Solar Lighting
(1 vote, average 1.00 out of 5)
Bookmark and Share

The history of lighting is dominated by the use of natural light. The Romans recognized a right to light as early as the 6th century and English law echoed these judgments with the Prescription Act of 1832. In the 20th century artificial lighting became the main source of interior illumination.

Daylighting systems collect and distribute sunlight to provide interior illumination; they are passive systems. They directly offset energy use by replacing artificial lighting, and indirectly offset non-solar energy use by reducing the need for air-conditioning. The use of natural lighting offers physiological and psychological benefits compared to artificial lighting, which is difficult to quantify though. Daylighting design implies careful selection of window types, sizes and orientation; exterior shading devices may be considered as well. Individual features include sawtooth roofs, clerestory windows, light shelves, skylights and light tubes. They may be incorporated into existing structures, but are most effective when integrated into a solar design package that accounts for factors such as glare, heat flux and time-of-use. When daylighting features are properly implemented they can reduce lighting-related energy requirements by 25%.

 An important active solar lighting method is the hybrid solar lighting (HSL). HSL systems collect sunlight using focusing mirrors that track the Sun and use optical fibers to transmit it into a building''s interior to supplement conventional lighting. In single-story applications these systems are able to transmit 50% of the direct sunlight received. Solar lights that charge during the day and light up at dusk are a common sight along walkways.

Although daylight saving time is promoted as a way to use sunlight to save energy, recent research has been limited and reports contradictory results: several studies report savings, but just as many suggest no effect or even a net loss, particularly when gasoline consumption is taken into account. Electricity use is greatly affected by geography, climate and economics, making it hard to generalize from single studies.