MicroShade; A Bridge to the Future of Efficient Shading Design

Along with many benefits of daylight in interior space, undesirable solar heat gain and glare have been always challenging. Shading strategies like overhang, louvers, manual and automatic blinds, etc.; are to control unfavorable direct sunlight. Solar UV, IR, and glare control glazing materials are increasingly used instead of shading design, especially for high-rise buildings. Notwithstanding the advantages of solar control glazing, there is a concern about how LowE glazing affects the overall daylight availability in a space. On the other hand, in lack of shade, glare is still a big challenge for solar control glazing strategies. In this study, a MicroShade strategy (solar control coating with 37% VT) is proposed in between interior heat-control clear-glass panes and based on an optimized shading design. A single 12’ * 16’ office room is then studied based on a MicroShade window for south orientation and is compared with an ASHRAE 90.1 code approved LowE glazing strategy (65% VT) without shade. Annual daylight simulations show that totally LowE glass window contributes to higher available daylight. However, close to the window, the MicroShade system has less undesirable illuminance (above 2000 lux), and possible glare. The result of glare simulations, for 7 representative days during hot and warm seasons (5 times per day), show not many differences. Although probably due to reflections of MicroShade materials in general MicroShade system shows 1-2 DGP higher than the other two systems, for the times that solar angle is lower, MicroShade plays a better role in terms of glare control.

Retrieval of High Temporal Resolution Aerosol Optical Depth Using the GOCI Remote Sensing Data

High temporal resolution aerosol optical depth (AOD) products are very important for the studies of atmospheric environment and climate change. Geostationary Ocean Color Imager (GOCI) is a suitable data source for AOD retrieval, as it can monitor hourly aerosol changes and make up for the low temporal resolution deficiency of polar orbiting satellite. In this study, we proposed an algorithm for retrieving high temporal resolution AOD using GOCI data and then applied the algorithm in the Yangtze River Delta, a typical region suffering severe air pollution issues. Based on Moderate-resolution Imaging Spectroradiometer (MODIS) surface reflectance determined by MODIS V5.2 algorithm and MODIS Bidirectional Reflectance Distribution Function (BRDF) data, after spectral conversion between MODIS and GOCI, the GOCI surface reflectance at different solar angles were obtained and used to retrieve AOD. Five indicators including correlation coefficient (R), significant level of the correlation (p value), mean absolute error (MAE), mean relative error (MRE) and root mean square error (RMSE) were employed to analyze the errors between the Aerosol Robotic Network (AERONET) observed AOD and the GOCI retrieved AOD. The results showed that the GOCI AOD retrieved by the continental aerosol look-up table was consistent with the AERONET AOD (R > 0.7, p ≤ 0.05). The highest R value of Taihu Station and Xuzhou CUMT Station are both 0.84 (8:30 a.m.); the minimum RMSE at Taihu and Xuzhou-CUMT stations were 0.2077 (11:30 a.m.) and 0.1937 (10:30 a.m.), respectively. Moreover, the results suggested that the greater the solar angle of the GOCI sensor, the higher the AOD retrieval accuracy, while the retrieved AOD at noon exhibited the largest error as assessed by MAE and MRE. We concluded that the inaccurate estimation of surface reflectance was the root cause of the retrieval errors. This study has implications in providing a deep understanding of the effects of solar angle changes on retrieving AOD using GOCI.

Effects of Receiver Parameters on Solar Flux Distribution for Triangle Cavity Receiver in the Fixed Linear-Focus Fresnel Lens Solar Concentrator

The objective of the study is to investigate and optimize the solar flux uniformity of a fixed linear-focus Fresnel lens solar concentrator using a triangle cavity receiver. The effects of receiver parameters including the vertical distance from the cavity opening plane to the Fresnel lens f, receiver internal surface absorptivity αab, end reflection plane reflectivity ρr, solar declination angle δ and solar angle ω on the uniformity factor (UF) of a triangle cavity receiver were carried out. The effects of receiver parameters are evaluated with a significance test of critical factors. The results showed that the increase in f and δ would result in an increase in the UF. The average UF with f = 600, 625, 650, 675 and 700 mm, respectively, are 0.5030, 0.5858, 0.6337, 0.6576 and 0.6784 for ω in range of 0–60°. Moreover, the UF increases as αab decreases when other receiver parameters are constant for the δ of 0–8°. The ρr has a limited effect on the UF until δ becomes relatively larger and ω becomes relatively smaller. Furthermore, ω effects are most significant on the UF, followed by δ, f and αab. Setting a suitable f is the most economical and effective way to improve the UF.

