Solar-Array Panels

Requirements for solar cells and solar panels are strictly dependent on continuous electrical power consumption an additional 30 to 40% more electrical power is needed to meet power consumption requirements depending on the operating 

Operating Life (yrs.) Power Output (W) Reduced Power Level (%) 

1 Solar Panel Performance Requirements to Charge the Space-Based Batteries 

Installation of solar panels is required to charge the onboard batteries that are providing the electrical power to various electronics devices, stabilizing and attitude control sensors, space parameter monitoring instrument, lighting, and a host of other electrical systems that are vital in maintaining the desired performance of the satellite or spacecraft over the intended mission duration. 

3 Battery Power Requirements and Associated Critical Components 

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Some designs use solar arrays that are several kilometers long on each side. The largest solar panels in space are being used on the International... 

Another solar firm, SolFocus (www.solfocus.coml has developed solar arrays that use just one-thousandth as much semiconductor material as standard solar panels. The arrays are set with curved mirrors that focus sunlight onto solar cells measuring one-square centimeter, which concentrates the light 500 times. These cells efficiency is greater than 38%, compared to the 13% to 19% efficiency for silicon photovoltaic cells. SolFocus projects that costs per kilowatt-hour will fall from 24 to 28 cents in 2008 to 13 to 14 cents by 2010. 

Figure 2.3. A schematic of the Chandra Observatory showing the typical components including the solar arrays, aspect cameras, mirror assembly, instrument module, and optical bench. The Chandra Observatory weighs 4800 kg and orbits the Earth every 64 hours in a 10,000 by 140,000 km orbit that extends 1/3 of the distance the moon. Including the solar panels, the observatory s dimensions are 14m by 20m.

To maximize the output of a solar array, angle the panels according to your latitude and to the season. To find your latitude, look at a paper map or atlas, or access the US geological survey map information URL via the Resources page at the end of this book. There are also many other sites on the internet that give this information for wherever you live in the world. On the USGS site, for instance, all you have to do is put in the name of your town, state and country. 

Solar panels used to power homes and businesses are typically made from modules holding about forty cells. A typical house requires an array of ten to twenty solar panels to provide sufficient power. The panels are mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to maximize solar energy capture. For lai e electric facility or industrial applications, hundreds of solar arrays are interconnected to form a lai e utility-scale photovoltaic system. 

Acknowledgement This research was supported in part by the Jet Propulsion Laboratory, California Institute of Technology (Flat Panel Solar Array Project) and the Mobil Foundation. 

IdaTech (USA) is one of only two companies listed here that can provide an off-grid fuel cell package to the market now. Its 2.4 kW hybrid system (1.4 kW PEMFC and a 1 kW solar array) is linked in with a solar panel for rural locations. Though primarily intended to provide power to telecommunications, the unit does produce useable heat, potentially allowing it be used as an off-grid mCHP unit. 

The electrical power output capability of the solar array is strictly dependent on the number of solar cells used, cell conversion efficiency, array orientation with respect to the solar energy impingement direction, panel mounting scheme, and the maximum allowable size of the array. The body-mounted arrays shown in Figure 2.3 could provide several hundreds of watts, whereas the fixed-paddle array configuration is best suited for applications in which tens of kilowatts of electrical power levels are needed. 

PV systems consist of arrays of cells that ate interconnected in panels or modules to increase total power output. Often the systems include sun-tracking equipment, as well as power-conditioning equipment to convert dc to ac. The systems can range in size from a simple one-panel, fixed-orientation unit to a vast field of modules that accurately track the movement of the sun. Electric utiUties in Europe, Japan, and the United States have hosted several experimental PV power plants. The largest to date was a 5.5-MW plant at Carrisa Plains, California, built by Siemens Solar Industries (formerly ARCO Solar). 

Since 1970 the subject of amoiphous semiconductors, in particular silicon, has progressed from obscurity to product commercialisation such as flat-panel hquid crystal displays, linear sensor arrays for facsimile machines, inexpensive solar panels, electrophotography, etc. Many other appHcations are at the developmental stage such as nuclear particle detectors, medical imaging, spatial light modulators for optical computing, and switches in neural networks (1,2). 

But, such a system has its disadvantages. A terrestrial solar station intercepts only one third of the solar energy that an array of equal size could intercept in space, since no power is generated at night and less light strikes the panels when the Sun is low in the sky. 

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