Ans: Today in India, the per capita availability of energy is much less than the energy in
developed countries. The demand for energy is always out placing availability, the shortfall being
ten percent per annum. The present cost of thermal power is about Rs. 4.00crores 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. 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
(i) 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.
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.
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.
(ii) 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.
Fur commercial interiors, from the energy saving point of view, 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.
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.