Active vs. Passive Solar Systems

It’s a sunny, clear, fall day. You get out of bed, pour your coffee, and shiver. It’s still a bit cold, but you want to conserve energy and it’s way too early in the season to turn on the heat. So you put on your robe and open the blinds so the south-facing sun comes pouring through your bay windows. As you bask in the glow, staring at the leaves that turn your suburban neighborhood into a palette of color, and sip your coffee, you begin to warm up. Congratulations! You’ve started your morning taking advantage of passive solar energy!

A passive solar system can be as simple as letting the sun pour through your windows to heat up your room, or a solar hot water system installed on your roof, which uses the warmth of the sun’s rays to heat your water, then stores it until you need it. This is sometimes called a thermal solar system.

But that’s not how an active solar PV array works. Many people get confused between a passive solar system and an active solar system — understandably!

What Is An Active Solar System?
The key difference between an active solar system and a passive solar system is this: Passive solar energy uses the heat of the sun, while an active solar system uses the sun’s irradiance, or radiation (the sun’s rays), which it converts to electricity to power systems in your home.

One example of an active solar system is a photovoltaic solar array. In a solar PV array, it doesn’t matter how hot the sun is by the time its light and warmth reach your home, as long as some of the sun’s rays are hitting the solar panels. The photovoltaic panels — made from silicon or something the solar industry calls thin-film technology (a variety of elements shown to effectively conduct electricity) — convert the sun’s rays into electricity, which is used to power your home.

When your solar PV array is connected to the grid, the excess power can be sold back to the electric company for credits on your electric bill. At times when your solar array isn’t powering your home, you’ll pay for the electricity with those credits in a process called net metering. That’s why a solar array may permit you to see electric bills as low as $5 (the average monthly charge just to be connected to your electric provider.)

Active or Passive Solar: Which Benefits You More?
When we think of all the ways the sun can help us live better, more comfortable lives, we realize it’s no wonder solar power is gaining popularity every day. Using passive solar energy in easy ways every day (like opening your blinds for the sun’s warmth on a cool morning) can lower your electric bills, but you’ll see real savings by combining these practical, everyday passive solar measures with a solar PV installation.

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