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Solar Photovoltaic Cells for the Kingston Home FAQ

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A [[solar cell]]{{wpsup|solar cell}}, or photovoltaic (PV) cell [[Photovoltaics]], is a device that converts solar energy into electrical energy via the [[photoelectric effect]]{{wpsup|photoelectric effect}}. A [[solar array]]{{wpsup|solar array}} is a grouping of individual solar cells that are electrically connected to produce electrical power. By installing a solar array, users can generate electricity for their personal use or for distribution on a connected electrical grid. Solar arrays can offer environmental and financial benefits for both the homeowner and the community at large. Many people are curious about solar technology and this page aims to answer questions relating directly to photovoltaics in general and also addresses specific questions related to installing a PV array in Kingston, Ontario, Canada.
== Technological FAQs ==
===How do solar cells work?===
Solar cells function by converting electromagnetic radiation (primarily light from the sun) into electrical energy. Solar cells convert light into electricity using the [[photoelectric effect]]{{wpsup|photoelectric effect}}. When light strikes the active material in a photovoltaic cell, the light (in the form of [[photons]]{{wpsup|photons}}) promotes [[electrons]]{{wpsup|electrons}} in the material to a higher state of excitement. To maintain charge neutrality, an excited electron will also have a corresponding ‘hole’ that balances the electron’s charge. The excited electron will eventually come back down and re-united with an electron hole, so a solar cell needs to collect the electrons and holes before this occurs. A [[P-N junction]]{{wpsup|P-N junction}} can be used to collect the electrons and holes, generating an electrical potential that allows a current to flow. Solar cells are often discussed in terms of efficiency, which is a measure of how much electrical power is output per unit of incident light input power. For example, if a solar array has an overall efficiency of 10% and an exposed area of 1 square meter, the expected electrical power output would be 10 watts if the incident light [[irradiance]]{{wpsup|irradiance}} was 1000 watts per square meter.
A substantial amount of information on the technical workings of photovoltaic exists on the Internet. Several good starting resources can be found here:
=== Can they be recycled? ===
While there are many types of solar cells available, most of the current photovoltaic technologies are fully recycleable. The majority of commerical solar cells are primarily made of silicon, which can be fully recovered. A number of different chemical processes can be used to recycle the silicon in the photovoltiac cells into pure silicon wafers. As well, the glass, aluminum frame and electrical wiring can be recovered and recycled.<ref> Muller, A., Wambach, K., Alsema, E. ‘’Life Cycle Analysis of a Solar Module Recycling Process’’, (2003) Materials Research Society. Avaliable online at http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=6228&DID=170203&action=detail </ref> Recycling of solar panels is economically attractive as most of the raw silicon processing steps can be bypassed when using recycled materials.<ref> Fthenakis, V.M.’’End-of-life management and recycling of PV modules’’, (2000) Energy Policy, Vol. 28, Issue 14. Pg. 1051-1058. Available online at http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2W-4177N2J-7&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=3ac8336c226cb9e89cac8f0b6381708b </ref> The recycling process is currently done by several companies such as [http://www.solarworld.de/solarmaterial/english/modulrecycling/ SolarMaterial.]
For other photovoltaic technologies, such as Group-III thin film technologies, the material components can still be recovered but the recycling technolgies are not as well established as silicon-based photovoltaic recycling. For example, [[cadmium telluride photovoltaics]]{{wpsup|cadmium telluride photovoltaics}} can be recovered using a [[pyrolysis]]{{wpsup|pyrolysis}} process.<ref> Patent for Process for recycling CdTe/Cds thin film solar cell modules. Available online at http://www.freepatentsonline.com/6572782.html </ref> It is also important to note that the long lifespan of photovoltaic panels (upwards of 20-30 years) will allow for the further development of recycling technologies.
Some manufacturer's indicate recycling in their goals:[http://www.firstsolar.com/recycling.php]
Solar cells will produce more electricity if the incident light is concentrated by using mirrors or reflectors. Concentrating the light through optics and reflectors can be an economical way to improve the power capacity of a system. An example of a light concentrator device is a fresnel lens system, and an example of using this technology with solar cells can be found [http://news.cnet.com/8301-11128_3-10007431-54.html here.]
[[Solar trackers]]{{wpsup|Solar trackers}} are devices operate by changing the angle of the solar panels to follow the sun as it moves across the sky. With the solar panels facing the sun for most of the day, the power generated is larger than the power generated without the tracker installed. Trackers come in a variety of options depending on the different number of rotational axis used to track the sun. The cost of the tracker often is not worth the additional power increase they provide.
It is important to be aware of the concentrator and tracking options for solar installations, but the cost often does not justify their installation. It is a good idea to ask about them when consulting with a company for a roof-top solar installation. A good resource on solar trackers/concentrators can be found [http://www.pvresources.com/en/concentrator.php here.]

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