LEDs application to the photovoltaic street lighting M. Fathi and A. Chikouche
Abstract—We propose the development and optimization of a new generation of photovoltaic powered street lighting systems which integrate LEDs devices. The combination of high efficiency photovoltaic panels with whites LEDs of last generation allows the release of an autonomous and performing solar lighting system. We present the methodology and design tools applied in order to respond to a specific energetic and lighting need. The present approach is structured in tow design levels of the solar LEDs lighting system. The first level is the electrical sizing of the solar system in order to respond to energetic need versus potential solar irradiation. The second design level is the optical study of light repartition on street. 3D illuminance simulation has been accomplished and permits us the establishment on the luminance reparation on the street versus spatial parameters of the installation (poles spacing, luminary height and lamp photometry characteristics).
Keywords—Photovoltaic Energy, LED, Solar Lighting, PV system sizing, 3D illuminance rendering. I. INTRODUCTION
T
ODAY, Energy-efficient lighting is an important factor for sustainable development and energy strategies. Indeed, Lighting consumes about 20 percent of the electricity for a nation. Also, renewable energy utilization development permits the reduction of CO2 emission and contributes to the decrease of fossil energy dependency. The association of a solar energy to High efficiency lighting technology as LEDs (Light Emitting Diodes) is the focus of this article and contributes to the development of a clean energy (Solar) and green lighting technology (LEDs). In comparing LEDs to other lamps technologies, we can say that LEDs are the Greenest lighting choice. Indeed, high power LEDs (Light Emitting Diode) devices permit the design and fabrication of street lighting units in order to replace existing luminaries which are using sodium or metal halide or CFL (Compact Fluorescent Lamp) lamps. A simple LED light bulb that can fits standard E40 bulb holders can be applied for solar powered street light system which is
M. Fathi is with the Solar Equipments Development Unit (UDES), RN11 Bouismaïl, 42415 Tipaza, ALGERIA (phone: +213-772-873199; fax: +213244-10133; e-mail:
[email protected]). He is a PV project Manager and a Research Senior. A. Chikouche, is with the Solar Equipments Development Unit (UDES), RN11 Bouismaïl, 42415 Tipaza, ALGERIA. He is the General Manager of UDES and a Research officer.
totally independent of power mains. The high power LEDs of last generation and technology offer a considerable alternative to a conventional street lighting with energy savings of up to 75 % and an important reduction in carbon emissions [1]. The photometric properties of high power LED street lights adding to their bright, natural light color, give a uniform rectangular beam pattern that is 50% brighter and 50% larger than the oval beam pattern produced by a conventional lamp [2]. This highly focused beam pattern allows LED lights to be spaced at much wider intervals than sodium and CFL lights. II. STRUCTURE OF SOLAR POWERED LEDS SYSTEMS Solar Street Lights system includes: solar panel, battery, solar controller, LED lighting unit and pole. The solar LED street light system converts the sun energy into electricity and stores it to provide green illumination. Luminaries utilize High Power white LED with superior thermal management design [3]. These extremely durable fixtures are waterproof and designed for multiple applications including indoor and outdoor. LEDs lamps have a lifetime of more than 50 000 hours. Fig. 1 gives a schematic representation for the structural composition of a PV LEDs lighting system. Composition of a Solar LEDs lighting system 1-Tilted solar modules placed on a mounting structure facing the sun path 2- LED lighting unit suspended on a pole short arm 3- Vented steel enclosure, (contains the battery/ies and the solar charge controller) 4- Structural anticorrosion parts consists of the pole, the affixing base, the short arm and the modules mounting structure
Fig. 1 Structural schematic of Solar LEDs lighting system
The PVS-syst software has been applied for the sizing of the solar LEDs systems (photovoltaic panel power and battery capacity) [4]. By using the Dialux software, we will study the impact of optical design of street lighting on the poles according to the height and spacing of the poles luminaries.
III. ELECTRICAL DESIGN OF A SOLAR POWERED LEDS STREET LIGHT SYSTEM
In this project, we are interested in the optimization of solar street lighting by LEDs lamps for an airport peripheral area. Here after, we will present electrical and optical performance simulation reported to the solar lighting pole systems using LEDs. The general conditions are as following: -Site: Oran (North West region of Algeria), - PV Module Tilt: 36°, -Daily Lighting use: 12Hours/day, -Autonomy: 4 Days.
