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Comparative Life Cycle Assessment (LCA) of streetlight technologies for minor roadsin United Arab Emirates

Sabina Abdul Hadi, Muna R. Al Kaabi, Meshayel O. Al Ali, Hassan A. Arafat ⁎Water and Environmental Engineering Program, Masdar Institute of Science and Technology, P.O. Box 54224, Abu Dhabi, United Arab Emirates

a b s t r a c ta r t i c l e i n f o

Article history:Received 4 September 2012Revised 2 May 2013Accepted 2 May 2013Available online 29 May 2013

Keywords:StreetlightLight Emitting Diode (LED)Ceramic Metal Halide (CMH)Photovoltaic (PV)Life-cycle assessment (LCA)United Arab Emirates

In this work, the Life Cycle Assessment (LCA) method is used to investigate the environmental impacts of tworecent energy efficient streetlight technologies, Ceramic Metal Halide (CMH) and Light Emitting Diode (LED),with the aim of assessing their application in Abu Dhabi — United Arab Emirates (UAE). The cradle to graveanalysis for CMH and LED streetlights includes raw material extraction, production of streetlight fixture, useand end of life scenario, all modeled using the SimaPro software package. The results show that LED lightshave larger environmental impact during the production stage, but this is offset during the operational lifeof the lamp, due to the lower energy consumption of LEDs. For both types of lamps, the production stagehas significantly less overall impact when compared to the impact during their operational life. The analysisin this paper also covers a scenario where stand-alone light fixtures are powered by photovoltaic (PV) panels,with and without battery recycling, in addition to a scenario where the energy used for operation comes froma solar power plant. In all the cases analyzed, the LED lamp has a lower overall environmental impact. Fur-thermore, our analysis shows that most environmental impacts come from battery production, consumptionof fossil fuels for energy, and transportation of parts.

© 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved.

Introduction

The need for street lighting has existed for a long time. On January28, 1807, Pall Mall in London witnessed the first street lightingpowered by gas. About 70 years later, the first electric street lightingwas developed by Russian Pavel Yablochkov (Pohl, 2006).

Many different lighting technologies have been developed andused for outdoor illumination, with energy efficiency and lightingquality increasing continuously over the years. Electric street lightinghas varied from using incandescent bulbs, to the use of more energyefficient technologies, such as high pressure sodium (HPS), metalhalide (MH), Ceramic Metal Halide (CMH), Light Emitting Diode(LED) and induction lamps. With increasing world population andurbanization, the amount of energy used for lighting of public areasis also increasing, so energy savings in this field would have signifi-cant positive impact on the environment.

When choosing the appropriate lighting technology for roadwaylighting, care has to be taken to ensure that the level of illuminationsatisfies road safety standards. In order to have safe roads at night, lu-minous flux (lm) and illuminance (lumen/m2 = lux) should be suffi-ciently high to provide adequate illumination of the road and qualityof colors perceived by human eye should preferably be as high as pos-sible. Acceptable standards for illuminance on roads, parking areasand highways can range between 5 to 30 lx, with higher lux levels

at cross sections and places with more pedestrians (Schreder, 2012).The color rendering index (CRI) is a factor that indicates the comparisonof lamp light to daylight, where CRI is considered to be 100 if colors areperceived similarly to daylight conditions (Descottes and Ramos, 2011).

This project aims to compare two types of lamps from the lateststreetlight technologies, dedicated Light Emitting Diode (LED) andCeramic Metal Halide (CMH) bulb, in order to determine whichlamp is more efficient and could be installed on the internal(minor) roads of the Emirate of Abu Dhabi, UAE. The lamps are cho-sen based on the same range of luminescence and CRI, according tostandards for safe road lighting. While high pressure sodium (HPS)lamps are currently most widely used in street lighting since theyare very efficient, with lumen efficacy greater than 100 lm/W, theircolor temperature of 2000 K and low CRI in the range of 20–30(OSRAM, 2013) do not compare favorably with the state of the artstreetlight technologies. The main motivation for choosing road light-ing in Abu Dhabi as a study subject is that most of the roads in UAEare very well illuminated, consuming a significant amount of energy.The total length of Abu Dhabi internal roads is 8379 km (StatisticsCentre — Abu Dhabi, 2011) with an average distance of 20–50 m be-tween two light poles on junctions and internal roads. If it is assumedthat 70% of internal roads are lit and that the distance between thelight poles is fixed at 50 m, then it can be calculated that there areabout 117,000 high intensity lamps working 12 h a day, throughoutthe year. Having even a minor added environmental improvementper light pole will result in a significant decrease in greenhouse gasemissions. Moreover, Abu Dhabi has committed itself to sustainable

Energy for Sustainable Development 17 (2013) 438–450

⁎ Corresponding author. Tel.: +971 28109119; fax: +971 2810 9101.E-mail address: [email protected] (H.A. Arafat).

0973-0826/$ – see front matter © 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved.http://dx.doi.org/10.1016/j.esd.2013.05.001

Contents lists available at ScienceDirect

Energy for Sustainable Development


development (Abu Dhabi Sustainable Group, 2012). The results of com-parative LCA analysis for CMH and LED streetlight technologies couldhelp the government of Abu Dhabi in choosing the most efficient andenvironment friendly option while accommodating the increasing en-ergy needs of the constantly growing population. However, the meth-odology developed in this work is equally applicable to other citiesaround the world.

Ceramic Metal Halide (CMH) lamps

Metal halide (MH) lamps belong to the group of high pressure dis-charge lamps, similar to high pressure sodium lamps, where light isgenerated by a gas discharge of particles created between two her-metically sealed electrodes in an arc tube (OSRAM AG, 2012). EachMH lamp contains approximately 5 mg of mercury, and an arc tubefilled with a gaseous mix of metal halides that are used to producebright white color (Navigant Consulting Europe, Ltd., 2009). Thefirst generation of MH lamps were made with high purity quartz arc

tubes (OSRAM AG, 2012) but are susceptible to color shift duringthe operational life, due to loss of the arc material and mitigation ofhalides (GE Lighting, 2005). Ceramic Metal Halide (CMH) lamps useceramic arc tubes as opposed to quartz tubes. Ceramic arc tubes canwithstand higher temperatures than quartz, allowing more efficientuse of chemicals, providing improved luminous efficacy and colorrendering index. While quartz MH lamps operate at ~80 lm/W (GELighting, 2013), CMH lamps are as efficient as HPS lamps with100 lm/W lumen efficacy (GE Lighting, 2005; OSRAM, 2013). Further-more, CMH lamps have constant color throughout the lamp's opera-tional life and CRI > 90, providing almost daylight conditions (GELighting, 2005), unlike quartz MH or HPS lamps, with CRI ~70 and~20, respectively (GE Lighting, 2013; OSRAM, 2013). CMH lampscombine the bright white light properties of MH technology, such ashigh CRI and color temperature above 3000 K (GE Lighting, 2013),with lumen efficacy of HPS technology. With these properties, CMHlamps provide very efficient street illumination. A big advantage ofCMH bulbs is that they can be used as retro-fit to HPS light fixtures,

Fig. 1. (a)MasterColor HPS— retro fit CMH bulb by Phillips (Philips Lighting Solutions, 2012), (b) Schematic drawing of OSRAM's LED and the cross section of an LED chip (OSRAM, 2009).

