Passive solar is a form of “power generation” that is not explicitly “electricity generation.” These are a variety of simple (and mostly cheap) technologies that allow use of the sun in creative ways to produce some of the outcomes for which we usually rely on electricity (i.e. heat).
Before getting into what you can actually build, let me throw out an example or two of what might be considered “passive solar.” Let’s say you have south facing windows. These windows will get a lot of sunshine (well- more than anywhere else- I live in a desert right now, but I’ve also lived in a rainforest, so I certainly realize the difference). Let’s say it’s winter. So when you get up in the morning, you make sure all the curtains are drawn on the south-facing windows. If it’s summer, you do the opposite. You have just created a passive solar system- you use the sun for heating in the winter and block it in the summer.
Obviously, though, this site is primarily focused on generating green energy. So when I say “passive solar,” I’m talking about a more active system. That said, with exception of a few types of passive solar, most of these systems are primarily design features.
Passive Solar Overview
Orientation and Windows: As I mentioned above, the primary form of passive solar technology involves the orientation of the house and windows. If you live in a climate where your primary need is heating, orienting windows to the South will allow maximum sun exposure. Simultaneously, designing a house with minimal exposure to the North will do exactly the opposite- prevents the sun from heating the house up too much while still allwing for natural light.
In addition to their orientation, however, modern windows can add an additional benefit to your house. Let’s suppose you don’t have the ability or desire to add more windows to your house. You can replace the glass, however. This can be beneficial in two ways. Many of the more up-to-date windows are more insulating. In addition, some modern windows are glazed with heat trapping substances that allow the windows to trap heat from the sun and warm your house.
Passive Heaters: I will go more into detail about this, but the basic idea of this system is like the heat trapping windows mentioned above. Glaze a piece of glass or plastic- or simply paint it black- so that it traps heat. Then place it on the outside of box with a small opening to allow air in. The glazed piece heats the air inside the box, which is connected- either directly to a window, or through tubing, into your house. It is elegantly simple and uses the heat produced by the sun to heat without any cost to you. Furthermore, when you don’t need it, simply disconnect it from your window.
As a brief aside on this technology, I was surprised on a visit to my uncle in coastal Oregon to see that he had built one of these system to heat his own home. This is place where it’s cloudy nearly all day every day during the cold months. Yet his system worked efficiently to heat their house. It’s easy to write this off, but it works.
Thermal Mass: The most basic form of this technology involves placing some heat absorbing substance around the base of your house. It’s often simply rocks and earth that are in a position to be exposed to the sun. For some, it’s simply a hard floor, such as concrete, that is exposed to windows, allowing it to trap heat during the day and release it as it gets c0oler. It can be upgraded to allow transfer of heat through in-floor masses or heated water to create radiant heat on the floor.
If you live somewhere hot, different designs can prevent solar heat from entering your house. Think of the adobe houses so classically part of the American Southwest. Thus, thermal mass storage is valuable in any climate and it is up to the builder to decide which design is appropriate. This is a design element worth extensive research.
Natural Lighting: This seems like a sort of “well duh” kind of statement, but the sun doesn’t just produce heat, it produces light. I originally thought that this wasn’t really worthy of mention as it seems too obvious, but I have a large, south-facing window in my office. I never turn on my lights and it is much more pleasant than the long fluorescent tube lighting and doesn’t require energy generation. I have received comments from at least 30 people that I work in the dark- but it’s not true! In fact, many days, I have to close my blinds to block out some of the light.
In terms of what we’re trying to do here, it’s worth considering a few design elements. If you have an area in the middle of your house that needs more light, consider putting in a skylight. It is also worth thinking about how to get natural light to the most used areas. Not only deoes this prevent energy use, it really is more pleasant.
Summary: Passive solar tends to be simpler than active solar or other technologies. It does not require complex electrical skills, building permits (in most cases), or installation of large elements like wind towers. Most passive solar technologies are more akin to home design elements than they are to PV cells or wind turbines. Nevertheless, they should be part of any green energy system.
