Here is a design for an inexpensive and easy to make portable solar water distiller.
It works by allowing evaporated water to collect in a reservoir created by the space between two concentric plastic bottles.
The reservoir is another plastic bottle covered in a black colored fabric to make it hotter than the surrounding structure.
The collector is kept at a lower temperature using evaporative cooling.
The temperature differential created by the evaporated cooling should allow the condensation process to happen a little faster than it would without it.
Step 1: Materials
a hot knife for cutting plastic
a vapour mask to avoid fumes
one or more white socks
one or more black socks
Step 2: Cut the Bottoms Off the Larger Bottles
Cut slowly through the plastic bottles, removing the lowermost portions as illustrated.
Step 3: Insert the Tapered Neck Bottle Into the Larger Domed Bottle
Slide the large bottle with the tapered neck inside the large domed bottle so they are concentric.
Leave a bit of clearance between the cap of the domed bottle and the opening of the tapered bottle.
Step 4: Remove the Top Portion of the Smaller Bottle
Step 5: Cover the Smaller Bottle With the Black Sock and Fill With Water
Fill it with the water to be distilled.
Step 6: Saturate the White Socks and Put Them Over the Top Bottle
Step 7: Set the Larger Bottles on Top of the Reservoir
Step 8: Place in Full Sun and Wait a Very Long Time
When enough water has collected in the reservoir, remove the top portion cap and pour the distilled water from the reservoir.