Solar Water Purification in India

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'Solar water purification' involves purifying water for drinking and household purposes through the usage of solar energy in many different ways. Using solar energy for water treatment has become more common as it is a usually low-technology solution that works to capture the heat and energy from the sun to make water cleaner and healthier for human use and consumption. Solar water treatment is particularly beneficial for rural communities, as they do not have other forms of water purification infrastructure and more importantly, electricity to run such structures. The most positive feature about solar water purification is that there is no requirement of fuel. It's precisely due to the lack of fuel that makes solar applications relatively superior than conventional sources of energy as it does not cause pollution (global warming, acid rain, ozone depletion) or health hazards associated with pollution.

There are four main types of solar water treatment: solar water disinfection (SODIS), solar distillation, solar water pasteurization, and solar water treatment systems. Some of these technologies have been around for a very long time, but most are new adaptations to the concept of solar energy. These technologies are quite simple and easy to understand, usually require low financial input, and are proven effective.

The Technology

The four most common methods for solar water purification: [1]

  • Solar Water Disinfection (SODIS)

    Solar water disinfection is a low technology, simple process of purifying water using solar energy and solar radiation. SODIS as a technology was first introduced in 1980 by Aftim Acra et al. from the American University of Beirut. The process involves contaminated water being filled in transparent PET or glass bottles which are then exposed to the sun for approximately 6 hours. The UV rays of sun eliminate the diarrhoea-causing pathogens, thereby making the water fit for consumption.

  • Solar Water Distillation

    Solar water distillation uses a solar still to condense pure water vapour and settle out harmful substances to make clean, pure drinking water. This process is used when the water is brackish containing harmful bacteria, or for settling out heavy metals and also for desalination of sea water.

  • Solar Water Pasteurization

    Solar water pasteurization involves the use of moderate heat or radiation to kill disease - causing microbes. This heat is provided from cookers that trap solar energy. This method has proven to kill bacteria, viruses, worms and protozoa.

  • Solar Water Purification

    This method integrates electricity generated from solar energy for water purification. Solar panels generate power for a battery which is used for filtration and purification systems. These structures are generally mobile and are immensely helpful for disaster - relief efforts. They also come in various sizes meant for small scale use to commercial/community supply.

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Research and Pilot Schemes in India

  • National Institute of Ocean Technology (NIOT)

NIOT has been focusing on utilizing ocean resources for fresh water and renewable energy technology. One of their specific areas of work is the LTTD process, where fresh water is produced using low temperature thermal desalination (LTTD). The LTTD concept involves using the variation in the temperatures of ocean water at different depths. The warm water at upper levels is evaporated using low pressure and the resulting vapour is condensed with the lower levels cold seawater.

Efforts: They initially began with a small capacity, laboratory based model of 5 cubic metres/ day to commissioning one land based model of 100 cubic metres/day in Kavaratti and also a desalination plant of 1000 cubic metres/day off the Chennai coast (2005). They have also commissioned and put into operation demonstration power plants based on the LTTD process at North Chennai Thermal Power Station and Tuticorin Thermal Power Station. [2]

  • Department of Science & Technology (DST)

DST has supported KG Design Services (KGDS), Coimbatore and National Institute of Ocean Technology (NIOT) to develop and demonstrate a solar thermal desalination plant which harnesses solar energy, concentrates it and produces steam which in turn is used for desalination of sea water through the Linear Fresnel Reflector (LFR) system.[3]

Efforts: They have identified a section of land in Kuthiraimozhi village near Narippaiyur, Ramanathapuram where a plant will produce desalinated water at the rate of 6000 liters/ hour; which if successful would be installed in Coimbatore.

Gerindtec in India has two solar desalination pilot projects based on the patented technology called Multi Effect Humidification (MEH) process. The MEH technology consists of two repetitively applied work processes in which the first involves, solar collectors delivering the energy to evaporate sea/brackish water and the second part condenses the purified water in the process. (J. Malaviya, Solrico)

Efforts: One of the two pilot projects was set up in Chennai, Tamil Nadu and operation of the project was started in August 2011. The so-called MiniSal 1000 has a daily capacity of 1,000 litres of purified drinking water.

  • Bhabha Atomic Research Centre (BARC) [5]

    BARC scientists in Mumbai have developed a water purifying technology which is either driven by solar or wind energy for desalinating contaminated water besides removing toxic elements, pathogens and turbity. For treating the water, electricity locally produced from sunlight, is used to operate a pressure-driven, membrane-based reverse osmosis process.

