Solar Water Distillation Solutions
Distilling and reverse-osmosis filtering are the two best methods for purifying water. Both approaches remove more contaminants than activated carbon filters do. The U.S. Environmental Protection Agency says only reverse-osmosis systems and distillers may be called water "purifiers." All other systems are water "treatment" devices, in spite of the performance claims many manufacturers make. But reverse-osmosis filtration wastes water: For every gallon of purified drinking water produced, the process consumes 2 to 4 gallons of water. In contrast, solar distillation wastes no water and is powered by the sun. instead of removing specific contaminants, as filtration systems are designed to do, solar distillation purifies water by removing only one thing: water.
Distillation takes advantage of the principle that chemicals vaporize at different temperatures. Most potential chemical contaminants in drinking water have vaporization points higher than water. When untreated water is heated in a solar distiller, pure water vaporizes first, leaving contaminants behind.
A simple solar distiller removes salts, heavy metals and bacteria, as well as arsenic and many other contaminants. According to a paper by Horace McCracken, a leader in solar distiller design, laboratory tests show distillers can remove trichloroethylene (a dry-cleaning chemical) and nitrates. Both are common pollutants and suspected carcinogens. A simple solar distiller paired with a carbon finish filter which removes any residual chlorine byproducts, will give you the cleanest drinking water for the least expense.
Simple Solar Distillers
Solar distillers work by mimicking the natural water cycle: The sun provides energy to warm the water, the water evaporates (forms clouds) and condenses (makes rain) when it meets a cooler surface. Unlike electric distillation, boiling is not required for solar distillation. Some people believe water from a solar distiller is purer than boiled water. Florida Solar Energy Center principle research scientist W.R. McCluney, Ph.D., says vigorous boiling "can force unwanted residue into the distillate (distilled water), defeating purification."
Types of Solar Water Distillers
The simplest solar distiller is a singlebasin distiller—a rectangular, black box fitted with a piece of angled glass sealed to the top. The basin is filled with untreated water; as the sunlight penetrates the glass, the water warms and evaporates, leaving most contaminants behind. The temperature difference between the cover, which does not absorb much heat, and the water surface causes the water vapor to condense, forming a thin film on the underside of the cover. When enough water condenses, it runs down the cover to a collection trough. Simple single-basin distillers work best on flat, level surfaces, and can be constructed fairly easily.