Skylight with Compound Parabolic Diffusers for Uniform Daylighting
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Solution Overview
Problem
Current skylights face challenges in maximizing visual light transmittance while minimizing solar heat gain, as they often lose light through total internal reflection and fail to efficiently distribute sunlight from various sun angles, leading to glare and increased cooling costs.
Innovation Solution
The use of compound parabolic diffusers, which are three-dimensional structures that deflect sunlight from all possible angles, directing it as if from overhead into a wider angular distribution to provide more efficient and uniform illumination over a larger area, replacing traditional refracting prisms to minimize heat gain and glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional refracting prisms are used in skylights, then light collection from overhead angles is achieved, but total internal reflection causes significant light loss and narrow beam distribution
Solution Approach 1:
The patent changes the optical mechanism from refraction-based prisms to reflection-based CPC structures. This parameter change in the optical principle eliminates total internal reflection losses by using controlled reflection off the CPC surfaces, achieving up to 50% additional light transmission while maintaining overhead light direction.
Solution Approach 2:
The patent substitutes the refraction mechanism with a reflection mechanism. Instead of relying on refractive index differences that cause total internal reflection, the design uses geometric reflection off the compound parabolic concentrator surfaces to redirect light, replacing the optical mechanism to eliminate the harmful effect.
2Illumination intensity
If skylights collect sunlight from all overhead angles, then daylighting coverage is improved, but solar heat gain increases causing uncomfortable heat in building interiors
Solution Approach 1:
The patent applies local quality by using multiple CPC structures with different acceptance angles arranged in zones across the skylight surface. Each zone is optimized for specific sun angles, allowing selective collection of beneficial diffuse light while rejecting intense direct solar radiation that causes heat gain.
Solution Approach 2:
The patent segments the skylight into multiple independent CPC structures rather than using a single large aperture. This segmentation allows each CPC to handle specific angular ranges independently, distributing the light collection function while limiting the total solar energy admitted to the building.
3Illumination intensity
If refracting prisms are used to direct sunlight, then light from overhead angles is provided, but the beam remains narrow causing glare to eyes
Solution Approach 1:
The patent adds angular distribution as an additional dimension to the light output. The CPC structures not only redirect light overhead but also inherently spread it across a wider angular range through their geometric design, transforming a narrow beam into a distributed illumination pattern that eliminates glare.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for broader light distribution and reduced heat gain, achieving comfortable illumination with less glare and lower energy costs by collecting sunlight from a wider range of angles and distributing it effectively over a wider area, combining the benefits of summer and spring sunlight conditions.
Implementation Method 1
Each such compound parabolic diffuser—CPD—will be defined by an entrance aperture, an exit aperture and height of the parabolic sections between these apertures... The CPDs will be arranged in the layers of the skylight such that their entrance apertures will be positioned substantially towards the exterior of the building and their exit apertures will be positioned substantially towards the interior of the building.
Data Source
AI summary
A skylight to provide daylighting is described that includes a plurality of compound parabolic diffusers into one or more layers that may be dome or pyramid-shaped to enable more efficient collection of sunlight and its distribution through wider angles resulting in more comfortable illumination with less glare and heat gain—more light less heat—over wider areas of building interiors.