  • Developing Indigenous Resources (DIR)

DIR has a small scale water purification pilot project concerning around 270 households in Punjab. The aim of their pilot project is to determine which method of water purification is accepted best by the people living in the 'bustee'. Their three methods involve solar, chemical and filtration. [6]

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International Projects Which Includes India in Their Future Efforts

  • Solvatten [7]is a Swedish invention that uses solar energy to make unsafe water fit for consumption purposes. It is in collaboration to the UN Millennium Development Goals of promoting good health and protection of the environment. The usage of this invention is considered to be easier and cheaper than firewood. As of now, they do not have any pilot projects in India but do have a Solvatten project in Nepal where they have involved 25 households in collaboration with Environmental and Public Health Organization (ENPHO), Nepal. According to the website link[8] it appears that rural India would feature in the future projects of the Solvatten efforts.

  • Mörk Water Solutions [9] currently has a pilot project in Zanzibar, Tanzania in cooperation with GIZ, which is being funded by the German Ministry for Economic Cooperation and Development (BMZ) and Dow Chemical. The aim of the project is to improve access to ecologically sustainable and inexpensive drinking water supply for the area of Zanzibar. Their development partner Hochschule Karlsruhe Technik und Wirtschaft has developed a technical system concept based on their expertise and references from a pilot trial in Bangladesh and on-going projects in India (2010-11) on water treatment.

    The desalination plants that they use for their operations at Zanzibar runs on wind energy but could be easily modified to run on solar energy through the usage of solar photo voltaic panels.

  • Pentair [10]is a company that has a pilot project in Kureb, Uttar Pradesh and this initiative seeks to provide clean, drinking water in a manner that is market-based, commercially viable and locally owned. It involves building a small water treatment center with a reverse osmosis system and have an operator sell water that is generated from this system.

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The Market


According to a World Bank report, 80% of communicable diseases in India are water related and with a population of 1.17 billion, only 15% have access to water fit for consumption purposes. Also, ground water sources have been over-exploited, which has caused the levels of mineral contaminants to increase dramatically. For example, in places such as Rajasthan, Gujarat and Andhra Pradesh, the population is consuming water that has high fluoride content which in turn will lead to increasing health risks such as mass poisoning.

Solar distillation is a proven technology for water disinfection and the system can be customized from one person to community sized systems. They have a long life span of about 20 years and generally do not require moving parts.The water purification business in India is undergoing major changes, not just in terms of technology, but also in terms of pricing and competition. The drivers of change include scarcity of clean drinking water, low penetration of water purifiers, increasing urbanization, and waterborne diseases. The main challenges are the lack of standards (for manufacturers) and low awareness levels amongst potential users. The market has also started evolving for a category of consumers who do not have access to running water electricity and lower price point products. [11]

As almost 30% of rural India has no access to safe drinking water, consistent electricity source or even the financial means to afford the relatively expensive modes of water purifying products. Therefore providing them with solar water purifiers, which makes use of solar photo voltaic systems would be a step in the right direction as an access to clean, safe, consumable water. There is an untapped opportunity in the rural areas but it is definitely an effort for the long haul.

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There are various companies, which are looking into solar water purification as a potential product for untapped rural communities and markets. In India, however a number of factors have to be considered before the initiation of such an effort. For most companies, some of the relatively important factors range from the type of business model to community acceptance of safe water for a price besides having these ventures turn into stable, sustainable operations. The period and amount of returns are uncertain and most companies are still nascent.

Government of India is too now willing to work with private parties. For instance, California-based WaterHealth International is in the process of setting up 225 water treatment plants for panchayat blocks in Andhra Pradesh on a build-own-operate-transfer (BOOT) basis. WaterHealth will make its profit from fees charged to users.

Moreover, the listed companies under the Research and Pilot Schemes of this article are also actors in this context for solar water purification.

  1. National Institute of Ocean Technology
  2. Department of Science and Technology
  3. Gerindtec
  4. Bhabha Atomic Research Centre
  5. Developing Indigenous Resources

In addition, the major players of water purification market in general, Eureka Forbes and Hindustan Unilever Limited are also considering extending their product lines to include renewable energy based products. The Indian market has tremendous potential, which is evident from the fact that global companies (Solvatten, Mörk Water Solutions, Pentair, WaterHealth) in the water purifiers segment have stepped in and are looking to increase their share of the market. [12][13]

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Remaining Bottlenecks

  • Low Awareness Levels

In India, the most predominant form of water purifiers is chemical based technology. The use of chlorine in such a method of purification can be harmful if the dosage is not regularly monitored and administered. In contrast, solar water purification is a much safer method of water treatment, which has no possibility of chemicals decomposing themselves during the treatment of water, thereby producing products harmful to health. However it should be noted, that this method and its products is relatively less known to the general population.

