KEYWORDS: Compound parabolic concentrators, Solar cells, Solids, Solar concentrators, Silicon, Chromium, Photovoltaics, Concentrated solar cells, Mirrors, Solar radiation
This research presents the static flexible concentrator photovoltaics (Static CPV) systems for electric vehicles (EVs). The CPV system includes solid CPC, 3‐junction solar cells, and a crystalline Si cell. Direct sunlight with an incident angle satisfying the acceptance angle of the solid CPC is focused on the 3‐junction solar cells, while diffuse sunlight is collected by crystalline Si cells. When direct sunlight and diffused sunlight have an incident angle greater than the acceptance angle of the CPC, they will leak out of the solid CPC and be collected by the Si solar cell. This structure allows to manufacture of Static CPV with a geometrical concentration ratio of 4× for 3‐junction cells, The module was designed using the commercial optic simulation software LightTools™, the simulation results show that the module can achieve 25% annual efficiency, moreover, it can be flexible to meet the requirement of car roof application.
In this paper, a primary lens of concentrator photovoltaic (CPV) system is designed by using freeform optics. The designed lens is constructed based on a basic idea of a combination of Fresnel lens and freeform optics, in which the lens is divided into an array of sub-lenses, which are designed using the conservation of optical path length and the edge ray theorem to get uniform irradiance distribution over the receiver. In this design, every sub-lens is designed to guide the direct sunlight over the receiver with uniform irradiance so that the whole of the primary lens will converge uniformly the direct sunlight over the receiver. The structure of the lens is designed firstly by using Matlab program for every sub-lens. The Matlab data of the designed lens structure is then used to build the three-dimensional (3D) lens in LightTools™ software. The ray tracing technique in LightTools™ software is used to find out the optimum structure of the freeform lens. Furthermore, the simulation is performed to estimate the efficiency of the lens as a concentrator of a CPV system by using the light source with the sunlight spectrum. The designed lens can achieve high geometrical concentration ratio and uniform irradiance distribution over the receiver. The simulation results show that the lens can easily reach a high concentration ratio (494 times) with uniform irradiance distribution and good optical efficiency (86%).
We present a cost-effective and large scale optical fiber daylighting system using non-imaging optics device such as array of linear Fresnel lenses and stepped-thickness waveguide as concentrator. The stepped-thickness waveguide is an optical component that can redirect focused sunlight from vertical to horizontal and guide light to the optical fiber. Our simulation results demonstrate an optical efficiency of up to 56.4% when the concentration ratio of the system is fixed at 100. The simulation also shows that this design has high tolerance for input angle of sunlight. The high tolerance allows replacing a dual axis sun tracking system with a single axis sun-tracking system as a cost-effective solution. Therefore, our results provide an important breakthrough for the commercialization of optical fiber daylighting systems that are faced with challenges related to high costs.
We propose a new method of minimizing the gain-transient recovery time of wavelength-division-multiplexing (WDM)
signals in cascaded erbium-doped fiber amplifiers (EDFAs) in WDM network as the gain of signals in EDFA fluctuates
due to channel add/drops. To minimize the gain-related errors at the receivers, the gain of the signal should be recovered
back to its original level as fast as possible. In this paper, we have applied, for the first time in our knowledge, the wellknown
control theory of disturbance observer technique to the control of gain-transient recovery of cascaded EDFAs.
We have used a disturbance observer to detect and compensate the gain variations due to WDM channel add/drops.
While the major compensation of the gain is performed by the disturbance observer, the fine control process for exact
gain recovery is done by a proportional/integral/differential (PID) controller. The proposed gain control algorithm for
EDFA was implemented by MATLAB and the performance of the technique was verified by simulations for the cases of
different numbers of cascaded EDFAs in WDM networks. For simulation, we have used a commercially available
numerical modeling software package such as the OptsimTM. Simulation results show that the technique decreases the
amount of gain-transient recovery time to less than 3μsec in all the cases. This amount of gain recovery time is just
about 1% of the one for commercial WDM EDFAs in these days.
A new mechanism is described that is based on the modulation of the confinement factor with carrier density in quantum-well lasers. This new mechanism may limit modulation bandwidth for quantum-well laser with high threshold carrier density and narrow confining layer.
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