Electric Lighting - Energy Conservation PDF

12. ENERGY CONSERVATION 12.0 SYNOPSIS Today in India the per capita availability of energy is much less than the energy in developed countries. The demand for energy is always outplacing availability, the shortfall being ten percent per annum. The present cost of thermal power is abou...

12. ENERGY CONSERVATION 12.0 SYNOPSIS Today in India the per capita availability of energy is much less than the energy in developed countries. The demand for energy is always outplacing availability, the shortfall being ten percent per annum. The present cost of thermal power is about Rs. 4.00 crores per MW and the others are higher. So, to tackle this demand of power, an enormous amount of investment is necessary. A review of the entire situation demands that to overcome the grim situation, some useful immediate measures have to be taken. One of the most fundamental step is to find the possibilities of conservation of energy by all means. In India 17% of the total energy is consumed by lighting. So, with careful measure, it is possible to achieve a substantial amount of energy saving in artificial lighting. Energy conservation practice, can provide equivalent or improved visual performance and visual comforts while producing substantial energy and power savings. Referring back to the time when incandescent lamps gave way to fluorescent lamps in commercial buildings", other trends such as rising urban land costs, the advent of building air-conditioning systems and low cost electricity combined to eliminate daylight as an essential element in building design. Any lighting system with an energy conservation objective and with the intention of providing increased productivity and safety should comply with six basic rules in order to produce the most cost effective results. Use of the most efficient light source practicable. Use of the lamp light output efficiently. Maintain lighting equipments in good order. Use well designed energy effective lighting schemes. Control the switching operation and usage of the lighting installation. Consider the utilization of daylight and the effect of the surrounding décor 12.1 Efficient light Source The need is clearly, to use the type of lamp which gives the maximum amount of light (lumens) for each watt of electrical energy consumed, consistent with the colour rendering and other needs of the installation For lighting, the commonly used light sources are incandescent, fluorescent lamps, T5 fluorescent lamps, CFL, high pressure mercury (HPMV), metal halide lamps and high pressure sodium vapour (SON) lamps, and the the LED lamps. The high pressure sodium vapour lamp is undoubtedly a very efficient light source. This high efficacy lamp is ideal for all applications where colour rendition is not important.. But due to poor colour rendering index , they are being replaced by high luminous efficacy metal halide lamps except in general road highways and some rail yards. Modern T5 lamps are available with luminous efficacies ranging from 90 to 104 Lumens/watt and are now preferred for use in indoor lighting in offices, street lighting and in railway platforms. Future holds a lot of potential for LED lighting. Already street light luminaries with luminous efficacy of 120 Lumens/watt are available which are most energy efficient. In India, many industries still use incandescent lamps because of their low cost. Vast amount of savings in energy are possible by replacing the high wattage incandescent lamps with CFLs or appropriate fluorescent luminaries. 68  Two types of fluorescent lamps are available in our country, namely the cool daylight (colour 54) with a colour temperature of 6500° K and the white (colour 33) with a colour temperature of 4300°K. The white fluorescent lamp gives 14% more light than the cool daylight fluorescent lamp and thus for the same illuminance a 14% saving of energy is possible, although the colour rendition of cool daylight fluorescent lamp is better than that of the white fluorescent lamp. The modern T5 lamps have even better luminous efficacy than the cool daylight and the white fluorescent lamps and are ideal for replacement. For home lighting, the incandescent lamp can be conveniently replaced by CFL. In the recent years, developments in the field of low wattage gas discharge lamps and High Frequency, Electronic lighting have changed the situation dramatically. The new generation 'fluorescent HF electronic lamps have achieved a luminous efficacy of more than 100 lumen power Watt. These lamps operate on a frequency of more than 25kHz and give exceptional performance. The important features of these lamps are Instant starting, Superb colour appearance with high colour rendering index. No stroboscoplc effects. - Excellent lumen maintenance, and Wide temperature range. These lamps on HF electronic circuits are suitable for initial and conversion projects in a wide range of commercial and industrial applications. In streetlighting, the preferred light sources are HID metal halide lamps and T5 lamps with wide angle reflectors. The latest developments are LED luminaries. 12.2 Efficient Use of lamp light output It is all too common in many lighting installations to see instances of energy wastage with consequent total money-wastage due to poor quality or inefficient luminaries for either commercial, industrial, or road light use, purchased possibly on the grounds only of less capital cost Generally, provided that the light distribution is acceptable and care is taken to reduce glare, the light output ratio is a reasonable indicator of efficiency. In addition to the photometric efficiency account should be taken of the power consumed by the luminaire control gear, e.g. ballast. The total wattage consumption of any discharge lamp circuit is always greater than the rated wattage of the lamp at a given reference voltage. The power loss in the control gear is dissipated as heat within the luminaire causing problem there. The amount of the power lost in this, way depends on the design and the quality of the components used. In a large installation, watt-loss may represent a significant waste of money. Lighting equipments should be checked as to the control gear losses before purchase. Fur commercial interiors, from the energy saving point of view, the ideal solution would be to use the fluorescent lamps without any screening louvre or diffuser. However, from the point of view of illumination engineering, this is not advisable because bare lamps give rise to considerable amount of discomfort glare. lt is therefore, necessary to use louvres/diffusers, not only to screen the lamp from view in order to reduce glare, but also to give a aesthetic appearance to the room. The types of louvres/diffiusers normally used are - metallic louvre, clear polycarbonate diffuser , translucent diffuser and opal acrylic diffuser.. 