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Creating Drinking water with Solar Power

The world is faced with a major fresh-water crisis as a result of explosive population and industrial growth. A long-term viable solution for this acute shortage is to transform salt water from the vast oceans and seas that make up about 3/4th of earth’s water, into potable water that is safe to drink. This process of converting salt water into fresh, potable water is known as “desalination”. Though this idea sounds promising, the introduction of desalination plants in developing countries faces two major obstacles – the cost of setting up a desalination plant and the energy it requires to function. Two scientists from the Indian Institute of Science have addressed this problem with a novel idea.

Construction of massive desalination plants incurs huge costs and makes it unaffordable for developing countries. A more viable alternative is to construct smaller decentralized plants which have lower construction and maintenance costs. Using fossil fuels to power these desalination plants is expensive and results in environmental damage in the long run. A better and cleaner alternative is to use green and renewable energy sources such as solar, wind or geo-thermal. Sunlight is especially predominant and easily available in the coastal areas. Using decentralized desalination plants powered by solar energy can make these plants affordable.

To address this very need, Dr. Ravinder Kumar and Dr. Umanand L from the Department of Electronic Systems Engineering at IISc, Bangalore, have developed a solar hybrid desalination system. “In 2004 when I was in Chennai, there was a huge water crisis and people were struggling to even get water tankers to their homes. That was my starting point to think about this. There was a vast amount of sea water sitting next door but people were still suffering” explains Dr. Kumar about the inspiration behind this work.

The new desalination system incurs lower construction and maintenance costs compared to traditional desalination systems while still performing optimally. It uses a process of flash evaporation and subsequent condensation to desalinize sea water. “Evaporation of water under normal atmospheric pressure requires more energy than flash evaporation. Through flash evaporation, what we did was vary the pressure inside the evaporation chamber so that water can evaporate at any temperature, not just at 100 degrees.” The energy required for flash evaporation is supplied by solar concentrators, which are essentially Scheffler dishes used as concentrators of solar energy. The concentrators raise the temperature inside the evaporation chambers. Subsequently, to pump water into chambers, photovoltaic panels are used as a source of energy.

The desalination system converts sea and brackish water to potable water through flash evaporation and condensation using a clean, affordable and efficient process. A major objective of this desalination system was to reduce the life span cost - the total building and operating costs - of the desalination plant while still meeting optimal performance requirements. According to Dr. Kumar, the success shown by this system shows promising signs that “the problem of clean drinking water can be solved in any coastal area where seawater and sunlight is available freely.”

About the researchers:

Dr. Ravinder Kumar was a PhD scholar at the Department of Electronic Systems Engineering at the Indian Institute of Science, Bangalore during the publication of this research (September, 2008). Dr. Umanand L was his thesis advisor during this research.

Email: (Ravinder Kumar)