About 30 per cent of sunlight is scattered back into space by the outer atmosphere, but the rest reaches the earth's surface, which reflects it in the form of a calmer, more slow-moving type of energy called infrared radiation. Infrared radiation is carried slowly aloft by air currents, and its eventual escape into space is delayed by greenhouse gases such as water vapour, carbon dioxide, ozone, and methane.
* Human activities are making the blanket "thicker" -- the natural levels of these gases are being supplemented by emissions of carbon dioxide from the burning of coal, oil, and natural gas; by additional methane and nitrous oxide produced by farming activities and changes in land use; and by several long-lived industrial gases that do not occur naturally.
* These changes are happening at unprecedented speed. If emissions continue to grow at current rates, it is almost certain that atmospheric levels of carbon dioxide will double from pre-industrial levels during the 21st century. * The result, known as the "enhanced greenhouse effect," is a warming of the earth's surface and lower atmosphere. The IPCC assesses with very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming. * A rise in temperature will be accompanied by changes in climate -- in such things as cloud cover, precipitation, wind patterns, and the duration of seasons. * Carbon dioxide is responsible for over 60 per cent of the "enhanced greenhouse effect." Currently, atmospheric levels of carbon dioxide are rising by over 10 per cent every 20 years.
Lighting is one major area of electricity consumption and it is estimated that about 19% of global electricity is consumed for lighting. This comprises of both indoor and outdoor lighting. Manually controlling the lighting circuits is laborious and is prone to errors and unaffordable costs calling for reliable automation systems to save on cost and energy. The lighting automation offers a substantial scope for conservation and there by contributing to reduction of Green house Gases. Many of the efforts are being recognized under Clean Development Mechanism called CDM leading to grant of Carbon Credits either as CER's or VER's eligible for carbon trading.
The device behaves erratically due to dust accumulation on the sensor window.
The device failure due to rain.
The device failure due to short circuit in the load line.
The device failure due to thermal factors.
The experience regarding timers
Many timers mostly mechanical type are available in the country and many users have resorted to them as next best solution due to poor performance of light sensor based Automation solutions in India. Power failure and interruption have also called for resetting of clock in some timer models, which calls for a laborious service that negated the very purpose of Automation. The only advantage, which a timer enjoys, is that it can be a part of the panel and so the outdoor-induced factors like dust, rain etc are minimized.
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