How does water heated by a solar collector circulate through the supply system?

Water heated by a solar collector circulates through the supply system primarily due to convection. In this process, the water in the solar collector absorbs heat from the sun, causing it to become less dense. As the temperature of the water rises, the heated water rises to the top of the collector or system, while cooler water, being denser, sinks down to take its place. This creates a continuous flow of water, allowing for an efficient transfer of heat throughout the system.

Understanding convection is essential in the context of solar heating systems because it highlights the natural movement of fluids due to temperature differences, which is a fundamental principle in thermodynamics and fluid mechanics. In contrast, gravity would simply pull the water down without active circulation, conduction refers to heat transfer through direct contact (not movement), and radiation describes energy transfer through electromagnetic waves, which is not applicable to the movement of water in this context. Thus, convection correctly defines how the heated water moves within a solar collector system.