Artificial lighting accounts for a significant part of all electrical energy consumed worldwide. In offices, from 20 to 50 percent of the total energy consumed is due to lighting. Most importantly, for some buildings over 90 per cent of lighting energy consumed can be an unnecessary expense through over-illumination. Thus, lighting represents a critical component of energy use today, especially in large office buildings and for other large scale uses where there are many alternatives for energy utilisation in lighting.
There are several techniques available to minimise energy requirements in any building:
a) identification of lighting requirements for each area
This is the basic concept of deciding how much lighting is required for a given task. Lighting types are classified by their intended use as general, localised, or task lighting, depending largely on the distribution of the light produced by the fixture. Clearly, much less light is required for illuminating a walkway compared to that needed for a computer workstation. Generally speaking, the energy expended is proportional to the design illumination level. For example, a lighting level of 800 lux might be chosen for a work environment encompassing meeting and conference rooms, whereas a level of 400 lux could be selected f or building corridors:
●general lighting is intended for the general illumination of an area. Indoors, this would be a basic lamp on a table or floor, or a fixture on the ceiling. Outdoors, general lighting for a parking area may be as low as 10 − 20 lux since pedestrians and motorists already accustomed to the dark will need little light for crossing the area
●task lighting is mainly functional and is usually the most concentrated, for purposes such as reading or inspection of materials. For example, reading poor quality print products may require task lighting levels up to 1500 lux, and some inspection tasks or surgical procedures require even higher levels.
b) analysis of lighting quality and design
●the integration of space planning with interior design ( including choice of interior surfaces and room geometries) to optimise the use of natural light. Not only will greater reliance on natural light reduce energy consumption, but will favourably impact on human health and performance
●planning activities to optimise the use of natural light
●consideration of the spectral content required for any activities needing artificial light
●selection of fixtures and lamp types that reflect best available techniques for energy conservation.
Types of electric lighting include:
●Incandescent light bulbs: an electrical current passes through a thin filament, heating it and causing it to become excited, releasing light in the process. The enclosing glass bulb prevents the oxygen in air from destroying the hot filament. An advantage of incandescent bulbs is that they can be produced for a wide range of voltages, from just a few volts up to several hundred. Because of their relatively poor luminous efficacy, incandescent light bulbs are gradually being replaced in many applications by fluorescent lights, high intensity discharge lamps, light-emitting diodes (LEDs), and other devices
●arc lamps or gas discharge lamps: an arc lamp is the general term for a class of lamps that produce light by an electric arc (or voltaic arc). The lamp consists of two electrodes typically made of tungsten which are separated by a gas. Typically, such lamps use a noble gas ( argon, neon, krypton or xenon) or a mixture of these gases. Most lamps contain additional materials, such as mercury, sodium, and/or metal halides. The common fluorescent lamp is actually a low pressure mercury arc lamp where the inside of the bulb is coated with a light emitting phosphor. High intensity discharge lamps operate at a higher current than the fluorescent lamps, and come in many varieties depending on the material used. Lightning could be thought of as a type of natural arc lamp, or at least a flash lamp. The type of lamp is often named by the gas contained in the bulb including neon, argon, xenon, krypton, sodium, metal halide, and mercury. The most common arc or gas discharge lamps are:
○ fluorescent lamps
○ metal halide lamps
○ high pressure sodium lamps
○ low pressure sodium lamps.
The electric arc in an arc or gas discharge lamp consists of gas which is initially ionised by a voltage and is therefore electrically conductive. To start an arc lamp, usually a very high voltage is needed to 'ignite' or ' strike' the arc . This requires an electrical circuit sometimes called an 'igniter', which is part of a larger circuit called the 'ballast'. The ballast supplies a suitable voltage and current to the lamp as its electrical characteristics change with temperature and time. The ballast is typically designed to maintain safe operating conditions and a constant light output over the life of the lamp. The temperature of the arc can reach several thousand degrees Celsius. An arc or gas discharge lamp offers a long life and a high light efficiency, but is more complicated to manufacture, and requires electronics to provide the correct current flow through the gas
●sulphur lamps: the sulphur lamp is a highly efficient full spectrum electrodeless lighting system whose light is generated by sulphur plasma that has been excited by microwave radiation. With the exception of fluorescent lamps, the warm-up time of the sulphur lamp is notably shorter than for other gas discharge lamps, even at low ambient temperatures. It reaches 80 % of its final luminous flux within twenty seconds (video), and the lamp can be restarted approximately five minutes after a power cut
●light emitting diodes, including organic light emitting diodes (OLEDs): a light emitting diode (LED) is a semiconductor diode that emits incoherent narrow spectrum light. One of the key advantages of L ED-based lighting is its high efficiency, as measured by its light output per unit of power input. If the emitting layer material of an LED is an organic compound, it is known as an organic light emitting diode (OLED). Compared with regular LEDs, OLEDs are lighter, and polymer LEDs can have the added benefit of being flexible. Commercial application of both types has begun, but applications at an industrial level are still limited.
Different types of lights have vastly differing efficiencies as shown in Table 3.27 below.
The most efficient source of electric light is the low pressure sodium lamp. It produces an almost monochromatic orange light, which severely distorts colour perception. For this reason, it is generally reserved for outdoor public lighting usages. Low pressure sodium lights generate light pollution that can be easily filtered, contrary to broadband or continuous spectra.
Data on options, such as types of lighting, are available via the Green Light Programme. This is a voluntary prevention initiative encouraging non-residential electricity consumers ( public and private), referred to as ' Partners', to commit to the European Commission to install energy efficient lighting technologies in their facilities when (1) it is profitable, and (2) lighting quality is maintained or improved.
c) management of lighting
●emphasise the use of lighting management control systems including occupancy sensors, timers, etc. aiming at reducing lighting consumption
●training of building occupants to utilise lighting equipment in the most efficient manner
●maintenance of lighting systems to minimise energy wastage.
這是決定ㄧ項工作需要多少照明的基本觀念。照明型式以其使用區別可分為：ㄧ般照明、場所照明及工作照明三種，視燈具照度分布而定。顯然地，走道需要亮度和電力工作站亮度就有不同。ㄧ般來說，照明所須能量與其設計照明亮度水準是成正比的，如工作環境中的會議室亮度水準有800 lux，建物的走道用400 lux就可以。
Certain types of lamps, e .g. mercury vapour, fluorescent, contain toxic chemicals such as mercury or lead. At the end of their useful life, lamps must be recycled or disposed of correctly.
Techniques such as the identification of illumination requirements for each given use area, planning activities to optimise the use of natural light, selection of fixture and lamp types according to specific requirements for the intended use, and management of lighting are applicable to all IPPC installations. Other measurements such as the integration of space planning to optimise the use of natural light are only applicable to new or upgraded installations.
The Green Light investments use proven technology, products and services which can reduce lighting energy use from between 30 and 50 %, earning rates of return of between 20 and 50 %.
Energy Efficiency (2009) 3.10