A bulb developed by N.B. Institute for Rural Technology and adopted by the Centres Department of Science and Technology under its Technological Advancement for Rural Areas programme, doesn’t use electricity to light. Instead of electricity, the unit, called ‘Surya Jyoti’, uses the micro-solar dome to stream diffused sunlight into poorly-lit rooms through the roof in thatched, tiled or tin-roofed houses of the poor. Around 5,000 solar domes are in use in the slums of Delhi and in West Bengal, Tripura, Assam, Madhya Pradesh, Karnataka and Uttarakhand.
Surya Jyoti works on the principle of capturing sunlight using a micro-solar dome. The light is filtered through a PVC pipe with a highly reflective lining. Bright light emerges at the other end (within the room) through a glass shade. The domes provide light equivalent to a 60W bulb.
Surya Jyoti is ideal for tile-roofed or tin-roofed houses. The government has high hopes on this invention. The Science and Technology Ministry estimates that Surya Jyoti can help some 10 million households. Most importantly, these are off-grid, and can be used in urban and rural areas, without reliable access to electricity and also in inaccessible and remote areas. The unit comes in three models and the cost varies between Rs 100 and Rs 300.