Passive Solar Heating vs Active Solar Heating

father and son in front of active solar powered house
  • 1-100 hours
  • Intermediate
  • 0-20,000

The concept of solar power isn’t new. In fact, harnessing energy from the sun is a practice that dates back to at least 1839 when Alexandre Edmond Becquerel discovered the photovoltaic effect that's credited with explaining how electricity can be generated from sunlight.

In the years since his discovery, the science of solar power has advanced, bringing with it new technology. While you may immediately think of solar panels when considering solar power, there are many variations that allow us to harness the energy of the sun. Actually there are two primary ways. The first is passive and the second is active.

Passive Solar Heating

Easily explained, passive systems take advantage of structural location and building materials to optimize heat directly from the sun. Passive systems do not rely on any external devices to function. They are ‘passive’ because they don’t require electricity in order to collect or transfer the sun’s heat. This type of system can be as simple as situating large windows on the south side of a building during construction or renovation. A sunroom on the south side of the home can also trap warm air from the sun, providing heat to the home.

passive solar roof with skylight windows

In addition to orienting the building towards the sun to take advantage of the sun’s benefits, proper insulation inside also contributes to passive solar heating. Insulation throughout the building reduces the amount of cold and hot air transfer. That helps keep the area cool when it’s hot outside and warm when there’s a chill in the air. Insulation can be placed in the roof/attic, flooring, and walls. Additional insulation around doorways, windows, and even outlets are another form of passive solar heating.

Using Trombe walls, which are made of dark materials such as concrete, is another effective use of passive heating. On the outside of the Trombe wall, a glazing is applied, leaving a gap between the glazing material and the wall to act as a greenhouse. This process naturally stores heat during the day and slowly releases it at night for passive temperature control.

passive solar greenhouse hallway solarium

Another passive heating technique is the use of natural landscape to shade the building against intense heat or to open the building up to receive sunlight as needed.

Basically any process, material, or design that naturally heats and cools a space is seen as passive. The obvious advantage of a passive system is that it is free and requires no additional hardware to maintain. A more subtle benefit is that passive solar heating doesn’t come with any potential health risks.

Active Solar Heating

hands connecting solar panel to multimeter

Active systems rely on devices to convert the sun’s energy into a more consumable form, such as hot water or electricity. This is where those ubiquitous solar panels come into the picture.

Active solar heating requires the installation of the entire system. This may be a small plug-and-play device that supplements power to an RV, or a comprehensive interlinked system used to power a business. In addition to the flat photovoltaic panels, the system uses either liquid or air as a conductor for the energy. Systems relying on liquid are known as hydronic collectors, while those using air are called air collectors. One type of system traps warm air and relies on a fan to move the air around the home, while the other collects heat and relies on a radiant heating system or a heat exchanger to transfer it.

apartments with active solar power

The energy produced by active solar heating systems is reliable even after the sun goes down due to the ability to store the energy in batteries for later use. However, active systems are expensive to install and maintain. Even with the initial cost and upkeep, active solar heating will save you significantly on your monthly energy costs, with most systems paying for themselves in seven to ten years.

On the down side of active solar panels, some reports claim the fluids used to store heat in the solar panel have the potential to release toxins into the air and create a health risk. The equipment used in active systems also wear out, and disposal is deemed an environmental hazard.