How do active solar energy systems differ from passive solar energy systems?

• A. Active uses mechanical devices such as PV cells; passive does not
• B. Both rely solely on passive designs
• C. Passive uses fossil fuels to augment heat
• D. Active relies on wind power

Answer: (A)

This question tests the difference between active and passive solar energy systems. Active systems rely on mechanical or electrical devices to collect, convert, or move solar energy. For example, photovoltaic panels directly convert sunlight into electricity, and solar thermal setups use pumps or fans to circulate a heat-transfer fluid to collectors and storage. Passive systems, on the other hand, harvest and store heat without any moving parts or external power—using building design and materials such as south-facing windows, thermal mass, insulation, and natural air-flow to collect and distribute heat.

So, the statement that active uses mechanical devices like PV cells while passive does not is the best answer. The other ideas don’t fit: passive does not need fossil fuels to add heat, active does not rely on wind power, and both cannot be described as relying solely on passive designs.