Greenhouse your water…say what?

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The use of solar is becoming increasingly poplar as a source of energy. By capturing this technology and manipulating it to treat water is rather simple. It has been used since the 1800’s when it was invented to deliver drinking water to miners using a high nitrate brackish influent. Since then, solar distillation is increasingly becoming a common method for supplying clean drinking water.

The method is really simple: solar heat increases water temperature to where it is evaporated into the atmosphere, captured and collected. It is basically creating a man-made cloud and making it rain. This ‘collected rain’ will be free from salt and microbes, making it then, safe to consume.

Dirty water is put into a container or basin that has a blacked out bottom. Then it is covered with glass that is at an angle, allowing the clean water to collect or drain. The sun heats the water causing evaporation and condensation to collect on the glass. Since it is covered at an angle the condensed water moves down the angle cover to collect in a separate container. Water in the feed should be added in order to clean out the basin.

The size of these systems can be large or small, however their production is somewhat limited. A system set up for a family can create up to 3 gallons a day. This is a great option for those communities that suffer from drought because these areas tend to have a hot climate great for distilling salt contaminated water sources. In some areas the contaminated water source has a built structure directly on the source to create a greenhouse-like effect.

The technology is remarkably simple and somewhat inexpensive. The basin where the feed water is located should be shallow and of a dark color such as black in order to absorb the heat. Choosing a cover such as glass allows for the solar energy to go through without becoming the same temperature as the basin, hence the creation of condensation.

There is a possibility of recontamination in the catchment system, so it is recommended using a PVC plastic piping made specifically for water systems. The reason being that some PVC pipes degrade in time thus releasing various chemicals which can be dangerous to consume. There are pipes made specifically for water systems and are manufactured to avoid this danger and would be clearly identified at any hardware store. Another way to minimize contamination is to leave the materials to build the solar distiller in the sun for approximately a week so that any chemicals will be ‘burned’ off and released without it entering into the water system. Also, a disadvantage of this process is that the gathered water is tasteless. By adding a small amount of chlorine (5 drop per liter) or by allowing the water to flow through marble to obtain some lost minerals. Both of these methods will make the water taste better.

The United Nations states that the cost of solar distilled water is $3-6 per 1,000 gallons. This is less than buying bottled water, but a bit more expensive than the average municipal supplied water. However, although it is a little more expensive, there is more guarantee of cleanliness in the context of variations of municipal drinking water quality around the world.

According to the University of Central Florida, who specializes in solar distillation research, ‘if it costs about $40-60 per square meter to build the still and it is worth roughly $15 USD per 1,000 gallons, the still should pay for itself in 2,500 to 4,000 days or 7-11 years.” This is a great idea as the prices of water rise and the valuable resource becomes scarcer.

Distillation by solar energy has been used for a rather long time and is widely accepted by both water quality engineers and those communities/families/persons who use and maintain these systems. This choice for obtaining clean drinking water is most effective where somewhat clean water is difficult to come by or where there is a shortage in water supply. This is because it may be most beneficial to pump and purify where water is more plentiful.

The simplicity of this method and the result of quality drinking water is ideal in humanitarian assistance and natural disaster emergencies. It is worthy of being a viable option to increase clean water consumption.

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