Solar Irradiance Variations Research Articles

A comparative performance analysis of sensible thermal energy storage (with concentrated solar field and sCO2 Brayton Cycle) and hydrogen energy storage (with solar PV field)

Utility scale energy storage is an integral part of renewable energy installations to achieve sustainable and reliable transition to a net zero energy economy. There exists a myriad of such storage solutions each having unique characteristics. This paper attempts at a systems level quantitative study and comparison between two different energy storage technologies, Thermal Energy Storage System (TESS) which is already mature, and Hydrogen Energy Storage System (HESS) which gained a lot of momentum recently, with the former coupled with a concentrated parabolic trough solar field using molten salt as heat transfer fluid and a power block running on high efficiency sCO2 Brayton cycle while the latter is coupled with a solar photovoltaic (PV) field. So that comparisons can be made on similar scale, both the systems are normalized on the total equipment area used for capturing incident solar irradiation, i.e., total aperture area for the PTC field and total flat surface area of PV modules. Both the systems are subjected to year-long variations of ambient conditions and solar irradiance and off-design performances are simulated over various seasons. The results show superior performance of TESS in terms of roundtrip efficiency (96% as opposed to 32% with HESS) which also results in superior capacity utilization factor (CUF of 64.5% and 48% for TESS and HESS respectively) and better specific energy and energy density. However, HESS offers virtually infinite idling time where TESS has a shorter self-discharge time (17 h), and better power performance (specific power and power density) in 10MWe output range.

Method for Spatiotemporal Solar Power Profile Estimation for a Proposed U.S.–Caribbean–South America Super Grid under Hurricanes

Solar photovoltaic (PV) generation technology stands out as a scalable and cost-effective solution to enable the transition toward decarbonization. However, PV solar output, beyond the daily solar irradiance variability and unavailability during nights, is very sensitive to weather events like hurricanes. Hurricanes nucleate massive amounts of clouds around their centers, shading hundreds of kilometers in their path, reducing PV power output. This research proposes a spatiotemporal method, implemented in MATLAB R2023b coding, to estimate the shading effect of hurricanes over a wide distribution of PV solar plants connected to a high-voltage power infrastructure called the U.S.–Caribbean–South America super grid. The complete interconnection of the U.S., the Caribbean, and South America results in the lowest power valley levels, i.e., an overall percentual reduction in PV power output caused by hurricane shading. The simulations assess the impact of hurricanes in 10 synthetic trajectories spanning from Texas to Florida. The Caribbean would also experience lower power valleys with expanded interconnectivity schemes. The U.S.–Caribbean–South America super grid reduces Caribbean variability from 37.8% to 8.9% in the case study. The proposed spatiotemporal method for PV power profile estimation is a valuable tool for future solar power generation expansion, transmission planning, and system design considering the impact of hurricanes.

Lithium-ion battery: Battery sizing with charge scheduling for load levelling, ramp rate control and peak shaving using metaheuristic algorithms

Renewable energy sources (RES) are considered the most promising alternatives to fossil fuels, especially solar photovoltaic (PV). However, the variation in solar irradiance leads to power mismatching with load demand based on the required power distribution. Hybrid solar PV battery is a clean and reliable technology for compensating the load demand during peak hours. In this research, the solar PV is modelled by Nasik Wani substation datasets, and the lithium-ion battery is considered for power scheduling. The proposed work used the emperor penguin optimization (EPO) for battery scheduling to provide the required power to the load during increasing demand and to store the excess energy during lower demand. This proposed work schedules the battery by considering peak shaving and load levelling constraints. Optimum sizing of the battery is an important factor in achieving cost-effective units based on battery operation. In this regard, battle royale optimization (BRO) is used for optimum battery sizing to consider the capital cost, operating cost and maintenance cost. The proposed work is modelled through the MATLAB platform, and the results will be compared using existing Binary Particle Swarm Optimization (BPSO), Teach and Learn Based Optimization (TLBO) and Chimp Optimization Algorithm (COA) for battery scheduling; moreover, the PSO and simulated annealing (SA) approaches for optimum sizing. The capital cost of the proposed method is 821,400$, and the operational and maintenance cost is 11,625.5($/year). The comparative analysis shows that the proposed method outperforms existing approaches for proper scheduling and sizing the battery to meet the load demand.

