WORKROOMS Journal Nº1 – July 2013
This is the title of the work, must be in English. Este es un trabajo ficticio y sin. Times
New Roman 12 pp and Bold
Rico-Secades, Manuel (http://orcid.org/000-0002-5372-0330)
Abstract.- The maximum number of words allowed in the abstract are 250. Tables and figures are not allowed. In the
authors section (below the title) put first surname and the name. Use international ORCID reference to identify authors. Use
Times New Roman 9pp and cursive.
Index Terms.- List of key words in English. For example: Lighting Smart Grid, Street Lighting, LED lighting, Energy
Storage, Smart Cities, Staggered arrangement
Affiliation: All authors are from EPI Gijón. Electrical Engineering Department. Campus de Viesques- Building 3 – ES33204 - GIJON – ASTURIAS – SPAIN.
E-mail of authors: Rico-Secades M. is the corresponding author (mrico@uniovi.es),
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WORKROOMS Journal Nº1 – July 2013
I. INTRODUCTION
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El trabajo tendrá también una parte teórica, con cálculos, método de diseño, etc y también una parte práctica,
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Acabaremos el trabajo con unas conclusiones, con una breve panorámica de lo que se ha hecho y las
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añadirlas como anexo al final del trabajo.
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WORKROOMS Journal Nº1 – July 2013
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4
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y modelos para figuras, ecuaciones y tablas. No es un trabajo válido, pero puede utilizarse como referencia en
lo relativo a aspectos recomendados para la presentación de los trabajos.
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WORKROOMS Journal Nº1 – July 2013
Todo lo que está de aquí en adelante es ficticio.
Lighting Systems are suffering an important evolution, moving to Lighting Smart Grids (LSG) and
introducing new capabilities and new services to citizens [1]. A correct lighting system design considering all
the advantages of power LED is a fundamental task in order to achieve high energy efficiency levels and provide
lighting regulation capability, introducing flexibility without affecting quality of Illuminance (E) and uniform
light levels in the street. New concepts about LED drivers can be found in technical literature, thermal studies,
applications for street lighting and dimming strategies [2][3][4] [5][6][7] [8][9][10] . Works on topics about
efficiency of drivers and Power LEDs are growing continuously. LEDs are directional lighting elements more
powerful day by day. Design of lamps using this elements are completely different from the previously designed
ones, it is possible to guide the light where required and with the adequate intensity to match specification. Also
individual regulation of each lighting point can be easily implemented. This works deals with the question:
What is the correct way to conduct these new designs?
This paper focus on street lighting with staggered arrangement usual in urban lighting which is moving to
Smart City concepts. The question is: What is the correct way to design a lighting system based on LED to
energy efficiently and introducing flexibility and additional possibilities? This question is planned to be solved
in this work. A proposed target region has been proposed and over this region a design methodology thinking
about LED flexibility has been established.
II. DESCRIBING TARGET STREET LIGHTING SCENARY.
Figure 1 shows the typical structure of a Staggered Lighting System. Dimension of the road is denoted as R
and sidewalk wide is represented by S. The height of the Lamppost is marked as LP.
Road area has been divided in two symmetric regions (RL – Road Left and RR – Road Right) and similarly
sidewalk has been divided in other two sector (SL-Sidewalk left and SR-Sidewalk Right). With the proposal of
this target’s geometry, staggered configuration can be easily implemented with two considerations: Perfect
matching for staggered arrangement and independent control of lighting level in road and sidewalk areas. The
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WORKROOMS Journal Nº1 – July 2013
flexibility of LED, must be exploited in the best way possible.
The lateral dimension H of the target region is chosen in staggered designs between 1 to 2 times the heights of
the lamppost (LP). In a typical specification for a street lighting design a specified Illuminace (E) level in lux
is the goal (e.g. E target of 25 lx) and as uniform as possible over the target region and also using the lowest
power as possible. Se ha preparado un marco para insertar las figuras que incluye la imagen y el pie de figura.
ME GUSTA
Fig. 1. Street lighting in staggered arrangement. Target region, nomenclature and basic
dimensions.
III. THEORETICAL DESIGN. PROPOSED METHODOLGY.
The first step in the work is to define, using a parametric description, the target area in order to calculate all
photometric values according to the requirements.
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WORKROOMS Journal Nº1 – July 2013
y
ΩL1
(0, +H)
SL1
DMAX
SL2
Ω
(-S, 0)
RL
x
(+R, 0)
SR2
RR
SR1
(0, -H)
360º-ΩL1
Fig. 2. Target region over xy coordinate system showing the parametric angle (Ω) used in
the study and distance to the border of the target region market over floor level (D MAX).
The border of the target region marked over floor level and using as parameter the angle Ω has been obtained
for all the lines in the border of the target region. Angle Ω is chosen as the basic parameter to moving across
the target region, and it has been defined to move counterclockwise from x axis. (See figure 2). Using this
reference equations for all the borders of the target region have been mathematically obtained:
Region RL: (0o ≤ Ω ≤ 90o)



