Abstract
It is generally accepted that small to medium level concentrators could be used as cost-competitive replacements for tracked solar panels. The objective is to design a system that can reach a good level of sun concentration with only one sun-tracking axis and is cheap to fabricate. As the most critical parameter for all concentrator designs, optical efficiency needed improvement to reduce the cost of power produced by our system. By using a graded-index planar waveguide with an index profile similar to SELFOC fiber, the ray's path can be controlled. Also, the concentrator can be fabricated in a single block, which reduces Fresnel reflections. Overall, the optical efficiency can be improved by as much as 33% compared to the same system made with a homogeneous waveguide. Furthermore, the ability to cost-effectively fabricate the concentrator by molding can be preserved, making it possible to reduce the cost of the solar power produced.
Highlights
The use of concentrated photovoltaics (CPV) is an interesting technology to reduce the cost associated with solar power
The light losses in planar waveguide concentrators come from the coupling prisms which are much larger than the ones required for dual axis tracking
It was shown that the use of an index gradient in a range from 1.491 for pure polymethyl methacrylate (PMMA) to 1.55 can increases the optical efficiency of the system by as much as 33% compared to a homogenous polymer waveguide with an index of 1.52
Summary
The use of concentrated photovoltaics (CPV) is an interesting technology to reduce the cost associated with solar power. The light losses in planar waveguide concentrators come from the coupling prisms which are much larger than the ones required for dual axis tracking. To increase the optical efficiency of the single-axis tracking planar waveguide concentrator, we must reduce the interactions between the light rays and the backside surface of the waveguide containing the coupling prisms. We were inspired by the technology used in graded-index optical fibers In such systems, all rays coupled with different angles propagate the same length along the fiber axis before being re-imaged. The propagation losses into the waveguide will be minimised To our knowledge, this is not something that has been previously considered to increase the efficiency of cylindrical planar concentrators. This paper proposes a low-cost concentrator alternative to the traditional one-axis tracked solar panels using graded index polymer waveguides. A discussion about the method for manufacturing a low-cost graded-index planar waveguide made of polymer is presented
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