Integral non-pressurized solar water heaters, also known as passive solar water heaters, work using thermodynamic principles. Here is a brief breakdown of how it works:

Components: A solar water heater typically consists of a solar collector (usually a flat plate or vacuum tube), an insulated tank, racking, and connecting piping.

Heating Process:

Solar collector: The collector absorbs sunlight and converts it into heat, in which the water is heated. Generally flat plate or vacuum tube structure.

Hot water rises: The heated water in the collector becomes less dense and rises to the storage tank, usually located above the collector.

Gravity flow: As the system is not pressurized, the flow of water is achieved by gravity without needing a pump or external pressure.

Cold water replenishment: As the hot water rises, the cold water in the storage tank is drawn into the collector to be heated, creating a cycle.

Storage and insulation: The heated water is stored in the tank for use when required, such as for bathing or cooking.

Insulation: The storage tank is usually insulated with good thermal insulation to minimize heat loss and ensure that the hot water remains warm for as long as possible.

This solar water heater design system is simple, reliable, and low maintenance, making it the preferred choice for residential hot water heating.