Instantaneous Solar Irradiance Research Articles

Model-Based Power Management for Smart Farming Wireless Sensor Networks

A model-based strategy for an efficient power supply control used in a wireless sensor network is presented. The strategy, based on Pulse-Skipping Modulation, regulates the current charging a battery, delivered by a photovoltaic source, resulting in an accurate current regulation and highly efficient power management. The strategy is implemented on a microcontroller unit and compensates for the microcontroller self-absorbed current. The modulation signal is generated through a full software interface, reducing the requirement for external components. Experimental validations, performed on a charger prototype by using a laboratory photovoltaic device simulator, proved that both regulation accuracy, regulation resolution and converter efficiency achieved are superior to the classic Pulse-Width Modulation. The approach results in a simple practical implementation, carries over the advantages of an up-to-date model for the photovoltaic device, and serves the auxiliary purpose of using the photovoltaic source as an instantaneous solar irradiance sensor.

Impact of instantaneous solar irradiance on refrigeration characteristics of household PCM storage air conditioning directly driven by distributed photovoltaic energy

AbstractMature and inexpensive ice thermal storage was employed to replace battery bank in energy storage, and photovoltaic directly driven technology was also combined in this paper. A 3HP household air conditioning assisted with ice thermal storage was investigated in four operating conditions. First, directly driven by photovoltaic arrays, the (COP)rs were almost 6.31% than that of refrigerator driven by power grid for the instantaneous solar irradiance, and the stored cooling capacity decreased 18.63% under the intermittent influence of solar irradiance. Moreover, the (COP)r of refrigerator operating in out‐of‐box mode was about 1.38 times that of operating in ice storage mode. Next, the inevitable compress motor fluctuation, caused by instantaneous solar irradiance, was investigated by experiment and simulation. In three typical weathers, compressor fluctuating time was approximately 65.22 s, 197.05 s, and 270.48 s in full irradiance range. When the lower solar irradiance limit was optimized from 150 to 80 Wm−2, refrigerator operated stably and continuously in any weather conditions. The ice production and the (COP)r were improved by 40.91% and 12.36%, respectively.

Evaluation of Using Photovoltaic Cell in the Electro-Fenton Oxidation for the Removal of Oil Content in Refinery Wastewater

In this study, the refinery wastewater treatment system by the photovoltaic electro-Fenton oxidation process was presented, which integrates the environmentally friendly photovoltaic and autonomous solar energy along with the capability of electro for oil content removing in the refinery wastewater. The direct connection between the photovoltaic panel and the electro-oxidation reactor can be accomplished without using batteries. This connection increases the sustainability of the system and eliminates the environment hazard resulted from the inappropriate disposal of the batteries. The photovoltaic electro-oxidation system is commonly made for multipurpose usage depending on the instantaneous solar irradiation by setting the volume of the wastewater to the supplied current intensity that provided by the photovoltaic array. The effect of several parameters that have critical impacts on the system efficiency of the presented process has studied by the Minitab-17 and the response surface methodology. Speed of agitation, solution electrolysis time, and the temperature have been presented and the optimal levels that corresponds to the optimal conditions were investigated and presented as well. Results of the experimental work showed that the working conditions of the agitation speed was 175 rpm, temperature was 70 oC and 15 min-reaction time, the concentration of oil in the treated refinery wastewater (RWW) was significantly decreased from 96.5 ppm (initial value) to specific values less than 2 ppm (the permissible limit), a removal percentage with an amount more that 98% and 20.4 kWh/m3 for the energy consumption were obtained. The suggested process is suitable for refinery wastewater remediation, especially for small amounts of oil content in RWW.

Estimation of Aerosol-Corrected Surface Solar Irradiance at Local Incidence Angle over Different Physiographic Subdivisions of India and Adjoining Areas Using MODIS and SRTM Data

