Heat Absorption and Insulation

To absorb and release heat you would desire an excellent thermal conductor. good thermal conductors are poor thermal insulators (in fact there is an inverse relationshp between them). Plastics tend to be poor thermal coductors, were as metals tend to be good thermal conductors, however solar radiation is mostly blocked by metal.

Do you want to evaporate water inside a capsule to collect pure water, or release it for cooling? What is your objective?

I know thing that you don't know, but I don't know what you do know.

Yes, the objective is to evaporate water inside a capsule to collect pure water. I know materials such as copper are good absorbers of heat, and also good because they slow release the heat. So heat collected during the day could be slowly released at night to keep the evaporation process going. But how about the use of a double-wall? Ie, like Bodum's double-walled coffee mugs. I know the layer of air between the two walls insulates the heat inside - BUT does it also prevent heat from entering through the two walls too?

check these too: http://www.waterpyramid.nl/ http://www.particlepanels.com/ Good luck!

Heat moves by three methods. Conduction, Convection, and Radiation. You are gathering heat energy from a radiative heat source (the sun) this type of energy can pass through materials such as glass which are barriers to heat movement by convection, and can be more or less conductive based on design (single or double pane, etc) What you must account for is the cooling effects of evaporation, and the introduction of additional water.

You can build a thermal reservoir to help the process coast in to the night, but that will also require lost process time to recharge.

In short my recommendation is to make your still as efficent as possible while the sun shines, and let it rest while the energy source is not available.

this is a mature process, called solar distillation.

It usually has an insulated flat tank with a black bottom and sides with a clear cover that is tilted to allow water to condense on it and run down to a collecting channel.

Look at these sites.

http://www.google.ca/#hl=en&source=hp&q=solar+distillation+of+sea+water&aq=1&aqi=g10&aql=&oq=%22solar+distillation%22&gs_rfai=&fp=7767a3cd0aa0c10f

Very cool web site!!!

For your info:

Some solar heating panels use what is called HEAT PIPES.

Basically, a copper tube runs inside a Glass Tube. This is exposed to the sun rays. Radiation heat from the sun will heat the tube and the gap between the glass and the tube works as an insulation against loss by convection.

The Heat collected is used to evaporate the liquid (closed circuit) inside the tube which migrates to an insulated part of the tube, which is floded by the water to heat (or any media). The cooling of the vapor or steam, generates mor heat transfer (mor efficient) than ordinary solar heating panels.

Therefore, by shifting the heat out of the panel, you can insulate it and store it and ....

@LAA Lucke - That was an exceptionally poor explanation of the vacuum tube collector- sorry 'bout that.

Do some research on Phase Change Materials.

They can be formulated to absorb heat and slowly give it off as they change phases.

Look at vacuum solar collection tubes or aka evacuated tube solar collectors. They allow the sun's heat in to heat the water which circulates through a heat exchanger in an insulated water tank.

The vacuum prevents heat loss while the heating is taking place and the insulated storage holding tank prevents heat loss of the stored water.