| This article explains the fundamental terms related to | | | | Azimuth - Describes the direction from east to west in |
| sunlight and residential solar energy systems. You will | | | | degrees (°). North is 0 degrees. East is 90 |
| learn about units of measure, forms of solar radiation, | | | | degrees. South is 180 degrees. West is 270 degrees. |
| spectral distribution, energy distribution, and solar | | | | The layout of this grid is not unlike the face of a |
| position. | | | | compass. The markings are in degrees indicated on |
| Germany and Japan are often cloudy or foggy but is | | | | the face. |
| where most solar panels now sold in the United States | | | | Altitude - Is the measurement in degrees, like on a |
| are produced. Because of the way solar modules | | | | compass, that the sun is from the horizon. Altitude is |
| produce power from direct, diffused and reflected light | | | | measured in degrees as well. Altitude is the point in the |
| it works great in these conditions. A very high | | | | sky where it is located right over head often referred |
| performing solar array can be found on a foggy beach | | | | to it's highest point in the sky. Just like a plane has an |
| in California. | | | | altitude that it travels at across the sky as it is |
| Measuring Light and How Solar Panels Use It | | | | measured above the horizon. So does the sun. |
| The following terms related to different aspects of light | | | | Irradiation Example for a Solar Energy System |
| and their characteristics as they come in contact with | | | | In the coast area of California, residential solar energy |
| different physical formations on Earth. The definitions | | | | systems are sized using an average of 5.5 sun hours |
| below will help explain how some residential solar | | | | per day. More often than not, most people think or |
| energy systems seemingly in areas with poor sun | | | | comment that their house gets more like 8 to 15 hours |
| quality can actually achieve respectable power output. | | | | of sunlight per day. This is true but sunlight is different |
| Irradiance - The rate of solar radiation falling on a given | | | | than solar sun hours per day. |
| area at a moment in time. Irradiance is measured in | | | | The number of hours per day that your house |
| units of kW/m2 (read kilowatts per square meter). | | | | receives direct sunlight must take into account |
| Irradiation - The amount of solar energy over time. | | | | challenges like fog, rainy days, number of night hours, |
| Irradiation is measured in units of kWh/m2/day and | | | | and deflection or the amount of light not converting to |
| read kilowatt-hours per square meter per day. | | | | energy. The sun hour ratings listed for different places |
| Different locations through the United States (and the | | | | throughout the United States is the amount of solar |
| World) have different levels of irradiation. As in | | | | irradiation available to be converted into electricity by a |
| previous articles, you can find many maps on the | | | | fixed mounted solar array facing true south at the |
| Internet that will show the average annual solar | | | | optimal tilt angle. A solar module produces its full rated |
| irradiation throughout the United States. | | | | power only when in direct sunlight, so when the sun is |
| Light Characteristics and Solar Fundamentals | | | | to the East or the West of the module it is not at full |
| Deflection - The amount of light lost when the solar | | | | production. |
| panels aren't facing the sun squarely as the sun | | | | Rethinking the Economics of Residential Solar Energy |
| moves across the sky. This loss of light is called | | | | Doing your part to choose green, solar power can be |
| deflection. Even though solar cells are etched on the | | | | a bit confusing and complex at times. There are many |
| surface into little pyramids to collect light from all angles, | | | | terms, aspects of the installation, and details about your |
| coated with a light diffusing coating, and protected with | | | | sun light hours per day that all influence decisions to |
| light diffusing glass, more light is deflected when the | | | | upgrade your home to solar energy. A very interesting |
| sun is not directly in front of the panels. | | | | and attractive option currently development in the solar |
| Spectral distribution - The bulk of the solar light | | | | market is the option to rent a residential solar energy |
| spectrum which reaches the Earth's surface is ideally | | | | system versus having to pay out up to $40,000 for |
| suited for conversion by solar (PV) cells into electrical | | | | your own solar panels and related equipment. |
| energy. | | | | The economics of residential solar power have |
| The Sun's Position as It Relates to Solar Energy | | | | changed. Every American homeowner can decide to |
| Systems | | | | upgrade to solar energy and avoid large purchase of a |
| Two coordinates describe the position of the sun at | | | | solar energy system. New rental programs are now |
| any given time. These coordinates allow solar | | | | available that give homeowners the chance to adopt |
| technicians to calculate and orientate the solar panels | | | | residential solar energy without having to make a huge |
| to optimal attract and convert the sun's light into solar | | | | investment. |
| generated electricity. | | | | |