A simple, low-cost solar water purifier (SWP) for rural households, which does not require electricity or waste precious water has been developed. The SWP consists of four tubular solar water heaters attached to a manifold. Non-potable water is filled in the SWP after filtering with four-layered cotton cloth and heated in the stagnation mode by solar energy to make it potable. The cost of the SWP is around Rs 2500–3000 (~US$ 40–50) and is so simple that any small rural workshop can fabricate it. In large-scale production it is envisaged that the cost can come down to Rs 1500. 

Historically, technology development for rural areas has followed tinkering approach or use of rudimentary technology. It is shown that very sophisticated science and technology is needed for producing devices for rural applications. This process can also result in fundamental research.

The dismal situation and poor quality of life in rural India is because of unavailability of energy. It is shown that sophisticated technology can help solve this and other problems of rural areas. A call is made to the global technological community to help provide such technologies. Finally issues of how much energy is needed for sustainable development are discussed.

Rural areas of India are characterised by very low per capita energy consumption and in most places commercial energy like electricity is not available. Thus, it is a matter of concern that 60% of rural households still use kerosene for lighting. Besides, 180 million tons of biomass is used in rural areas for cooking through very inefficient and smoky stoves. Cooking and lighting energy constitute 75% of total energy used in rural areas. Jan-Mar 2005

Majority of rural households in India use only kerosene for lighting. Most of the lamps are hurricane-type, which produce very poor light intensity of about 60