What Are The Different Kinds Of Solar Power?

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There are several different kinds of solar “power,”  but they all fit into one of two categories. Solar power is either PASSIVE or ACTIVE in nature.  We’ve seen a lot of interpretation on the web of what these two categories represent, but when you look back to the original experts that wrote the first complete books on the subject, they define them as below.

Passive vs Active

Passive solar power is doing something to harness the power of the sun that doesn’t involve electricity.  This can be as simple as opening your curtains and letting the sun shine into your home to heat the tile floor – or as “complex” as a solar air heater.   (We’ll write more on solar air heaters in a few days.)  Things that usually fall into the passive category are solar ovens or water-based systems that circulate the water through in a principle known as thermosyphoning.  In thermosyphoning, the water is “pulled” through the system not by a pump, but by an action which causes the warmed water to rise up and out of the heating panel, which draws in cooler water at the bottom.

Active solar power involves electricity.   Examples are photovoltaic panels or any system that uses pumps or fans to move the heat created by the sun.

Each one of these categories can be further broken down into various subcategories – with some cross-over.

Concentrated

You can utilize “concentrated” solar power in either passive or active solar applications.  Concentrated solar power can be achieved through a parabolic dish or trough – or just by leaning a mirror or two at the correct angle next to your solar collector.

Photovoltaic

Photovoltaics (also referred to as PV) are usually flat dark-looking panels that are mounted on a rooftop.  They fall into the active category, even though they create electricity, they also require pieces of auxiliary (electric) equipment to do so.  Many people unfamiliar with solar power think this is the only kind.

Solar Thermal

This is another category that could be either passive or active.  Solar thermal captures the power of the sun to heat something – usually a liquid, then utilizes that heated liquid for something like a hot shower, or to heat a room (as in radiant heating).  Most passive types of solar are of this type.

Closed or Open Loop Systems

Either of these terms can refer to air or water heating systems.  An open loop system is one in which a substance is heated, then stored for use or used immediately.  Think of a shower – the water is heated, it could be stored or used directly, the water is used to wash you, and the water goes down the drain.  You may capture the used water for watering your garden, but the water is not returned to the heating system.

In a closed loop system, a substance is heated, that substance is usually transferred to another area where the heat is dispersed, then the substance returns to the original heating area to be heated again.  Think of a radiant floor system – the water is heated in a solar thermal collector of some kind, the water is routed to the floor of a room where it releases some of its heat up through the floor to heat the room, then the “spent” (less warm) water comes back to the solar collector to be heated again.

Well, there you have it.  Pretty simple.  These are most of the often used words for solar power.  There are a few more, but if you’re familiar with these, you can carry on a conversation.