SolarSacks are a new, World Health Organization-approved method for purifying water in low income areas with limited access to the essential resource. They consists of four-liter pouches that harness the Sun's energy to remove more than 99.9 percent of pathogenic bacteria in water.
The biggest benefit of SolarSacks is their cost efficiency. Each sack costs less than 25 cents to produce, and they only get marked up to about one dollar per sack for the end consumer (presumably aid organizations and local governments.) That markup accounts for the cost of distribution — the Danish students behind SolarSacks will not take any profit from the endeavor. Further, since sunlight is free and abundant in Kenya and Uganda, the two countries where the product has undergone trials, there is no cost to power them.