DMAX _ RL   
 1   tan(
 ) 

180


H  R  tan(
 )
180
H R
2
(1)
Region SL1: (90o ≤ Ω ≤ ΩL1)
DMAX _ SL1   
H
 

cos
   90o 
 180



(2)
Region SL2: (ΩL1 ≤ Ω ≤ 180o)
DMAX _ SL 2   
S
 

cos
 180o   
 180



(3)
With:
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WORKROOMS Journal Nº1 – July 2013
 L1  90 
o
S
 a tan  

H
180o
(4)
The border of the symmetric regions can be obtained easily from previous expressions using the complementary
angle (360o- Ω), that is to say:
Region SR2: (180 o ΩL1 ≤ Ω ≤ 360o- ΩL1)

DMAX _ SR2   DMAX _ SL2 360o  

(5)
Region SR1: (360o- ΩL1 ≤ Ω ≤ 270o)

DMAX _ SR1   DMAX _ SL1 360o  

(6)
Region RR: (270o≤ Ω≤360o)

DMAX _ RR   DMAX _ RL 360o  

(6)
Once geometric dimensions of target area have been defined, relationships between distance from target point
to the lamp (d), the light angle (β) and distance of the target point from lamppost over floor (D) can be easily
obtained according to basic geometry shown in figure 3:
 MAX  a tan(
DMAX
)
LP
 

D  LP  tan  o   
 180

d
(7)
(8)
LP
 

cos
 
o
 180

(9)
The maximum light angle (βMAX) required in order to cover the target region has been obtained for any value
of the parameter Ω, and it is represented in a polar diagram in figure 4.
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WORKROOMS Journal Nº1 – July 2013
z
 

D  LP  tan
 
o
180


β
βMAX
2
   
 

dD  LP 
 1  tan
     d
180o    180o  

β
LP
dMAX
d
d
D
DMAX
LP
 

cos
 
o
 180

Fig. 3. Geometric references and basic relationships. Light angle (β), distance lamp to
target point over floor (d) and distance of target point to lamppost over floor (D).
According βMAX values: near, middle and far regions have been introduced in the study looking for establish
a design procedure with three light angles in each direction (see figure 5 for details). Any other proposed
strategy can be also established considering angle β versus distance D variation.
90
120
60
SL105
60
RL75
 MAX RL45
40
150
2
 MAX
3
SL135
20
 MAX
deg rees
30
1
 MAX
3
RL15
SL165
180
0
0
near
SR195
middle
SR225
RR345
far
210
330
RR315
SR255
RR285
240
300
270
Ω [degrees]
Fig. 4. Maximum light angle (βMAX) required with regions nomenclature (Dates from Oviedo
City street lamps: R=9m, S=2m, LP=5m and H=2.LP=10m).
Over de polar diagram, the target region has been cut into 30 degree bends and denoted using the central angle
and also the zone reference letters. (i.e. RL45 region means central angle of 45 o in the zone RL). Using this
simple procedure referencing to different areas over the target region can be easily done. (i.e. RR285-middle).
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WORKROOMS Journal Nº1 – July 2013
See experimental section for details of use of this regions applied to different design strategies.
z
1
 MAX
3
LP
near
1
 MAX
6
middle
1
 MAX
2
far
5
 MAX
6
 MAX
Fig. 5. Near, middle and far regions according maximum light angle (βMAX).
Knowing distance d, angle β and target Illuminance (E) level required in each target point, Luminous Intensity
(I, in candle) required in the lamp has been also obtained. This a basic information in order to specify the
radiation diagram in the lighting system under design.
E d2
I
 

