Lack of access to clean water causes the deaths of millions of people worldwide and in regions such as sub-Saharan Africa, clean water can be several days walk away. Producing a simple and cheap method of purifying water which doesn’t rely on first-world amenities such as a steady electricity supply, or batteries, has proven a significant challenge thus far, but a new prototype device created by Ryan Lynch and Marcus Triest offers hope of doing just this, for an estimated cost of around US$5.

Like the Solaqua we previously reported on, the Solar Bag uses the SODIS (or solar water disinfection) method of water purification, which typically works as follows: PET (polyethylene terephthalate) bottles commonly used to transport soft-drinks are filled with unclean water and left in the Sun. Following exposure to the Sun’s UV-A radiation, the overwhelming majority of germs contained within the water are eventually eliminated, rendering the water safe to drink.

However, while PET bottles can usually only purify up to three liters per every six hours of sunlight, the Solar Bag's makes claim that its combination of high clarity polyethylene and black polyethylene allows the device to purify 2.5 gallons (9.4 liters) in the same time-span, and that it will start working on the purification process while still being transported. These two differences could potentially save lives, making the Solar Bag project an exciting prospect, even in this early stage of development.

At present, there's no definite information as to when we can expect the Solar Bag to be manufactured.

Sources: Ryan Lynch, Marcus Triest, via TreeHugger