Solar radiation is a general term for the electromagnetic radiation emitted by the sun. We can capture and convert solar radiation into useful forms of energy, such as heat and electricity, using a variety of technologies. The technical feasibility and economical operation of these technologies at a specific location depends on the available solar radiation [...]
Posts from ‘May, 2009’
How to Evaluate Your Site’s Solar Resource for Solar Electricity
The solar resource across the U.S. is ample for solar electric systems—also known as photovoltaic (PV) systems—because they can use both direct and scattered sunlight. However, the amount of electricity generated at a particular site depends on how much of the sun’s energy reaches it. Thus, PV systems function most efficiently in the southwestern United [...]
Considering a Small Solar Electric System
To help evaluate whether a small solar electric system will work for you, you should consider the following: Your available solar resource—do you have clear and unobstructed access to sunlight for most or all of the day, throughout the year? The system size—do you have a roof or area large enough to accommodate it? The [...]
How Small Solar Electric Systems Work
Solar electric systems, also known as photovoltaic (PV) systems, convert sunlight into electricity. Solar cells—the basic building blocks of a PV system—consist of semiconductor materials. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms. This phenomenon is called the “photoelectric effect.” These free electrons then travel into a [...]
Small Solar Electric Systems
A small solar electric or photovoltaic (PV) system can be a reliable and pollution-free producer of electricity for your home or office. And they’re becoming more affordable all the time. Small PV systems also provide a cost-effective power supply in locations where it is expensive or impossible to send electricity through conventional power lines. Because [...]
Energy Performance Testing, Certification and Labeling
The National Fenestration Rating Council (NFRC) operates a voluntary program that tests, certifies, and labels windows, doors, and skylights based on their energy performance ratings. The NFRC label provides a reliable way to determine a window’s energy properties and to compare products. The NFRC label can be found on all ENERGY STAR® qualified window, door, [...]
A window’s, door’s, or skylight’s ability to transmit sunlight into a home can be measured
A window’s, door’s, or skylight’s ability to transmit sunlight into a home can be measured and rated according to the following energy performance characteristics: * Visible transmittance (VT) A fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through a window’s, door’s, [...]
Energy Performance Ratings for Windows, Doors, and Skylights
You can use the energy performance ratings of windows, doors, and skylights to tell you their potential for gaining and losing heat, as well as transmitting sunlight into your home. Heat Gain and Loss Windows, doors, skylights can gain and lose heat in the following ways: * Direct conduction through the glass or glazing, frame, [...]
Heat-Absorbing, Tinted Window Glazing or Glass
Heat-absorbing window glazing contains special tints that change the color of the glass. Tinted glass absorbs a large fraction of the incoming solar radiation through a window. This reduces the solar heat gain coefficient, visible transmittance, and glare. Some heat, however, continues to pass through tinted windows by conduction and re-radiation. Therefore, the tint doesn’t [...]