# Solar still and how it works

I use a solar still that holds 182 cubic feet of water. Here is how it works:

There is an insulator on both sides of the metal bowl. On the outside it covers the whole thing. on the inside it covers the sides but not the bottom. This collects the rain and also heats up the rainwater during sunny days so that the evaporation rate is faster. I have the pipe nearest the metal bowl the largest it can be while the metal bowl still collects rain and gets heated up by the sun. The water and any gases pass through there and into the condenser. I have this cold enough to condense water into a liquid but not so cold that the water turns solid and the ${CO2}$, ${O2}$, ${N2}$ etc. turn liquid. Last but not least there is a spigot at the very end and a bucket below it. This separates atmospheric gases from liquid water with ${CO2}$ being the main concern.

There is also dust and pathogens from the air in rainwater.

The dust most likely will stay behind and just make the bowl dusty. The pathogens get killed by the heat that there still is when all the water has been evaporated.

I would say the maximum loss with this system is from 1 pint or so to 1 gallon or maybe more depending on the water level in the bowl.

However I think there is a way to calculate maximum and minimum loss(neither of these is 0).

How could I calculate maximum and minimum loss based on the depth of the water(because obviously at different depths there is a different amount of loss) and the size of everything(which by the way the pipe slowly tapers off to a certain size and so you have to take pressure into account as well as volume)?

Also how could I calculate the pressure in the pipe based on the fact that it tapers off and starts at the maximum size possible with the bowl still collecting rain and being heated by the sun?

The water gets into the bowl by rainfall and gets heated up by the sun. Also my pipe starts off as large as it can be without blocking sunlight and I am afraid that if the bowl is closed that 3 things would happen: 1) There would be an insulator up top making the water even hotter because of raised conduction and 2) the sunlight would be blocked by the insulator and lastly 3) Rain will not be able to fall into the bowl.

How can I solve this problem so that rain can fall into the bowl, the bowl is closed except for the hole that the pipe goes into, and the water still gets heated up by the sun?

Also with the simplified truncated cone with a small radius of 5 feet and a large radius of 10 feet and a depth of 1 foot as well as a volume of 182 cubic feet how much does the total volume increase per inch as far as % increase because then I can just divide it by 100 to get per 100th of an inch and then multiply that by the depth in hundreths.

• It seems that solar distillation set up are used where there is no rain en.wikipedia.org/wiki/Solar_still to get clear water. what is the purpose of your still? If you close it up with a metal surface the heat will still come. If you build a collecting bowl/area on the side you can pipe the rain water in. Why do you need insulation if you want to heat the water? I use a complete metal 1 ton water container to get warm water for rinsing from the sea in the summer. Gets sun from the sides too. – anna v Jul 2 '14 at 4:33
• While physics lies at the mathematical heart of engineering, it is often the case that some practical acumen is more use in getting started than asking for ab inito calculations. Like time lords, engineering has more than one heart and the other one involves art, creativity and a good sense for tradeoffs. – dmckee Jul 2 '14 at 4:46
• An insulator around a conductor keeps the heat the conductor produces nearer the conductor whereas the conductor by itself makes the heat diffuse into every single cubic inch and even into the atmosphere. The purpose of my still is also to get pure water but in this case I get quite a bit of rain with at least 1 sunny day between the times that it rains and usually more and want as much water as possible because of how water is first on the list of importance in survival and in this case I am on a planet completely new to me with nothing but earth-like conditions and landscapes. – Caters Jul 2 '14 at 5:07
• An insulator on the sunny side keeps the heat out. That is what insulation means. The sun supplies up to 1200watts/meter square vertical. Is your sun always vertical? tropics? then insulation on the sides makes sense. Otherwise you lose energy. Closing the top completely with a metal cover or a glass one ( hot houses) makes sense to get heat. Rain water can be collected from the roof or a specially designed raised area. Since you are distilling the extra dust is no problem. It will settle at the bottom of the bowl or be distilled. Of course you can always incline the glass top for the rain. – anna v Jul 2 '14 at 5:21
• but a bare conductor means the heat is more diffuse than it would be with an insulator around it. In fact this is the reason wires have insulation around the metal except this is for electrical conduction and not heat conduction. I am in the same latitude range as Memphis, TN which has a last frost in the 3rd week of march and in every month there is a lot of warm and/or hot weather and very little cold weather in the winter but because of how there are days in the 60s, 50s, 40s, 30s and below it isn't the tropics which tend to be in the 80s and 90s at the lowest. – Caters Jul 2 '14 at 5:32