Solar energy in a Water Purification System

I found this project on how to do your own solar energized water purification system, you can find more information about it at

This project was sponsored by the State of Texas Energy Conservation Office (SECO). In 1995, EPSEA received funding from SECO, for a solar project. That was when we decided to study the viability of using solar energy to purify water. In case it worked, solar purification systems would be delivered to people who reside near from El Paso, TX (and all the zone along the American/Mexican Border). Those towns, called “Colonias” have a lack of a safe water supply and good quality sewers. The problems faced by many colonias residents include contaminated water, as well as water with very high salt content. This pollution has 3 different origins: insecticides and fertilizers, industrial pollution or due to the proximity of septic systems. This problem is present in both sides on the border, causing may endemic diseases. As always, the causes of these problems can be traced to pollution, poverty, ignorance and greed.

Solar Solutions

EPSEA’s demonstration project represents a small example of how we can use solar energy in water treatment and disease prevention. Water distillation is a well known solution for water disinfection. Community or personal systems that have no moving parts may be built, needing only solar energy and a minimum of human participation. It should last more than 20 years. Another indirect use of solar energy is the use of photovoltaic panels to start water chlorinating systems which can be operated in remote locations with no access to electric lines. It is hoped that our contribution with these technologies will be replicated in other regions currently facing similar conditions.

In order to complete the design, EPSEA got technical consulting from Mr. Horacio McCracken, a pioneer on solar energy water distillation subjects, with more than 30 years of experience. By using that accumulated experience, he helped us on the design of a passive solar distiller, easy to produce in series and using affordable materials. The heart of the distiller is an earthen bowl filled with the amount of water to be purified by the sun, also using a glass cover, as it is described later. It uses standard patio glass (34″ x 76″). If you can get a similar dimensioned standard glass, you will get similar results, as long as the level of solar radiation remains to the one at El Paso, TX. Our evaluation shows that during summer it produces over 3 liters per day, and about 6 during winter. The most attractive feature is still its simpleness, because it has no moving parts, uses only solar energy, and it can be easily cleaned.


Solar energy penetrates through the glass cover into the closed collector and because that cover is panted in black, it is capable of attracting more radiation. Internal walls have a white colored surface, reflecting the light that they got, which raises the condensed heat on the accumulated water. After a while, water starts to evaporate. And because the lower part of the cover is less warm, water condenses on itself. That cover is mounted with a small inclination, allowing condensed drops of water to slip into a collector channel, that ends on an exit where a glass bottle is used to collect it.

The distiller must be filled each day with twice the volume the earthen bowl can retain. That overflow allows the distiller to be cleaned every day. As it’s seen, it does not require a pressurized water supply or specially designed sewers. “Colonia” residents often have their drinking water delivered by truck, and it is then stored in a 2000 liters recipient. This is low-quality water that must be purified with a solar distiller, providing its users great quality water, they even say that those children are more will in to drink the supposed daily average amount of water .

All the details given on the manuals (with assembling instructions) shows that the most important material is used to build the earthen bowl, the collector channel and the in-and-out water conductors. Those materials must be inerts to distilled water effects, highly active in a chemist point of view. The only special care that this solar energized water purification system need is not to leave it waterless, at any time, even when its glass surface is covered, because high temperatures cause irrevocable damage on it.