Carrying large amounts of freshwater with you is rarely a practical or sustainable solution for back-up or emergency situations when away from your reliable water taps at home.
You could be hiking in remote areas with brackish water streams or near the sea, you could be sea kayaking, boating or just be living near the sea in areas where the freshwater supply grid is unstable.
In such situations, a collapsible bottle-sized desalinator, that functions independent of a power source and of limited size and weight, could be of high, and potentially critical, value. Such a solution is exactly what CowaTech is working on. A first-generation prototype is expected ready by third quarter of 2020.