Design and Evaluation of Uniform LED Illumination Based on Double Linear Fresnel Lenses

Redistribution of LED radiation in lighting is necessary in many applications. In this article, we propose a new optical component design for LED lighting to achieve a higher performance. The design consists of a commercial collimator and two linear Fresnel lenses. The LED radiation is collimated by a collimator and redistributed by double linear Fresnel lenses to create a square-shaped, uniform distribution. The linear Fresnel lenses design is based on Snell’s law and the “edge-ray principle”. The optical devices are made from poly methyl methacrylate (PMMA) using a high-speed computer numerical control (CNC) machine. The LED prototypes with complementary optics were measured, and the optical intensity distribution was evaluated. The numerical results showed we obtained a free-form lens that produced an illumination uniformity of 78% with an efficiency of 77%. We used the developed LED light sources for field experiments in agricultural lighting. The figures of these tests showed positive effects with control flowering criteria and advantages of harvested products in comparison with the conventional LED sources. This allows our approach in this paper to be considered as an alternative candidate for highly efficient and energy-saving LED lighting applications.

Гибридные солнечные элементы с системой концентрации оптического излучения

Hybrid solar cells based on InGaP/Ga(In)As/Ge and Si elements integrated in a crystalline silicon heat-removing base with a system for optical-emission concentration based on linear Fresnel lenses and carbon-fiber body shell have been developed and their characteristics examined. These hybrid elements with light concentrators provide a specific electric power of 390 W/m2 (AM0, 1367 W/m2) at a specific mass of the photogenerating part reduced to 1.0 kg/m2. The improved photoelectric characteristics and the radiation hardness of the cells enable application of the hybrid elements with light concentrators in space solar cells and in stand-alone terrestrial power plants with solar light concentration.

Tri-Sol (Building-Integrated, Three-in-One Solar) Technology Development

A unique solar technology that can be building-integrated, which harnesses both visible and infrared spectrums of solar radiation, utilizes direct and diffuse radiation to produce electricity and hot water, and delivers daylight, has been conceptualized. This technology is a three-in-one (named Tri-Sol), low/medium-concentration, building-integrated, skylight system for commercial buildings. However, this technology can be utilized for building facades and other building envelope components. A key component of the technology is linear Fresnel lenses. These lenses can be designed to be thin and light-weight. Sunlight, concentrated by the linear Fresnel lenses with a low-cost single axis tracker, focuses on a high-efficiency, thin Photo Voltaic (PV) strip that is in contact with a thermal absorber. Electricity produced by PV strips can be processed and distributed from an electric power management system. The thermal absorber houses a sealed heat pipe for cooling the PV strip and producing hot water. The water-cooled condenser section of the heat pipe is external to the skylight so that there is no issue of water leakage through the skylight. Hot water produced can be used for end-use, space heating, or absorption cooling. All diffuse light that cannot be concentrated by Fresnel lenses is delivered into the building interior space. A pre-prototype of Tri-Sol technology was designed and built at University of New Haven (UNH). Solar Testing and Training Laboratory (STTL) at UNH houses solar thermal collector equipment with a capability to perform Solar Rating and Certification Corporation (SRCC) tests. The Tri-Sol module was mounted on the SRCC test equipment at UNH and was tested outdoors to identify any issues or design enhancements.