Which of the following is an example of a passive solar technology?

• A. Photovoltaic panels
• B. South-facing windows designed to capture and store heat
• C. Solar water heater with a circulating pump
• D. Wind turbine array

Answer: (B)

Passive solar technology uses the design of a building and its materials to capture, store, and distribute heat from the sun without relying on pumps, fans, or electrical devices. The best example is south-facing windows designed to capture and store heat. In the northern hemisphere, these windows allow abundant daytime sunlight to enter and heat interior spaces. The heat is then stored in materials with high thermal mass, such as concrete, brick, or stone, and released slowly as temperatures drop, helping to reduce the need for mechanical heating.

In contrast, photovoltaic panels convert sunlight directly into electricity, which is an active solar process. A solar water heater with a circulating pump uses a pump and moving fluid to transfer heat, another active system. A wind turbine array is not solar energy at all.