User:Bernmeister1/Solar basics

If you are considering adding solar energy to your home or business, you may feel a bit overwhelmed by all of the technical information available online. There are a few organizations that organize information related to renewable energy. Solar energy is also explained on Shockoe Solar's site and on the American Solar Energy Society's site [www.ases.org]

In order to add solar electricity or "photovoltaics" to your home or business, you must consider several critical elements of a well designed system. These elements include solar access (shading), orientation of the building (if roof mounted), available roof or ground space, desired goal of energy production (usually a percentage of your annual electric consumption), and last but not least, your budget. Determining solar access with a reasonable level of accuracy requires some tools of the trade. Some solar contractors will use the appropriate tools, while others may use educated guesses. If your home or business has literally no obstructions between it and the horizon, you are probably in a good location, but you should still have the shading and solar access checked. These numbers are used to accurately predict the annual output of your system. You might be surprised to find out that even homes that appear to have no obstructions (with 1000 acres of field between the roof and the southern horizon) will often only have 97-99% solar access. If your system has less sunlight available, it becomes less efficient and will have a longer return on investment. Depending on available federal and state incentives, you may find that anything less than 80% is not worth the investment. If you have a particular tree that is obstructing the view, you may simply want to have it topped. The Sol Metric SunEye will allow you to edit the skyline (add or remove shading) to see how the change affects the results.

Photovoltaic modules (commonly referred to as "solar panels" are more efficient when aimed directly at the sun. A tracking system makes it possible for your solar modules to actually follow the sun as it crosses the sky. A single axis tracking system can follow the sun from East to the West, but cannot change the pitch to follow the high sun in the summer or the much lower sun in the winter. A dual axis tracking system can follow the sun more accurately. Tracking systems are frequently used for remote pumping stations (where 1 or 2 modules are needed to run a water pump) or for larger commercial arrays in rural areas where ample land is available.

Most photovoltaic installations are attached to a roof or "roof mounted." Sometimes the system is mounted on the ground due to roof space limitations, shading on the roof, or simply out of personal preference. They are referred to as "ground mounted" and require concrete footings and a metal frame called "racking" that can be set to the desired or optimum pitch (lattitude -10 degrees) and the correct azimuth (180 degrees South). Roof mounted systems can basically be divided into two main groups; flat roof tops, and all others. If the roof is flat or nearly flat, the modules can be mounted on a tilt-up racking system such as the one pictured below. If the roof is flat and the structure is structurally capable, a ballasted system can be used to prevent putting unnecessary holes in the roof. Unirac's Rapid Rac is an excellent example and is pictured below. Most homes have a pitched roof, between 3/12 and 12/12. This can be converted to degrees using an online pitch calculator. If you don't know the pitch of your roof, you may want to look at the original plans. If you don't have the plans for the building, you will need to get close enough to the roof to measure it. This can sometimes be done from a window, but usually requires a ladder. You can also measure rise and run at the end of the roof or you can get a simple tool from the hardware store that measures pitch.

Pitch isn't as critical as orientation to the sun. If you have a compass and know how to use it, you can stand near the building and determine which direction the roof is facing. The direction is referred to as the "azimuth" and ideally is 180 degrees or South (assuming that you are in the northern hemisphere). If your home has a roof area which faces between 135 and 225 degrees South, your azimuth is not likely to be a problem. If the only roof area with sun exposure is facing the East or West, your system's efficiency will be significantly reduced.