Final answer:
The book 'The Boy Who Harnessed the Wind' provides an example of energy conversion through solar cells, where sunlight is converted into electricity and then into mechanical energy.
Step-by-step explanation:
An example from the book The Boy Who Harnessed the Wind demonstrating how the sun can be used to produce energy is the use of solar cells. Sunlight hitting a solar cell generates electricity, which can then power an electric motor. This is an illustration of energy conversion where solar energy is transformed into electrical energy and subsequently into mechanical energy, aligning with the law of conservation of energy that states energy can be converted from one form to another but not created or destroyed.