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Abstract This paper proposes a generalized analytical approach to model the photovoltaic (PV) arrays under partial shading conditions (PSC). The proposed method is simple: it requires only the standard test condition (STC) parameters of the PV modules and the irradiance level imposed on each module. By using this information, the P-V and I-V curves of shaded PV arrays are obtained by simple steps. Firstly, the current-voltage (I-V) curves for all assembled submodules receiving the same level of irradiance are generated using the two-diode model. The parameters of the latter are computed using a fast parameter extraction method. Secondly, the I-V curve of each shaded string is computed using the computed I-V curves of its submodules. In the last step, the resulted I-V curve of the array is obtained by summation of all I-V strings curves. The proposed method is simple, fast, and can be coded in any development platform. Besides, the prediction accuracy is enhanced by incorporating the real effect of bypass and blocking diodes in the model. Furthermore, the proposed method could be generalized for any number of series/parallel connections in a shaded PV array. The method can be useful to generate critical shading patterns for maximum power point tracking (MPPT) algorithms evaluation. It can also be used as a tool to obtain instant shading patterns in PV array simulators.

Abstract Complex fenestration systems (CFS) have proven to enhance the daylight quality inside spaces when designed correctly. While research in this area focuses on assessing CFS performance accurately, the number of CFS daylight analysis frameworks are too complex for the building designer to use for selecting a suitable CFS. Also, some CFS design frameworks focus only on light redirection efficiency without considering the spatial or environmental context. The paper demonstrates a new framework to analyse CFS considering both architectural and environmental conditions. The framework is presented as a computational tool (CFStrace), which accepts parametric geometric input and uses forward raytracing to simulate the complex optical behaviour of CFS. The framework also introduces new metrics for the assessment of CFS, which are developed to suit the forward raytracing simulation technique, that predicts the uniformity of redirected sunlight in the built environment and ensures adequate visual comfort to the occupants. A comparison study is carried out to state the effectiveness of the metrics where various CFS designs from previous literature are tested. The comparative case study revealed which CFS designs would be more suitable at the specific setting and location and provided insight on metrics that can be used to assess the feasibility of one design over the other in terms of daylight performance. The new framework will involve less technical and modelling capabilities making it “architect-friendly” encouraging building designers to include CFS in their design process, especially in the early design phase, and pave the way for new CFS designs possibilities.

Abstract Simultaneously generating both electricity and low grade heat, photovoltaic thermal (PVT) systems maximise the solar energy extracted per unit of collector area and have the added benefit of increasing the photovoltaic (PV) electrical output by reducing the PV operating temperature. A graphical representation of the temperature rise and rate of heat output as a function of the number of transfer units NTUs illustrates the influence of fundamental parameter values on the thermal performance of the PVT collector. With the aim of maximising the electrical and thermal energy outputs, a whole of system approach was used to design an experimental, unglazed, single pass, open loop PVT air system in Sydney. The PVT collector is oriented towards the north with a tilt angle of 34°, and used six 110 Wp frameless PV modules. A unique result was achieved whereby the additional electrical PV output was in excess of the fan energy requirement for air mass flow rates in the range of 0.03–0.05 kg/s m 2 . This was made possible through energy efficient hydraulic design using large ducts to minimise the pressure loss and selection of a fan that produces high air mass flow rates (0.02–0.1 kg/s m 2 ) at a low input power (4–85 W). The experimental PVT air system demonstrated increasing thermal and electrical PV efficiencies with increasing air mass flow rate, with thermal efficiencies in the range of 28–55% and electrical PV efficiencies between 10.6% and 12.2% at midday.

Abstract Geostationary satellites offer the possibility of producing high-frequency time series irradiance datasets, covering a large geographical area. Here, we derive half-hourly global irradiance (GHI) at 4 km spatial resolution from visible channel radiance of INSAT-3D satellite using a semi-empirical model and validate it against 19 ground stations over 2015–16, across India. Our model uses the Advanced Solis clear-sky model with monthly climatological values of modern-era retrospective analysis for research and applications-2 (MERRA-2) aerosol optical depth (AOD) and precipitable water (PW) as inputs. The relative root mean squared error (rRMSE) and relative mean bias error (rMBE) are 24.02% and −0.05%, respectively. Over the validation period, INSAT-3D derived GHI outperformed SARAH-E model and MERRA-2 reanalysis GHI.

Abstract Photocatalysis has emerged as a vital tool for purification of waste water and also to obtain alternate fuels (H2) through water splitting. TiO2, ZnO and other non-carbide systems (ZnS, metallic nanoparticles (NPs), etc.) have been studied thoroughly to enhance their photocatalytic performances through doping and the formation of heterojunctions. But, niobium carbide (NbC) is gaining interest of researchers due to its ability to catalyze electrochemical reactions (hydrogen evolution reaction and oxygen reduction reaction) along with excellent thermal and chemical stability. In the present work, NbC has been synthesized using conventional oxide precursor (Nb2O5), Mg metal powder and parthenium hysterophorous (PH; carrot grass, an agricultural hazardous weed) as carbon source at relatively low temperature (800 °C) as compared to conventional synthesis temperature (1200 °C). For the phase confirmation and morphological studies, X-ray diffraction and transmission electron microscopy have been done. It has been observed that the presence of NbCxOy/NbOz inside NbC nanoparticles induced the optical active sites resulting photocatalytic degradation of methylene blue (MB) dye under visible irradiation. With the help of various techniques (UV–visible, PL, XPS, RAMAN spectroscopies and scavenger tests), degradation mechanism has been established for the observed photocatalytic performance of synthesized NbCxOy/NbOz/NbCx/g-C heterostructure under optimized conditions. Further, for the confirmation of photodegradation of MB dye, mass spectrometry and TOC have also been carried out.

