Day Daylight Harvesting Research Paper

Daylight Harvesting is an energy management technique aiming to reduce the use of overhead electric lightings by utilizing natural light present in the atmosphere. It takes advantage of naturally available light and thus a key energy saving strategy. The basic principle is that as level of natural light increases , the electric light level should decrease so that acceptable level of light can be maintained. Maximizing & Distributing the natural light in building, using more energy efficient lighting systems, automated lighting systems are few methods to maintain illumination in the building. It is done using photosensors, electric ballasts and reflective surfaces which maintain the threshold light level. The efficient building design ;

Inside the building facing window Allows different areas of building to be controlled by single photosensor

2. Closed Loop System - In this system, photosensors detect the combination of daylight and electric light. Positioning – a. Away from direct sunlight b. Away from direct artificial light c. Where it can measure reflected lights both from natural and artificial light. Each independently controlled zone requires a photosensor

Types Of Daylighting

1. Switching – In this technique; once the desired daylight level is reached, all electric lights go off. For example all lights Off or all lights On. Advantages – a. Low initial cost b. Simple Design c. Easy to commission Disadvantages – a. Only 2 levels thus low energy savings b. Abrupt Changes in light are not considered

2. Dimming – This technique involves continuous dimming from low level to high level so as to maintain the desired illumination limit. Advantages – a. Higher energy saving b. Exact illumination can be

They may cause glare, admit a lot of heat during the summer when it is usually not wanted, and contribute little to solar heating during the winter

3. Obstructions – Obstructions in daylight may lead to loss of entering light. So more investment has to be made in case of buildings with close proximity than in case of less crowded environment.

4. Solar Heat Gain – It is the increase in temperature due to sunlight. Using shades, low air leakage, low heat gain coefficient glass, low heat flow through glass can reduce solar heat gain.

5. Glare – It is difficulty in seeing in bright light. It is of 2 types-

i. Discomfort Glare results in instinctive desire to look away from bright light source. ii. Disability Glare impairs vision of objects without causing discomfort.

Glare makes working hard and can be avoided using proper window placement, using shades and proper light adjustment.

6. Investment Return – (Cost of daylight harvesting system)-(energy saving)

7. Payback Time – (Cost of Daylight Harvesting System)/(Annual Energy Saving). Less the payback time, more likely the owner will invest in the