Dedicated LED

HousingHousing

Lamp

a) b)

Fig. 2. CMH (a) and LED (b) streetlight fixtures (CMH Street Light, n.d; LED Street Light, n.d).

439S. Abdul Hadi et al. / Energy for Sustainable Development 17 (2013) 438–450


since they both use a ballast for ignition. Fig. 1(a) shows an exampleof a CMH bulb designed as HPS retro-fit by Phillips (Philips LightingSolutions, 2012).

For our study of minor roads, we chose the 250 W CMH lamp,with CRI ~90 and luminous flux ranging from 25,000 to 17,500 lmthroughout lamp life (GE Lighting, 2010).

Light Emitting Diode (LED) lamps

LED lamps are solid state electronic devices made of semiconduc-tor materials with direct band gap, such as gallium arsenide, whichemit light when charged with an electric current. Phosphorus coatingis used to modify light emitted by a diode into a white and usablelight (Navigant Consulting Inc., 2003). The light emitted by the solidstate electronic material strikes a phosphorous coating, which thenemits the usable light (Navigant Consulting Inc., 2003). All stepsinvolved in production of LEDs are carried out in cleanrooms andinvolve energy intensive processes. Fig. 1(b) shows schematics of atypical LED lamp (OSRAM, 2009).

In recent years, the efficiency of LED lamps, expressed in lumens/watt, has increased significantly (OSRAM, 2009). Depending on thesemiconductor materials and design used in fabrication process, lu-minous efficacy of high power, state of the art LEDs is reported torange between 142 lm/W to a record 231 lm/W when operating at350 mA/mm2, with CRI b 80 (Tan et al., 2012). CRI of LEDs can be in-creased by adding red or nitride-based phosphors, in an attempt tointroduce the missing red component in the spectrum of the emittedlight. However, adding phosphor causes very broad spectrum and farred emission spilling beyond the eye sensitivity, resulting in de-creased luminous efficacy of optical radiation (Tan et al., 2012). Fur-thermore, under high current injection in LED, luminous efficacysignificantly drops, which is known as efficiency droop (Tan et al.,2012).

Dedicated LED luminaries are composed of many light emitting di-odes, whose power can range between 1 and 3 W (E-Lite Opto Tech;Energy Works; OSRAM, 2011). Since commercially available street-light luminaries have approximately 0.7–0.85 LEDs per watt (EnergyWorks; OSRAM, 2011), for simplicity, we assume in this work thatone light emitting diode corresponds to 1 W of system power.

For our study, an LED streetlight fixture with 180 LEDs was chosen,which is equivalent to 180 W energy consumption and 15,000–19,000 lm (E-Lite Opto Tech; Energy Works), matching the minimumluminous flux of a 250 W CMH bulb during its lifetime. Illuminance of

180 W LED light fixture installed on a 12–14 m pole was found tovary between 20 and 60 lx (Energy Works; E-Lite Opto Tech), whichis within the range of the road safety standards. Furthermore, therated lifetime of LEDs is about 50,000 h, but satisfactory lighting is gen-erated during 30,000 operational hours approximately (EnergyWorks).

Life Cycle Assessment (LCA)

Life Cycle Assessment (LCA) provides a detailed inventory of allthe impacts associated with each and every stage of a process or aproduct, from cradle to grave. LCA widens the view of system attri-butes during environmental and economic assessments, providing agood basis for comparison between different technologies, by takingevery single step of the process into consideration (Tester et al.,2005). Life Cycle Assessment standards are governed by the standardsISO 14040:2006 and ISO 14044:2006, which identify the followingstages of an LCA (International Standard Organization, 2010):

▪ Goal and scope definition: The goal of the LCA along with the sys-tem boundary and level of detail are determined in this step, alongwith the selection of the functional unit. The functional unit is theunit of comparison among different systems or products that arebeing analyzed by an LCA.

▪ Inventory analysis: The inventory is a list of the materials, energy,and emissions involved in the production, use and disposal of thesystem under study. Inventory includes inputs to the systemboundary such as raw materials, and outputs from the systemboundaries such as emissions to the atmosphere. Data relating toinputs and outputs (e.g., energy, materials, emissions) is collectedin this stage.

Transportation

Extraction

Exploration

Production

Processing

UseManufacturing Ultra Efficient

LampPackaging

Earth materials

Others

Tungsten

Electronics

Plastics

Aluminum

Copper/Bras

Steel

Mercury

Ceramics

Energy

Glass

Phosphorus

Emissions

Disposal

Landfill Reuse / Recycle

Fig. 3. Process flow diagram for material and processes used throughout lamp's life (Navigant Consulting Europe, Ltd., 2009).

Table 1Weight breakdown of material components for LED and CMH indoor lamps (NavigantConsulting Europe, Ltd., 2009).

Component LED lamp (kg)(containing 16 LEDs)

CMH bulb (kg)

Base 0.14 0.16Ballast 0.31 0.14Lamp 0.03 0.10Lens 0.03 n/aPackaging 0.003 0.014Total (kg) 0.52 0.41

440 S. Abdul Hadi et al. / Energy for Sustainable Development 17 (2013) 438–450


▪ Impact assessment: The environmental impacts from the in-ventory's inputs and outputs are calculated, showing the environ-mental significance of the considered product or system. By usingimpact assessment methods, the inventory can be used to esti-mate the environmental impact of the product or a system underthe study.

▪ Interpretation: Finally, the results of the inventory and impact as-sessment are summarized into meaningful outcomes, results, andrecommendations.