Investigating the effect of employing a 24-hour radiative cooling system on the photovoltaic/thermal systems performance: A case-based research

This study aims to investigate the potential of a renewable hybrid system that integrates a nocturnal and diurnal radiative cooling system (RC) and photovoltaic/thermal system (PV/T) as a novel system to supply highly efficient electricity, while also providing a 24-hour radiative cooling system and diurnal preheated water supply. The proposed system comprises a photovoltaic system (PV) fitted with a transparent layer instead of glass, along with two cooling systems. The first cooling system involves water flow within aluminum pipes beneath the photovoltaic panel, while the second cooling system utilizes a silicon dioxide layer as RC. The study employs a novel approach by analyzing the impact of utilizing both nocturnal and diurnal RC on PV/T performance. The results are based on simulations conducted over four days during various months of the year, including January, March, July, and October. The findings of the simulations demonstrate that the utilization of the first cooling method increases the electrical efficiency of PV by 9.1%. Furthermore, the incorporation of RC along with the first method again leads to a 3.7% increase in electrical efficiency. Additionally, the thermal efficiency is estimated to be 37.1% and 20.62% for PV/T and RC-PV/T, respectively. The cooling power of RC during the night reached 287.13 W/m2 in July. A sensitivity analysis of the input parameters reveals that variations in solar radiation and inlet water temperature have the greatest impact on the system's electrical efficiency.

Sizing of Battery Energy Storage Systems for Firming PV Power including Aging Analysis

The variability of solar radiation presents significant challenges for the integration of solar photovoltaic (PV) energy into the electrical system. Incorporating battery storage technologies ensures energy reliability and promotes sustainable growth. In this work, an energy analysis is carried out to determine the installation size and the operating setpoint with optimal constant monthly power through an iterative calculation process, considering various operating setpoints and system parameters. A degradation model is integrated according to the curves offered by battery manufacturers and the charge–discharge cycles are calculated using the rainflow method to guarantee a reliable analysis of the plant. Through massive data analysis in a long-term simulation, indicators are generated that allow for establishing a relationship between the energy unavailability of the system and the BESS dimensions.

Comparative study of maximum power point tracking control for PV arrays system integration process

Given the stochastic nature of solar energy, integrating PV arrays with energy storage systems (ESSs) is crucial for a consistent power supply. Effective maximum power point tracking (MPPT) control is of great importance in this context. The significance lies not just in achieving high energy efficiency but also in ensuring overall system safety and reliability, as rapid and stable power tracking control alleviates power stress on ESSs. Challenging factors like parameter uncertainty from the PV array linearization process, dynamic DC bus variations induced by pulsed power loads, and sudden irradiance variation under cloudy weather, make the maximum output power of PV arrays largely dependent on the effectiveness of the control laws. Therefore, this paper presents a comparative study for MPPT control using PV-interfaced DC/DC converters. The aim is to demonstrate the advantages of employing average large-signal model-based sliding mode-type controllers in PV system integration with health-conscious objectives. A comprehensive system-level control-oriented modeling process is presented, followed by the theoretical background of three types of controllers (classical proportional–integral (PI)-type controller, μ-synthesis-based robust controller, and sliding mode controller) for practical applications. Extensive tests with real experimental data reveal sliding mode-type controllers’ superiority in various integration scenarios. For example, with random solar irradiance variation over 0.5 s, they achieve a 54.75% reduction in energy loss, outperforming the commonly used PI-type counterparts.

