Lighting in is reported to consume as much as 21% of the total energy use in buildings (Levine et al., 2007), and to account for about 17.5% of global electricity use (Pike Research, 2010). A market shift to energy-efficient alternatives would reduce the world’s electricity demand for lighting by an estimated 18% (UNEP, 2009). Therefore, efficient lighting systems are one of the most important climate change mitigation measures for the building sector. Efficient lighting technologies include energy efficient lamps, ballasts and light fixtures. The requirements to implement efficient lighting system include incorporating natural daylight, zone control, user-control, and dual lighting circuit systems.
Technologies used in modern artificial lamps to emit light include thermal radiators, discharge lamps, and electro-luminescent radiators. Thermal radiators, such as incandescent and halogen lamps are not energy efficient, in general. Lamps that generate light through thermal radiation require energy to heat a material to a high temperatures in order to give off light. Therefore, in addition to emitting light within visible light range, a large amount of radiation is emitted into the surroundings in the form of heat and radiation in other wavelengths. Discharge lamps (e.g., fluorescent lamps) generate light by means of electrical discharge through gases and vapours. They are more energy efficient than thermal radiator lamps. For example, compact fluorescent lamp (CFL) converts some 25% of the energy to visible light, while an incandescent lamp converts only 5% of the energy consumed into visible light, leaving 95% to be emitted as heat (UNEP, 2009).
Electro-luminescent radiators, used in light-emitting diodes (LED), are also energy efficient. LED relies on a semiconductor circuit to convert electrical current into light. This technology is at least ten times more efficient than incandescent lamps.
Different lamp types have different characteristics. The selection of energy efficient light should take into consideration the following criteria: high luminous efficacy (lumen/watt), miniaturisation, longer lifespan, use of recyclable materials, and avoiding hazardous substance (DLS, 2009).
In addition to lamps, ballast and luminaries also play a part in energy efficient lighting. Ballasts help to increase energy performance, such as a dimming function. Luminaries are generally made of reflective materials and in the form of lenses, refractors, louvres or blades to enhance light output by reflecting indirect light to brighten an area, such as surrounding walls, or task surfaces.
Energy efficient lamps. There are two groups of commonly used energy efficient lamps: gas-discharge lamps and LED. Gas-discharge lamps are classified into low-pressure lamps and high-pressure lamps. Low pressure lamps are also called fluorescent lamps. The technology includes linear T5/T8 tubes and CFL. Both are advanced technology with highly energy efficient performance, are compact in size and have a long lifespan. CFLs provide good diffuse light and are often used for downlighting and wall lighting. They can also be used for task lighting. High pressure lamps, also known as high-intensity discharge (HID) lamps, are another type of energy-efficient lamps. They are suitable for illuminating large areas and for outdoor applications. HID metal halide lamps, for example, have very high luminous efficacy and replacement life of up to 9,000 operating hours (Hausladen et al., 2005). PAR metal halide lamps with ceramic arctube enclosures have good colour rendering and can replace halogen lamps for accent lighting. One disadvantage of HID lamps is that they take longer to start. Therefore, they are more suitable for application in spaces requiring long hours of operation, where they are less frequently switched on and off.
LED lamps emit light in a very narrow spectral band but can produce white light that is good for application in daily life environments, such as homes and offices. White light can be formed by mixing individual LED lamps that emit red, green, and blue array, or coating a blue LED lamp with phosphor (Nelson, 2010). LED lamps have very long lifespan of 40,000 to 100,000 operating hours, depending on the colour. In the earlier stage of development, LED lamps had very limited applications, such as exit signs and decorative applications, due to having poor colour rendering index and poor efficacy. However, LED lamp technologies have been greatly improved, now they can be found in a wide range of applications – from landscaping lighting, task lighting, wall wash lighting, retail use spotlights, to lighting for artworks.
Ballasts help to improve lamp efficacy, increase lamp lifespan and reduce power losses. High frequency electronic ballasts help to improve visual performance and eye fatigue. For example, the frequencies range of 20kHz and above provides high quality, non-flickering lighting that reduces strain to the eyes (Nelson, 2010). Dimming electronic ballasts for fluorescent lamps help to reduce energy consumption when bright lighting is not required, i.e., in the space and at the time when daylight is strong.
Light fixtures help enhance the performance of lighting output, improve distribution, control glare, and further increase energy efficiency. A variety of light fixtures designed to accommodate energy efficient lighting have become available in the retail market and for business uses. Examples of energy efficient light fixture applications are:
- Recessed downlights offer a round shape to be used with CFL lamps.
