Best options to light up homes and offices
by Harsha Wickramasinghe
Different lamp types have different uses. Last week’s series discussed the many types of lamps available in town, with particular reference to their efficiencies. Hence, this week’s series would extend the discussion by analysing the many options of using these lamps under different lighting requirements.
The behaviour of light
Light is emitted by light sources. The Sun and the stars in the faraway skies and the lamps in your home are both light emitting sources. If light hits a mirror, it is reflected. If it hits a black surface it is absorbed. Coloured objects on the other hand, fall in between these two and therefore absorb a portion of light and reflects the remainder. The light our eyes grasp or ‘see’ is actually this reflected portion of light.
Daylight harnessing
A window with clear glass planes in your home would let in natural light. It is of course a very common observation, but science holds a brighter explanation to express this phenomenon. Light, apart from being absorbed and reflected, can also be transmitted. Transparent material (i.e., material which lets light pass through completely) and translucent material (i.e., material which lets only a faction of the light pass through), such as glass and plastics are capable of transmitting light. Hence, the simple window at home is actually an ingenious lighting device which transmits sunlight indoors, at the same time cutting short Nature’s vagaries like the scorching heat, cold and dust.
Since daylight harnessing does not incur any operational cost, windows and even roofing material ranging from glass tiles to translucent corrugated sheets have been used in the construction industry for many a decade to illuminate enclosures during day time. Another way to use daylight is to have daylight shafts where light is taken through a skylight and channelled towards a reflective surface, rendering a pleasant light in enclosed spaces. The best example for this in Sri Lanka is the guest rooms of Hotel Ranwali.
However, one must be careful in letting in sunlight to air-conditioned spaces. If not, the sunlight streaming into a room would cause the cooling system to work on a higher key, thereby increasing the energy bills in many folds.
With the escalation of energy costs, newer ways of harnessing daylight have been invented. A simple pipe having mirror like reflective surfaces built-in, has been used as a duct to convey light from a roof top to a work floor, effectively replacing the many day time light fixtures. The light tube is fashioned in such a manner, that it has a hemispherical light inlet at roof level and a suitable diffuser at the task end – resembling a common luminaire. This device has been further streamlined by incorporating an additional component capable of sensing the prevalence or the absence of sunlight up above, and accordingly switching on an electric back up lamp in response.
Advanced research on daylight harnessing has rendered special material capable of greatly cutting off heat emitted by the device, which in turn has also encouraged the increased usage daylight harnessing options in modern building designing. Yet another innovation in the optical fibre technology that enables an enclosed room to capture sunlight elsewhere and channel it to specific locations, even as far as many floors below the point at which daylight is harnessed – often the rooftop.
The cardinal principle in harnessing daylight in less developed countries like ours lies in the usage of colour within buildings. Colours of walls, ceilings, floors and even curtains really matter in daylight utilisation. Lighter the shade, better the efficiency of daylight utilisation. This is due to the ability of lighter colours to reflect more light than darker colours.
Hence, make it a point to select appropriate colours and drapery during the coming festive season.
Strategic Lighting Choices
When choosing lamps, most of us are in the practice of considering the aesthetic appeal but energy implications.
Not all rooms in home are equally occupied. As in the general case, we tend to occupy certain rooms more whereas others tend to be less occupied. This also depends on the lifestyle of the individual as well as the family as a whole. Therefore it is important to identify the proper lamp types that best fit the lighting requirements of a given room.
Given below is a simple guide to help identify suitable options.
Hours of use – In case you wish to replace lighting equipment in your home, please consider the following. Opt to use linear fluorescent lamps (LFLs) in places where lamps are burnt more than 3 hours a day. It is cheaper and more efficient than using an incandescent lamp for the purpose. Compact fluorescent lamps (CFLs) can be used in locations where aesthetic appeal is of prime concern, like that in the living room. Incandescent lamps may be retained in locations where lighting is used sparingly, like that in toilets, store rooms…etc.
Location factor – If aesthetics matter, go for warm white LFLs or CFLs. Even tulip shaped CFLs, suitable for chandeliers are now available in the market. IFLs may be retained in places where lamps are lit up very rarely, probably for special occasions. However, if aesthetics is not a major concern, say in the kitchen or pantry, always opt to use LFL or CFL. Apart from these, the position at which the light is fixed too matters. If the distance between the lamp and the lit up surface is greater, the effective strength of illumination decreases. Thus, opt to use the lowest hanging / mounting position without of course jeopardising the safety of users.
Purpose – If lamps are for general lighting purposes such as rooms, use either wall hung or ceiling hung devices. If lighting is for a task such as reading or sewing, always use a lower powered table lamp. For instance, a 100 Watt IFL ceiling lamp used for reading can be easily replaced by a 75Watt CFL table lamp. If more than one person uses the same table for reading, the ideal option would be an LFL of 36 Watts
What’s in a fitting?
Probably many things we do not realise. A simple LFL mounted on the cheapest fitting comprising of a box of sheet metal gives you less light than when mounted on a good fitting. The reason that of being, nearly all the light from the upper side of the lamp is dissipated on the ceiling or surroundings, leaving you much less light for the task at hand. A good polished aluminium reflector can increase the light output tremendously. Thus, if proper fittings are used, you could effectively replace a 4 foot LFL with a 2 foot LFL. This is because a good fitting incorporates a reflective surface to redirect light from upper side of the lamp back to the task area. A good fitting also helps to scatter light in required direction, adding to efficiency as well as aesthetic appeal. Studies carried out by the Sri Lanka Sustainable Energy Authority have shown that one out of every three LFLs can be removed by fixing simple polished aluminium reflectors in the apparel industry.
Another key feature of a good fitting is the avoidance of glare from the lighting source. This aspect is clearly displayed in many shop lighting solutions in Sri Lanka. Several lamps are just fixed onto show cases or hung up to ‘illuminate’ merchandise, little realising that the target consumer is blinded by the glare before he actually sees the merchandise. A good fitting will shield the lamp from the user and illuminate the objects in a very attractive manner. A case in point is where jewellry shops that showcase jewellry with sufficient light, but in the absence of the blinding glitter of the light source. The source is carefully placed underneath the edging of the glass structures. This approach will not only illuminate places in a better aesthetic sense but will also save a lot of energy.
New Technology
Getting the best use from electrically operated lamps require the use of newer technologies such as people sensors and movement sensors. In bygone days when electricity was cheap, it was a common practice to keep security and perimeter lamps burning right throughout from dusk to dawn. However, with the fast rising electricity tariffs in the present context, these practices are no longer favourable.
A simple infrared sensor – that is capable of detecting moving warm blooded creatures – can be used to trigger a lamp turn on, instead of leaving it light unnecessarily throughout the night. Perhaps, security lamps too can be operated in a similar fashion and can be rendered more advantageous if it were combined with an audible alarm, alerting the security personnel or inhabitants of the incoming person / animal. This devise costs only 600 rupees, but is capable of saving money and electricity tremendously.
Let’s be more energy conscious when planning our homes and offices. Let us make strategic choices when choosing lighting equipments bearing in mind that saving energy is a matter of undisputable importance. Such wise decisions would benefit the country as well.
No comments:
Post a Comment