Solar distiller prototype underway

I posted recently about the Carocell 1000 solar distiller panel, that was given to me about five years ago:

http://bkhome.org/news//201904/fcubed-solar-water-distiller.html

Then, posted about initial plans to do a DIY panel:

http://bkhome.org/news/201904/planning-a-diy-solar-water-distiller.html

Construction is now underway. Originally, I planned to build a dual-glass-pane panel, like the Carocell, however, ran into various technical difficulties regarding suitable materials.

The dual-pane design gives highest output, as condensation occurs on both front and back panes. There is a cloth membrane that water trickles down, and evaporated water may condense on the front pane. The heated air will rise, and will then flow down behind the cloth membrane, a much cooler environment, and condensation will occur on the back glass pane. This gives rise to a circulating current of air.

I did see an article in "Mother Earth News", back in the 80's, with a similar dual-pane design.

The dual-pane design will require a sheet of glass/metal/plastic, with black cloth laid on top, mounted at an angle of about 25 - 30 degrees. As I wanted to build the first prototype with wood, I would have had to coat the central wood sheet to make it totally waterproof, and to tolerate 100°C. The coating would have to be suitable for potable water and high temperature. Could not find any suitable paint, though there was one epoxy that met the specs -- but the fact remained, enclosing a plywood sheet with waterproof membrane may not be a good idea, as any vapours emitted from the wood will cause the coating to lift off.

Decided that the dual-pane design would have to be entirely aluminium frame, with glass or plastic inner sheet. Could not find a plastic sheet that met the specs -- though I know that there are such plastics, as my electric kettle is made of plastic.

Instead, for the first prototype, decided to build a trickle-down design with just one glass pane, no back pane. Wood construction, "premium ply" sheet. On top of the ply sheet is a 0.5mm thick sheet of aluminium. The water collection runoffs, for the leftover "dirty" water and the distilled water, has been fabricated with 0.3mm aluminium flashing. Selleys 401 silicone sealant is to be used, as this is rated as food-safe, for potable water, and a very high temp rating.

The construction is such that no wood will be exposed to water vapour. The solar collection area is about 600 x 880mm.

Construction is at an advanced state, well, maybe 2/3 done. One thing not yet figured out is how to mount the glass pane. I want a semi-rigid silicone "gasket" around the wood frame, onto which the glass can be lowered, and held in place with some aluminium brackets.

I could just squeeze out the Selleys 401 sealant around the frame, then put the glass on top, however, the glass will then be stuck on. I want to be able to remove the glass pane, so as to be able to make internal changes. This is a prototype, and want to be able to pull it all apart and put together again.

If there was some kind of silicone tape, that would be nice. Otherwise, will attempt to spread the 401 sealant as an even layer around the frame, let it set before putting the glass pane on top. may need to construct some kind of spreader to achieve a perfectly level surface.

Here is info on Selleys 401 sealant:

http://www.selleys.com.au/trade/building-products/silicone-and-other-sealants/silicone-401-rtv/

Photos will be posted when it is completed.

Tags: nomad