AbstractSurface solar irradiance is considered as an important component of the surface radiation budget and constitutes one of the essential climate variables. In the present study, clear-sky instantaneous solar irradiance was estimated over 15 physiographic regions of India during January. Dewpoint temperature profiles were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Aqua satellite to calculate actual vapor pressure following Clausius–Clapeyron equation, which was further used in the Zillman parameterization for solar irradiance. The effect of terrain slope and aspect on direct radiation was taken into account by modifying the parameterized incoming shortwave flux by introducing the local incidence angle. A significant positive correlation was found between terrain-corrected MODIS irradiance and measured radiation data but the RMSE was very high (187 W m−2). Further, the effect of aerosol extinction was introduced by multiplying the terrain-corrected flux by a transmission factor obtained from satellite-derived aerosol optical depth and Ångström exponent. Due to the inclusion of the aerosol transmittance, the correlation was significantly improved (R2 = 0.84) and RMSE was reduced (31 W m−2). Further the effect of surface orientation on surface irradiance was evaluated on six hilly subdivisions. A large variation in the flux (135 to 161 W m−2) was noticed among different aspect classes. The variability was highest in the Eastern Himalayas subdivision (>250 W m−2) and was a minimum in the Eastern Hills subdivision (<28 W m−2). In absence of ground radiation data in hills, Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), was used for validation of model output but it performed poorly and got saturated at higher surface irradiance values.

Outdoor assessment of solar irradiance using camera: experimental proof of concept and application to MPP identification

In this paper, a novel image-based concept for estimating solar irradiance received on a photovoltaic (PV) array under normal conditions of irradiance is proposed. The approach is based on the variation of colors intensity in the images of the PV array with respect to solar irradiance. The images of the PV array, which are taken using fixed standard camera and undergo appropriate processing (filtering and intensity averaging), allow the approximation of the instantaneous solar irradiance. The effectiveness of the proposed approach is supported by series of outdoor experimental tests. The results demonstrate that the proposed approach has a good accuracy. As a direct application of the proposed concept, the instantaneous P-V curve of the PV array is approximated using analytical model of the PV array, measured temperature and the estimated irradiance. Once the P-V curve is available, the Maximum Power Point (MPP) can be easily located in real time and then the operating point of the system can be maintained at the MPP.

On the properties of aggregate clear-sky index distributions and an improved model for spatially correlated instantaneous solar irradiance

An important factor in grid integration of solar power is the so-called dispersion-smoothing effect, i.e., that differences in cloudiness over dispersed systems make the aggregate output less variable. This effect has been studied for irradiance step-changes on different time horizons, but not so much for instantaneous irradiance. In this paper, an improved probabilistic model is proposed for how instantaneous solar irradiance is correlated and aggregated over a network with arbitrary number of sites and dispersion. The model is fitted to irradiance data with a 1-s resolution from a network with 17 pyranometers in Hawai’i. A previously proposed three-state model of the instantaneous clear-sky index is partly confirmed by showing that clear and cloudy states can be separated and modeled by independent distribution models. It is also shown that the station-pair correlations for the instantaneous clear-sky index, as well as the shape of the distribution for the cloudy states, depend characteristically on the average degree of cloudiness, represented by the daily clear-sky index. For dispersed sites within the studied network, separated by distances up to 1km, and for daily clear-sky indices above approximately 0.5, the model performs better in reproducing the aggregate clear-sky index than non-spatial data. The proposed model could assist distribution system operators (DSOs) in grid planning and operation, as shown in a case study.

A copula method for simulating correlated instantaneous solar irradiance in spatial networks

This paper presents a method for generating correlated instantaneous solar irradiance data for an arbitrary set of spatially dispersed locations. Based on the empirical clear-sky index distribution for one location and the cross-correlation between clear-sky index data at all location pairs, a copula is used to represent the dependence between locations. The method is primarily intended for probabilistic simulations of electricity distribution grids with high penetrations of photovoltaic (PV) systems, in which solar irradiance data for nodes in the grid can be sampled from the model. The method is validated against a 10-s resolution solar irradiance data set for 14 locations, dispersed within an array of approximately 1km×1.2km, at the Island of Oahu, Hawai’i, USA. The results are compared with previous results for along- and cross-wind pairs of locations, and with models for adjacent (completely correlated) and dispersed (completely uncorrelated) locations. It is shown that the copula approach performs better than the adjacent model for a majority of all location pairs and for all but one pair of locations separated more than 500m. It outperforms the dispersed model for all pairs of locations. In conclusion, the proposed method can generate correlated data and estimate the aggregate clear-sky index for any set of locations based only on the distribution of the clear-sky index for a single location.

