电气093-200909228-邵丽萍 英文原文

G Model ARTICLE IN PRESS ENB-3287;No. of Pages 11Energy and Buildings xxx (2011) xxxxxxContents lists available at ScienceDirectEnergy and Buildingsj ourna l ho me p age: /locate/enbuild ReviewEnergy saving potential and strategies for electric lighting in future NorthEuropean, low energy ofce buildings: A literature reviewMarie-Claude Dubois , ke BlomsterbergInst. of Architecture and Built Environment, Div. of Energy and Building Design, Lund University, P.O. Box 118, SE-221 00 Lund, SwedenPlease cite this article in press as: M.-C. Dubois, . Blomsterberg, Energy saving potential and strategies for electric lighting in futureNorth European, low energy ofce buildings: A literature review. Energy Buildings (2011), doi:10.1016/j.enbuild.2011.07.001a r t i c l e i n f oa b s t r a c tArticle history:Received 28 January 2011Received in revised form 10 June 2011Accepted 3 July 2011Keywords: Ofce LightingDaylight harvestingOccupancy controlsManual or automatic dimming Potential electricity savings IlluminanceWindowsShading devicesReectanceThis article presents key energy use gures and explores the energy saving potential for electric lighting in ofce buildings based on a review of relevant literature, with special emphasis on a North European con- text. The review reveals that theoretical calculations, measurements in full-scale rooms and simulations with validated lighting programs indicate that an energy intensity of around 10 kWh/m2 yr is a realistic target for ofce electric lighting in future low energy ofce buildings. This target would yield a signicant reduction in energy intensity of at least 50% compared to the actual average electricity use for lighting (21 kWh/m2 yr in Sweden). Strategies for reducing energy use for electric lighting are presented and dis- cussed, which include: improvements in lamp, ballast and luminaire technology, use of task/ambient lighting, improvement in maintenance and utilization factor, reduction of maintained illuminance levels and total switch-on time, use of manual dimming and switch-off occupancy sensors. Strategies based on daylight harvesting are also presented and the relevant design aspects such as effects of window char- acteristics, properties of shading devices, reectance of inner surfaces, ceiling and partition height are discussed. 2011 Elsevier B.V. All rights reserved.Contents1.Introduction: energy use in ofce buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .002.Energy saving potential and strategies for ofce lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .002.1.Actual energy use for ofce lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .002.2.Energy saving potential for ofce lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .002.3.Strategies to reduce energy use for lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .002.3.1.Strategies related to electric lighting installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .002.3.2.Strategies related to daylight harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .003. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 001. Introduction: energy use in ofce buildingsCommercial buildings, and primarily ofce buildings, are classied among the buildings presenting the highest energyconsumption. The total annual energy use in ofce buildings varies in the range 1001000 kWh/m2 yr, depending on the geographic location, use and type of ofce equipment, opera- tional schedules, type of envelope, use of HVAC systems, type of lighting, etc. 1. In Northern Europe, ofce energy inten- sity lies in the range 269350 kWh/m2 yr and for ofces all over Europe, it is about 306 kWh/m2 yr, with mean electricAbbreviations: CFL, compact uorescent lamp; DLQ, designers lighting quality;EEG, electroencephalography; HF, high frequency; LCD, liquid crystal display; LED,index 150 kWh/m2yr and mean fuel index 158 kWh/m2yr 2.light emitting diodes; LENI, lighting energy numeric indicator (kWh/m2 yr); LOR, light output ratio; LPD, lighting power density (W/m2 ); MF, maintenance factor; NPD, normalised power density (W/m2 100 lx); U, utilance; WWR, window-to-wall ratio. Corresponding author. Tel.: +46 46 222 7629.E-mail address: marie-claude.duboisebd.lth.se (M.-C. Dubois).Recently, an inventory of energy use in 123 Swedish ofcebuildings of different age revealed that ofce buildings have an energy intensity of 210 kWh/m2 yr in average, with a high elec- tricity use by square meter (93 kWh/m2 yr excluding heating) 3,4.0378-7788/$ see front matter 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.enbuild.2011.07.001NomenclatureEtask illuminance on the task area (lx)Swindow window area (m)Soor oor area (m)Greek letterslumluminous ux emitted by the luminaire (lm)lampluminous ux emitted by the lamp (lm)TALuminous ux reaching the task area (lm)calculated as the power density divided by the mean maintained illuminance on a reference plane is a more interesting metric since it allows a simple and straightforward comparison between dif- ferent