SOLAR POWER 101by onlinethymes
The sun provides an abundant and ubiquitous energy source that will be available as long as it continues to shine. In fact, the amount of energy that the earth receives from the sun in one hour is more energy than the world consumes in one year, we just need to harness that energy. A common misconception exists that solar power could not supply a significant portion of US or world electricity demand, but the truth is the entire electricity needs of the US could be met by using photovoltaic (PV) modules in a 100 square mile area of Nevada. PV technology is only one of many ways to harness solar energy, which range from passive to active systems and from small building-scale to large-scale utility-type systems.
Photovoltaics, also called solar cells, convert sunlight directly into electricity. Solar cells are the smallest component of a PV, or solar electric, system. Because alone they can only supply a small amount of electricity, solar cells are interconnected to form larger modules with the ability to produce more power. PV modules are then connected into larger PV arrays, the major part of a PV system. Balance of system (BOS) components are required to complete the system; these can include wiring, mounting hardware, batteries for storage, and power-conditioning equipment to convert the direct current (DC) electricity produced by the arrays to alternating (AC) currents. PV systems can be used from a scale as small as a calculator to a large utility application containing hundreds of interconnected arrays.
As PV technology advances, solar cells are becoming more efficient, less expensive, and in some cases, thinner. Thin film PV technology has enabled solar cells to be integrated into building components such as roof shingles, the building façade, or window glazing. When Building Integrated Photovoltaics (BIPV) systems are used, a building component, for example roof shingles, perform their originally intended function with the same protection and durability, but have the added bonus of converting the sun's energy to electricity for use in the building. BIPV has positive implications for both system cost and building aesthetics.
A solar hot water system is another strategy used to harness the sun's energy. These systems are utilized to heat water for use in buildings or swimming pools. Like PV, solar collectors are mounted on south-facing rooftops, but they work very differently. Solar collectors are typically thin, flat rectangular boxes that contain tubing attached to a black absorber plate. The sun heats up the solar collector just as it would black top on a warm day, in turn the heating fluid, such as antifreeze, in the collector's tubing. The hot fluid is kept in an insulated storage tank, and water is heated by passing it through tubing in the tank.
Methods also exist to capture the sun's energy that simply require thoughtful design. Passive solar heating and daylighting take into consideration things such as building orientation, window size and location, and various building materials and components. Buildings with large, south-facing windows and floors and walls made of thermally absorbent materials, like concrete, will have ample natural light during the day while absorbing the sun's heat. This will keep the building warmer at night as the trapped heat is slowly released, and proper shading devices will avoid unwanted heat gain from the high summer sun. These are just a few examples of passive solar design.
The solar power technologies discussed so far can be applied at various scales, but there are some that would only be practical when applied to larger scale buildings or at the scale of utility energy production. Large commercial and industrial buildings often require fresh air ventilation in addition to having high heating and cooling loads depending on their region. Ventilation air preheating, solar process heating and solar cooling are ways of utilizing energy from the sun for these large-scale loads. Utilities can replace fossil fuels by using the sun as their heat source. Concentrating solar power systems use mirrors in a variety of ways to concentrate the sun's energy. Similar to fossil fuel derived electricity, the concentrated energy is then used to heat a fluid which then powers a turbine and/or generator to produce electricity. The difference is that this is clean, renewable energy produced from the sun.
With the variety of technologies available, it's a wonder why we aren't taking better advantage of this free, renewable resource. Why not harness the sun?
*All information was obtained from the US Department of Energy (DOE) and National Renewable Energy Laboratory (NREL)
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