Do-Right Solar is proud to offer for sale a solar water still that is hand-crafted from quality components. The model SWS-200 solar still produces exceptionally pure water, at a rate of 2-3 quarts/day (depending on climate and season), enough to satisfy the drinking water requirements of 1-2 adults. The solar distillation process removes contaminants such as heavy metals, nitrates, pathogens, chromium-6, and pharmaceuticals. It is a cheaper and greener alternative to a reverse osmosis (RO) system. You simply place it in a sunny spot in your yard and hook it up to a hose faucet. About once a week you replace the filled collection vessel (glass carboy) with an empty one. It can also be used in emergencies when there is no pressurized tap water, capable of distilling even sea water (functioning as a desalinator). The SWS-200’s high performance and versatility provide true water security to the individual!
The SWS-200 solar still is a “wick” design, meaning that inside there is a black cloth kept moist by a slow steady stream of water. This wick, having only a small mass, heats up quickly upon exposure to the sun, resulting in a fast response time. Water from the hot wick evaporates, rises, and subsequently condenses on the glass pane. The condensed distilled water droplets then run down the glass pane and out of the still into the receiving vessel.
The SWS-200 solar still is hand-built, and is essentially an enclosed glass box structurally supported by a wood frame. Joints between glass faces are sealed with food-grade silicone caulk (FDA compliant and NSF-51 and NSF-61 certified). The output plumbing consists of stainless steel pipe (alloy 316) and silicone tubing, while the receiving vessel is typically a 3- or 5-gallon glass carboy that the user places on a dispensing crock when full. This careful choice of materials ensures that the distilled water remains pure. All of these materials are inherently inert and therefore will impart no taste or contaminants to the distilled water. Any remaining volatiles in the distilled water are removed at the output by a granulated activated carbon (GAC) post-filter. This filter consists of a silicone tube filled with coconut husk GAC. The silicone tube is permanent, and only the GAC itself is periodically replaced. Finally, the SWS-200 is weather-resistant (siding stain, EPDM gasket, silicone sealant) and should last for many years.
The SWS-200 solar still should provide enough drinking water for an individual when the unit stays fixed pointing south. Greater output (up to 40% more), though, can be achieved if the user actively points the unit directly at the sun. Families, who require yet higher quantities, can easily daisy-chain together multiple units that share the same input and output lines. Finally, in the event of an emergency when no pressurized tap water is available, the SWS-200 can deliver pristine distilled water from sources such as sea or pond water. It is only necessary to slightly elevate the source water above the level of the still in order to create a little pressure. For particularly murky source water, some pre-filtering (e.g. with a simple sand filter) is recommended.
Installation of the SWS-200 solar still is very simple. In the most typical passive configuration, the still sits on a table or cinder blocks in a sunny spot in your yard pointing south. The still hooks up to a standard hose faucet using tried-and-true drip irrigation technology, with the flow of water controlled to a slow drip into the still. An optional timer can automatically shut the flow of water off during the night to save a little water. Maintenance of the SWS-200 consists mostly of replacing the full carboy with an empty one (about once a week). Less frequently, the carbon in the GAC post-filter will need to be replaced, and the wick will need to be cleaned of sediments. Even less frequently (perhaps every couple of years), the wick will need to be entirely replaced, as over time it is expected to slowly fade, reducing the still’s productivity. Replacement wicks are available.