spaces with different illuminance requirements. Depending on room size, room surface reectance, light source and the appli- cation, actual target NPD-values for efcient lighting installations with uorescent lamps and a high degree of installation mainte- nance should be 1.92.3 W/(m2 100 lx) 14.Assuming, for example, a task illuminance (Etask ) target of 500 lx, we obtain:LPD = NPD Etask = 1.92.3 W/(m2 100 lx)2The recent 2010 Energy Performance of Buildings Directive(EPBD) places a high demand on building professionals to pro- 500 lx = 9.511.5 W/m(1)duce (and eventually retrot) ofce buildings to near-zero energy use levels. The good news is that according to previous research, modern ofce buildings have a high energy savings potential 5,6. Electric lighting is one area where energy savings are possible at reasonable cost in new buildings as well as in retrot projects. One recent study 7 indicated that investments in energy-efcient lighting is one of the most cost-effective ways to reduce CO2 emis- sions and many studies show that electricity use for lighting could be reduced by 50% using existing technology 8,9.This article explores the potential and strategies for energy sav- ings in ofce lighting including control systems mainly in Northern Europe with some specic information from Sweden. The article is based on a literature review carried out as part of the Swedish project Energy-efcient ofce buildings with low internal gains: simulations and design guidelines.2. Energy saving potential and strategies for ofce lighting2.1. Actual energy use for ofce lightingGlobally, lighting is an important issue in minimizing over- all energy consumption 10. In Sweden, for example, lighting accounts for around 10% of total energy consumption in the coun- try, and this area offers considerable potential for energy savings 11.In commercial buildings, lighting constitutes generally 2045% of electricity demand 6 but it varies a lot from one building to another and the consumption of electric lighting can sometimes be as much as 40% of the gross energy consumption in some build- ings 8. The most signicant environmental impact (8090%) of lighting is generated during the operation of the lighting system; the cost of an electric lighting installation typically represents only15% of total costs, while electricity use during operation repre- sents around 70% of total costs 12. In Sweden, lighting normally accounts for 2530% of electricity use in non-residential premises 4,12,13. The recent inventory of 123 ofce buildings of vary- ing age by the Swedish Energy Agency 4 revealed an average energy intensity of 21 kWh/m2 yr for ofce lighting and an aver- age installed lighting power density (LPD) of 10.5 W/m2 , which varies according room type: 13.1 W/m2 for individual ofce rooms,12.4 W/m2 for landscape ofces, and 8.6 W/m2 for common rooms(including corridors). Note that in 1990, ofce electric lighting was30 kWh/m2 yr in Sweden; a reduction of around 9 kWh/m2 yr has thus occurred in 20 years 3. Average LPDs of 711 W/m2 is achiev- able using efcient lamp circuits (based on T8 i.e. 26 mm uorescent tubes and standard electronic high frequency ballasts) for general ofce lighting of 300500 lx see 14.Regarding the average LPD, Hanselear et al. 10 noted that this widely used indicator does not take into account the requirement for the mean illuminance. According to these authors, the nor- malized power density (NPD, expressed in W/m2 100 lx), which isThese values are in line with the values measured in the recentSwedish inventory reported earlier 4.2.2. Energy saving potential for ofce lightingAccording to Borg 15, an existing ofce (in Sweden) uses around 23 kWh/m2 yr for electric lighting whereas a modern advanced installation may only use 11 kWh/m2 yr. If occupancy and daylight sensors are integrated in the installation, the annual energy consumption for lights may come down to as low as5 kWh/m2 yr.Recently, Blow-Hbe 9 investigated the daylight availability and electricity use for lights in ofces located in Gothen- burg, Sweden, through simulations using the validated programs Rayfront/RADIANCE and DAYSIM. The study included single-cell and open-plan ofces with three different fac ades (30, 60 and 100% window-to-wall ratios). Assuming a LPD of 12 W/m2 , annual elec- tricity use for lighting was calculated to be 28 kWh/m2 yr if the lights were switched on 9 h/day, 5 days/week. Assuming manual light switching, with a mix of active and passive users, the elec- tricity use obtained dropped to 2023 kWh/m2 yr. With a perfectly commissioned photosensor dimming system, and mixed users, lighting electricity use obtained was in the range 1118 kWh/m2 yr. This study thus demonstrated by simulation that it is possible to cut down electricity use for ofce lighting by about 50% (from 23 to 11 kWh/m2 yr) using existing technology, and in comparison to a case with manual on/off switch near the door.In other countries, Santamouris et al. 16 reported the ndings of a large monitoring campaign in 