User:Mmanchanthasouk/sandbox

“Heroes may not be braver than anyone else. They're just braver 5 minutes longer.”- President Ronald Reagan

Overview
A solar still is a water collection method used typically for emergencies. The principle of the solar still is to use the sun’s heat energy magnified by a clear sheet of glass or plastic into a hole with a focus point. The water is evaporated out of the ground to land onto the underside of the plastic wrap that acts a dish to prevent water from going into the atmosphere. The condensate from the evaporation pools into the center point created by a weight and drips into a container, typically a bowl or cup. To maximize water output, a sunny day and damp soil is preferred.

Typical materials for a Basin-type Solar Still
2-4 stones, plastic wrap or transparent glass, a weight for the center to make a point and a container for the condensate.

Variations of the Solar Still
An alternative method of the solar still is called the transpiration bag. The bag is a simple plastic bag and it folds over a stemmed plant with a corner pointing down to allow the condensate to pool. From there a person can remove the water by taking the bag off and pouring the water out or one can make a tiny incision into the corner to drip water into a cup. Its advantage over the basin type solar still mentioned before is that it only requires a bag like one can get at the grocery store. It doesn’t need to be completely transparent. A disadvantage is the requirement of the transpiration bag is the requirement of a plant in direct sunlight or heat to take the condensate.

In a study performed in 2009, variations to the angle of plastic and increasing the internal temperature of the hole versus the outside temperature made for better water production. Other methods used included using a brine to absorb water from and adding dyes to the brine to change the amount of solar radiation absorbed into the system. During the adjusted tilt angle experiment, the different angles used by the different researchers created different results and it was difficult for any of them to get a definite answer. In the graph, a bell curve is noticed with the maximum water output being at 30 degrees angle adjustment. Each brine depth created a different amount of water and it is noted on the graph that about an inch is optimal with a decreasing trend if more is used.

Another method for the solar still is the “wick” type solar still. A box is constructed and held at angle. Salt water is poured in from the top and then the heat from glass panel magnifying sunlight evaporates the water and has the condensate drip to the bottom leaving puddle of brine in the still attacked to the wicks that separate the water into banks to increase surface area for heating. The distilled water comes out of the bottom and depending on the quality of construction most of the salt has been purged from the water. The more wicks, the more heat can be transferred to the salt water and more product can be made. A plastic net can also catch salt water before it falls into the container and give it more time to heat up and separate into brine and water. The wick type solar still is made vapor tight, as in the vapor does not escape to the atmosphere. To aid in absorbing more heat, some wicks are blackened to take in more heat. Glass’s absorption of heat is negligible compared to plastic at higher temperatures. A problem, depending on application, with glass is that it is not flexible if the solar still is not a standard shape

Problems with the system
The system is inefficient for how much work is put into it versus the water output. Digging a hole to requires energy and makes a person lose water through perspiration and the amount of time needed to fill the container isn’t guaranteed. Because of this, it is advised to make a solar still to supplement another water source, such as a reverse-osmosis unit or purification tablets. In a survival situation where you are stationary, this wouldn’t be too big of an issue if you are being saved from that location. But, if you are constantly on the move, this wouldn’t be a great idea due to the stop time needed to make one.