cos
 
0
 180

(10)
Radiation diagram (I, β) can be obtained for each target point inside the target region. Critical design points
appear in SL1 and SR1 regions and depending on the wide of the road (R), point with Ω = 0o, could be another
critical point. On the other hand, lighting level required in SL2, SR2 regions and in general near areas can be
easily obtained with lower Luminous Intensity (I) levels required.
In order to obtain the Total Luminous Flux () or the Total Power (P) required in the application, to cover
the whole target area or to be used with independent modules established in the design strategy, two important
elements have been introduced: The concepts of Angular Flux Density (β) and Angular Power Density (Pβ).
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WORKROOMS Journal Nº1 – July 2013
90
8
120
60
6
150
30
4
 MAX
2
2
2
 MAX
3
 MAX
I candle 180
5
 MAX
6
0
0
 MAX
3
 MAX
6
210
330
240
300
270
Ω [degrees]
Fig. 5. Luminous Intensity (I) required in the target region. Radiation Diagram (I, β) required
in the LED lamp under design. (Dates from Oviedo City street lamps: R=9m, S=2m, LP=5m
and H=2.LP=10m).
A differential of Area (Figure 6) has been used to characterize the above mentioned parameters. Relationship
with target region dimensions and with design parameters β and Ω have been obtained and presented in equation
11.
z
dβ
β
d
dD
LP
D
dΩ
Ω
dArea
x
Fig. 6. Differential Area of target region used during design procedure.
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WORKROOMS Journal Nº1 – July 2013
2
 
    
 
dArea 
 LP  tan 
    1   tan 
      d  d
2
o
o
 180
    180
  
180o
2

2

(11)
For simplicity, equation 11 can be written as:
dArea  G  d  d
(12)
Where G(β) is a fundamental function in the design procedure implemented in this work (13):
2
G  
180 
o 2
2
 
    
 
 LP  tan 
    1   tan 
    
o
o
 180
    180
  
2
(13)
As verification, the total area of the target region has been obtained:
Data from Oviedo City street lamps: R=9m, S=2m, LP=5m and H=2.LP=10m implies area of the target region
equal to 130 m2 and verified in equation (14).
360o
Area 

0o
  MAX (  )

 G    d   d 130 m 2
 

 0

(14)
Next, differential of Solid Angle (SA) from lamp point of view is then obtained:
dSA 
dArea
d2
(15)
Considering expression of Luminous Intensity (I) obtained in figure (10) and its relationship with differential
of Luminous Flux () (see equation 16), an interesting and useful expression for parameter d has been
obtained (17).
d  I  dSA
(16)
And then:
d  E 
G( )
 d  d 
 

cos
 
 180 
(17)
Integration in different ways of equation (17) inside the target region allow implementation of different design
strategies. The concept of Angular Flux Density (β) has been introduced. Units of β are Lm/(degree)2. This
parameter depends only on both LP parameter from target area geometry and light angle β. (See equation 18).
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WORKROOMS Journal Nº1 – July 2013
Considering Luminous Efficacy of LED used (L in Lm/W), the Efficiency of the Electronic LED drivers (E
in p.u.) and the Optical Efficiency of the lamp fixture (O in p.u.), the additional concept of Angular Power
Density (Pβ) has been also introduced in similar way. Units of P β are W/(degree)2. (See equation 19)
  E 
P 
G( )
 

cos
 
 180 
(18)
E  G( )
 

cos
    L  E O
 180 
(19)
Both concepts seek to simplify the designs because can be used to evaluate watts or lumens required in any
zone inside the target region, between two light angles or in the whole region under study obtaining lamp power
or luminous flux.
15
P
 mW 
 deg ree 2 


