This paper presents a study on the use of optical fiber and a solar concentrator for a building daylighting system. Daylighting is essential for improving indoor environments and reducing electric lighting power consumption in office buildings. Traditionally, optical fiber daylighting systems were implemented only on a small scale. More complicated technologies are required for more amounts of daylight over further distance via a smaller light guider. The proposed solar lighting system with optical fiber is composed of an array of linear Fresnel lenses and a stepped thickness waveguide. The linear Fresnel lenses collect light into the stepped thickness waveguide. The stepped-thickness waveguide is an optical component which redirects focused sunlight from the vertical direction to the horizontal direction, and it guides light to the attached optical fiber. Simulation models were developed using commercial optical simulation tools (LightTools™). The optical efficiency and angular tolerance of the system are analyzed. The overall system cost is also estimated. Some considerations on the economic expansion of the system in terms of efficiency and estimated annual average energy saving are discussed. The results show that the presented optical fiber daylighting system is a strong candidate for low-price and highly efficient solution for solar energy application to building energy savings.

In this paper, we present a design and optical simulation of a novel linear Fresnel lens. The lens can be applied to a concentrator photovoltaic (CPV) system as a primary optical element (POE) to increase the concentration ratio and improve the uniformity of irradiance distribution over the receiver. In addition, the CPV system can use the proposed lens as a concentrator without involving a secondary optical element (SOE). The designed lens, which is a combination of two linear Fresnel lenses placed perpendicular to each other, can collect and distribute the direct sunlight on two dimensions. The lens is first designed in the MATLAB program, based on the edge ray theorem, Snell’s law, and the conservation of the optical path length, and then drawn in three dimensions (3D) by using LightTools^TM. Furthermore, in order to optimize the structure and investigate the performance of the lens, the ray tracing and the simulation are also performed in LightTools^TM. The results show that the newly designed lens can achieve a high concentration ratio of 576 times, a high optical efficiency of 82.4%, an acceptable tolerance of 0.84°, and high uniform irradiance of around 77% for both horizontal and vertical investigation lines over the receiver.

In this paper, we present a design and optical simulation of a daylighting system using a novel design of linear Fresnel lens, which is constructed based on the conservation of optical path length and edge ray theorem. The linear Fresnel lens can achieve a high uniformity by using a new idea of design in which each groove of the lens distributes sunlight uniformly over the receiver so that the whole lens also uniformly distributes sunlight over the receiver. In this daylighting system, the novel design of linear Fresnel lens significantly improves the uniformity of collector and distributor. Therefore, it can help to improve the performance of the daylighting system. The structure of the linear Fresnel lenses is designed by using Matlab. Then, the structure of lenses is appreciated by ray tracing in LightTools^TM to find out the optimum lens shape. In addition, the simulation is performed by using LightTools^TM to estimate the efficiency of the daylighting system. The results show that the designed collector can achieve the efficiency of ~80% with the tolerance of ~0.6⁰ and the concentration ratio of 340 times, while the designed distributor can reach a high uniformity of >90%.

We present a linear Fresnel lens design for light-emitting diode (LED) uniform illumination applications. The LED source is an array of LEDs. An array of collimating lens is applied to collimate output from the LED array. Two linear Fresnel lenses are used to redistribute the collimated beam along two dimensions in the illumination area. Collimating lens and linear Fresnel lens surfaces are calculated by geometrical optics and nonimaging optics. The collimated beam output from the collimating lens array is divided into many fragments. Each fragment is refracted by a segment of Fresnel lens and distributed over the illumination area, so that the total beam can be distributed to the illumination target uniformly. The simulation results show that this design has a compact structure, high optical efficiency of 82% and good uniformity of 76.9%. Some consideration of the energy savings and optical performance are discussed by comparison with other typical light sources. The results show that our proposed LED lighting system can reduce energy consumption five-times in comparison to using a conventional fluorescent lamp. Our research is a strong candidate for low cost, energy savings for indoor and outdoor lighting applications.