1-axis and 2-axis solar trackers

Abstract

A one-axis sun position tracking device with its rotation axis parallel to the rotation axis of the Earth, rotates perpetually at a constant speed in the opposite direction of the Earth's rotation. This device comprises a shaft that is aligned to the Earth's polar axis, one or more crossbars are rigidly attached to and perpendicular to the shaft, solar energy collectors are mounted on the crossbar and could rotate around the crossbar that defines declination angle. A self-latched declination angle adjustment mechanism keeps the declination angle constant at most of time. A drive mechanism keeps this solar tracker to rotate perpetually. An automatic and abrupt declination angle change will keep the declination angle updated to correct value each day. A similarly configured two-axis tracker that continuously updates its declination angle by a mechanism derived from a differential coaxial rotation. Two independent driving mechanisms control the speed and/or duration of the two coaxial rotations, and are programmed to eliminate all tracking errors from various sources.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of provisional application Ser. No. 61 / 269,462, filed 2009 Jun. 26 by the present inventor.FEDERALLY SPONSORED RESEARCH[0002]Not applicableSEQUENCE LISTING[0003]NoneBACKGROUND[0004]1. Field[0005]This invention relates to solar energy collections, specifically to sun position tracking that is used in sunlight concentration and collection.[0006]2. Prior Art[0007]Sun position tracking is very important to solar energy collection, especially for solar concentrators. Different implementations have been invented, they could be categorized as 1-axis tracking and 2-axis tracking. 1-axis tracking is simple, however, it is commonly believed that 1-axis tracking has a poor tracking capability, that is not true in a special case; 2-axis tracking can have a very good tracking accuracy, however, it is usually very complicated because of the coupled rotation of 2-axis.[0008]Most 2-axis tracking methods are using local ...

AI Technical Summary

Benefits of technology

[0015]As known in the prior arts, polar tracking has advantage of simple driving and control requirement, while the rotation around the polar axis is almost at steady speed: 360 degrees per day, the declination angle change is very slow, only changes ±23½° back and forth per year. It would be a good approximation that the declination angle could be kept constant for a day. As a matter of fact, the declination angle change rate varies, its fastest change rate is less than ±0.1° for ±6 hour, while the sun itself has a ±0.267° angular size.

Problems solved by technology

Of course we have to set the next correct declination angle for the next day, a manual adjustment is tedious, a continuous adjustment is an overkill as others alre

Images