- Linear strip light fixtures are mainly ceiling mounted with or without side reflectors typically used with T8 lamps. It is small in size, low-cost, and easily dimmed. It is most suitable for mechanical rooms, lockers, garages, etc. It can also be used for workplace ceiling lighting.
- Wall sconces are wall mounted for decorative purposes, and can be used for CFL lamps. They can be used on lobby walls, corridors, formal meeting rooms, etc.
- Indirect/direct linear light fixtures can be hung under a ceiling or be wall mounted and are usually used with T5s or T8s. In combination with bright ceiling surface, indirect linear light fixtures can provide soft and comfortable visual effect and are easily dimmed. Indirect linear light fixtures are usually applied in high ceiling spaces, such as classrooms.
A complete energy efficient lighting system includes energy efficient lamps, ballasts and light fixtures. There are at least four main design principles that need to be considered when implementing energy efficient lighting systems.
Use in association with natural daylight. Artificial lighting should be designed and used along with daylight harnessing technologies (see Section 4.7) to reduce energy demand in the first place. For light fittings installed on ceiling areas near windows, spacing for lamps can be further apart. Task lamps can be deployed as supplementary lighting.
Zone control. It is particularly useful to divide spaces of a building into zones of different levels of artificial lighting requirements, and to provide multiple control circuits to facilitate various lighting demand. An example of zone control is to incorporate daylight into zone lighting in corridor or rooms located closed to window areas and installed multiple circuits to enable switching on/off or dimming in response to available daylight.
User controllability and motion sensors. This requirement addresses the wiring of lighting in office buildings, especially in open office layout. The conventional application is to provide one circuit to link many (if not all) light fixtures in a large space together with one or two centralised switch points. This type of application wastes energy and reduces light fixtures’ lifespan in low occupancy hours. Therefore, providing flexibility for user controllability at individual workspaces or smaller workspace zones can save energy. Motion sensors can also be installed so that lighting can be automatically switched off when there are no occupants in the zone.
Dual lighting circuit system: Such system allows alternate lights to be turned off at times when bright lighting is not critical. The suitable areas for this application include garages, residential complex corridors, and landscaping areas. These areas are used substantially less after midnight. Part of the lights can be turned off to save energy. Research shows that a saving of 30% on lighting electricity consumption can be achieved, and the payback period is as short as about 6 months (BCA, 2007).
Feasibility for implementation
Energy efficient lighting technologies are among the technologies that are most feasible to implement at a large scale. This is due to their smaller investment cost, easy and straightforward installation, and the fact that they are a necessity for daily life. With such characteristics, energy efficient lighting technologies can be implemented from both bottom-up and top-down approaches. In a bottom-up approach, individual building/house owners can make a decision to adapt and use energy efficient lighting fixtures with a onetime small investment cost, which will be paid back through savings from energy bills. The decision to switch to energy efficient lighting systems from the bottom-up approach can be facilitated by top-down supporting policies, which include:
- Reducing/removing import tariffs on energy efficient lighting components
- Initiating energy efficient lighting programs which provide or subsidise energy-efficient lighting
- Supporting local manufacturers to produce energy efficient lighting components and systems, to further bring down the costs and to create new local jobs
- Providing public education and campaign programmes to introduce energy efficient lighting technologies and their benefits
- Providing safe disposal of CFLs at the end of their life due to the mercury used in the lamps. One measure is to establish a CFL recycling plant, which can handle mercury and other environmental safety issues.
Energy efficient lighting has been adapted widely, thanks to proven business cases showing its energy saving and return on investment. The Environmental Leader Insight projects that the global market potential for energy efficient lighting is expected to increase from US$13.5 billion to US$32.2 billion from 2010 to 2015, representing a annual growth rate of 19%. It is also projected that the growth will be strongest in commercial lighting from 2010 to 2012, followed by residential lighting from 2012 to 2015. Among the various energy efficient lighting technologies, LED holds significant long-term potential, because LED is at the early stage of market penetration, with costs potentially coming down and with improving technologies leading to wider commercial applications (Pike Research, 2010).
The markets for energy efficient lighting technologies are in both developed and developing countries. In recent years, the markets for energy efficient lighting in developing countries have been growing strongly for three reasons. Firstly, in 2009, the Global Environment Facility, the United Nations Environment Programme and lighting industry partners started Global Market Transformation for Efficient Lighting Project, known as the en.lighten initiative – Efficient Lighting for Emerging and Developing Countries. One of the objectives of the initiative is to phase out incandescent lights worldwide (en.lighten, 2009). The initiative estimates a saving of 409 terawatt hours/year, or 2.3% of global electricity consumption, by replacing all incandescent lamps with CFLs). Secondly, developing countries are implementing programmes to promote CFL, and even distribute them for free. These programmes are often part of rural development strategies, especially in African countries, India and China. Ethiopia’s CFL programme, as detailed in the case study below is an example of such programmes. Thirdly, the costs of CFL and LED have been brought down significantly over years. For example, in South Asia countries, the cost of CFL has dropped from an average of US$12 in the mid-90s to an average of US$3-$5 in 2008 (Goswami et al., 2010).