Fig. 2 Schematic view of LEDs device
Fig. 3 Schematic view of a LEDs light unit
LEDs components are made of Gallium Nitride (GaNi) semiconductor material which is doped by phosphorous chemicals. The electronic structure of LED is a diodes or tandem structures [5]. After processing of this electronic device the produced LEDs chips are connected by microwiring or flip-chip technology and then packaged in a transparent epoxy material of specific composition which is different from one manufacturer to another. The Fig. 2 and 3 show respectively a picture view of a single LED device and the LEDs light Unit. The table 1 gives some Illumination Data for a LED light unit. TABLE I TABLE 1: EXAMPLE OF ILLUMINATION DATA FOR A LED LIGHT UNIT Suspension Distance (m)
Lighting Area (m X m)
6
8 X 20
Illuminance (lux) at maximum lumen based on the illuminated area and the LED street light LED LED LED LED 18W 30W 50W 65W 10 Lux 19 Lux 30 Lux 39 Lux
8
10X25
6 Lux
12 Lux
18 Lux
23 Lux
10
13 X30
4 Lux
8 Lux
12 Lux
15 Lux
12
16X35
2 Lux
5 Lux
8 Lux
11 Lux
Fig. 4 PV-syst software application to sizing of PV system
Also, the LEDs luminary power will vary from 20 to 30 W. After entering all of these conditions in PV-syst software we calculated the PV panel power and Battery capacity (see Figure 4). As an example, for 20 W LED lighting Unit (1400 lumens) we obtained a recommended PV panel of 101W and a battery of 89 Ah. In practice, we will use a PV of 110W and a battery of 100Ah. The table 2 recapitulates all of these results for LEDs and CFL lamps configurations. TABLE II PV-SYST SOFTWARE APPLICATION FOR THE SIZING OF SOLAR POWERED LED LIGHTING SYSTEM Sizing
LED20W
LED25W
LED30W
CFL23W
CFL25W
PV (W) Battery (Ah) Light (Luns)
101 89 1400
132 111 1680
159 133 2400
118 102 1380
133 111 1500
On the other hand, in order to confirm our obtained results we have done a comparative study of PV-syst software results with two others software (EOS-BP solar and a homemade simulator: PVSST1.0); we founded nearly the same sizing results for PV panel power and battery capacity (see table3).
For this project we have definitely recommended PV panel of 110W and a battery of 100Ah.
C-The simulate effect drawing (3D)
TABLE III COMPARATIVE SIZING WITH 3 DIFFERENT SIMULATOR OF AIRPORT PROJECT (CFL 23W / LED 20W) System Sizing
PV Power (W) Battery (Ah)
Simulator type EOS-BP Solar Industrial software 110 95
PV-Syst 4.37 University software (Geneva) 104 89
Home Simulator, PVSST1.0 R&D simulator 110 102
IV. OPTICAL DESIGN OF SOLAR POWERED LEDS STREET LIGHT SYSTEM
The Designed project is for implantation of solar lighting systems for an Airport peripheral area. Following to airport recommendation of using LED lamp superior to 1200 Lumens and total height (including PV modules on the top of the pole) we have selected a 20 W LED Luminary unit having 1432 Lumens of light intensity output. We have simulated 3 different poles spaces 15, 18 and 20 meters. By using the Dialux software we can simulate light intensity distribution on street. The road width is 5m and LED lighting hight is 5.5m. The optimal and economical result is presented here below for 18 m of space between 2 poles. Here after all figures and of a road lighting simulation obtained by Dialux software. Airport Peripheral Street lighting Design, pole space is 18 m - 20W LED light, Street Width: 5m, - LEDs Unit Height: 5.5m, - 18 meters between 2 poles, - Put lamps on one side. - Cement flag pavement. A-As the drawing
D- The ground lux effect value (LX)
-
Airport Peripheral Street lighting Design, pole space is 20 m - 20W LED light, Street Width: 5m. - LEDs Unit Height: 5.5m. - 20 meters between 2 poles, - Put lamps on one side. - Cement flag pavement.
A-As the drawing
B-3D Rendering B-3D Rendering
C-The simulate effect drawing (3D)
[3]
[4]
[5]
[6]
D-The ground lux effect value (LX)
We can see that in the case of 20 m of spacing, a dark area start to take place between poles which a sign of low lighting (we can measure from the curve D of “The ground lux effect value (LX)” Emin= 1.6 lux, Emin represents the minimum light illuminance). The optimal results lighting simulation is for 18 m of pole spacing, all area between pole are illuminated and Emin = 2.29 Lux. Then, we recommend placing poles at a distance of 18 meters when applying 20W LEDs lighting Unit.
V. CONCLUSION This project destined to an Airport peripheral street lighting has been designed by using PV-syst software to sizing the system PV panel and Battery in order to respond to the energy need of a 20W LED Lighting unit. We have recommended PV panel of 110W and a battery of 100Ah. Then, by using Dialux software we simulated the optical effect on road illuminance repartition versus the distance between poles, we have shown that optimal space between poles is 18m. We have presented electrical and optical performance simulation reported to solar lighting pole using LEDs. This study opens the way for the development of a third level design which is the design of LEDs lighting unit prototype adapted to a specific street and project situations. REFERENCES [1]
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