Different impact assessment methods exist with a variety of as-sumptions and details. Eco-Indicator 99 was the method used for thelife cycle impact assessment in this study and it is a damage orientedmethod (Baumann and Tillman, 2004) This method provides a way toevaluate different environmental impacts and present the final resultin a single score. Under this method, there are three different perspec-tives: 1-Hierarchist, 2-Individualist and 3-Egalitarian (Eco-indicator 99Impact Assessment Method for LCA). While all three approaches wereused to observe the impacts in this study, the results presented hereare focused on the Hierarchist view on impact assessment, since ourstudy is more oriented toward municipalities/governmental entities,as the most likely decision makers in terms of public roads lighting.

Methodology

The objective of this LCA is to assess the life-cycle environmentalburdens of two technologies, which are candidates for lighting inter-nal streets in the Emirate of Abu Dhabi. The study considers the CMHand LED streetlight technologies. Figs. 2(a) and (b) show an example

of CMH and LED streetlight fixtures, respectively (CMH Street Light;LED Street Light).

Lighting technology varies widely in many aspects such as lumenefficacy, color rendering index, wattage, lifetime etc. CMH bulb's aver-age lifetime is 20,000 h while LED's average lifetime with sufficientlight output is 30,000 h (GE Lighting Technologies, 2009; EnergyWorks). Therefore, as a functional unit for this study, we chose60,000 h of lighting (as the least common multiple). During this peri-od, a CMH bulb would need to be replaced twice, while an LED lampwill have to be replaced once, after the initial installation of each.Moreover, models of both lamps were chosen such that they haveCRI greater than 80 and lumen efficacy greater than 90 lm/W (GELighting, 2010). In other words, raw materials and energy requiredto produce and operate the lights with satisfactory luminescenceand CRI are compared in this study, over 60,000 h.

Time frame

The time horizon in this study is 60,000 h of operational life. Thisoperational time is equivalent to approximately 14 years. The study ofinventory and data gathering for production, operation, and end of lifedisposal or recycling is done for the current time period (2011) as abase case.

Geographical boundary

In our base case, we assumed that all lamps and fixtures were pro-duced in the USA and used in Abu Dhabi—UAE. Later in the study, thegeographical boundaries were extended in order to accommodate the

Table 2Housing raw material for streetlight CMH bulb for 60,000 h of operation (Hartley et al., 2009).

Lamp components Material SimaPro material Weight (kg)

Bottom housing Aluminum Aluminum alloy, AlMg3, at plant/RER Sb 0.957 × Ba

Metal separator Aluminum Aluminum alloy, AlMg3, at plant/RER S 0.0153 × BReflector Aluminum Aluminum alloy, AlMg3, at plant/RER S 0.422 × BTop housing Aluminum Aluminum alloy, AlMg3, at plant/RER S 2.417 × BScrews (brass) Brass Brass, at plant/CH S 0.039 × BBracket rocker Cast aluminum Aluminum, cast, lost foam, at plant/kg/US 0.1101 × BCeramic bulb holder Ceramic Sanitary ceramics, at regional storage/CH S 0.177 × BPhotocell circuit board Circuit board Printed wiring board, through hole mounted, unspecified, solder mix, at plant/GLO S 0.041 × BCopper from circuit board Copper Copper, secondary, from electronic and electric scrap recycling, at refinery/SE S 0.0051 × BFelt heat shield Felt Textile, jute, at plant/IN S 0.003 × BAttachment Galvanized steel Galvanized steel sheet, at plant/RNA 0.147 × BBolt Galvanized steel Galvanized steel sheet, at plant/RNA 0.044 × BBracket pieces Galvanized steel Galvanized steel sheet, at plant/RNA 0.295 × BPhotocell holder cover Galvanized steel Galvanized steel sheet, at plant/RNA 0.0054 × BScrews (steel) Galvanized steel Galvanized steel sheet, at plant/RNA 0.018 × BSmall screws (steel) Galvanized steel Galvanized steel sheet, at plant/RNA 0.002 × BLens Glass Glass bottles FAL 2.359 × BPaper insulator Paperboard Paperboard Unbl. Semichem. FAL 0.0013 × BBlack plastic insulator Plastic PS (GPPS) FAL 0.074 × BPhotocell cap Plastic PS (GPPS) FAL 0.024 × BPhotocell plastic Plastic PS (GPPS) FAL 0.011 × BPhotocell plugin Plastic PS (GPPS) FAL 0.0543 × BPlastic circuit board Plastic PS (GPPS) FAL 0.023 × BWeather guard Plastic PS (GPPS) FAL 0.0102 × BMetal bulb screws Stainless steel X5CrNiMo18 (316) I 0.019 × B

FAL — Swiss Federal Research Station for Agroecology and Agriculture.GLO — ecoinvent country code for Global.GPPS — general purpose polystyrene.IN — ecoinvent country code for India.PS — polystyrene.RER — ecoinvent country code for Europe.RNA — ecoinvent country code for North America.S — ecoinvent process type-system.SE — ecoinvent country code for Sweden.US — ecoinvent country code for United States.

a B = 3, number of bulbs within 60,000 h.b CH — ecoinvent country code for Switzerland.



location of recycling centers and component manufacturers, includingUAE, India and Germany.

System boundary

System boundary includes raw material production, processing ofmaterials, energy required for manufacture and use, and disposal sce-nario at the end of life of light fixtures. Transportation of raw materialto the production factory is included in the Ecoinvent Database, buttransportation of light fixtures from USA to UAE had to be accountedfor. Aluminum content was found to be approximately the same forstreetlight fixtures of both lighting technologies and its impact wastherefore excluded from the base case scenario. Furthermore, themain-tenance of both kinds of streetlight technologies involves the bulbreplacement at the end of its life, and its impact can be estimatedthrough distance needed to travel to install and replace the lamp, 2times for LED versus 3 times for CMH over 60,000 operational hours.However, the location and time when each bulb would need to be re-placed is random and difficult to account for, regardless of the lightingtechnology. Preliminary hypothetical calculations were done and theimpact of travel for bulb replacement 2–3 times over 14 years of bulblifetime was found to be very minimal compared to the other impacts.Therefore, and given the impossible prediction of the actual distancebeforehand, the distance required to travel in order to replace bulbs atthe end of their life was excluded. On the other hand, maintenance ofPV panels in one of the studied scenarios was accounted.

The Life Cycle Assessment (LCA) software SimaPro V.7.3.2 (PRéConsultants, Netherlands) was used to assess the environmentalimpact of the various options considered for this study.