Abstract A generalized methodology is developed for thermal testing of various solar dryer designs operated for natural and forced air flow conditions. The steady state mathematical model based on heat balance concept of solar dryer without load is applied to identify the dimensionless parameter called no-load performance index (NLPI). Laboratory models of direct (cabinet), indirect and mixed mode solar dryer are designed and constructed to perform steady state thermal tests for natural and forced air circulation. The dryers with no-load are operated with air passage between absorber plate and glass cover for the range of 300–800 W/m2 and 0.009–0.026 kg/s of absorbed thermal energy and air mass flow rate respectively under indoor simulation conditions. The present study reveals that the forced convection operated dryer provides higher NLPI in contrast to that of natural convection. The comparative performance analysis of dryers indicates that the mixed mode dryer exhibits maximum value of NLPI followed by indirect and cabinet ones for both natural and forced air circulation. It is also found that for any dryer operating at given air flow condition, almost invariable NLPI values have been obtained for a wide range of absorbed energy and ambient air temperature data, thus facilitating performance comparison between different dryer designs on equitable basis. The results of statistical analysis showing low standard errors of mean further demonstrate good consistency in NLPI values for various dryer designs. The uncertainty in NLPI due to error in measurement of several parameters by instruments ranges from 0.79 to 1.96% for various dryer designs operated under different conditions.

Abstract Solar energy is key factor in the demand for clean energy development and management. In particular, global horizontal irradiance (GHI) and direct normal irradiance (DNI) are the foremost important solar resource components that need to be well characterized in order to seek an efficient operation of photovoltaic and concentrated solar power plants, respectively. The objective of the present work is to assess the quality of short-term (24 h) forecasts from a global Numerical Weather Prediction (NWP) model regarding the GHI and DNI components for solar energy applications. Forecast accuracy for the Integrated Forecasting System (IFS), the global model of the European Centre for Medium-Range Weather Forecasts (ECMWF), was verified through the comparison of the predicted hourly values with the corresponding ground-based measurements in southern Portugal. In this study, results from one year of IFS data are analysed, yielding a general good agreement between model and four ground-based measuring stations. High correlations occur particularly for GHI whilst DNI simulations are predominantly hindered by cloud and aerosol representation (i.e. the radiative effects of clouds tend to be underestimated by the model and the radiative effects of the aerosols are overestimated by the model under very clear atmospheric conditions), being closely linked to the parameterization of absorption and scattering phenomena as function of cloud and aerosol type and dimension. Relative differences of annual availabilities for GHI are found between ∼0.16% to ∼2.12% whilst for DNI values ranging from ∼7% to ∼12% are found. The respective correlations coefficients are around 0.95 for GHI and between 0.65 and 0.77 for DNI. Regional irradiation maps of GHI and DNI are presented, showing that NWP predictions are an important tool for the operation of electricity generation systems based on solar energy.

This paper presents the hourly mean solar radiation and standard deviation as inputs to simulate the solar radiation over a year. Monte Carlo simulation (MCS) technique is applied and MATLAB program is developed for reliability analysis of small isolated power system using solar photovoltaic (SPV). This paper is distributed in two parts. Firstly various solar radiation prediction methods along with hourly mean solar radiation (HMSR) method are compared. The comparison is carried on the basis of predicted electrical power generation with actual power generated by SPV system. Estimation of solar photovoltaic power using HMSR method is close to the actual power generated by SPV system. The deviation in monsoon months is due to the cloud cover. In later part of the paper various reliability indices are obtained by HMSR method using MCS technique. Load model used is IEEE-RTS. Reliability indices, additional load hours (ALH) and additional power (AP) reduces exponentially with increase in load indicates that a SPV source will offset maximum fuel when all of its generated energy is utilized. Fuel saving calculation is also investigated. Case studies are presented for Sagardeep Island in West Bengal state of India.

Abstract Shading devices, such as venetian blinds, are widely used to eliminate glare and maintain a comfortable working environment for occupants. This paper proposes an open-loop control of blind height and slat angle based on an analytic model of solar position, and geometry of venetian blinds and the windows. The algorithm enables completely blocking direct sunlight from entering the room beyond a certain user specified interior distance from the window while enhancing daylight utilization. We derive closed-form solutions for blind height and angle which are easily implemented in practice. Moreover, the proposed blind control algorithm is simulated with favorable performance. The algorithm has also been implemented and verified in real-time test-beds.