Apparatuses and methods for providing a secondary reflector on a solar collector system

Abstract

A solar collector system is provided that comprises an absorber tube, a primary reflector, and a secondary reflector. In certain embodiments, the primary and secondary reflectors are positioned on opposing sides of the absorber tube, such that their respective focal points converge upon a longitudinal axis of the absorber tube. The secondary reflector may be configured with a substantially transparent surface facing away from the absorber tube, so as to permit passage of light beams there-through. Opposing surfaces of the secondary and primary reflectors, namely those facing substantially toward the absorber tube contain a reflective coating thereon to facilitate redirection of light beams toward the absorber tube. The solar collector system includes in certain embodiments a frame assembly, whereby the primary reflector, the secondary reflector, and the absorber tube are all configured to unitarily rotate about a common pivot axis defined by at least a portion of the frame assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to and the benefit of both U.S. Provisional Application No. 61 / 548,536, entitled “Apparatuses and Methods for Providing a Secondary Reflector on a Solar Collector System” and filed Oct. 18, 2011, and U.S. Provisional Application No. 61 / 560,590, entitled “Solar Thermal Energy Collector” and filed Nov. 16, 2011, the contents of both of which are hereby incorporated herein in their entirety.BACKGROUND[0002]1. Technical Field[0003]Embodiments of the present invention relate generally to solar concentrators and solar collector systems. More particularly, the various embodiments provide a solar concentrator that uses a secondary parabolic reflector assembly in conjunction with an absorber tube and a primary parabolic trough assembly to minimize the number of reflected solar rays that are never collected by the absorber tube.[0004]2. Description of Related Art[0005]Solar concentrators and solar collector systems ...

AI Technical Summary

Benefits of technology

The present invention is related to solar concentrators and solar collector systems. The invention provides a system that minimizes the number of reflected solar rays that are not initially collected by the absorber tube. The system includes a frame assembly with a primary reflector, a secondary reflector and an absorber tube positioned between them. The frame assembly is designed to rotate about a pivot axis so as to minimize misalignment between the different reflectors and the absorber tube. The method involves positioning the solar collector system in a first orientation to maximize the collection of light beams directed onto the primary reflector and then rotating it to a second orientation to maximize the collection of light beams directed onto the primary reflector in a different period of time. The invention allows for efficient use of solar energy and optimizes the collection of light beams.

Problems solved by technology

However, focusing errors and thus geometrically dependent optical losses occur in parabolic trough collectors due to a variety of factors.

For example, the mirror has a certain total shape tolerance, which may involve some degree of waviness, both of which lead to focusing errors.

Further, the positioning of the mirror during assembly is only possible to within certain tolerances, likewise causing at least a portion of the reflected sunlight to miss (e.g., not intercept) the elongated receiver tube.

Self-deformation (e.g., warping), manufacturing, and assembly tolerances of the steel structure, on which the parabolic trough collector is built, may also lead to inefficiencies.

External factors such as the non-limiting examples of wind and dirt occurring in the vicinity of the parabolic trough and / or the elongated receiver tube may also cause deformations of portions of the structure sufficient to impact sunlight collection efficiency.

Still further, as should be appreciated, the sun moves across the sky during the day and is positioned at different locations in the sky depending upon the time of year thus presenting challenges in the collection of solar light.

Although capable of capturing some solar light, misalignment may occur since the tracking may not be completely accurate and small losses of solar light for each primary reflector add up to a large amount of loss for the system overall taking into account the large number of primary reflectors that may be employed.

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