Probabilistic Load Flow for Power Grids With High PV Penetrations Using Copula-Based Modeling of Spatially Correlated Solar Irradiance

This paper presents and applies an improved model for the instantaneous power generation from distributed photovoltaic (PV) systems intended for probabilistic load flow (PLF) simulations. The model combines a probability distribution model for the instantaneous solar irradiance at individual sites with an improved spatial correlation model and uses a Gaussian copula to allow correlated sampling from the distributions for an arbitrary set of distributed PV systems. We show that the model realistically reproduces the spatially distributed clear-sky index over a set of sites, based on comparisons with irradiance sensor network data. We also demonstrate that the probability distributions for system parameters such as customer voltage, substation loading, and power losses, obtained from PLF simulations with the model, differ substantially from those of a nonspatial approach. The results show that spatial irradiance modeling needs to be incorporated in PLF simulations in order not to overestimate the grid impacts of PV systems.

Correlation modeling of instantaneous solar irradiance with applications to solar engineering

Estimating solar irradiance, in particular its variability, on Earth’s surface is paramount for solar engineering and for improving the utilization of solar energy. This paper presents a novel approach to statistical modeling of instantaneous solar irradiance by using a multivariate probability distribution—a copula—to describe the dependency between beam and diffuse indices. This approach significantly simplifies certain calculations for solar energy engineering, which is shown with simulated outputs for photovoltaic (PV) systems for different orientations. The PV power generation is expressed as probability distributions, which is directly applicable for power system operation and design. It is also shown that an Ångström-type equation, which is historically useful in relating time of bright sunshine to average solar radiation, is the statistical expectation of solar irradiance in this model.

Design of direct solar PV driven air conditioner

Solar air conditioning system directly driven by stand-alone solar PV is studied. The air conditioning system will suffer from loss of power if the solar PV power generation is not high enough. It requires a proper system design to match the power consumption of air conditioning system with a proper PV size. Six solar air conditioners with different sizes of PV panel and air conditioners were built and tested outdoors to experimentally investigate the running probabilities of air conditioning at various solar irradiations. It is shown that the instantaneous operation probability (OPB) and the runtime fraction (RF) of the air conditioner are mainly affected by the design parameter rpL (ratio of maximum PV power to load power). The measured OPB is found to be greater than 0.98 at instantaneous solar irradiation IT > 600 W m−2 if rpL > 1.71. RF approaches 1.0 (the air conditioner is run in 100% with solar power) at daily-total solar radiation higher than 13 MJ m−2 day−1, if rpL > 3.

Electrochemical Degradation of Indigo Carmine Textile Dye Powered by Solar Photovoltaic Energy

The proposed photovoltaic electro oxidation process combines the autonomous and environmentally friendly photovoltaic solar energy with the capability of electro oxidation at boron doped diamond electrodes to effectively decolorize and degrade indigo carmine textile dye from wastewater. The photovoltaic array can be connected directly to the electrochemical reactor without batteries increasing, in this way, the system sustainability and eliminating the environmental threat of improper battery disposal. The system is made versatile according to the instantaneous solar irradiation by adjusting the wastewater flow rate to the current intensity supplied by the photovoltaic panel. All operating parameters affecting the efficiency of the proposed process, such as wastewater conductivity, pH, flow rate, current density, electro processing time and solar irradiance were studied and optimal conditions were investigated. The experimental results showed that by applying current densities of 1, 2.5 and 5 mA cm2 the initial dye concentration of 100 mg L-1 in the treated wastewater was quantitatively eliminated in 45, 20 and 10 minutes of electro processing respectively. The process is appropriate for treatment of colored industrial textile dye house effluents and especially for applications in remote and isolated locations without connection to public electric grid.

A dynamic thermal performance model for flat-plate solar collectors based on the thermal inertia correction of the steady-state test method

In determining the dynamic thermal performance of a flat-plate solar collector, when the instantaneous solar irradiance changes sharply at one moment, most of the existing models cannot accurately predict the momentary thermal characteristics of outlet temperature and useful heat gain. In the present study, an analytical model in the form of series expansion is put forward to depict the momentary thermal characteristics of flat-plate solar collectors. The analytical model reveals that, instantaneous useful heat gain of a solar collector at one moment consists of the steady-state useful heat gain and corresponding thermal inertia correction. The model is then validated by the experimental data. It indicates that the analytical model can properly predict the dynamic thermal performance of the solar air collector. Besides, the model pertains to other types of solar thermal collectors, if they can be tested by the steady-state test method.