Comparison between IPSL Venus Global Climate Model results and aerobraking data

<p align="justify"><span>For fifteen years</span><span>, a G</span><span>lobal</span><span> C</span><span>limate</span><span> Model (GCM) </span><span>ha</span><span>s </span><span>been</span><span> developed for the Venus atmosphere </span><span>at Institut Pierre-Simon Laplace (IPSL), in collaboration between LMD and LATMOS, </span><span>from the surface up to 150 km altitude. Its recent extension up to </span><span>the exobase (roughly </span><span>250 km</span><span>)</span><span> within the framework of the VCD project now allows us to simulate the Venusian upper atmosphere and the key atmospheric parameters of the aerobraking phases. The aim of this presentation is to study the evolution of the density of the Venusian upper atmosphere as a function of different parameters such as solar irradiance, </span><span>latitude, </span><span>local time and zenith solar angle (SZA), </span><span>for regions from 130 to 180 km of altitude.</span><span> We will present here several comparisons of the upper atmosphere of Venus between our model results and a selection of aerobraking data from different missions such as Venus Express, Pioneer Venus and Magellan. </span></p>

Sun Position Identification in Sky Images for Nowcasting Application

Very-short-term photovoltaic power forecast, namely nowcasting, is gaining increasing attention to face grid stability issues and to optimize microgrid energy management systems in the presence of large penetration of renewable energy sources. In order to identify local phenomena as sharp ramps in photovoltaic production, whole sky images can be used effectively. The first step in the implementation of new and effective nowcasting algorithms is the identification of Sun positions. In this paper, three different techniques (solar angle-based, image processing-based, and neural network-based techniques) are proposed, described, and compared. These techniques are tested on real images obtained with a camera installed at SolarTechLab at Politecnico di Milano, Milan, Italy. Finally, the three techniques are compared by introducing some performance parameters aiming to evaluate of their reliability, accuracy, and computational effort. The neural network-based technique obtains the best performance: in fact, this method is able to identify accurately the Sun position and to estimate it when the Sun is covered by clouds.

In-flight calibration results of the TROPOMI payload on board the Sentinel-5 Precursor satellite

After the launch of the Sentinel-5 Precursor satellite on 13 October 2017, its single payload, the TROPOspheric Monitoring Instrument (TROPOMI), was commissioned for 6 months. In this time the instrument was tested and calibrated extensively. During this phase the geolocation calibration was validated using a dedicated measurement zoom mode. With the help of spacecraft manoeuvres the solar angle dependence of the irradiance radiometry was calibrated for both internal diffusers. This improved the results that were obtained on the ground significantly. Furthermore the orbital and long-term stability was tested for electronic gains, offsets, non-linearity, the dark current and the output of the internal light sources. The CCD output gain of the UV, UVIS and NIR detectors shows drifts over time which can be corrected in the Level 1b (L1b) processor. In-flight measurements also revealed inconsistencies in the radiometric calibration and degradation of the UV spectrometer. Degradation was also detected for the internal solar diffusers. Since the start of the nominal operations (E2) phase in orbit 2818 on 30 April 2018, regularly scheduled calibration measurements on the eclipse side of the orbit are used for monitoring and updates to calibration key data. This article reports on the main results of the commissioning phase, the in-flight calibration and the instrument's stability since launch. Insights from commissioning and in-flight monitoring have led to updates to the L1b processor and its calibration key data. The updated processor is planned to be used for nominal processing from late 2020 on.

Empirical acquisition of bidirectional reflectance of tropical forest ecosystems using unmanned aerial vehicles

<p>Both the sensor viewing angle and the solar angle influence the remote sensing signal of terrestrial ecosystems. This influence is characterized by the bidirectional reflectance distribution function (BRDF). Knowledge of this BRDF is needed to correctly interpret the signal, but can also provide information on vegetation characteristics and structure. Obtaining the BRDF is far from straightforward: at leaf scale, laboratory goniometers can measure reflected radiation over a range of sensor-solar angle; for very homogeneous ecosystems, such as grassland or agricultural cropland, unmanned aerial vehicles (UAVs) can be programmed as giant goniometer, scanning the BRDF of an area of up to a few m². For heterogeneous ecosystems such as forests, this is not feasible. In this case, BRDF could so far only be derived from theoretical radiation transfer models or semi-empirical models; yet these models do not always agree.</p><p>We here propose a new method for measuring BRDF of forest ecosystems with UAVs, by measuring a star-shaped area of the ecosystem, covering in total about 3600m² and capturing 6 different sensor-solar azimuth angle and three different zenith angles. This approach was applied over two sites of tropical rainforests in Queensland, Australia, with measurements with a RGB camera and a spectrometer. By repeating the flights several times during the day, we were able to test the Helmholtz reciprocity principle – that states the BRDF function of ecosystems remains the same, regardless of the solar angle – and are able to increase the range of sensor-solar angles. Our results present the first strictly empirical BRDF of tropical rainforests and confirm the importance of accurate BRDF correction of remote sensing products from forest ecosystems. </p>