Assessing radiometric calibration methods for multispectral UAV imagery and the influence of illumination, flight altitude and flight time on reflectance, vegetation index and inversion of winter wheat AGB and LAI

Radiometric correction is essential to unmanned aerial vehicle (UAV) precision agriculture applications, especially for crop multi-period analysis and quantitative inversion of phenotypic and physiological parameters. In this study, we investigated the performance of four radiometric correction methods: “Camera only” (A), “Camera and sun irradiance” (B) and “Camera, sun irradiance and sun angle” (C) methods provided by Pix4d Mapper and an irradiance sensor-based method (D) implemented with the R software. UAV campaigns were conducted at flight altitudes of 30 m, 60 m and 90 m under clear and cloudy skies at different times over an experimental field of winter wheat. The influences of illumination, flight altitude and flight time on reflectance and vegetation indexes derived from different radiometric calibration methods were analyzed. Moreover, we further assessed the impact of reflectance and vegetation index variations on the above-ground biomass (AGB) and leaf area index (LAI) estimations of winter wheat. Results showed that method D is a promising approach for radiometric calibration, which produced consistent reflectance with method A at noon (e.g., 10:44:41 AM March 17 and 11:39:37 AM April 7) and mid-afternoon (e.g., 15:30:02 PM May 1) and more reliable reflectance in the morning (e.g., 7:15:44 AM March 17). Methods B and C seriously underestimated the reflectance at 10:44:41 AM March 17 and 11:39:37 AM April 7. This was caused by the incorrect attitude angles of the irradiance sensor and further miscalculation of the solar irradiance by Pix4d Mapper. Interestingly, these errors were eliminated in the calculation of the ratio type of vegetation indexes. Methods B and C yielded vegetation indexes that were almost the same as those of methods A and D. Under cloudy sky, when direct sunlight is not blocked by clouds, method D was effective; with cloud occlusion, results on April 24 indicated that the method failed to estimate the total sunlight and direct sunlight ratio. Reflectance and vegetation indexes obtained from different radiometric correction methods were all obviously affected by flight altitude. Furthermore, the variations of NDVI with flight altitude increasing were different with reflectance. Changes in reflectance and vegetation indexes with flight altitude had little effect on the correlation coefficients yielded with AGB, but showed a significant influence on those of LAI. Through analyzing the variation of observed solar radiation at different time intervals, caution is recommended when using the assumption that solar radiation is stable during the UAV flight. The longer the flight, the greater the variation in solar radiation, especially at sunrise and sunset. Even at noon, when the flight duration is 30 min, the change in solar radiation may exceed 10 % (e.g., 16.5 % on March 20).

Correlations between Total and Spectral Solar Irradiance Variations

We compare short-term (seven solar rotations), wavelength-dependent temporal variations in spectral solar irradiance (SSI) with those from the total solar irradiance (TSI). Using space-based measurements, we empirically find good correlations across most of the visible and near-infrared (NIR) spectral range, suggesting that the TSI time variability can provide a useful estimate of SSI variability. These empirically determined correlations are consistent with physics-based bolometric variations, providing a straightforward wavelength-dependent parameterization of the SSI variability given a known change in the TSI. Using a solar-irradiance model to distinguish the facular and sunspot contributions, which are responsible for nearly all the irradiance variability on timescales longer than a day, we confirm these results and determine the correlation contributions due to each magnetic activity type individually. The correlations determined from the model agree in functional form to those of the empirical data, although we do note differences near opacity minimum (1.6 μm). Our results provide a simple TSI-based estimate of the time dependence of the spectral solar variability across the ultraviolet to NIR spectral regions, with the TSI accounting for 94% of the variability in the SSI over the 400–1200 nm range.

Voltage stability of a photovoltaic DC microgrid using fuzzy logic controller

This article employs a fuzzy logic controller (FLC) to investigate voltage stability in a PV-based DC microgrid. Several photovoltaic (PV) modules, a DC-DC converter, and loads make up the microgrid. Due to the widespread use of intermittent PV power, voltage stability is a crucial problem for DC microgrids and is difficult to accomplish. This study proposes an FLC-based voltage control technique that leverages input factors including PV output power, DC-DC converter duty cycle, and load current to identify the best course of action for preserving the system's voltage stability. The FLC's performance is assessed by simulation, and it is meant to be resilient to parameter fluctuations and uncertainties. The simulation results demonstrate that the suggested FLC-based control strategy successfully maintains the microgrid's voltage stability under a variety of operational circumstances, including changing solar irradiance and load variations. Moreover, the FLC performs better than other control methods.

