Solar Power - Solar Water Treatment

Using the energy from the sun to generate electricity gets a lot of press. But there are many other applications for solar power. One of the most important is for treating water.

Many countries around the world have impure water that causes diarrhea, typhus and other medical problems. The same is true of certain areas of the U.S. and other developed countries. Building small devices that can eliminate the problem is cost-effective using current technology. Individuals can even build their own.

Solar disinfection, or SODIS as it's sometimes known, uses a very simple principle. It's essentially the same as that used to pasteurize milk. Microorganisms that cause health problems can only function in liquids up to a certain temperature. Beyond that, even when they're not killed, they are deactivated. Amoeba, bacteria and many other small disease-causing organisms can be rendered harmless by this method.

Implementing the method can be ultra simple. A gallon of water in a plastic jug can be treated in a few hours. Simply place the water in a clear, plastic bottle, preferably on a black background to ensure good absorption, and place it in the sun. On a sunny day the process may take less than three hours if the water is moderately clear to begin with. River water, obtained while hiking for example, can be treated this way.

PET plastic is preferable to PVC plastic for this application. PVC, polyvinyl chloride, type plastics have a slightly bluish cast. They block more UV, which is a more energetic form of light, and hence reduce the effectiveness of this method of water treatment.

There are other methods of solar-powered water treatment, too.

A solar water still can be bought or built for a few hundred dollars or less that will treat considerably more water than jugs. They're usually made in the form of a rectangular container a few inches deep with a glass panel up the side and a siphon hose. The container is often covered with plastic. Glass blocks much of the UV.

As the sunlight heats the water, the moisture evaporates up and condenses on the relatively cooler glass above. The siphon hose draws off some of the water, which is not only freer of organisms, but contains fewer minerals and other compounds, such as chlorine.

The principle is basically the same as that used in desalination plants around the world.

Many locales have little drinkable water but large amounts of salt water readily available. Transforming the salt water into potable water employs the same evaporation technique, but generally on a much larger scale in desalination plants. Only a small amount of salt water can be consumed before it does damage to the kidneys. That's one major reason that seawater has killed more than one sailor who found himself in the ocean trying to survive.

Solar radiation can kill pathogens in water and it can provide drinkable water in specialized applications. In short, solar power can generate clean water, just as it can generate pollution-free electricity.