Passive Solar Water Heaters are simple, reliable systems that use natural convection to circulate water or heat transfer fluid through solar collectors without the need for pumps or mechanical devices. They rely on gravity and thermosiphon principles to move heated water from the collector to the storage tank, making them low-maintenance and energy-efficient. Ideal for residential and small commercial applications, passive systems provide sustainable hot water, reduce energy costs, and are particularly suitable for areas with consistent sunlight. Their simplicity, durability, and eco-friendly design make them an accessible and cost-effective solution for solar water heating.