Results and discussion

System design

Streetlights are composed of the lamp/bulb and the light fixturethat is fixed on top of the light pole. While a dedicated LED lightdoes not have a bulb, but instead light emitting diodes integratedinto the light fixture, CMH bulbs can be retro-fitted into existingHPS fixtures. Therefore, in further text, terms “bulb” and “lamp”would refer to CMH and LED lighting technologies, respectively. Inthis study, environmental impacts were compared for productionand use of lamp (LED)/bulb (CMH) and fixtures for both types ofluminaires. While both CMH and LED lights can be installed onpoles with various heights, depending on the wattage of the lamp,(250 W for CMH and 180 W for LED), both are assumed to beinstalled on 12–16 m high poles (GE Lighting, 2005; Energy Works).Fig. 3 shows a general flow diagram of the material and processesthroughout a lamp's life. Although there is a difference between theproduction of CMH bulb and LED lamp, the types of materials re-quired to produce light fixtures in both cases are very similar.

Due to the lack of information on streetlight CMH and LED lamps,the relative weights of indoor CMH and LED lamps (no fixtures),

Table 3Raw material for streetlight CMH bulb manufacture and 60,000 h of operation (Navigant Consulting Europe, Ltd., 2009).

Lamp component Item SimaPro material Weight (kg)

Ballast PCB Printed wiring board, surface mounted, unspecified, Pb free, at plant 0.065 × Ba

Ballast Housing Steel, electric, un- and low-alloyed, at plant 0.336 × BBallast Gear tray Steel, electric, un- and low-alloyed, at plant 0.607 × BBallast Wiring Copper, at regional storage 0.009 × BBallast Connectors Polypropylene, granulate, at plant 0.028 × BBallast Switch Polypropylene, granulate, at plant 0.056 × BBallast Coil Aluminum, production mix, at plant 0.159 × BBallast Capacitor Aluminum, production mix, at plant 0.019 × BBallast Capacitor Epoxy resin insulator (SiO2), at plant 0.009 × BBallast PET film Polyethylene terephthalate, granulate, amorphous, at plant 0.009 × BBallast Solder paste Solder, paste, Sn95.5Ag3.9Cu0.6, for electronics industry, at plant 0.009 × BFitting Plastic Polypropylene, granulate, at plant 0.495 × BFitting Clips Aluminum, production mix, at plant 0.495 × BFitting Wiring Copper, at regional storage 0.495 × BLamp Pins Steel, low-alloyed, at plant 0.019 × BLamp Pins Copper, at regional storage 0.001 × BLamp Pins Chromium, at regional storage 0.001 × BLamp Pins Copper, at regional storage 0.001 × BLamp Base Polycarbonate, at plant 0.103 × BLamp HIDb capsule Mercury, liquid, at plant 5.6E–05 × BLamp HID capsule Argon, liquid, at plant 2.8E–06 × BLamp HID capsule Krypton, gaseous, at plant 2.8E–06 × BLamp HID capsule Rare earth concentrate, 70% REO, from bastnasite, at beneficiation 8.4E–05 × BLamp HID capsule Aluminum oxide, at plant 0.215 × BLamp Reflector & lens Glass tube, borosilicate, at plant 0.560 × BPackaging Card Packaging, corrugated board, mixed fiber, single wall, at plant 0.134 × BPackaging Plastic Polyethylene, LLDPE, granulate, at plant 0.080 × BLamp HID capsule Rare earth concentrate, 70% REO, from bastnasite, at beneficiation 8.4E–05 × B

Variable explanation and values are given below c

Transportation B × W × flight/103 Transport, aircraft, freight, intercontinental/RER S (tkm)Transportation B × W × F_L/103 Truck 28 t B250 (tkm)Transportation B × W × AD/103 Truck 28 t B250 (tkm)Operational Energy Natural gas, burned in power plant/ASCC S 15 (MWh)

Flight = 10,735 km, Boston–AD airport distance.F_L = 65.5 km, factory–Boston Airport distance.AD = 38.5 km, Abu Dhabi airport–warehouse distance.

a B = 3, number of bulbs within 60,000 h.b HID — high intensity discharge.c W = 11.1 kg, estimated CMH fixture weight.



shown in Table 1, were utilized (by scaling up) to estimate the weightcomposition of high wattage roadway lighting technologies (NavigantConsulting Europe, Ltd., 2009).

As a disposal scenario, the flow diagram in Fig. 3 shows options oflandfill and recycling. Since UAE currently has a low rate of recycling,limited mostly to the recycling of construction waste (StatisticsCenter Abu Dhabi, 2011), we have assumed 100% landfill in the basecase. However, at a later stage, recycling of some of the light compo-nents is considered, along with the transportation of recyclable mate-rial to the recycling centers.

Inventory analysis

For this study, as the two street lighting technologies are fairly re-cent, detailed information on high wattage CMH and LED roadwaylight bulb/lamp and their light fixtures was not readily available andit had to be collected, calculated, or estimated, as discussed in thissection.

Both light fixtures are assumed to be produced in USA. Consequent-ly, the energy used for production is chosen to be USA mix, fromEcoinvent Database in SimaPro. Transportation of light fixtures is as-sumed to take place from the manufacturing facility in Boston, USA, toan arbitrary warehouse in Abu Dhabi, by intercontinental cargo aircraftand land transport (latter for transport from/to airports).

All energy consumed during the operational life of lamps ismodeled by SimaPro to be 100% from a natural gas power plant, themain energy resource currently used in Abu Dhabi (Abu DhabiWater and Electricity Company (ADWEC), 2011). An alternative sce-nario was also studied in which the operational energy is consideredto come from off-grid photovoltaic (PV) panels with batteries forpower storage. This was considered as Abu Dhabi now aims to maxi-mize its solar energy utilization. The scenario with off-grid PV energysource is further divided into scenarios with and without batteryrecycling at the end of battery life. Finally, a third scenario where en-ergy comes from a solar PV power plant is considered and its impactis analyzed.

CMH streetlightAs CMH is a relatively new technology, no inventory data was

found for CMH street lighting in open literature. Hence, data was col-lected for CMH bulbs for indoor use (Navigant Consulting Europe,Ltd., 2009) and for HPS light fixtures (Hartley et al., 2009). Inventoryfor CMH light fixtures was assumed to be the same as the available

inventory for HPS light fixtures, due to the retro-fit property of theCMH bulb under study. From commercially available information,the average weight of CMH streetlight (bulb and fixture) was foundto be approximately 11 kg (GE Lighting, 2011). This informationwas used, along with available data for indoor CMH bulb composition,to calculate (by scaling up) the weights of high wattage roadwayCMH lamp components.

