Beyond the 2D limit: étendue-squeezing line-focus solar concentrators

Johnsen, Håkon Jarand Dugstad; Aksnes, Astrid; Torgersen, Jan

doi:10.1364/ol.406280

Cited by 5 publications

(2 citation statements)

References 13 publications

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“…Concentrations ranging from 1-100× are considered, as well as temperatures up to 225 • C. Each of these ranges corresponds to the performance of a class of deployed or proposed line-focus solar concentrators. "Etendue-squeezing" concentrators with dual-axis tracking have been proposed for thermal and chemical applications that can reach 100× concentration factors with a 1-degree acceptance angle [57]; 200-250 • C is the upper limit of the performance of low-concentration compound parabolic collector (CPC) modules that are currently in commercial production [58]. While this temperature range is seen as too high for PV cell operation, this is not necessarily the case as can be seen from the figure.…”

Section: Pv-thermal Applicationsmentioning

confidence: 99%

The CPV “Toolbox”: New Approaches to Maximizing Solar Resource Utilization with Application-Oriented Concentrator Photovoltaics

2021

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As the scaling of silicon PV cells and module manufacturing has driven solar energy penetration up and costs down, concentrator photovoltaic technologies, originally conceived as a cost-saving measure, have largely been left behind. The loss of market share by CPV is being locked in even as solar energy development encounters significant obstacles related to space constraints in many parts of the world. The inherently higher collection efficiency enabled by the use of concentrators could substantially alleviate these challenges, but the revival of CPV for this purpose requires substantial reinvention of the technology to actually capture the theoretically possible efficiency gains, and to do so at market-friendly costs. This article will discuss recent progress in key areas central to this reinvention, including miniaturization of cells and optics to produce compact, lightweight “micro-CPV” systems; hybridization of CPV with thermal, illumination and other applications to make use of unused energy streams such as diffuse light and waste heat; and the integration of sun-tracking into the CPV module architecture to enable greater light collection and more flexible deployment, including integration into built structures. Applications showing particular promise include thermal applications such as water heating, industrial processes and desalination; agricultural photovoltaics; building-integrated photovoltaics with dynamic daylighting capabilities; and chemical processes including photocatalysis and hydrogen production. By appropriately tailoring systems to the available solar resource and local energy demand, we demonstrate how CPV can finally achieve real-world efficiencies, or solar resource utilization factors, far higher than those of standard silicon-based PV systems. This makes the argument for sustained development of novel CPV designs that can be applied to the real-world settings where this efficiency boost will be most beneficial.

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Section: Pv-thermal Applicationsmentioning

confidence: 99%

The CPV “Toolbox”: New Approaches to Maximizing Solar Resource Utilization with Application-Oriented Concentrator Photovoltaics

2021

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“…[3][4][5][6] In previous research, we have demonstrated that one way to perform this symmetry-breaking is through étendue squeezing. 7,8 An alternate and lesser known principle for breaking the continuous translational symmetry of an optical system is étendue rotation. 9 Here, we show through two different configurations how this principle can be used to increase the concentration of line-focus solar concentrators beyond the 2D concentration limit.…”

Section: Introductionmentioning

confidence: 99%

In search of a sharper line focus: Rotating the étendue

Johnsen

Miñano

2022

Nonimaging Optics: Efficient Design for Illumination and Solar Concentration XVIII

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Conventional line-focus solar concentrators are limited by the 2D concentration limit, two orders of magnitude lower than the three-dimensional limit. This leads to low concentration ratios and strict manufacturing tolerances. It has been shown that by eliminating the continuous translational symmetry of these systems, it is possible to go beyond the 2D limit while maintaining the linear geometry of a line focus. We demonstrate that one way to break this symmetry is through étendue rotation, and we present two new concentrator configurations based on this insight. The first configuration uses an étendue rotating retroreflector array to boost the concentration of a parabolic trough. Ray-tracing simulations show that this configuration can achieve very high geometric concentration ratios or very high acceptance angles (1484 x at ➧9 mrad acceptance angle, or 25 x at ➧70 mrad). However, this configuration requires two-axis external solar tracking. To get around this, we demonstrate a second configuration that uses an étendue rotating lens array with tracking integration. We demonstrate a design that achieves a geometric concentration of 146x at a ➧9 mrad, with a simulated average yearly efficiency of 94.9% when used with conventional horizontal single-axis external tracking at an installation latitude of 30➦. The extra constraints of the tracking integration gives this design a more modest concentration ratio, but it is still higher than the 2D concentration limit and more than three times as high as the concentration of a parabolic trough evaluated under the same conditions. We believe that these new configurations show that the design landscape for line-focus solar concentrators can be widened, and that a practical high-concentration line-focus concentrator may be within reach.

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Imaging performance of an ultra-precision machining-based Fresnel lens in ophthalmic devices

Hasan

Youn

et al. 2021

Opt. Express

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This study aims to resolve the trade-off between the constraints and capabilities of ultra-precision machining to achieve ophthalmic Fresnel lenses. A general Fresnel lens pattern has a narrow variable pitch and curved grooves. However, we obviate the limitations of the tool nose radius constraint and the long tool path via ultra-precision machining of the modified Fresnel lens, ensuring a constant pitch of 0.1 mm and varying the height of straight grooves from 0 to 11 µm. Photorealistic raytracing visualization and MTF simulation verified the compatibility of the lens pattern with human perception sensitivity. Copper-coated mold was fabricated using a diamond tool with a tool nose radius of 5 µm. The replicated flexible Fresnel lens demonstrated a relative MTF imaging performance of 89.1% and was attached to the goggles for the qualitative assessment. The proposed Fresnel lens design and fabrication approach can be extended to applications in the visual and infrared ranges as well.

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Beyond the 2D limit: étendue-squeezing line-focus solar concentrators

Cited by 5 publications

References 13 publications

The CPV “Toolbox”: New Approaches to Maximizing Solar Resource Utilization with Application-Oriented Concentrator Photovoltaics

The CPV “Toolbox”: New Approaches to Maximizing Solar Resource Utilization with Application-Oriented Concentrator Photovoltaics

In search of a sharper line focus: Rotating the étendue

Imaging performance of an ultra-precision machining-based Fresnel lens in ophthalmic devices

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