  • Cost

Using solar energy as a source of power for products is currently high on absolute costs compared to other sources of power, say coal or kerosene in some states. Potential users of solar water purification systems find themselves unable to pay the full price of the solar still as they simply can't afford the higher up-front capital cost. [14]

  • Lack of any Social Program

Without any social program to increase awareness, the question arises if the community residents would both accept and use the technology even if there is no doubt about the success of solar water purification systems. It’s also difficult to gain acceptance from area residents and thereby identify potential clients within that area. The acceptance of the technology is made easier when families learn and are recommended such a system by an institution they knew and trusted. [15]

  • Evaluation issues

Even if the design experts of solar water purifiers are fully experienced and possess the expertise in the topic of solar water purification, a few of them can understand the conditions under which these purifiers would work in a community. Only a resident could tell if the purifiers were easy to use and what could be done to improve it. Without such crucial inputs, the spread of solar water purification methods is effectively reduced.

  • Quantity Requirements

It is difficult for most users to estimate how much water requirements they have as per seasonal change. In most pilot projects, the most common issue even though it is of a minor nature, is the problem that their water requirements are higher than they availed of via solar water purifiers. In addition, solar water purifiers require a longer time period than say other water purifying methods to deliver its service.[16]

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Market Support Schemes

The National Solar Mission is a major initiative of the Government of India and State Governments to promote ecologically sustainable growth while addressing India’s energy security challenge. The objective of the National Solar Mission is to establish India as a global leader in solar energy, by creating the policy conditions conducive to its spread within the country. The immediate aim is to focus on setting up an environment for solar technology penetration in the country both at a centralized and decentralized level.

According to this mission Solar power as a resource would find its greatest usage in decentralized and off-grid applications as grid penetration is neither feasible nor cost effective, solar energy applications are cost-effective. The key problem is to find the optimum financial strategy to pay for the high-end initial costs in these applications through appropriate Government support. Currently, market based and even micro-credit based schemes have achieved only limited penetration in this segment.

The Mission would consider up to 30 per cent capital subsidy for promoting innovative applications of solar energy and would structure a non-distorting framework to support entrepreneurship, up-scaling and innovation. Also, to create a sustained interest within the banking community, the Mission proposed to provide a soft re-finance facility through Indian Renewable Energy Development Agency (IREDA) for which Government will provide budgetary support. IREDA would in turn provide refinance tNBFCs and banks with the condition that it is on-lend to the consumer at rates of interest not more than 5 per cent.
The general plan envisaged by the National Solar Mission for solar power application is as follows: [17]

Serial Number

Application Segment

Target for phase I (2010-13)

Target for phase II (2013-17)

Target for phase III (2017-22)


Solar collectors

7 million sq

15 million sq

20 million sq


Off grid solar

200 MW

1000 MW

2000 MW


Utility grid power,
including roof top



20000 MW

The Mission seeks to create a policy and regulatory environment which provides a predictable incentive structure that enables rapid and large-scale capital investment in solar energy applications besides encouraging technical innovation, thereby cost reduction.

Solar water purification is another unexplored avenue of solar power application which could be considered under this Mission. As of now, solar water purification lacks market mechanisms to promote its growth and spread but if its application uses are considered, it would be a considerable venture for solar applications along with solar photo voltaic products.

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Further Information

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  1. Solar Water Treatment:
  2. National Institute of Ocean Technology:
  3. Department of Science & Technology:
  4. Gerindtec:
  5. The Indian Express (January 2012) - BARC develops low-cost solar water purifier:
  6. Developing Indigenous Resources - India:
  7. Solvatten Safe Water System:
  8. Advantage Environment - Solar Powered Water Purification:
  9. Mörk Water Solutions:
  10. Pentair Project Safe Water: Kureb:
  11. TV Veopar Journal (April 2012):
  12. The Water Purifier Market Today:
  13. TV Veopar Journal (April 2012):
  14. Ten Years of Solar Distillation Application Along the US - Mexico Border:
  15. EPSEA Solar Water Purification Project:
  16. Ten Years of Solar Distillation Application Along the US - Mexico Border:
  17. Jawaharlal Nehru National Solar Mission - Towards Building Solar India: