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