Table 2 shows raw materials for housing of streetlight CMH bulbfor 60,000 h (Hartley et al., 2009). Total weight of the housing isabout 8 kg, and total weight of the light fixture with lamp is assumedto be 11 kg (GE Lighting, 2011), which leaves about 3 kg of weight forballast and the streetlight bulb. Raw materials required for manufac-ture of CMH bulb are extrapolated by using fraction of each compo-nent of indoor lamp from Navigant Consulting Europe, Ltd. (2009)and scaling it up to 3 kg of assumed outdoor lamp's weight, asshown below:

CMH streetlight component ¼ Indoor bulb componentIndoor bulb weight

� 3kg: ð1Þ

The data in Table 3 shows the raw materials required for CMHstreetlight bulb manufacture and operation over 60,000 h. Materialand resources required to process raw material for manufacture ofstreetlight CMH Luminaire System for 60,000 operating hours(expressed in kg of material that needs to be processed) are shownin Table 4.

LED streetlightA slightly different approach was taken to extrapolate the data for

LED streetlight, since the lamp and fixture are not clearly differentia-ble. Components corresponding to diode production and operationare scaled up linearly according to the number of diodes in a street-light lamp, while other materials are scaled up, percentage wise, inorder to complete an average weight of LED streetlight fixture.

Light emitting diode fabrication in cleanroom is an energy inten-sive process, due to uninterrupted operation of devices at high tem-peratures and under high pressure. Energy required for fabricationof one light emitting diode in cleanroom facilities ranges from 0.02to 0.07 kWh/diode (Matthews et al., 2009) and is assumed here tobe on an average 0.045 kWh/diode for the base case analysis.

Inventory available for indoor LED lamps with 16 diodes (NavigantConsulting Europe, Ltd., 2009)was examined carefully and componentscorresponding to light emitting diodes were linearly scaled up for a

Table 4Resources required to process raw material for streetlight CMH Luminaire System for 60,000 h of operation (expressed in kg of material that needs to be processed). Data takenfrom Navigant Consulting Europe, Ltd. (2009) unless otherwise specified.

Lamp component Item SimaPro material Weight (kg)

Ballast Housing Steel product manufacturing, average metal working 0.336 × Ba

Ballast Gear tray Steel product manufacturing, average metal working 0.607 × BBallast Wiring Wire drawing, copper 0.009 × BBallast Connectors Injection molding 0.028 × BBallast Switch Injection molding 0.056 × BBallast Coil Wire drawing, copper 0.159 × BBallast Capacitor Sheet rolling, aluminum 0.019 × BBallast PET film Extrusion, plastic film 0.009 × BFitting Plastic Injection molding 0.495 × BFitting Clips Aluminum product manufacturing, average metal working 0.495 × BFitting Wiring Wire drawing, copper 0.495 × BLamp Pins Chromium steel product manufacturing, average metal working 0.019 × BLamp Base Injection molding 0.103 × BLamp Reflective coating Aluminum, production mix, at plant 0.019 × BPackaging Plastic Extrusion, plastic film 0.0805 × BHousing b Metal manufacturing process Metal product manufacturing, average metal working/RER Sc 4.496

S — ecoinvent process type-system.a B = 3, number of bulbs within 60,000 h.b Additionally adjusted from Hartley et al. (2009).c RER — ecoinvent country code for Europe.



lampwith 180diodes, as the LED streetlight under the study. Remainingraw materials are scaled up percentage wise in order to complete lightfixture weight of 12 kg (Energy Works). An exception was made forglass and aluminum, since larger percentage of these materials areused for street lighting, due to the larger and thicker glass lens, largerhousing and the presence of reflector, compared to indoor LED lampfrom (Navigant Consulting Europe, Ltd., 2009). Table 5 shows the ex-trapolated inventory for raw materials which were then used to inputto SimaPro software in order to simulate manufacturing and operationof the LED streetlight over 60,000 h. Furthermore, required resourcesto process those raw materials during LED manufacture are shown inTable 6.

Stand-alone PV powered streetlight without battery recyclingIn this case, streetlights are assumed to get their power from PV

panels mounted on the same pole as the light fixture itself. Theseare stand-alone systems which are not connected to utility powerlines and are self-sufficient. These systems consist of solar panels pro-ducing direct current (DC) electrical power, batteries to store DC en-ergy, and charge controller/inverter (Solar Street Lighting Systems,2011). Although lead-acid batteries are more commonly used instand-alone PV systems, in simulations for this work, the batterywas assumed to be a rechargeable Li-ion one, since its model is builtin SimaPro. Battery density was assumed to be 170 Wh/kg (Rydhand Sandén, 2005; Tester et al., 2005; Verma et al., 2010). Battery

life was assumed to be 7 years, assuming that average operationaltemperature is 40 °C (Rydh and Sandén, 2005). Battery efficiencywas assumed to be 90% (Verma et al., 2010) and its capacity 3 days,in order to provide additional 2 days power supply during cloudy orsandy days, when PV efficiency drops. Overall system losses wereassumed to be 10% (GE Lighting, 2010) and batteries were assumedto be imported from India, which was found to be the closest batterysupplier in the region.

A multi-crystalline Silicon, 210 Wp PV panel, which is built intothe SimaPro database, was assumed to be the panel to be used. Re-quired panel area was calculated based on the power needs of thelight fixture, system losses and global horizontal irradiation (GHI) inthe UAE. GHI in UAE is about 2360 kWh/Wh/m2 (Alnaser andAlnaser, 2009), performance ratio (PR) is around 0.74 and gain (G)due to panel tilt is estimated to be approximately 1.074 (Goeble,2010). Using this information, PV peak operation time, known asfull load hours, per day can be calculated as (Goeble, 2010):

Full load hours=day ¼ GHI� PR � G365

¼ 5:1h: ð2Þ

Furthermore, it was found that the average weight of multi crystal-line Si PV panel per meter square is around 11.5 kg (Solar BP;Microsol International LL FZE). Table 7 summarizes PV panel specifica-tions used in the simulations.

Table 5Raw material for a 180 W LED lamp streetlight fixture for 60,000 h of operation.