FAR
10
MIDDLE
5
0
NEAR
0
20
40
60
β [degrees]
Fig. 7. Evaluation of the Angular Flux Density (β) for different light angles β. (LP= 5 m and βMAX =
60o)
The profiles of Pβ or β are extremely interesting in LED lighting design because both shown the lumens or
watts profile required in the lamp with different light angles. Figure 7 shows this evaluation for a βMAX angle
of 60o with emphasis in near, middle and far regions. Power or lumens required in the lamp grows
exponentially and must be taken into account in designs.
The integration of the Angular Flux Density (β) or Angular Power Density (Pβ) covering the complete range
from 0 to βMAX it is important and allows obtain the radiation profile of the lamp under design.
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WORKROOMS Journal Nº1 – July 2013
Integration of β is shown in equation (20) and it has been plotted in the figure 8, for a specific design.
  0,  MAX  
 MAX  
    d
(20)
0
Similarly, Integration of Pβ is shown in equation (21) and it has been plotted in figure 9, for a specific design.
P 0,  MAX  
 MAX  
 P  d
(21)
0
90
120
60
20
150
30
10
  0,  MAX 
180
0
0
lumen

deg ree

210
330
240
300
270
Ω [degrees]
Fig. 8. Evaluation of the Angular Flux Density (β) over a line Ω inside the target region. (Data from
Oviedo City street lamps: R=9m, S=2m, LP=5m and H=2.LP=10m).
Integration of Angular Flux Density (β) over all the range of Ω (22) is the way to obtain the Total Luminous
Flux (TOTAL) of the lamp.
360o
TOTAL 
   0, 
MAX
() d
(22)
o
0
Evaluating this value applied to the target region in the example (Data from Oviedo City street lamps: R=9m,
S=2m, LP=5m and H=2.LP=10m), the Total Luminous Flux (TOTAL) required from the lamp under design is
of 3,250 Lm.
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WORKROOMS Journal Nº1 – July 2013
Integration of Angular Power Density (Pβ) over all the range of Ω (23) is the way to obtain the total power
required from the lamp.
360o
PTOTAL 
 P 0, 
MAX
() d
(23)
0o
Evaluating this value according the target region in the example (Data from Oviedo City street lamps: R=9m,
S=2m, LP=5m and H=2.LP=10m), the Total Power (PTOTAL) required for the lamp under design is 38.69 W
(with L=150 Lm/W, E = 0.9 p.u. and O = 0.7 p.u.).
90
120
60
0.2
150
30
0.1
P 0,  MAX 
W