Global Solar Radiation and Its Interactions with Atmospheric Substances and Their Effects on Air Temperature Change in Ankara Province

On the analysis of solar radiation and meteorological variables measured in Ankara province in Türkiye from 2017 to 2018, an empirical model of global solar radiation was developed. The global solar radiation at the ground and at the top of the atmosphere (TOA) was calculated and in good agreement with the observations. This model was applied to compute the losses of global solar radiation in the atmosphere and the contributions by atmospheric absorbing and scattering substances. The loss of global solar radiation in the atmosphere was dominated by the absorbing substances. The sensitivity test showed that global solar radiation was more sensitive to changes in scattering (described by a scattering factor S/G, S and G are diffuse and global solar radiation, respectively) than to changes in absorption. This empirical model was applied to calculate the albedos at the TOA and the surface. In 2017, 2018, and 2019, the computed albedos were 28.8%, 27.8%, and 28.2% at the TOA and 21.6%, 22.1%, and 21.9% at the surface, which were in reasonable agreement with satellite retrievals. The empirical model is a useful tool for studying global solar radiation and the multiple interactions between solar energy and atmospheric substances. The comparisons of global solar radiation and its loss in the atmosphere, as well as meteorological parameters, were made at some representative sites on the Earth. Some internal relationships (between G and the absorbing and scattering substances, air temperature and atmospheric substances, air temperature increase and latitude, etc.) were found. Thus, it is suggested to thoroughly study solar radiation, atmospheric substances, and climate change as a whole system and reduce the direct emissions of all atmospheric substances and, subsequently, secondary products (e.g., CO2 and non-CO2) in the atmosphere for the achievement of slowing down climate warming.

Towards clean energy: Design and integration strategy of photovoltaics for residential electrification

Rapid global population growth and rising energy demands are causing environmental damage, particularly in developing countries dealing with climate change, pollution, and fuel shortages. Adopting cleaner, more sustainable energy sources could be one solution to this problem. In the context of hybrid energy systems, one proposition is to incorporate renewables into residential developments. This manuscript proposes a grid-connected hybrid (GCH) photovoltaic (PV) system for residential electrification in Dhaka, Bangladesh, and evaluates the technical feasibility. The proposed design includes four scenarios for PV and battery energy storage systems (BESS). The primary goals of the assessment include lowering net present cost (NPC), cost of energy (COE), and unmet load, as well as reducing grid dependence, lowering greenhouse gas (GHG) emissions, and providing grid support. Solar irradiation fluctuations, demand variations, and voltage sag are all factors to consider when evaluating technical feasibility. The four cases were simulated using hybrid optimization with HOMER Pro, to achieve a system that maximizes renewable energy utilization. The analysis concludes that the GCH PV system is best suited for residential power needs, with lower COE, NPC, and grid dependency. The system achieves a COE of $0.0643/kWh, lowers GHG emissions, and attains a renewable fraction of 40%. Technical feasibility is verified using MATLAB-Simulink simulations at the point of common coupling (PCC), which include solar irradiation variations, active and reactive power adjustments based on demand, and voltage sag analysis for grid integration. The proposed system is cost-effective, convenient, and sustainable, with few salvageable components.

Active power compensator for a DC voltage bus of a renewable source

Renewable energy sources generate intermittent electrical power due to weather conditions, such as variations in wind speed and solar radiation. The distributed nature of renewable energy sources requires new techniques to maintain the quality of electrical service and efficient use of energy. One of these techniques uses of battery bank when a renewable energy source does not generate the power level contracted by the utility grid. In this article, a power compensator is proposed. It consists of a bidirectional DC converter located between the battery bank and the DC bus of the renewable source. This compensator has two operation modes: one to store the excessive power in a battery bank; the other to deliver power when power intermittency occurs. The validation of the proposed power compensator is made using a prototype where the DC voltage bus of a renewable energy source is emulated through a DC generator-motor group, which allows bidirectional power flow.

Assessment of the Impact of PM2.5 Air Pollution on River Dynamics: A Case Study of Daqing, China.

