In the era of pollution of all types (soil, water and air) all around everyone desire to have pure air and water to breath and drink. Various methods of water purification (water purifiers) available are either place specific, energy consuming and costly. There is always a quest to find a low cost and mobile water purifier system which can cater to the growing demands of people for pure water and low-cost solar-powered water purifier is such an innovation. With other advantages like: converting any source of water - seawater, rainwater, brackish tapwater, etc. - into potable water, it removes both inorganic contaminants (arsenic, fluoride, heavy metals, etc. and organic contaminants (disease causing bacteria). It does not require periodic replacement of filters as in other water purifiers’, where the filters get clogged and become useless.  Developed by researchers of Indian Institute of Sciences, Bangalore, it is easy to construct, and is being given as an open source design, so that anyone interested can download and build it.  This open source solar water purifier can transform water from any source – be it from sea, river, pond, wells, or even water collected from rain – into potable water. The low-cost device can also provide clear drinking water in areas where the only sources are contaminated with arsenic, fluoride or sewage.  In this device, impure water is evaporated using solar energy and the vapours are condensed to pure water on a cold surface. This leaves behind bacteria, heavy metals, arsenic, fluoride and other impurities. It can effectively produce 1.5 litres of potable water from 3 litres of impure water daily.

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 purification involves purifying water for drinking and household purposes through the usage of solar energy in many different ways. 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. Mobile water purifiers have arrays of solar panels, batteries, and high-pressure pumps and the machines usually wind up in natural-disaster zones, off-grid villages, or military operations around the world. Using solar-power, the mobile-operating system puts raw water through six filtration steps, meeting the requirement standards of safe drinking water and is capable of producing 200 liters of drinking water per hour – the device was created to be easily transported – fitting into the back of a pick-up truck, trailer, or a flat hull boat in cases of emergency on, or off land.

Designing fundamentals

Water purification comprises various processes such as removing suspended solid particles, undesirable chemicals, and gases from contaminated water. Most water is purified for human consumption (drinking water), but water purification may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacological, chemical, and industrial applications. Purification of water mainly consists of two processes, i.e., filtration and disinfection. The solar water purifier makes use of both these processes. Water filtration is carried out using pre-filter (washable debris filter), 0.5 micron sediment filter, and activated carbon filter where solid particles like sand, debris, fine particles are removed from water. Water disinfection is carried out using UV filtration. As UV light from the sun is known for its ability to destroy micro-organisms, in recent years, equipments producing UV light have been manufactured for residential use. UV energy is produced by low mercury vapour enclosed in a tubular lamp. Energy produced by the UV lamp has the ability to destroy micro-organisms such as parasites, bacteria, etc. This water purifier is compactly assembled on a four wheel trolley for easy transportation from one place to another in nearby locations. It also facilitates charging the battery from mains supply during low sunshine days or in rainy season when the sun’s radiation level is insufficient to charge the battery. Also, one can take external DC supply from a vehicle to operate this equipment. The design is made considering the aspect of human machine interface. Various and displays are provided for the operating parameters, which makes this machine very easy to operate.

The mobile systems range from the size of golf carts to food trucks, depending on their desired output. Solar panels lie on top, generating electricity that charges the GEL-sealed, lead-acid batteries, which in turn run the motor that pumps water through filters. Clean water pours out a hose, and depending on the filtration process, contaminants flow out in a discharge stream or remain in mechanical membranes. Internet-connected monitors remotely display the systems’ water quality, output, and equipment performance. Such a system can be deployed anywhere and literally take contaminated, poisoned water and turn it into drinking water in minutes. If water comes from ponds, lakes, or municipal taps, it passes through four filters to remove microbes, sediment, and other contaminants. An ultraviolet light then sterilizes the filtered water. Brackish water or seawater undergoes reverse osmosis, in which water is forced through a thick membrane that blocks sodium and chloride ions and lets freshwater pass. The process uses a substantial amount of energy, so those units require more solar panels and batteries and cost thousands of dollars more. Lead-tainted water also requires reverse osmosis, because of the metal’s low molecular weight.

Developmental status

PV Pure, a startup founded by MIT researchers, has delivered its small units across Latin America, the Caribbean islands, and the Middle East. Tata Group is building village-scale desalination systems and solar-driven water pumps in India. Another model developed by Kenneth M. Persson and engineer Ola Hansson from Lund University in Sweden, the so-called Micro Production Centre (MPC) disinfects and purifies water using UV-LED technology and it features intelligent software and WiFi connectivity for monitoring the machine. The system is very energy efficient and can be run by just one solar panel, keeping it lightweight and portable. The solar panel charges a battery for back-up energy so that the system can work at night, too.

Advantages

• The system is very compact, easy to install and to maintain.
• The system is highly demanded in various industries for the purification of water.
• Manufactured with the help of modern technology and high quality raw material, the system is provided in different technical specifications to cover the different needs of the clients. 
• The system has some useful characteristics as: operational fluency, low power consumption and rugged design
• Mobile systems could provide communities an affordable alternative to the bounty of bottled water and home filters.
• It is important that the cost of purifying water is sustainable. Many people can now begin to purchase inexpensive, clean water, and at the same time a lot of them can make a small profit by running the water purification plants.

Bottlenecks of technology

Experts agree that a key challenge with solar-powered water purifiers is the intermittent nature of solar energy. If a system operates with any fluctuations, it can quickly degrade the equipment. To address this, operators can either use small batteries to maintain steady power flows, or turn the system on and off to match the sunlight. Even if you include batteries, you’re still going to have to operate the system intermittently. To be able to run a system 24 hours a day, like a traditional desalination plant, is something you can’t cost-effectively do. Larger batteries can bank power and extend operating times, but they add considerable costs to the overall system.