Lamp comp. Item SimaPro material Weight (kg)

Ballast Foam Polyurethane, rigid foam, at plant La×0.069 b

Ballast Inductor Cast iron, at plant L × 0.072 b,c

Ballast Inductor Copper, at regional storage L × 0.048 b,c

Ballast Zener diodes Diode, unspecified, at plant L × 0.0012 b,c

Ballast Capacitors Aluminum, production mix, at plant L × 0.06 b,c

Ballast Resistors Resistor, unspecified, at plant L × 0.12 b,c

Ballast Transistor Transistor, unspecified, at plant L × 0.036 b,c

Housing PCB (Al. machined tooled block) Aluminum, production mix, at plant L × 4.615 b,d

Ballast Wiring Copper, at regional storage L × 0.046 b

Ballast Solder paste Solder, paste, Sn95.5Ag3.9Cu0.6, for electronics industry, at plant L × 0.023 b

Ballast Housing (polypropylene) Polypropylene, granulate, at plant L × 0.808 b

Ballast Integrated circuit Integrated circuit, IC, logic type, at plant L × 0.24 b,e

Ballast PET film Polyethylene terephthalate, granulate, amorphous, at plant L × 0.046 d

Fitting Base Aluminum, production mix, at plant L × 2.52 b,d

Fitting Metal clips Aluminum, production mix, at plant L × 0.692 d

Fitting Wiring Copper, at regional storage L × 0.231 d

Lamp Copper pins Copper, at regional storage L × 0.0023 d

Lamp Base contacts Copper, at regional storage L × 0.009 d

Lamp Base contacts Solder, paste, Sn95.5Ag3.9Cu0.6, for electronics industry, at plant L × 0.005 d

Lamp LED Light emitting diode, LED, at plant L × 0.36 d

Lens Glass Glass tube, borosilicate, at plant L × 0.96 d

Lens Coating Aluminum, production mix, at plant L × 0.012 b

Lens Coating Aluminum, production mix, at plant L × 0.012 b

Housing Estimated d Aluminum L × 0.84 b

Packaging Card Packaging, corrugated board, mixed fiber, single wall, at plant L × 0.069 b

Variable explanation and values are given below f

Transportation L × W × flight/103 Transport, aircraft, freight, intercontinental/RER S (tkm)Transportation L × W × F_L/103 Truck 28 t B250 (tkm)Transportation L × W × AD/103 Truck 28 t B250 (tkm)Production Energy (LEDs ∗ E_d) ∗ L Energy I USA mix 16 (kWh)Operational Energy Natural gas, burned in power plant/ASCC S 10.8 (MWh)

W = 12 kg, estimated weight 180 W LED lamp.F_L = 65.5 km, factory–Boston Airport distance.AD = 38.5 km, Abu Dhabi airport–warehouse distance.LEDs = 180 diodes to produce 180 W LED lamp.E_d = 0.045 kWh to produce 1 light emitting diode.

a L = 2, number of lamps needed during 60,000 h.b Data from Navigant Consulting Europe, Ltd. (2009).c Data from Energy Works.d Data from Hartley et al. (2009).e Data from OSRAM (2009).f Flight = 10,735 km, Boston–AD airport distance.



Considering energy needs of both the luminaire technologies and as-suming 10% losses, required PV panel area and weight, and batteryweight are calculated as shown in Table 8. Inverters are assumed to bedelivered together with PV panels from a factory in Fujairah—UAE,Microsol, which operates a modern cell manufacturing plant in UAEwith an annual production capacity of 150 MW which is expected toincrease to 250 MWbymid 2012 (Microsol International LL FZE).Main-tenance of PV panels is assumed to be by wipe-cleaning, every 10 days,involving a maximum of 1 l of water per meter square of panel(Interview with Lopez CV, 2011). To account for maintenance perpole, we have assumed that a truck with crane (Commercial TruckParts) would pass 250 m of distance, carrying 2 workers and the re-quired quantity of water. Water used for cleaning the PV is desalinated,so “tap water” is used in SimaPro model. Energy for desalinating thisclean water is assumed at 1.8 kWh/m3 of water (International AtomicEnergy Agency (IAEA), 2000). The detailed inventory for stand-alonePV powered streetlight without battery recycling can be found inTable 9.

Stand-alone PV powered streetlight with battery recyclingThe inventory for this scenario is same as the case with stand-

alone PV powered streetlight without battery recycling, with the ex-ception that batteries are assumed to be recycled at an 80% recyclingrate. The closest battery recycling center that accepts internationalrecyclable material was found to be in Frankfurt, Germany (ReduxRecycling GmbH, Germany). Transportation is considered to be oneway, from Abu Dhabi to Frankfurt, involving an intercontinentalcargo flight.

Impact assessment

The results we report in this paper are focused on energy con-sumption, carbon dioxide emissions during manufacture and use, aswell as overall environmental damage assessment. Out of many

different impact assessment methods, Eco-Indicator 99 Hierarchistview (H) was used to compare the impact of the different scenarios.Eco-Indicator 99 (H) considers all possible contributors to an impactif they are backed up by scientific and political bodies widely recog-nized in the environmental community (Baumann and Tillman,2004). Those impacts include carcinogens, respiratory organics, respi-ratory inorganics, radiation, climate change, ozone layer depletion,acidification/eutrophication, eco-toxicity, land use, minerals andfossil fuels. Effects from carcinogens, respiratory organics, respiratoryinorganics, radiation, climate change, and ozone layer depletion arepresented here using the common unit of Disability Adjusted LifeYears (DALY). An additional way of quantifying the impact assess-ment is by use of single score weighting method, which adds up allimpacts into a single number by applying weighting of individualdamaging factors. The single score method can be used to quicklycompare overall impacts of different systems, and it was used to com-pare different scenarios in our analysis.

Fig. 4 compares 250 WCMHand 180 WLED streetlight technologiesin terms of energy consumption (a) and carbon dioxide emissions (b)both for production and the operational life of the lamps. The CMHlight consumes less energy than LED during themanufacturing process,but LED uses about 28% less energy than CMH during its operation.Overall energy needs of LED are about 6% lower than those of CMH. Inlinewith the energy consumption, CMHhasmore CO2 emissions duringuse, while LED contributes more to greenhouse gasses (GHG) duringthe manufacturing phase, which can be seen in Fig. 4(b). These calcula-tions show that CMH streetlight fixture has approximately 8% higheroverall carbon footprint than does the LED fixture.

Overall, LED has a greater environmental impact during themanufacturing phase, while CMH affects the environment more neg-atively during usage, due to its higher energy consumption. Fig. 5 il-lustrates the overall environmental impact, using the single scoremethod, of CMH and LED during manufacturing only (a) and for thewhole life cycle (cradle-to-grave) (b), assuming all fixture parts are100% landfilled. During the manufacturing stage, largest single impactfor LED production comes from fossil fuels and respiratory inorganics,while the impact categories in CMH manufacture are more evenlydistributed, with use of fossil fuels being the largest contributor. Onthe other hand, Fig. 5(b) shows that during the entire life of thelamp, by far, the most significant environmental impact comes fromfossil fuel usage for energy generation needed during lamp operation.Due to its higher energy consumption, CMH lamps have a larger over-all environmental impact during production and use.

