Modular fresnel solar energy collection system

Abstract

A modular linear Fresnel solar energy collection system comprises one or more reflector units having a number of spaced, elongated solar panels that extend between a pair of opposed, light-weight aluminum beams. A first drive mechanism rotates the solar panels at angles progressively increasing from the center of the two beams to their ends so that each panel reflects incident sunlight to a secondary reflector located above the panels. The secondary reflector, in turn, reflects the sunlight it receives from the solar panels onto a receiver tube mounted in a fixed position substantially concentric to a central axis extending between the two aluminum beams. A second drive mechanism is coupled to one of the beams which is operative to pivot the assembly of beams, solar panels and secondary reflector between a generally easterly direction and westerly direction in order to track the apparent movement of the sun during the course of a day.

Description

FIELD OF THE INVENTION[0001]This invention relates to the generation of electrical energy through solar thermal power collection, and, more particularly, to a modular Fresnel solar energy collection system that employs a secondary reflector, light-weight solar panels and a fixed linear receiver through which a heat transfer fluid is circulated.BACKGROUND OF THE INVENTION[0002]Systems for the generation of electricity by collecting solar thermal radiation were first introduced in 1914, and have become increasingly popular with the rise in fossil fuel costs and concerns over global warming. A majority of solar energy collection systems currently in use employ parabolic, trough-shaped reflectors that focus the sun's energy on a receiver such as an engine. Recently, a new type of system has emerged known as a linear Fresnel reflector that includes a series of long, narrow mirrors having a shallow curvature, or none at all, which focus light onto one or more linear receivers positioned a...

AI Technical Summary

Benefits of technology

[0005]This invention is directed to a linear Fresnel solar energy collection system that improves solar field efficiency, lowers operational and maintenance costs, and therefore reduces the overall cost of generating electricity per kilowatt-hour.

[0006]One aspect of this invention is predicated on the concept providing a simple, modular linear Fresnel solar energy collection system comprising one or more reflector units each fabricated using light-weight materials arranged in a construction that is highly accessible, easily maintained, and lower in initial cost. In one embodiment, each reflector unit comprises a number of spaced, elongated solar panels, having a slightly curved or flat reflective surface, that extend between a pair of opposed, light-weight aluminum beams. A first drive mechanism rotates the solar panels at angles progressively increasing from the center of the two beams to their ends so that each panel reflects incident sunlight to a secondary reflector located above the panels. The secondary reflector, in turn, reflects the sunlight it receives from the solar panels onto a receiver tube mounted in a fixed position substantially concentric to a central axis extending between the two aluminum beams. A second drive mechanism is coupled to one of the beams which is operative to pivot the assembly of beams, solar panels and secondary reflector between a generally easterly direction and westerly direction in order to track the apparent movement of the sun during the course of a day.

[0007]Preferably, each solar panel comprises a honeycomb aluminum section and a highly reflective silver-metallized surface connected together by an adhesive layer. The solar panels are strong, durable, light-weight and efficiently reflect incident sunlight many times its normal intensity onto the secondary reflector. The reflective surface of such panels may be washed to maintain cleanliness which enhances the efficiency with which they reflect incident sunlight to the secondary reflector.

[0008]A heat transfer fluid is circulated through the receiver tube for heating by the sunlight directed thereto from the secondary reflector. Because the receiver tube is fixed relative to the pivoting beams, it may be connected to a fixed transfer conduit that communicates with a steam generator and turbine. Since both the receiver tube and transfer conduit are mounted in a fixed position, heat losses resulting from the transfer of fluid out of the receiver tube are minimized and maintenance problems are reduced.

[0009]In an alternative embodiment, a reflector unit includes solar panels that are formed in smaller segments and mounted to a number of shafts extending between the opposed beams described above. The shafts are operative to tilt the segmented solar panels at a desired latitude angle, e.g. in a generally northerly or southerly direction, dependent upon the geographic location of the system. This allows the system of this invention to account for the varying incidence angle of the sun with the earth as the seasons change so that the solar panels more directly face the sun throughout the year. An improvement in solar collection efficiency of at least 5% may be realized by this enhancement of the present invention.

[0010]The several embodiments of this invention are modular in construction in the sense that several reflector units may be mounted side-by-side, and their receiver tubes connected, to form a linear Fresnel solar collection system with increased capacity and overall efficiency.

Problems solved by technology

Despite these advantages, there is more heat loss due to the larger width dimension of the receiver which is needed to compensate for the lack of curvature in the mirrors.

Another disadvantage of current linear Fresnel reflectors is that although they work well when the sun is nearly vertical in the sky, e.g. between about 10:00 a.m. to 2:00 p.m., rapid performance degradation occurs at other times during the day.

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