The diagrams illustrate how a solar panel is constructed and how it can be used to heat either air or water.
Overall, the panel is a simple structure consisting of just two components, and the only difference between the two applications is the medium being heated: air in the first case and water in the second.
The basic solar panel is a shallow box with a transparent cover placed on top. The box is dark in colour, which allows it to absorb as much heat as possible.
In the first application, the panel is used to heat air. Sunlight, which carries heat energy, passes through the transparent top and warms the interior of the box. Cool air enters through an inlet on one side, is heated as it moves across the box, and then leaves through an outlet on the opposite side as warm air.
The second application works on a very similar principle, but a water pipe is installed inside the box. Once again, the sun’s rays penetrate the transparent top and heat the interior. Cool water flows into the pipe, absorbs the heat while travelling through the box, and finally exits as warm water.