Search Results (3)

The exploitation of bifacial solar cells in photovoltaics aims to provide cost-effective solutions to maximize solar power collection on specific surfaces. A prerequisite for this is the effective collection of backscattered diffuse light from albedo, to which self-shading is an obstacle. We discuss the benefits of bifaciality for an asymmetric low-concentrating and spectral-splitting photovoltaic optics system that features a wedged right-prism geometry to address self-shading. The performance of the conceptual design is analyzed, using commercial ray-tracing software, for four different latitudes of installation, by assuming a standard solar AM1.5G spectrum as input. The daily Relative Optical Power Increase (ROPI) is evaluated with respect to standard flat bifacial configurations, reaching ROPI = 293% at a latitude of 25° north at winter solstice. The photocurrent and total Power Conversion Efficiency (PCE) in a four-terminal (4T) configuration are estimated, assuming the operation of a commercial Si HJT bifacial cell and a commercial single-junction GaAs cell. A global increase in PCE of up to 23% is obtained with respect to the best-performing trackless standard bifacial configuration. From this perspective, the use of high-performance, high-bandgap solar cells in 4T configurations might further leverage the advantages of the optics proposed here. Full article

Background and Purpose: Nanofluids are a new class of heat transfer fluids that are used for different heat transfer applications. The transport characteristics of these fluids not only depend upon flow conditions but also strongly depend on operating temperature. In respect of these facts, the properties of these fluids are modified to measure the temperature effects and used in the governing equations to see the heat and mass flow behavior. Design of Model: Consider the nanofluids which are synthesized by dispersing metallic oxides (SiO₂, Al₂O₃), carbon nanostructures (PEG-TGr, PEG-GnP), and nanoparticles in deionized water (DIW), with (0.025–0.1%) particle concentration over (30–50 °C) temperature range. The thermophysical properties of these fluids are modeled theoretically with the help of experimental data as a function of a temperature and volume fraction. These models are further used in transport equations for fluid flow over both wedge and plate. To get the solution, the equations are simplified in the shape of ordinary differential equations by applying the boundary layer and similarity transformations and then solved by the RK method. Results: The solution of the governing equation is found in the form of velocity and temperature expressions for both geometries and displayed graphically for discussion. Moreover, momentum and thermal boundary layer thicknesses, displacement, momentum thicknesses, the coefficient of skin friction, and Nusselt number are calculated numerically in tabular form. Finding: The maximum reduction and enhancement in velocity and temperature profile is found in the case of flow over the plate as compared to the wedge. The boundary layer parameters are increased in the case of flow over the plate than the wedge. Full article

A chemically defined patterned surface was created via a combined process of controlled evaporative self-assembly of concentric polymer stripes and the selective surface modification of polymer brush. The former process involved physical adsorption of poly (methyl methacrylate) (PMMA) segments into silicon oxide surface, thus forming ultrathin PMMA stripes, whereas the latter process was based on the brush treatment of silicon native oxide surface using a hydroxyl-terminated polystyrene (PS-OH). The resulting alternating PMMA- and PS-rich stripes provided energetically favorable regions for self-assembly of high $\chi$ polystyrene-block-polydimethylsiloxane (PS-b-PDMS) in a simple and facile manner, dispensing the need for conventional lithography techniques. Subsequently, deep reactive ion etching and oxygen plasma treatment enabled the transition of the PDMS blocks into oxidized groove-shaped nanostructures. Full article