Passive versus Active Solar Energy

Jess Hutton | July 27, 2015 | Industry Knowledge

We hear of passive solar energy and active solar energy, but what are they exactly? What is the difference between them? How do we apply them?

In modern times, capturing solar energy and advancements in the solar industry are popular topics that continue to gain momentum. This is largely due to the concerns regarding fossil fuels and their environmental impact. Coupling technological advancements with strategic planning, we can harness the sun’s energy to use for heating and electricity in both passive solar energy and active solar energy systems. Both are important and have their benefits, so let’s explore them a bit further.

What is Passive Solar Energy?

Passive solar energy takes advantage of existing radiation generated from the sun by capturing it, but not using anything to actively enhance the process. The biggest component in determining the efficiency of passive solar energy is thermal mass. Thermal mass is a material’s ability to absorb, store, and release heat. Materials such as rock, brick, and tile have a high thermal mass, which means they retain heat for longer periods of time than less dense materials, such as lumber. We see examples of this when it snows. During a season’s first snow, the roads generally melt snow pretty quickly, while snow sticks to trees, leaves, and plants. The thermal mass in concrete roads is denser than that of the surrounding flora. Efficiency is improved by positioning a home, building, or object in a way that enables it to absorb, store and release heat efficiently.

Examples of Passive Solar Energy

  • Cars – The sun shines on a car, and the heat is trapped inside by the seats and floor.
  • Greenhouses – The sun penetrates the greenhouse windows. The heat is absorbed by the plants or contents inside the greenhouse, and then it is reflected back towards the windows.
  • Home windows – The most efficient way to experience the benefits of passive solar energy is to position windows in a way that allows heat to enter in the winter but not in the summer months. This varies by location, but south-facing homes in the northern hemisphere are typically the most effective for passive solar energy absorption.

What is Active Solar Energy?

Active solar energy uses mechanical and electrical equipment to enhance the sun’s conversion of solar radiation to heat and electric power. Active solar energy systems require a solar collector, which is used to absorb solar energy. The most well-known solar collector is a solar panel system. Solar panels are made of photovoltaic cells, devices which directly convert solar radiation into useable electricity. A solar collector (or panel) heats the fluid through the panels and pumps it through a system of piping to heat a space or building or to store electricity for later use. The typical solar conductors used are air or liquid such as water or a special type of antifreeze. Other solar collectors may be solar towers, solar air heaters, flat-plate collectors, evacuated tube collectors, or solar bowls- all more complex systems for generating heat and electricity on grander scales.

Examples of Active Solar Energy

  • Liquid-based solar heating – Used for central heating and water heating in domestic systems
  • Room air heaters – Installed on a roof or home exterior, this system has a plate that is heated by the sun’s radiation. An electric fan or blower pulls the air from the room, heats it, and blows it back into the room.
  • Solar panels – Heat radiated from the sun is collected by solar panels, and transferred via air or liquid to provide electricity or heat for homes, buildings, or rooms. This is the most well-known type of active solar energy systems.

So what do you do with all of this new information? Hopefully, your interest has been peaked, and we can answer any new questions you may have about a residential solar panel system.



Wikipedia Solar Thermal Collector


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Wikipedia Solar Cell Efficiency


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