This study aims to explore the causal relationship between air pollution and river flow in Daqing City, specifically focusing on PM2.5 particle concentration. During comprehensive five-year research, a progressive decrease in air quality was seen, shown by a rise in the yearly average PM2.5 concentration from 13.4 µg/m³ to 18.7 µg/m³. This work utilizes hydrological modeling to reveal a strong negative association between the rise in PM2.5 concentration and the decline in river flow. The decline observed can be attributed to variations in solar radiation and surface temperature, which are clearly impacted by pollution. Ecological investigations showed that the decrease in river flow led to severe ecological impacts, including higher water temperature and alterations in nitrogen levels. This study emphasizes the crucial need to implement thorough environmental management strategies to successfully reduce the detrimental effects of air pollution on river ecosystems. This study enhances our comprehension of the intricate connection between air pollution and river dynamics, on both a regional scale and within the wider context of the southern hemisphere. It highlights the worldwide significance of safeguarding clean air and water resources.

CFD Analysis for a New Trombe Wall Concept

The envelope (façade) of a building is the first barrier between the exterior and the interior of the building and withstands the highest variation in temperature and solar radiation. Trombe walls are used to take advantage of that and contribute to the heating of interior air, helping the heating system. In this study, a new Trombe wall design is presented to contribute significantly to the indoor ventilation of residential buildings. For this, an exterior wall equipped with a proposed Trombe system was studied in a numerical simulation analysis. The proposed systems consist of two important sections, an exterior one and an interior one. The air cavities on the exterior of the wall, covered with silica glass, are the first heat-transfer layer. The secondary layer used for heat transfer, on the interior, is comprised of a MPCLB wall of 115 mm. The air circulation from the exterior to the interior was established as forced convection with a ventilator. The air circulates through the first heating layer on the exterior air cavities and then passes through the second heating layer on the interior MPCLBs. Two cities in Romania were considered to represent the coldest and hottest climates in Romania. Brașov represents the cold climate and Constanța represents the hot climate. In the investigation, both the presence and absence of solar radiation were taken into account. In total, four cases were established. For all four cases, monthly research was made using monthly mean temperatures, and direct and diffuse solar radiation. The results are promising and illustrate that the system works best during the transitional seasons of spring and autumn. The lower the outdoor temperature, the higher the temperature can be increased. Overall, solar radiation accounted for an average 2 °C increase. The temperature increase varied between 3.4 °C and 15.99 °C for Brașov and between 6.42 °C and 12.07 °C in Constanța. This study presents an alternative way to use the Trombe wall for indoor ventilation purposes throughout the year, compared to traditional uses for the Trombe wall for indoor heating.

Efficiency Comparison of Floating, Ground, and Rooftop Solar Systems: Environmental and Social Impacts of Floating Solar Grids

The global fossil fuel shortage and environmental concerns underscore the imperative for transitioning to renewables. Developing nations like Sri Lanka are prioritizing green technologies, notably solar energy, to bridge the gap between current usage and its substantial potential. This study compares technical efficiency among floating, ground, and rooftop solar in Sri Lanka. Analyse local perceptions of floating solar. Assess the environmental impact and sustainability of floating solar systems in Sri Lanka. This study compares the energy production efficiency of floating solar, ground solar, and rooftop solar systems in Sri Lanka. This study compares the technical efficiency of floating, ground-mounted, and rooftop solar systems. Kilinochchi, chosen for floating solar, a nearby ground solar site facilitates a direct comparison, and Mass Vidiyal in Kilinochchi represents rooftop solar. The study strategically gathers data from inverters to assess performance metrics. The goal is a representative analysis, minimizing solar irradiance variations for accurate comparisons. Conducting a literature review to analyse the environmental impact of floating solar systems, drawing insights from past published research papers, and A socio-economic survey was conducted among the local community to assess the socioeconomic viability of a proposed floating solar plant near Chandrika Lake. The survey considered factors such as job creation, local employment opportunities, skill development, and alignment with national energy policies. Floating solar systems were found to have the highest energy generation capability and efficiency, followed by rooftop solar systems, while ground-mounted solar systems had lower energy output. The advantages of floating solar systems over ground-mounted systems were significant (43.69% advantage) and outperformed rooftop solar systems (30.81% advantage). According to the survey, stakeholder engagement and mitigation measures were identified as crucial, considering concerns related to water quality, safety, fisheries, agriculture, and the aesthetic value of the lake This study highlights technical efficiency, socioeconomic viability, and environmental impact of solar systems in Sri Lanka, emphasizing responsible deployment. While floating solar exhibits energy efficiency, addressing altered water flow and aquatic habitat concerns through mitigation measures is crucial for sustainable implementation.
 