CMH and LED streetlight technologies powered from grid andfrom PV stand-alone system, with and without battery recycling,were compared as shown in Fig. 6. PV panels were assumed to bewiped-clean every 10 days, to preserve PV efficiency. Fig. 6 shows en-ergy consumption (a) and CO2 emissions (b) in those three scenariosfor CMH and LED lights. Results show that the system powered bygrid has the lowest energy consumption and CO2 emissions. AlthoughPV power is a renewable source of electricity, producing andtransporting PV panels and their batteries, along with their frequentmaintenance seems to outweigh the benefits of using renewable re-sources in terms of energy consumption and CO2 emissions. Theleast favorable performance was for stand-alone PV-powered street-light without battery recycling. Table 10 shows major emissions to

Table 6Resources to process raw material for LED luminaries system for 60,000 h of operation.Data from Navigant Consulting Europe, Ltd. (2009); and Energy Works.

Lampcomponent

Item SimaPro material Weight (kg)

Ballast Inductor Wire drawing, copper La×0.092Ballast Capacitors Sheet rolling, aluminum L × 0.115Ballast PCB (aluminum machined

tooled block)-housingAluminum productmanufacturing, averagemetal working

L × 4.615

Ballast Wiring Wire drawing, copper L × 0.0462Ballast Housing (polypropylene) Injection molding L × 0.808Ballast PET film Extrusion, plastic film L × 0.046Fitting Base Aluminum product

manufacturing, averagemetal working

L × 2.308

Fitting Metal clips Aluminum productmanufacturing, averagemetal working

L × 0.692

Fitting Wiring Wire drawing, copper L × 0.231

a L = 2, number of LED lamps within 60,000 h.

Table 7Stand-alone PV panel specification used in simulations.

PV panel specifications Value Unit

PV panel peak power (by SimaPro model) 210 WArea of a panel (by SimaPro model) 2.4336 m2

Full load hours per day 5.1 hMulti c-Si PV panel average weight a 11.5 kg/m2

Energy delivered by panel 443 Wh/m2

a Data from (Solar BP, Microsol International LL FZE).

Table 8Stand-alone PV panel area and weight required for CMH and LED lights for 60,000 h ofoperation.

CMH LED Unit

Rated power 250 180 WPanel area to deliver required energy 7.45 5.36 m2

Total PV panel weight 85.7 61.7 kgTotal Li-ion battery weight (3 days capacity) 129.4 93.2 kg



air, water and soil in kg, as a result of manufacture and operation ofCMH and LED streetlight fixtures for all analyzed scenarios. Four gas-ses that are most emitted to air, CO2, SO2, CH4 and NOx, are slightlyhigher for CMH lighting technology than they are for LED lighting.Similarly, emissions to water are higher for CMH, except for silicon,where LED has almost ten times higher emissions, due to silicon usein diode processing. Emissions to soil are negligible and the highestones are oils, where LED has significantly higher contribution.

Impact assessment by single score method for CMH and LEDstreetlight technologies for grid and stand-alone PV power supply(with and without battery recycling) are also compared in Fig. 7.Here, PV-powered lamps with an assumed 80% battery recycling effi-ciency, have the least environmental impact among all compared

systems, with LED having a lower overall impact than CMH. WhilePV-powered lamps with battery recycling didn't register the lowestenergy consumption or CO2 emissions (Fig. 6), it was found to havethe least environmental impact (Fig. 7) after assigning weights to allthe other contributing factors. To further explore these factors,Fig. 8 shows the processes with the largest contributions to the envi-ronmental damage for all investigated cases for CMH and LED street-light technologies. For systems powered by the grid, the largestenvironmental impact comes from burning natural gas, followed byaircraft transportation. For PV stand-alone systems without batteryrecycling, the process with the largest impact is battery production,followed by aircraft transportation. For PV stand-alone systems withbattery recycling, the largest contributor is aircraft transportation,

Table 9Inventory relevant to PV Stand-alone analysis for 60,000 h of operation.

SimaPro Material Value Unit Description

Variable explanation and values are given belowa

PV panel, multi-Si, at plant/RER/I S b P_A m2 PV panel for CMH assuming 5.13 FLH/dayBattery, LiIo, rechargeable, prismatic, at plant/GLO S B_W × B kg 3 day capacity Li-Ion battery for 60,000 hTruck 28 t B250 (B_W × B) × AD/103 tkm Transportation needed for battery from AD-airport to warehouseTruck 28 t B250 PV_D × P_A × PV_M/103 tkm Transport of estimated weight of PV panels, from factory to warehouseTransport, aircraft, freight/RER S B × B_W × ND_AD/103 tkm Battery transport from New Delhi to AD airportTruck 28 t B250 B × B_W × BFA/103 tkm Battery transport from factory to new Delhi airportInverter, 500 W, at plant/RER/I S B p Inverter for stand-alone PVTransport, lorry >16 t, fleet average/RER S (1 + 120) × P_A ×

(60,000/12/clean) aM_dist/103tkm Transportation for PV cleaning assuming 120 kg for workers, 1 l/m2 of PV,

1 l = 1 kg, 250 m distance traveled per pole per visit, and visit every 10 daysTap water, at user/RER S P_A × (60,000/12/clean) kg Amount of water used to clean per panel every 10 days throughout 60,000 h

Electricity/heat Value Unit Description

Natural gas, burned in power plant/ASCC S P_A × (60,000 / 12/clean) /103 × E_desal

kWh Energy used to desalinate water used for cleaning of PV panels

B_W = battery weight (Table 8).M_dist = 0.25 km, assumed 250 m distance to clean panel.Clean = 10, assumed cleaning every 10 days.E_desal = 1.8 kWh/m3, assumed energy for water desalination.AD = 38.5 km, Abu Dhabi airport–warehouse distance.B_life = 7, assuming 33% charge–discharge at operation at 40%.PV_D = 11.5 kg/m2, estimated weight of PV panel per meter square.PV_M = 279 km, estimated distance between PV factory and warehouse.BC = 170 Wh/kg, assumed Li-ion battery capacity (average between 138 and 240).BFA = 40.7 km, battery factory to New Delhi airport distance.ND_AD = 5206 km, New Delhi to Abu Dhabi airport distance.B = 2, number of batteries needed for 60,000 operational hours (~14 years) assuming 7 years of life.I — infrastructure.RER — ecoinvent country code for Europe.S — ecoinvent process type-system.

a P_A = panel area (Table 8).b GLO — ecoinvent country code for Global.