Implementing energy efficient lighting technologies brings many benefits to environmental protection, and, energy resource conservation. Energy efficient lamps can substantially reduce GHG emissions from lighting buildings. For example, CFL or LED lamps consume one-fifth (or less) of the energy incandescent lamps require for the same illumination capacity and they are approximately 1,000 times more energy efficient than kerosene lamps (Mills, 2005). In terms of lifespan, compared to incandescent lamps, CFLs last eight times longer with a lifespan of up to 8,000 operating hours (Hausladen et al., 2005). LED lamps last 40-100 times longer with a lifespan of 40,000 to 100,000 operating hours depending on the colour.
Energy efficient lighting technologies also improve health and living conditions for building occupants. In rural areas, such as remote villages in Africa and South Asia, the use of CFL and LED technologies as replacements for kerosene lamps will help improve the lighting quality, provide longer study or work hours and reduce the fire risk from kerosene lamp use. In urban areas, the use of high frequency electronic ballasts helps reduce eyestrain and fatigue, increase productivity in workplaces and provide better quality of life.
In terms of economic development, large-scale implementation of energy efficient lighting in least developing regions/countries could potentially form a critical mass to set up local manufacture for lighting component production. This will help create jobs and upgrade skills of the local workforce, and provide cost effective energy efficient lighting fixtures to the local end-users.
The major financial requirement for energy efficient lighting technologies is the initial investment to purchase the products and installation. This cost is normally paid back in a short time period. For example, in India, the estimated payback period of replacing an incandescent lamp with CFL is 1.2 years, and that of replacing a kerosene lamp with CFL is less than a year (Bhattacharya & Cropper, 2010). Compared to CFLs, LED lamps require a higher initial investment, but their long lifespan (up to 10 times of CFL) makes up for the high investment cost. As a rule of thumb, the investment cost for LED light is usually paid off within the first year of use. Maintenance costs are negligible during the lifespan of energy efficient lamps and ballasts.
In general, it is expected that the investment cost for efficient lamps will continue to go down from the continuous technologies upgrades, the increase in mass production capacity through increased market demand, and shifting of component manufacturers to developing and least developing countries.
BCA (2007). Green Building Design Guide – Air-conditioned Buildings. Singapore: Building and Construction Authority.
Bhattacharya S. & Cropper L. M. (2010). Options for Energy Efficiency in India and Barriers to Their Adoption: A Scoping Study. Washington D. C.: Resources for the Future.
DLS. (2009). Green Building Products and Technologies Handbook. Singapore: Davis Langdon & Seah Singapore Pte Ltd.
en.lighten Initiative (2009). Efficient Lighting for Developing and Emerging Countries. [Online]: http://www.enlighten-initiative.org/Portals/94/Final%20English%20Brochur... 
Goswami A., Dasgupta M. & Nanda N. (2010). Mapping Climate Mitigation Technologies and Associated Goods within the Buildings Sector. India: International Centre for Trade and Sustainable Development.
Hausladen G., Saldanha M., Liedl P. & Sager C. (2005). Climate Design: Solutions for Buildings That Can Do More with Less Technology. Munich: Birkhauser.
Levine M., Urge-Vorsatz D., Blok K., Geng L., Harvcey D., Lang S., Levermore G., Mongameli Mehlwana A., Mirasgedis S., Novikova A., Rillig J. & Yoshino H. (2007). Residential and Commercial Buildings. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Metz B, Davidson O. R., Boshch P. R., Dave R. & Meyer L. A. (eds)]. United Kingdom & United States: Cambridge University Press.
Mills E. (2005) The spectre of fuel-based lighting. In Science 308 (27 May) pp. 1263-1264.
Nelson D. (2010). Energy Efficient Lighting. In Whole Building Design Guide. USA: Whole Building Design Guide. [Online]: http://www.wbdg.org/resources/efficientlighting.php 
Pike Research (5 May 2010). LED Lighting Penetration to Reach 46% of the Commercial Building Lamp Market by 2020. [Online]: http://www.pikeresearch.com/newsroom/led-lighting-penetration-to-reach-4... 
UNEP (25 Sep. 2009). Global Phase Out of Old Bulbs Announced by UN, GEF, and Industry (Press Release). [Online]: http://www.unep.org/resourceefficiency/News/PressRelease/tabid/428/langu...