Life & Style

Harness the sun’s power with light tubes

In the context of our cities today, where the affordable land area available per person is limited, it is common to see landlocked built spaces with limited to no access to the outdoors. This results in certain areas not having direct access to natural light and ventilation.

This not only affects the general health of its inhabitants, but also results in high electricity bills as lights and air conditioners are switched on even during the day. Sensible design is one way to ensure adequate openings to the outdoors in the case of limited space. Opting for open plans, skylights or sky windows are other features to consider.

Building technology

Although the fast paced of growth of our cities has resulted in unhealthy built environments, it has also led to research and innovation in the space of environmental technologies. In the field of daylighting, a ‘light tube’ or a ‘light pipe’ is one such technological innovation seen in contemporary architecture since the late 1980s (after it was patented by Solatube International, an Australian firm).

A light tube (also known as a tubular daylighting device or TDD) is a tube lined with a highly reflective material that transmits light either from a point on the roof or an external wall, all the way through a building. A diffuser is used to spread light into the space. A solar collector — which is in the shape of a dome — is placed on the external surface to collect and direct light into the solar tube. Some collectors also have additional reflectors or lenses that aid in better light collection and minimise losses in light transmission.

It is interesting to note that the first commercially available reflector lighting system was designed in the 1850s by Paul Emile Chappuis, a photographer. He manufactured daylight reflectors from his factory in London until it was destroyed in a fire during World War II.

Flexi tubes

Solar tubes are widely used today in large spaces to bring in natural light (horizontally) from the nearest exterior wall surface. They are also used vertically from the roof, alongside columns, to get light indoors. Long, angled and even flexible tubes can be used for the purpose, although the transmission efficiency is the most when the tubes are kept short and straight.

To increase efficiency and optimise the collection of daylight, a heliostat — a sun tracking device — can be installed on the exterior surface. This allows for light collection at almost all times of day, including the capture of moonlight at night.

The author is the founder of Green Evolution, a sustainable architecture firm

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Printable version | Feb 26, 2021 7:31:23 AM | https://www.thehindu.com/life-and-style/how-to-harness-the-suns-power-with-light-tubes/article30999625.ece

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