Fig. 4. Energy consumption (a) and carbon dioxide emissions (b) during manufacture and operation of CMH and LED streetlights powered by electricity from grid.



followed by PV production. Overall, the largest contributing processesto the environmental impacts of the systems under analysis are:

• Burning of natural gas for systems powered by grid• Battery production for PV systems• Transportation for all cases, with larger impact for PV stand-alonesystems.

Fig. 9 shows the assessment of damage to human health, in DALYunits, comparing lighting technologies powered by the grid and bystand-alone PV systems, with and without battery recycling. Fig. 10shows the damage assessment in terms of ecotoxicity, acidification/eutrophication and land use. We can see that the major contributorto ecotoxicity along with significant increase in respiratory inor-ganics, climate change and carcinogens, is disposal of batteries aftertheir use in stand-alone PV systems. Furthermore, the case of gridpowered streetlights has the lowest impact on land use and humanhealth, with its largest impact on the increase in respiratory inor-ganics and land acidification.

So far, comparative LCA analysis of CMH and LED streetlight technol-ogies powered by grid or by stand-alone PV systems (with and withoutbattery recycling) identified the three major impact contributors to be:battery production, fossil fuels for operation, and transportation, imply-ing that these should beminimized. In the particular case of streetlightsforminor roads of AbuDhabi, a solution that could potentiallyminimizeall three contributors is a PV-solar power plant to power streetlights.Fig. 11 shows the single-score impact assessment for CMH and LEDlights powered by PV-solar power plant, compared to the same

powered by grid or stand-alone PV system. Solar power plant wasmodeled using a built-in SimaPro process. Results show that havingsolar power plant is slightlymore environmentally friendly than havinga stand-alone PV system with battery recycling, but probably notenough to justify the infrastructure needed for it.

Fig. 5. Impact assessment by single score method for CMH and LED light fixtures during the manufacturing stage (a) and both manufacture and operational life (b) (Hierarchist view).

Fig. 6. Overall energy consumption (a) and carbon dioxide emissions (b) during manufacturing and operation of 250 W CMH and 180 W LED streetlights, comparing the systemspowered by grid and by PV panel, with and without battery recycling.

Table 10Most significant emissions to air and water (kg) due to manufacture and operation ofCMH and LED streetlight for all investigated systems, for 60,000 h of operation.

CMH LED PV with batteryrecycle

PV w/o batteryrecycle

250 W 180 W 250 WCMH

180 WLED

250 WCMH

180 WLED

Emissions to air (kg)Carbon dioxide, fossil 3566 3260 4109 3726 12,126 9501Sulfur dioxide 31 25 11 10 40 31Methane, fossil 18 14 8 7 35 27Nitrogen oxides 10 9 13 12 26 21

Emissions to water (kg)Dissolved solids 220 159 0.54 0.40 0.85 0.62Chloride 188 139 58 47 91 71Silicon 20 243 38 258 64 277Chemical oxygen demand 5 23 – – – –

Sodium, ion 54 42 18 17 21 20Calcium, ion 17 21 10 16 15 20

Emissions to soil (kg)Oils, unspecified 0.58 0.64 2.9 2.3 2.7 2.2



Furthermore, in the light of growing clean water scarcity world-wide, the amount of water used in production and operation stagesof CMH and LED bulbs was analyzed. The results are shown inFig. 12 and indicate that most of the water is consumed in the produc-tion stage. Moreover, LED technology uses significantly larger amountsof water compared to CMH, due to the nature of diode processing incleanrooms. The impact of water consumption is already captured inthe single-score results (Figs. 5, 7, 8, and 10).

Finally, water consumption by CMH and LED powered bystand-alone PV systems was compared to grid-powered streetlight,as shown in Fig. 13. Due to high water consumption in cleanroomsduring PV panel fabrications, grid-powered lights use significantlyless water, compared to PV-powered systems. Battery recycling isfound to decrease water consumption, but it remains 10 foldhigher in water consumption than the lighting system poweredby the grid.

Fig. 7. Impact assessment by single score method for CMH and LED light fixtures, for system powered by grid and by PV panel, with and without battery recycling (Hierarchist view).

Fig. 8. The largest process contributions to environmental impacts of all investigated cases (Hierarchist view).

Fig. 9. Damage assessment on human health for streetlight technologies powered by grid and PV systems with and without battery recycling, (Hierarchist view).



Conclusions

In this work, we compared two streetlighting technologies, CMHand LED, in terms of their environmental impact. Comparative LCAfor 250 W CMH and 180 W LED streetlights powered from the gridshowed that it is environmentally friendlier to use LED streetlights,

since CMH technology uses far more energy during its operationallife. With estimated 117,000 light poles on minor roads of the Emirateof Abu Dhabi, it can be calculated that roughly 2500 tons of CO2

would be saved per year if 180 W LED lights are used instead of250 W CMH lamps. Moreover, stand-alone PV-powered lights werefound to be an environmentally better choice than grid-poweredlights, only if the used batteries are recycled. Even small incrementalbenefits from applying these alternative power supply schemes, willbecome considerable when applied to the entire system of lightingof minor roads of the Emirate of Abu Dhabi.

It was found that factors with the highest environmental impact inthese lighting technologies are battery production (for the PV-powered system) and the usage of fossil fuels for power generation.In PV-powered stand-alone systems with battery recycling, transpor-tation of system components was found to be the highest contributorto environmental impact. Finally, powering these streetlights via acentral PV-solar power plant (instead of stand-alone PV panels)does reduce the environmental impact, although the added benefitswere not very significant and did not justify the infrastructure costs.

Acknowledgments

The authorswould like to thank the staff atMasdar Institute, CristobalVerdu, Mona Abdulla Al Ali and Dr. Ashraf Sadik Hassan, who providedvaluable information needed to complete our inventory analysis. We

Fig. 10. Damage assessment in terms of ecotoxicity, acidification and land use for streetlight technologies powered by grid and PV systems with and without battery recycling,(Hierarchist view).

Fig. 11. Impact assessment by single score method for 250 W CMH and 180 W LED light fixtures powered by PV-solar power plant, compared to power by grid and stand-alone PVsystems (Hierarchist view).

Fig. 12. Water consumption of 250 W CMH and LED technologies, powered by grid,during production and operation stages.



would also like to extend our appreciation to Kenan Jijakli for his help inSimaPro modeling.

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Fig. 13. Water consumption comparison of streetlights powered by grid and by stand-alone PV systems, with and without battery recycling.


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