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Eppley Solar Tracker  Eppley
Laboratory is the main manufacturer of manually adjusted Solar Trackers
used with the Eppley NIP or Cavity Radiometer. The Model ST-1 (see photograph)
is electrically driven using a clock-based motor
which makes one revolution every 24 hours. These trackers
have to be adjusted manually to account for changes in the declination of
the sun and the changes in true solar time (see
equation of time).
These trackers require sunny weather to
accurately align the NIP. During the equinoxes (March and September), the declination
is changing rapidly, and alignment should be done at least three times a week. Because true
solar time changes most rapidly during December, it is important to watch the
alignment during the winter.Useful alignment tricks One can make a tube that fits between the flanges of the NIP between the alignment target and the sunlight hole in the top flange. By cutting a window in the tube to see the target, one can more easily align the NIP during periods of intermittent cloudiness.
Since the tracker makes
a complete revolution once every 24 hours, the cord between the NIP and the
data logger either has to go through a rotary connector or be disconnected every
few days to prevent the wires from separating from the connector. By using a coiled
phone cord, the stress on the cable can be reduced, and the maximum period during
which the connection can be maintained without separating the cable from the
connector is approximately doubled.
With a well-aligned tracker, one can watch
the direction the sun dot moves on the target from day to day. During cloudy
periods, one can slightly over-adjust the light spot so that the next day the
sun spot moves closer to the target instead of away. This can extend the period
when the NIP is in alignment by a day or two. This is particularly useful during
cloudy months. © 2022, UO Solar Radiation Monitoring Laboratory. Last
revised: March 29, 2022.
Home page URL: solardata.uoregon.edu |