Optical concentrator and associated photovoltaic devices.

Disclosed is a transmissive optical concentrator, comprising an elliptical collector aperture and a non-elliptical exit aperture, the concentrator being operable to concentrate radiation incident on said collector aperture. The body of said concentrator may have a substantially hyperbolic external profile. Also disclosed is a photovoltaic cell employing such a concentrator and a photovoltaic building unit. The unit comprises an array of optical transmissive concentrators, each having an elliptical collector aperture, and an array of photovoltaic cells, each aligned with an exit aperture of a concentrator, wherein the area between adjacent collector apertures is transmissive to visible radiation

Effects of Nonuniform Incident Illumination on the Thermal Performance of a Concentrating Triple Junction Solar Cell

A numerical heat transfer model was developed to investigate the temperature of a triple junction solar cell and the thermal characteristics of the airflow in a channel behind the solar cell assembly using nonuniform incident illumination. The effects of nonuniformity parameters, emissivity of the two channel walls, and Reynolds number were studied. The maximum solar cell temperature sharply increased in the presence of nonuniform light profiles, causing a drastic reduction in overall efficiency. This resulted in two possible solutions for solar cells to operate in optimum efficiency level: (i) adding new receiver plate with higher surface area or (ii) using forced cooling techniques to reduce the solar cell temperature. Thus, surface radiation exchanges inside the duct and Re significantly reduced the maximum solar cell temperature, but a conventional plain channel cooling system was inefficient for cooling the solar cell at medium concentrations when the system was subjected to a nonuniform light distribution. Nonuniformity of the incident light and surface radiation in the duct had negligible effects on the collected thermal energy

Thermal Performance of a Solar Concentrating Photovoltaic Module with Spiral Mini Channel Heat Sink

ICP 2015: International Conference on Polygeneration, Chennai, India, 18-20 February 2015Concentrating Photovoltaic (CPV) power generation is one of the attractive choices for efficient utilization of solar energy due to its high cogeneration efficiency. The increase in temperature of solar CPV cell significantly reduces the performance. The efficiency of a CPV system can be improved by introducing effective thermal management or cooling system. In this paper, a new spiral mini channel heat sink with rectangular cross section is developed and its performance is numerically analysed using commercial CFD software ANSYS 14. The mini-channels provided high heat transfer over cell surface area and resulted in lower pressure drop. The coolant outlet temperature rise across the mini-channel is estimated as 343K in CPV module of 300 X 300 mm2 and with a pressure drop of 8.043 k Pa at a flow rate of 0.16 liter/s. Based on numerical simulations, it is found that the optimum configuration of micro-channel with 4mm width and height of 20mm, having higher figure of merit.Department of Science and Technology (DST), Government of Indi

Influence of Atmospheric Clearness on PDLC Switchable Glazing Transmission

Electrically activated switchable polymer dispersed liquid crystal (PDLC) is suitable for adaptive windows. A particular type requires 20V to become 71% transparent while in the absence of power it is 27% transparent. Glazing transmission changes with light incident angle. As the clearness of a sky changes the fraction changes alter of direct insolation (that has an azimuthally changing incident) and diffuse insolation (that has a largely constant incident). Thus, the effective overall incident angle determining the glazing transmittance also changes. In this work for the first time, the variation of PDLC glazing transmission with clearness index has been investigated

Supervisory control for power management of an islanded AC microgrid using frequency signalling-based fuzzy logic controller

In islanded AC microgrids consisting of renewable energy sources (RES), battery-based energy storage system (BESS), and loads, the BESS balances the difference between the RES power and loads by delivering/absorbing that difference. However, the state of charge (SOC) and charging/discharging power of the battery should be kept within their design limits regardless of variations in the load demand or the intermittent power of the RES. In this paper, a supervisory controller based on fuzzy logic is proposed to assure that the battery power and energy do not exceed their design limits and maintaining a stable power flow. The microgrid considered in this paper consists of a PV, battery, load and auxiliary supplementary unit. The fuzzy logic controller alters the AC bus frequency, which is used by the local controllers of the parallel units to curtail the power generated by the PV or to supplement the power from the auxiliary unit. The proposed FLC performance is verified by simulation and experimental results. IEE