186 ofce buildings in Greece, where the specic energy consumption of the buildings for heat- ing, cooling, and lighting purposes, as well as the consumption for ofce equipment were monitored. The data for electric light- ing showed average energy use ranging from 15 to 25 kWh/m2 yrdepending on type of building. Around 50% of the buildings pre- sented a lighting consumption inferior to 11 kWh/m2 yr while for the majority of buildings (86%), the consumption was less than20 kWh/m2 yr.The European standard EN-15193 17 presents LENI (Light- ing Energy Numeric Indicators) prescribing installed LPD for small individual ofce rooms of 10 W/m2 with preferable target around8 W/m2 (for normal illuminance levels for ofces). Taking intoconsideration a reference annual time of use (2500 h) and vari- ous lighting control strategies, the calculated annual energy use ranges from 20 to 7 kWh/m2 yr, which shows the large potential for energy savings through control strategies (up to 65% reduction). For large ofce rooms (12 m2 ), this standard recommends an installed LPD under 12 W/m2 with preferable target under 10 W/m2 , which results in annual energy use in the range 3017 kWh/m2 yr depend- ing on the selected lighting control strategy (see Table 1). A combination of occupancy sensors and daylight dimming provides the lowest energy intensity values.G Model ARTICLE IN PRESS ENB-3287;No. of Pages 11M.-C. Dubois, . Blomsterberg / Energy and Buildings xxx (2011) xxxxxx11Table 1Guidelines for installed LPD (W/m2 ), reduction factors and LENI (kWh/m2 yr).Type of roomLPD (W/m2 ) Reduction factor LENI (kWh/m2 yr)Individual ofce rooms (10 m2 )Manual control Absence/presence controlDaylight control Manual control + Absence/presence control+ Daylight controlObl.100.80.750.5620158Pref.80.80.750.5616127Large ofce rooms (12 m2 )Obl.1210.900.77302721Pref.1010.900.77252317CorridorObl.810.750.5720159Pref.610.750.5715116These various sources indicate that it is possible to achieve energy savings of the order of 4565% depending on room type and control strategy, and this, with existing technology. Loe 14 also presented detailed calculations showing that 50% savings are pos- sible when an installation has a task and building lighting approach and is controlled to provide illumination only when needed1 ; he also demonstrated with simple calculations that it is likely that greater savings are achievable.Also worth noting: besides direct electricity savings due to reduced use of lights, indirect energy savings can also be obtained because of the reduced heat production and cooling needs 10,18. However, in cold climates, there might be an increase in energy use for heating, which is likely to be smaller than the electricity savings. The next section examines the strategies to implement in order to reach such low energy intensities.2.3. Strategies to reduce energy use for lightingStrategies to reduce energy use for electric lighting in ofces include:1) Strategies directly related to the electric lighting installation: Improvement in lamp technology; Improvement in ballast technology; Improvement in luminaire technology; Use of task/ambient lighting; Improvement in maintenance factor; Improvement in utilance or utilization factor; Reduction of maintained illuminance levels; Reduction of switch-on time; Occupancy sensors and/or manual/automatic dimming.2) Strategies related to daylight harvesting: Effect of latitude and orientation; Effect of window characteristics; Effect of shading devices; Effect of reectance of inner surfaces; Effect of ceiling height; Effect of partition height.The next sections discuss each strategy in detail. An overview of the related energy savings is presented at the end (see Table 2).2.3.1. Strategies related to electric lighting installations. Improvement in lamp technology. Although T5 uorescent lamps have existed for 15 years, recent statistics (for Sweden) 4 indicate that many existing lighting installations still use T8 or even, older T12 lamps, which have a much lower luminous1 In his calculations, about half the savings were due to the task/ambient lighting approach and about half to the controls applied to the task/ambient lighting system.efcacy (lm/W). Replacing T12 with T8 lamps can save up to 10% of the energy consumption while giving 10% more light 19. Newer T516 mm lamps have even higher efcacies (90104 lm/W) achieving a 40% reduction in energy use (compared to T12 lamps of 60 lm/W with magnetic ballasts) but these lamps need different ttings 13,19. Note that the replacement rate of lighting systems is low, e.g. about 3% per year in Sweden, which implies that it takes about33 years to replace old lighting installations with new, energy- efcient ones 13. Since 1995, not even 40% of lighting installations have been changed and it will take another 20 years before the potential for energy savings is fully exploited 13.Recent statistics for Sweden show that uorescent lamps with conventional ballasts represent nearly half (46%) of the installed electric lighti