A concentrating photovoltaic (CPV) system with a steady electric output adopting an electrically tunable concentration ratio of the liquid crystals (LC) lens is demonstrated. The distribution of the LC directors of the LC lens can be controlled by an applied voltage in order to adjust the number of incident photons in an area. As a result, the CPV system adopting an LC lens can be operated with a static and maximum output power density under different ambient illuminations because the LC lens with an electrically tunable concentration ratio helps to increase the photocurrent at a low illumination and prevent the effect of the series resistance at a high illumination. The detailed operating principles are discussed, and the experimental results are performed. We believe this letter can help enhance the output power density of CPV systems by using active optical elements whose concentration ratio is tunable.

Unlike the conventional light-emitting diode (LED) luminaire with a planar substrate and only the forward emission, the proposed LED luminaire with a curved ceramic substrate can perform both the forward and the backward emissions and inherits the merits of good heat-dissipation and low cost from the ceramic substrate. Assembled with the proper primary optics, an illustrated LED bulb has been designed, fabricated and measured. The measured luminous intensity of the LED bulb has shown the backward emission and designed distribution with the beam-angle of 133 deg. To broaden the application areas, such a LED bulb on a curved substrate has been modularized as a streetlight. The measured results of the proposed streetlight have shown that the beam angle of the luminous intensity and the luminaire efficiency are 132 deg and 86%, respectively. Meanwhile, its luminous characteristics also fit the Chinese standard for lighting design of urban roads.

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