Improvement of BIPV Efficiency by Application of Highly Reflective Surfaces at the Building Envelope

The use of concentrated solar irradiation for the improvement of electric generation improvement has been implemented on different scales, mainly in photovoltaic systems. High-concentration Fresnel lenses are widely chosen for this approach in large installations, while low-concentration systems are rather applied in medium-low scales. For the latter, the improvement on electric performance was revealed, even when no solar tracking was implemented. The presented work aims to analyse a low-concentration photovoltaic installation by a numerical approach. First, the reflective surfaces were designed geometrically considering the optimal slope determined for each month. Subsequently, different simulation techniques were used separately for prediction of solar irradiation and energy production. Three criteria were selected to analyze power generation: the highest increase in total annual solar irradiance on panels with reflective surfaces, the highest total annual solar irradiance collected, and the optimal slope of panels for the entire year. The increase in energy was found to not exceed 10% in the winter months. Whereas in the spring and summer months the energy improvement is about 15–20%. Moreover, it was observed that the temperature of the proposed concentration photovoltaic system increased significantly, reaching more than 90 °C, while for traditional PV panels it did not exceed 75 °C.

Shiny Things: Reflective Surfaces and Their Mixed Meanings

Discusses meanings of shininess in art and in culture generally. Shininess is physically and metaphorically present in the construction of concepts such as utopia, the sublime, and camp; and the way its affects, rooted in excess produce irony, anxiety, pleasure and kitsch. A compelling subject that instantly attracts and fascinates.

Limited application of reflective surfaces can mitigate urban heat pollution

Elevated air temperatures in urban neighborhoods due to the Urban Heat Island effect is a form of heat pollution that causes thermal discomfort, higher energy consumption, and deteriorating public health. Mitigation measures can be expensive, with the need to maximize benefits from limited resources. Here we show that significant mitigation can be achieved through a limited application of reflective surfaces. We use a Computational Fluid Dynamics model to resolve the air temperature within a prototypical neighborhood for different wind directions, building configurations, and partial application of reflective surfaces. While reflective surfaces mitigate heat pollution, their effectiveness relative to cost varies with spatial distribution. Although downstream parts experience the highest heat pollution, applying reflective surfaces to the upstream part has a disproportionately higher benefit relative to cost than applying them downstream.

A Single-Switch-per-Bit Topology for mmWave and THz Reconfigurable Reflective Surfaces

<div> <div> <div> <p>We present novel multi-bit unit-cell topologies for reconfigurable reflective surfaces –RRSs– (e.g., reflectarray antennas) with compact designs for millimeter-wave and terahertz (mmWave/THz) applications. Typically, mmWave/THz RRSs utilize one or multiple single-pole-single-throw (SPST) switches leading to single- or dual-bit modulated surfaces. These surfaces utilize the switches to manipulate the phase of the imping waves, beamforming the reflected waves to the desired direction. As such, RRSs are leveraged either for imaging or wireless communication applications, which typically require the formation of a single beam (no grating lobes) and high gains. The gain and quantization lobe levels of an RRS is strictly related to the number of phase bits utilized in the unit-cell. Explicitly, more phase bits lead to lower quantization errors and better maximum gain/aperture efficiency. However, increasing the number of phase bits requires more SPST switches integrated within the unit-cell, leading to complex designs with high RF losses. Herein, we present, for the first time, RRSs with up to 4 phase quantization bits (16 states) that maintain one switch-per-bit topology thus retaining a low-complexity design. The proposed RRSs is presented alongside a series of analytical and full-wave simulated results. </p> </div> </div> </div>

A Single-Switch-per-Bit Topology for mmWave and THz Reconfigurable Reflective Surfaces

<div> <div> <div> <p>We present novel multi-bit unit-cell topologies for reconfigurable reflective surfaces –RRSs– (e.g., reflectarray antennas) with compact designs for millimeter-wave and terahertz (mmWave/THz) applications. Typically, mmWave/THz RRSs utilize one or multiple single-pole-single-throw (SPST) switches leading to single- or dual-bit modulated surfaces. These surfaces utilize the switches to manipulate the phase of the imping waves, beamforming the reflected waves to the desired direction. As such, RRSs are leveraged either for imaging or wireless communication applications, which typically require the formation of a single beam (no grating lobes) and high gains. The gain and quantization lobe levels of an RRS is strictly related to the number of phase bits utilized in the unit-cell. Explicitly, more phase bits lead to lower quantization errors and better maximum gain/aperture efficiency. However, increasing the number of phase bits requires more SPST switches integrated within the unit-cell, leading to complex designs with high RF losses. Herein, we present, for the first time, RRSs with up to 4 phase quantization bits (16 states) that maintain one switch-per-bit topology thus retaining a low-complexity design. The proposed RRSs is presented alongside a series of analytical and full-wave simulated results. </p> </div> </div> </div>