Solar Stills

Solar Water Purification Project

In 1995, EPSEA received funding through the State of Texas, State Energy Conservation Office (SECO), for a solar demonstration project. EPSEA’s project demonstrated the feasibility of using solar energy to purify water. The target audience (end users) are the people who reside in colonias along the Texas/Mexico Border. A colonia is an unincorporated settlement, lacking a safe water supply and waste water treatment. EPSEA’s work in solar water purification continued in colonias in Dona Ana County, New Mexico through a collaborative effort with the Southwest Technology Development Institute (SWTDI) at New Mexico State University. In 2000, EPSEA was able to install stills in Juarez, Mexico through a grant from “Border Pact”. EPSEA has since received funding through the U.S. Environmental Protection Agency (EPA) to continue it’s work in solar water distillation.

EPSEA has presented papers and hosted workshops at the American Solar Energy Society’s (ASES) national conferences and the Mexico National Solar Energy Conferences.

The problems faced by many colonia residents include contaminated water, as well as water with very high salt content. The sources of contamination include septic systems, industrial pollution, and run off of fertilizers and pesticides. These problems are seen on both sides of the border and like the resulting sickness and diseases, know no borders. These problems are not confined to only colonias, but it is the conditions that exist in colonias which allows for the proliferation of sickness and disease. The causes of these problems can be traced to pollution, poverty, ignorance and greed.

The Marcos family, Juarez, Mexico
Solar Solutions

EPSEA’s demonstration project is only a small example of the potential role for solar energy in water treatment, and disease prevention. Solar distillation is a proven technology for water disinfection. Systems can be sized for one person, up to community sized systems. They have no moving parts, relying only on the sun for energy, and should last 20 years or more. Larger disinfecting systems which generate chlorine and other gases can be operated in remote locations, using solar energy. It is hoped that through the success of our local project, these technologies will be replicated in other regions currently facing similar conditions.

The heart of EPSEA’s project is a basin solar still. EPSEA’s research resulted in a basin still, with emphasis on ease of replication and readily available materials. The still utilizes standard patio replacement glass (34″X76″), and during the summer months produces over 3 gallons/day. Winter production is about 1/2 that amount. The still has no moving parts, uses only solar energy to operate, and is self cleaning.

Project Update

The El Paso Solar Energy Association’s (EPSEA) solar water distiller projects (under an EPA grant for TX & NM, and Borderpact/Conahec for Mexico are progressing successfully. Only two more stills need to ben installed in the colonia areas of Ciudad Juarez, Mexico to complete the Borderpact project. The EPA project is just beginning Phase II which includes public community meetings and further education via energy fairs, etc., and a hands-on stills construction workshop that will be taught by Mike Cormier at the Water Festival in Columbus, NM in March. Applications are already being accepted by EPSEA from potential still recipients in the Luna, Dona Ana, and El Paso Counties of southern NM and west TX.

A selection process will be used to decide who will receive a still. A cost-share amount of $50-$100 per still (small or large, respectively) will be paid by the recipients who are chosen. A sponsorship and payment plan program is available for individuals who cannot afford the cost-share amount. A recent fundraising breakfast was held at St. Pius Church by the St. Pius Colonia Ministry to aid in achieving funds for such sponsorships.

Border Pact Presentation – PDF Document (327k)

For more information about these projects contact us at 915-772-SOLR email:

Final Update

Having completed this project, we presented a finalĀ paper to the Solar World Summit for the International Solar Energy Society in Orlando, Florida in 2005.


Solar energy is allowed into the collector to heat the water. The water evaporates only to condense on the underside of the glass. When water evaporates, only the water vapor rises, leaving contaminants behind. The gentle slope of the glass directs the condensate to a collection trough, which in turn delivers the water to the collection bottle.

EPSEA Still Cutaway (39k)

The still is filled each day with twice as much water as was produced. The still is fitted with overflow outlets, which allows the excess water to flush the still every day. A major advantage of the basin still is that it does not require a pressurized water supply. Colonia residents often have their drinking water delivered by truck and it is then stored in 55 gallon drums. Still recipients report that the water tastes very good and their children now drink more water than before.

Construction Cost

EPSEA material costs, with bulk purchasing, are approximately $200 per still. The cost of materials to build a single still should be less than $300. Only basic tools are required.

Construction Plans Available

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