9 1 5 . 6 0
DL zone 3 1 5 . 9 2 2 6 . 2 1 0 . 5 U
DL zone 4 49.9 702.7 0 0
Floor 4
DL zone l 3 7 . 7 8 5 3 . 3 t 5 . 7 0
DL zone2 6 3 . 8 4 0 1 I 1 7 . 3 0
DL zone 3 5 3 6 4 1 5 . 1 1 7 . 8
DL zone 4 5 9 . 4 9 4 1 . I 8 0
Floor 5
DL zone I 5 t . 6 7 1 2 . 0 1 5 . 7 4
DL zone 2 l 3 122.4 t 4 . 7 0
DL zone 3 4 t . 2 2 2 7 . ' 7 8 0
DL zone 4 2 s 0 1 4 6 . 8 8 0
Floor 6
DL zone I 6 8 8 5 3 9 . 9 t 4 0
DL zone2 1 6 5 t34 6 t6.2 0
DL zone 3 4 0 9 221 8 8 0
DL zone 4 2 3 . 9 142.9 8 . 9 0
DL zone 5 7 1 . 8 704.4 1 7 . 8 5 . 2
F l o o r Area (rt)
Daylighting area Base case
kWh/year
( m ' ) o/o
-) 796.30 6 1 0 . 5 5 86.'t2 42814 t . 4 2 7 . 5 2 6 7 2 . 6 8 4 7 . t 2 37843 5'" 1 . 3 8 3 . 8 5 9 7 5 . 2 3 7 0.47 '79405
o r .3 8 3 . 8 5 975.23 7 0 . 4 7 67086
Total 4.991.52 3.23J.69 64.78 221,148
Item Q u a n t i t y used
Cost per u n i t ( B a h t )
Total cost ( B a h t )
C o n t r o l l e r 49 | 0.400 509.600
Photo sensor 24 2.630 63. l 20
Sensor cable 45 500 22.500
Material cost 595.220 Baht
Source Electronics 2000)
) t
Iror Zui,
Ur IryWR
= Solar transmittance : Visible Iight transmittance : Heat transfer coelficient of slazin
w/m2oc)
= Window-to-wall ratio 9. References
[1] The Royal Gazette of the Kingdom of Thailand. Energy Conservation promotion Act, Office of the Prime Minister, Thailand,
1 9 9 2 .
[2] Chirarattananon, S. and Limmeechockchai.
B., Daylighting Potential in Thailand, Energy Resources, Vol. 18, pp. 875-883,
1996.
[3] Chrarattananon, S., Kaewkiew, J. and Suhail. S., Daylighting for energy efficient lighting: the case study of Thailand, RERIC International Energy Journal, Vol.14, June,
t 9 9 2 .
[4] Chirarattananon, S., Kaewkiew, J. and Suhail, S., A daylighting design methodology for Thailand: Use of the computed DF curves, lnternational Conference on Energy and Environment, November, 1990.
[5] Chaiyapinunt, S., Standard Metheorological Data (TMY-format) for using with Energy Simulation Computer Program for Buildings, Research report of Thailand Research Fund, 2000.
[6] Lawrence Berkley laboratory. DOE-Z manual and supplements version 2.1E,, 2 0 0 0 .
[7] Department of Energy Development and Promotion. Reference information for audited buildings, Chulalongkorn University, 1997.
[8] Chungloo, S., Limmeechokchai, B. and Chungpaibulpattana, S., Impact of Overall Thermal Transfer Values on Electricity Use in Thai Commercial Building, The First regional Conference on Energy Technology Towards a Clean Environment, December, pp. I 84- I 88, 2000.
[9] Kaufman, Jhorn. IES Lighting handbook, Illumination Engineering Society, 198 1 . [0] D.C. Pritchard. Lighting, Longman,
S i n g a p o r e , 1 9 9 6 .
I l ] ASHRAE. Fundamentals handbook (SI): Fenestration, ASHRAE, USA, 1993.
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