Electrochemical treatment of actual dye house effluents using electrocoagulation process directly powered by photovoltaic energy

In the present work, the decolorization treatment of colored wastewaters produced from polyamide textile dyeing is studied using the electrocoagulation process with sacrificial aluminum electrodes. The electrical energy is obtained from a solar photovoltaic array by directly connecting it to the electrocoagulator without batteries. The photovoltaic electrocoagulation (PV-EC) system is made versatile according to the instantaneous solar irradiation by adjusting the wastewater flow rate to the current intensity supplied by the photovoltaic array. All the PV-EC experiments were performed in Kavala Institute of Technology (latitude 40°55′, longitude 24°22′, and altitude 138 m above the sea level). The purpose of this paper is to investigate all parameters affecting the efficiency of the process, such as initial wastewater pH, conductivity, operating time, flow rate, and solar irradiation. The efficiency of the EC process was followed by measurements of turbidity and chemical oxygen demand (COD). According to the obtained experimental results, fast and effective decolorization of the treated wastewater occurred in a few minutes of electroprocessing. Turbidity was quantitatively reduced from 103 to 0.2 NTU, amounting to a removal percentage of over 99%, whereas COD was reduced by 65%. The proposed process is appropriate for decolorizing colored textile dye wastewaters and especially for small applications in remote and isolated locations without connection to public electric grid.

Photovoltaic electrocoagulation process for remediation of chromium plating wastewaters

The proposed photovoltaic electrocoagulation (PV-EC) process combines the autonomous and environmentally friendly photovoltaic (PV) solar energy with the capability of iron electrocoagulation (EC) to effectively reduce both trivalent and hexavalent chromium ions from electroplating effluents. The PV array can be connected directly to the EC reactor without batteries increasing, in this way, the system sustainability and eliminating the environmental threat of improper battery disposal. The PV-EC system is made versatile according to the instantaneous solar irradiation by adjusting the wastewater flow rate to the current intensity supplied by the PV array. The experiments were conducted in Kavala Institute of Technology (latitude 40° 55′, longitude 24° 22′, and altitude 138 m above the sea level). All operating parameters affecting the efficiency of the proposed process, such as wastewater conductivity, pH, flow rate, current density, electroprocessing time, and solar irradiance, were studied and optimal conditions were investigated. The experimental results showed that by applying a current density of 20 mA cm2, the chromium concentration in the treated electroplating wastewater was effectively reduced from its initial value of 96 mg L−1 to less than the permissible limit amounting to a removal percentage of over 99%. The corresponding electrical energy consumption was 8.4 kWh per m3 of treated wastewater. The proposed process is appropriate for removal of chromium from industrial effluents and especially for small applications in remote and isolated locations with lack of electric grid.

Assessment of a practical model to estimate the cell temperature of a photovoltaic module

Instantaneous solar irradiance profiles or solar irradiation data collected with small time intervals (e.g., minutes) are usually required for the energy simulation of photovoltaic systems, especially as concerns the estimation of the cell temperature. However, meteorological stations and technical standards often provide just monthly average values of the horizontal daily solar irradiation; extensive climate databases that make available up to date hourly observation data or satellite-derived data are seldom available. The goal of the present paper is to investigate the suitability and the accuracy of a methodology aimed at estimating the time profile of the cell temperature of a photovoltaic system on the basis of only the monthly mean values of the daily global irradiation on a horizontal surface. The methodology consists of a chain of well-established models that are applied one after another, in a step-by-step procedure, in order to derive the cell temperatures from the solar radiation data. In particular, we selected different models as possible candidates for each step of the methodology and compared their predictions with measured data to identify the most suitable ones. In addition, we tried several combinations of models in order to identify the most accurate combination. Comparisons with data measured in Rome confirm the suitability of the proposed approach and give information about its accuracy.

Assessment of a practical model to estimate the cell temperature of a photovoltaic module

Instantaneous solar irradiance profiles or solar irradiation data collected with small time intervals (e.g., minutes) are usually required for the energy simulation of photovoltaic systems, especially as concerns the estimation of the cell temperature. However, meteorological stations and technical standards often provide just monthly average values of the horizontal daily solar irradiation; extensive climate databases that make available up to date hourly observation data or satellite-derived data are seldom available. The goal of the present paper is to investigate the suitability and the accuracy of a methodology aimed at estimating the time profile of the cell temperature of a photovoltaic system on the basis of only the monthly mean values of the daily global irradiation on a horizontal surface. The methodology consists of a chain of well-established models that are applied one after another, in a step-by-step procedure, in order to derive the cell temperatures from the solar radiation data. In particular, we selected different models as possible candidates for each step of the methodology and compared their predictions with measured data to identify the most suitable ones. In addition, we tried several combinations of models in order to identify the most accurate combination. Comparisons with data measured in Rome confirm the suitability of the proposed approach and give information about its accuracy.