 deg ree
180
0
0
210
330
240
300
270
Ω [degrees]
Fig. 9. Evaluation of the Angular Power Density (Pβ) over a line Ω inside the target region. (Data
from Oviedo City street lamps: R=9m, S=2m, LP=5m and H=2.LP=10m).
IV. PRACTICAL APPLICATION
Concepts of Angular Power Density (Pβ) and Angular Flux Density (β) previously introduced a variety of
design strategies. Moving again to figure 4 two modular designs have been proposed in order to cover angular
ranges of 60o (design I) and 30o (design II) in Ω parameter (6 sectors or 12 sectors to cover the target region,
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WORKROOMS Journal Nº1 – July 2013
see figure 10 for details) and three different levels according βMAX value (near, middle and far regions).
Obviously LED allows a perfect fit of light angles β to target region using any number of discrete angles.
z
 MAX
1
 MAX
3
far
LP
middle
near
2
 MAX
3
1
 MAX
3
Ω
x
Fig. 10. Modular design with sectors of Ω and three level in the light angle.
Figure 10 shows the basic idea of the proposed design methodology. It is important to emphasize that any other
proposal about light distribution can be analyzed using the tools proposed in this paper. Modularity and
directionality of Power LED allows different strategies looking for the efficient use of the energy in order to
satisfy light level and uniformity required. Evaluation of power required in each independent LED module of
the lamp have been obtained in the particular case of both proposed designs (I and II).
90
120
60
10
SL105
RL75
150
30
5
RL45
SL135
RL15
SL165
DMAX
[m]
SR195
0
0
RR345
SR225
RR315
RR285
210
330
SR255
240
300
270
Ω [degrees]
Design I:
6 sectors (Ω=60º)
Design II:
12 sectors (Ω=30º)
Fig. 11. Proposed modular designs I and II.
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WORKROOMS Journal Nº1 – July 2013
Summary of calculations have been included in table I for Ω=60o design and table II for Ω=30o design.
SECTOR
Ω
[Degree]
βMAX
[Degree]
βMAX/6
[Degree]
βMAX/3
[Degree]
βMAX/2
[Degree]
5.βMAX/6
[Degree]
PTOTAL
[W]
PNEAR
[W]
PMIDDLE
[W]
PFAR
[W]
RL15+RR345
0o
60.945o
10.158o
20.315o
-
50.788o
9.159
0.457
1.895
6.806
RL45+RL75
60o
54.595o
9.099o
18.198o
-
45.496o
8.813
0.445
1.835
6.533
SL105+SL135
120o
38.660o
6.443o
12.887o
-
32.217o
5.607
0.238
1.139
4.185
SL165+SR165
180o
21.801o
-
-
10.901o
-
0.687
-
-
-
TOTAL ROAD
26.786
TOTAL SIDEWALK
11.901
Table I. Summary of proposed Ω=60o modular design I. (Data from Oviedo City street lamps: R=9m, S=2m,
LP=5m and H=2.LP=10m).
SECTOR
Ω
[Degree]
βMAX
[Degree]
βMAX/6
[Degree]
βMAX/3
[Degree]
βMAX/2
[Degree]
5.βMAX/6
[Degree]
PTOTAL
[W]
PNEAR
[W]
PMIDDLE
[W]
PFAR
[W]
RL15
15o
56.335o
9.389o
18.778o
-
46.946o
4.580
0.229
0.948
3.403
RL45
45o
53.263o
8.877o
17.754o
-
44.386o
3.579
0.202
0.805
2.572
RL75
75o
57.923o
9.654o
19.308o
-
48.269o
5.234
0.234
1.030
3.961
SL105
105o
57.095o
9.516o
19.032o
-
47.579o
4.920
0.220
0.933
3.767
SL135
135o
29.496o
-
-
14.748o
-
0.687
-
-
-
SL165
165o
22.495o
-
11.247o
-
0.344
-
-
-
TOTAL ROAD
26.786
-
TOTAL SIDEWALK
11.901
Table II. Summary of proposed Ω=30o modular design II. (Data from Oviedo City street lamps: R=9m, S=2m,
LP=5m and H=2.LP=10m).
Several considerations must be done from the proposed prototypes.
a).- Power required in SL135 and SL165 zones are very low and, simultaneously, the light angle (β) required
is lower than 30o, then only one LED module has been proposed to cover these regions in both designs. In
general, power required in near region is also very low (lower than 0.3- 0.5 W in each sector).
b).- Similarly, power required in middle region is also reduced around 1 W in 30o and 2 W in 60o designs.
c).- Higher power levels appear in far regions, close to 4 W in critical points.
d) The Total Power required for the lamp is 38.690 W, distributed in 26.786 W in the road area and 11.905
W in the sidewalk area.
c).- Using dimming capability and a good optical design, matching of light level required with an excellent
uniformity can be obtained with the additional advantage of independent dimming capability over the road
side and over the sidewalk side.
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WORKROOMS Journal Nº1 – July 2013
A laboratory prototype has been built to validate Ω=60o design I proposed and take advantage of developped
design methodology combined with a flexible electronic design allowing to cover the requirements of optimal
light design over target region combined with powerful strategies of energy saving introduced in Lighting Smart
Grids schemes. A new design II with Ω=30o is now under development following the same rules and will be
presented in future works.
A Cree Xlamp MC-E LED has been used in the design, this Power LED has four individual LED inside of each
chip allowing a nominal power of 1 W in each LED (350 mA/LED) i.e. 4 W/module, allowing serial or parallel
connection of the internal LED according to the design needs (in the prototype two in parallel and two in serial,
