Solar Panel Orientation
In cases where the roof slope does not face the sun or does not provide enough usable surface area for solar panels, wall mounting the panels may be a viable option. Wall-mounted solar panels must face south (or north in the southern hemisphere). Ideally, the sun should strike panels at an angle perpendicular to the panel face, but vertical walls work well, particularly in winter months when the sun is lowest in the sky and energy costs are highest.
Active or Passive Solar
When planning a solar home, the south wall is the most critical. Southern exposure is not only important for solar panels, but to allow daylight into the building and to take advantage of passive solar heating opportunities. South windows are key features of passive solar homes. When sunlight enters through a south window, it heats surfaces, providing passive solar heat gain that can significantly reduce heating costs. Sacrificing passive solar windows for active solar panels is a trade-off and not always a good idea. Small panels often fit between, above or below windows, maximizing the use of solar energy striking the south wall.
Building-Integrated Photovoltaic Panels
A drawback to wall-mounted solar panels is that they are more visible than roof-mounted panels and may be an eyesore. A solution to this is to use building-integrated photovoltaics (BIPV). These special solar panels are in fact building materials such as roof tiles, awnings, wall coverings and even windows that have solar cells integrated into their design. Solar roof tiles, for example, are sprayed with a thin layer of amorphous silicone to create a photovoltaic surface. Specially designed photovoltaic glass can generate electricity and still allow some light through the window. Building-integrated photovoltaic panels provide a way for buildings to generate their own electricity, thereby reducing use of grid electricity, in an aesthetically pleasing way.
As solar energy technology becomes more sophisticated, it integrates more fully with the entire building. Putting up solar panels on a wall or roof is a start; however, more benefit is derived from a solar system that considers the function of the entire building. Shading a south-facing window with an overhang that has integrated photovoltaics provides more than one function. The panels generate electric energy, and the overhang provides passive solar value to the home by shading direct sunlight in the summer and allowing lower-angle sun inside in winter.