• Brainly User
As the rays of the sun strike the collectors, they are converted into heat waves. The same type of principle applies to the heat that is trapped in a windowless room or the heat in a car with the windows rolled up. That heat energy is then transferred to the water storage tanks ,where it heats the water until is it called upon for use. You can break it down like this: Rays from the sun shine on the panel collectors that subsequently transfer that heat to the water storage tank.
The pipes of the water heater are painted black which improves the conduction of heat and since the sun rays are infrared rays the pass in the glass window but doesn't go out and thus making the water warm