see figure 13). With an optimal heatsink design nominal current can be also duplicated in each LED (700
mA/LED or 2 W/LED) in case of future applications. Efficiency of this type of Power LED are continuously
growing, last year 130 Lm/W and now 170 Lm/W with a continuously changing technology. This work has
been done assuming a Luminous Efficiency in the LED modules of 150 Lm/W.
One chip module has been used for near region and two chip modules for middle and far regions ones. Figures
12 and 13 show details of laboratory assembly using a custom made double side-PCB for each LED module
looking for an easy assembly over an aluminum support, allowing heatsink dissipation and angular light angle
required bending the support with the required β angle.
Fig. 12. Laboratory prototype for a Ω=60o sector.
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WORKROOMS Journal Nº1 – July 2013
THERMAL PAD
Fig. 13. Power LED module used in the prototype and detail of PCB design.
To electrically supply Power LED modules a low cost ZXLD1362 driver from ZETEX has been used. This
driver allows operation using an extremely flexible 18 to 36 DC bus and stabilized nominal current across the
LED of 1000 mA. An external resistance Rs has been used to personalize the nominal current in the module to
the required value. In figure 14, the Rs value used was 1/6 Ω is order to establish the nominal current in the
module to 600 mA or 300 mA in each LED (in general, 1/n Ω allows n.100 mA). A single PCB with three LED
drivers (near, middle and far regions) has been designed (see figure 15). Independent control of light level
required is easily obtained using these drivers under MCU control.
Fig. 14. LED driver design. Example with 300 mA in each LED. (3/4 W/LED or 3 W/module)
A control pin (ADJ) is used to dim the lamp between 0 and 100 % of nominal power established. A low cost
ARM-based 32-bit MCU from ST (STM32F051R8) has been used in order to implements the PWM control in
all drivers (A total of 18 independent LED drivers: 6 areas of Ω=60o with 3 light angles). MCU incorporates
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WORKROOMS Journal Nº1 – July 2013
ZigBee communications capability and full customization of light level required in each lighting point. A
powerful and flexible workbench has been built and allows verification of proposed design methodologies.
Figures 15 and 16 shows several photos of the laboratory prototype under operation using all the elements above
described.
Fig. 15. Laboratory prototype of a complete lamp (Ω=60o modular design I): Detail of LED drivers,
ARM-based 32-bit MCU and ZigBee interface.
Fig. 16. Laboratory prototype of a complete lamp (Ω=60o modular design I): Different overviews.
V. CONCLUSIONS
Lighting Systems are suffering an important evolution with the introduction of LED lighting capabilities
allowing new strategies of energy savings, incorporation of renewable energy sources and optionally a
bidirectional interconnection with the mains (AC grid or DC interconnection bus). Adaptability of light taking
into account application’s geometric dimensions is one important requirement thinking in energy efficiency.
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WORKROOMS Journal Nº1 – July 2013
This work keeps in mind the idea of new designs using the concept of sending the light in the correct direction
and with the required intensity. New lamps based on power LED must be designed in order to fit this
requirement and new tools and design procedures has been established in this way.
The work also consider the easy implementation capability of light level regulation, 0 to 100% as an additional
advantage to adequate light level requirements and also introducing dimming capability according to external
environmental conditions.
A complete methodology for street lighting with staggered arrangement and obtaining advantage of Power
LEDs possibilities has been presented and validated in this paper.
Two experimental design procedure according a real city geometry (City of Oviedo in Spain) have been
proposed in order to validate the introduced methodology, but tools described in this work allow different design
strategies in order to extract as much benefits as possible from LED advantages. The door is open to further
ideas and proposals according to the flexibility of LED devices with performances in continuous growth.
VI. ACKNOWLEDGMENT
This work has been supported by “Ministerio de Educación y Ciencia” of the Spanish Government
(ENERLIGHT project- reference MICINN-10-DPI2010-15889) and (LITCITY project –reference ENE 201341491-R). Acknowledge the assistance of the Workroom on Renewable Energy (WRE) collaboration of the
Engineering Polytechnic School of Gijon – Asturias - Spain (EPI-Gijon) in brainstorming and preparation of
prototypes.
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