69  Use of some kind of louvre or diffuser will depend on the aesthetic requirement and the extent of glare. But the use of these could be limited to minimum possible areas. In air- conditioned interiors, it found that substantial savings in energy can be achieved by integration of lighting and air-conditioning system. For industrial Interiors where decorative appearance is not important, the fluorescent lamps are normally used with through type reflectors, For mounting heights of 7m and above the work plane it is found that the use of highway luminaires with metal halide lamps are many times preferable. For street lighting, the design of the luminaire is very important. This is because only by proper design of the luminaire it is possible to ensure that maximum light leaches the road surface.. In streets of rural areas and side streets , street lighting luminaires with fluorescent lamps are used. As earlier discussed (2’ x 4 Nos) T5 fittings with reflector are very suitable even though single or twin 4’ T5 lamps are also suitable. 12.3 Maintenance of Lighting Equipments Poor maintenance and the accumulation of dirt and dust reduces the useful light output and so in effect increase the cost of the light provided and results in waste of energy. Lighting systems operate efficiently only when they are properly maintained.. If lighting strategies are planned with more efficient light sources then, because of fewer points, The maintenance schedule can be improved. To cite an example, study of a fluorescent lighting system was made, where different maintenance procedures were in use. The result showed that, When luminaries.were cleaned and relamped once every three years, the illumination dropped to 60% of the Initial value after three years. When luminaires were cleaned every one and half years and relamped every three years, the illumination level dropped to 68% of the initial value after three years. When luminaries were cleaned once a year and one third of the lamps replaced once a year, the illumination level dropped to 78% of the initial value after three years Lighting schemes are sometimes designed with equipments which is difficult to keep clean and allowances are made. In lighting calculations to allow for lack of maintenance, typically, up to 20% extra luminaires, are installed. 12.4 Use of well designed energy effective lighting schemes While designing lighting schemes, the illumination level should be chosen according to the task involved. The lighting scheme should be designed for an average level and then maintained at that level. It is uneconomic to design a lighting scheme for a higher level and then let it deteriorate to an average level for lack of proper maintennce. This involves wastage of energy and should be avoided. The effect of aesthetic considerations in lighting scheme should be fully evaluated in terns of energy costs and other parameters. For major new building developments an Integrated Environmental Design Concept, where the total energy requirements of the building are considered from the above point of view should be made: Orientation of the buildings Surface to volume ratio of the building Size of windows and glazing 70 12.5 Control of switching operations By having a flexibility in the switching arrangement a situation is avoided where due to certain reasons a work area changes to a non- working area and yet has the same illumination level as before, thus involving wastage of-energy. Switching operations of Artificial Lighting are, Mannual on/off Mannual dimming Automatic on/off Automatic stepwise control Automatic dimming For street lighting, after traffic has died down at night. it may not be necessary to provide high illumination levels and can be reduced by selectively switching off the luminaires. However, The luminaire arrangement must be so designed that selectively switches off the lamps and will not affect the uniformity. For outdoor lighting in general, It is advisable to use photo-cell switches to switch off/on the lights instead of using time switches. Even a single hour saving per day can result in tremendous annual savings of energy. 12.5 Utilization of daylight and the effect of the surrounding décor The surrounding decor can significantly affect the energy effectiveness of an interior lighting installation. The lighter the surface decor, the higher the reflection factor; less energy is therefore required for a given lighting result than when a darker decor is used. The relationship between the surface reflection factors and the luminaire photometric characteristics does to some extent, influence glare and therefore quality of the lighting result. Nevertheless, the objective should be to use surface reflectances which are as high as practicable. Use of daylight in buildings allows for some reduction of electricity for lighting purpose and thereby reduces the consumption of energy in buildings. The extent of this, however, shall depend on a number of variables, such as the availability of daylight and orientation of the bui1ding, size and location of light openings, level of lighting required. This is particularly advantageous because windows are typically located in the side walls of the room. Our basic aim of keeping the use of daylight is to achieve an aesthetically pleasant environment in which the occupants can see efficiently and comfortably. Thermal environment produced in the interior space as a result of daylight is a factor to be taken care of. Also the placement and variety of windows and other openings in a building also have significant effects on the passage of natural ventilation. 12.7 Role of Energy Management The fundamental objective of management is to avoid energy waste in a cost effective manner. The task of designing new energy/cost effective lighting schemes or the identification of energy/costs saving opportunities by converting existing lighting installations is frequently regarded as the responsibility of the engineering function. In practice, good energy management requires the assistance and co-operation of many other management and operational disciplines within the energy using organization. The best overall result can only be achieved by the coordination of Engineering , Finance, Purchasing, Administration and operational Staff at all levels. In conclusion it can be stated 71 that even with the limited resources indigenously available, it is possible to achieve substantial amount of energy saving if the lighting products and the lighting design are energy effective. The majority of existing lighting installations can be improved by adopting more efficient equipment and improved application techniques. Some conversions require very little investment to obtain substantial benefits. In other cases, investment in new equipment may be needed and evaluation of the capital Investment required against the operational savings is necessary. Experience has shown that in most of the cases, the pay back period has been quite short, often less than 3 years. Sometimes, it has been found that an increase in capital or replacement cost resulted in a significant reduction in the installed load for lighting. Many organizations have benefited from the approach of energy effective lighting; they have either saved power for other uses or improved their hitherto poor lighting without any additional power. -------------------------------------- 72