Solar tracker
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A solar tracker is a device for orienting a solar photovoltaic panel or concentrating solar reflector toward the sun. Concentrators require a high degree of accuracy to ensure that the reflected sunlight is directed to the absorber, which is at the focal point of the reflector. Non-concentrating applications require less accuracy. For low-temperature solar thermal applications, trackers are not usually used, owing to the relatively high expense of trackers compared to adding more absorber area. However, compared to photovoltaics, trackers are relatively inexpensive, thus making them especially effective for photovoltaic systems using high-efficiency panels. Some solar trackers may operate most effectively with seasonal position adjustment and most will need inspection and lubrication on an annual basis.
Solar trackers may be active or passive and may be single axis or dual axis. Single axis trackers usually use a polar mount for maximum solar efficiency. Single axis trackers will usually have a manual elevation (axis tilt) adjustment on a second axis which is adjusted on regular intervals throughout the year. There are two types of dual axis trackers, polar and altitude-azimuth.
Active trackers use motors and gear trains to direct the tracker as commanded by a controller responding to the solar direction. Devices of this type are manufactured by [Wattsun] and others.
Passive trackers use a temperature sensitive fluid that is driven to one side or the other (by solar heat creating gas pressure) to cause the tracker to move in response to an imbalance. As this is a non-precision orientation it is unsutable for certain types of concentrating photovoltaic collectors but works fine for common PV panel types. These will have viscous dampers to prevent excessive motion in response to wind gusts. Shader/reflectors are used to reflect early morning sunlight to "wake up" the panel and tilt it toward the sun, which can take nearly an hour. The time to do this can be greatly reduced by adding a self-releasing tiedown that positions the panel slightly past the zenith (so that the fluid does not have to overcome gravity) and using the tiedown in the evening. (A slack-pulling spring will prevent release in windy overnight conditions.) This type of tracker is supplied by [Zomeworks].
Active two-axis trackers are also used to orient heliostats - movable mirrors that reflect sunlight toward the absorber of a central power station.
External links
- [Knowing Sun Tracker, on Solar Energy Blog] – Discusses the prospects of using Sun tracker for solar panels.
- [An index of tracker manufactures]
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