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Mounting of PV Arrays

Posted By: Curtis Reddehase | Posted On: 2008-05-28 | Article ID: 63940

The suns path over the sky changes during the day. In the mornings it is low on the eastern horizon, in the mid day it is high in the sky and late in the afternoon it is low again but on the western side. A PV array can generate the most energy when it modulus are facing the sun directly. Those of us who want to get the most watt hour from the PV modules often look to tracking type systems. Trackers as they are called are available for almost all sizes of PV arrays. For smaller residential applications the system are usually mounted on top of a properly sized steel pole. A good site for a tracker system receives dawn to dusk sun. If you site does not begin receiving sunlight until 10 in the morning or you lose it at two in the afternoon due to shade from tall buildings, trees, or hillsides. When located at a site with a great solar view a tracked array will usually generate 25% to 40% more energy annually than a standard fixed or static array. There are two forms of PVC tracking, single axis and dual axis. The single axis style will follow the suns path from the east to the west and the array is fitted or angled at a fixed point off of the horizon. A dual axis tracker will adjust the PV array to track the suns path from east to west and will adjust the arrays tilt to factor in the suns altitude, very applicable the further north that you live. Trackers come in two basic versions the electronically operated and the other being thermally operated, most commonly referred to active and passive. Electrically operated trackers for residential systems usually rely on sensors that alert the motors to orient the array towards the sun as the position changes throughout the day. Thermal trackers use the transfer of weight to follow the sun. In a passive system a canister is attached the east and west sides of the tracker. These canisters or tubes are filled with a material, generally Freon that vaporizes at relatively low temperatures. As the sun contact one canister the Freon is heated and pushes some of the cooler liquid Freon to the other side. This then transfers weight to the other side and moved the array towards the sun. Both systems have associated advantages and disadvantages. Electrical systems are much more precise. But thermal trackers have proven to be very durable in the field. Electrical systems can get damaged by lightning, a big problem that manufactures are trying to address. On the flip side thermal systems can be slow to respond and may not maximize the available sun. And if in winter the heating process can take longer because they are dependent upon obtaining enough heat. Whether a tracker will be cost effective for your application will depend on your seasonal electrical use. Tracker s will give you more gain in the summer when the days are longer with decreased improvements in the winter. For a grid tied system with annual net metering this can be a bonus because the exec summer production will help offset you winter utility bill.

 

Article Source: http://www.articlecell.com

About The Author
Curtis Reddehase
Sky Realty is your choice for Green Homes in Austin. Steve Aubin knows about green construction such as Las Casas Verdes. skyrealtyaustin.com



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