Linear-Focus Solar Energy Concentrator Based on an Array of Parallel Slat Reflectors

Background

Several types of solar energy technologies use parabolic trough mirrors to concentrate sunlight before it is converted into heat and electricity. In parabolic trough solar power plants, such mirrors produce heat to generate steam in place of the conventional boiler fired by natural gas, coal, or nuclear reactions. Parabolic troughs are also used in sea-water desalination plants, concentrator photovoltaic systems and various process heat applications.

However, despite all of the benefits of enabling the use of free solar energy, parabolic troughs require a high-precision support frame to maintain the perfect mirror shape and resist wind loads which results in heavy and bulky structures and limits the cost effectiveness of solar energy technologies. Alternative designs of solar collectors could reduce the cost of solar energy and broaden the range of applications where solar could replace fossil fuels.

Description

Researchers at Lucent Optics have invented a new type of linear solar concentrator which employs an array of self-supporting slat reflectors instead of the continuous-surface parabolic mirror which normally requires an additional sophisticated support structure. A further difference from the parabolic troughs is that the slat reflectors are arranged to focus the sunlight on the back of the collector and not in front of the mirror. This allows for using relatively large receivers without the issues normally associated with the incident beam shading and with other design problems related to front-focus mirrors. Each slat is positioned at a prescribed position and at a specific angle with respect to the array so that all of the slats redirect and focus sunlight to the same area below, forming a highly concentrated focal line. The rear-focus arrangement of slat reflectors also creates ample spacing between the slats which drastically reduces the wind drag and soiling of the mirror surface.

The slat-array can focus sunlight onto almost any type of receiver: a fluid-carrying pipe, a linear strip of solar cells, a conveyor belt, or even simply on the ground below the collector.

The slat-array design allows for reducing the system weight and material intensity without sacrificing the sunlight collection power and optical efficiency. Reflective slats can be manufactured using low-cost sheet metal fabrication technologies and automated, high-volume processes. The optical configuration can be tailored from low to very high concentration (magnification) and also allows for obtaining a very uniform energy distribution in the concentrated beam. The versatility of the slat-array concentrator concept is complemented by dedicated optical modeling and raytracing software developed by our engineers which helps customize and optimize the concentrator’s optical design for various applications.