Distributed dynamic modeling and experimental study of PV evaporator in a PV/T solar-assisted heat pump

A novel photovoltaic/thermal solar-assisted heat pump (PV/T-SAHP) system is described in this paper. A specially designed direct-expansion evaporator (PV evaporator), which is laminated with PV cells on the front surface of the thermal absorber, has been adopted in our system to acquire simultaneously thermal energy and electricity from solar radiation. A dynamic model of the PV evaporator based on the distributed parameter approach is also presented. Given the instantaneous solar irradiance and ambient temperature, the numerical model is able to output the spatial distributions of refrigerant conditions, including pressure, temperature, vapor quality and enthalpy. A two-dimensional temperature distribution of the evaporator body is also computed. Comparisons between the simulation results and the experimental measurements show that the model is able to give satisfactory predictions. The results show that high electrical and thermal performance can be achieved. The PV efficiency and thermal efficiency are above 12% and 50% during the testing period.

Distributed dynamic modelling with experimental validation on a photovoltaic solar-assisted heat pump

The photovoltaic/thermal solar-assisted heat pump is a system that directly integrates a Rankine refrigeration device with a photovoltaic/thermal solar collector. A specially designed direct-expansion PV evaporator is employed in the system to acquire thermal energy and electricity from solar radiation simultaneously. In this paper, a distributed model is presented that describes the dynamic performance of the system. Numerical simulation was performed with instantaneous solar irradiance and ambient temperature based on the model. A testing rig was built in Hefei, China, and experiments were conducted to verify the model. The results show that high photovoltaic and thermal performance can be obtained by the system. The average electrical efficiency is around 13.02 per cent. The output electricity is about 85.5 per cent of the power consumption, which means that the system can offer most of the power consumed by itself. Neglecting the heat loss of the water box, the highest coefficient of performance (COPc) can reach up to 7.3 and the average value is around 3.41. Comparisons between the simulation results and the experimental measurements show that the model is able to give satisfactory predictions.

Electrocoagulation of a synthetic textile effluent powered by photovoltaic energy without batteries: Direct connection behaviour

The feasibility of the use of an electrocoagulation system (EC) directly powered by a photovoltaic (PV) array has been demonstrated. The model pollutant used was a reactive textile dye Remazol Red RB 133. It has been proved that PV array configuration is a factor of great influence on the use of the generated power. The optimum PV array configuration must be reshaped depending on the instantaneous solar irradiation. A useful and effective methodology to adjust the EC–PV system operation conditions depending on solar irradiation has been proposed. The current flow ratio, J v, is established as the control parameter.

An hourly solar radiation model under actual weather and terrain conditions: A case study in Heihe river basin

Abstract This paper describes an hourly incident solar radiation model, which could be used to estimate long-term global radiation, direct radiation and diffuse radiation with high spatial and temporal resolution under its de facto weather and terrain in large regions. The model is based on parameterized radiation transfer theory, and has referred to some data from the NCEP/NCAR (National Centers Environmental Prediction/National Center for Atmospheric Research) and some information about topography. The model was successfully used to calculate hourly instantaneous solar irradiance by a spatial resolution of 1 km×1 km in Alberts projection, in the Heihe river basin with a drainage area of 130,000 km2 in 2002. Now that only observed global radiation data at three automatic stations is available in Heihe river basin, global radiation at the three stations is used to validate the model. The three automatic stations are deployed in the mountain (Xishui), in the oasis (Linze), and in the desert area (Erjinaqi), respectively. The measured hourly instantaneous global radiation data do not comply with the calculated series at Xishui, with a determination coefficient R 2 = 0.71 . While at Linze and Erjinaqi stations, the determination coefficients are 0.90 and 0.91, respectively. The main reason why large errors are observed at Xishui station is that total cloud percent data from the NCEP/NCAR do not have a high spatial and temporal resolution. Also the spatial resolution of the observed data is not consistent with the calculated values. According to the model numerical test, topography is an important factor affecting model results on uneven land surfaces. Besides, in arid desert regions with even land surfaces, the 6 hourly model results agree with NCEP/NCAR global radiation data and measured data well.