 Keywords: Solar energy, Floating solar, Environmental impact, Social impact, Renewable energy

BrGDGT-based seasonal paleotemperature reconstruction for the last 15 000 years from a shallow lake on the eastern Tibetan Plateau

Abstract. Understanding Holocene temperature changes is vital for resolving discrepancies between proxy reconstructions and climate models. The intricate temperature variations across the Tibetan Plateau (TP) add complexity to studying continental climate change during this period. Discrepancies between model-based and proxy-based reconstructions might stem from seasonal biases and environmental uncertainties in the proxies. Employing multiple proxies from a single sediment core for quantitative temperature reconstructions offers an effective method for cross-validation in terrestrial environments. Here, we present an ice-free-season temperature record for the past 15 kyr from a shallow, freshwater lake on the eastern TP, based on brGDGTs (branched glycerol dialkyl glycerol tetraethers). This record shows that the Holocene Thermal Maximum lags the pollen-based July temperature recorded in the same sediment core. We conclude that the mismatch between the brGDGT-based and pollen-based temperatures is primarily the result of seasonal variations in solar irradiance. The overall pattern of temperature changes is supported by other summer temperature records, and the Younger Dryas cold event and the Bølling–Allerød warm period are also detected. A generally warm period occurred during 8–3.5 ka, followed by a cooling trend in the late Holocene. Our findings have implications for understanding the seasonal signal of brGDGTs in shallow lakes and provide critical data for confirming the occurrence of seasonal biases in different proxies from high-elevation lakes. To further investigate the significance of the brGDGTs and temperature patterns on the TP, we examined existing brGDGT-based Holocene temperature records, which interpret these compounds as indicators of mean annual or growing season temperatures. The existing and available temperature records show complicated patterns of variation, some with general warming trends throughout the Holocene, some with cooling trends, and some with a warm middle Holocene. We analyzed the possible reasons for the diverse brGDGTs records on the TP and emphasize the importance of considering lake conditions and modern investigations of brGDGTs in lacustrine systems when using brGDGTs to reconstruct paleoenvironmental conditions.

Influence of Terrestrial Parameters on the Ecophysiological Composition of Young Plants Kahya Senegalensis in Saline Environment

This study aims at analyzing the behavior of young African mahogany plants in a saline environment, focusing on perceptions related to transpiration, photosynthetically active radiation and water potential. The experiment was conducted in drainage lysimeters, using different salinity levels of irrigation water. Environmental data, such as photosynthetically active radiation, water potential and electrical conductivity, were collected to investigate their influence on the transpiration of African mahogany plants. The research was carried out in an experimental field in the northeast region of Brazil, over a period of four months, with young African mahogany plants (Khaya senegalensis), using water with an electrical conductivity of 0.5 dS.m -1 (control treatment); 1.25 dS.m -1; 2 dS.m -1; 2.75 dS.m -1; 3.5 dS.m -1; 4.25 dS.m -1 and 5 dS.m -1 in a total of seven treatments, with three replications and 21 experimental units (plants). Plant transpiration was measured using a steady-state diffusion porometer. The electrical conductivity of the irrigation water was monitored using a portable conductivity meter. The results presented in the analyzes indicate a complex and interdependent relationship between leaf transpiration, photosynthetically active radiation and plant water potential. Leaf transpiration is influenced by variations in solar radiation, which plays a crucial role in regulating this process. It was observed that leaf transpiration is lower in the morning, from 7 to 9 am and in the late afternoon, from 5 to 6 pm, when incident solar radiation is at lower values.

Sand and Dust Storms Impact on Photovoltaic Panels in Saudi Arabia

This research aims to assess the spatial potential of solar energy in Saudi Arabia by estimating the total sum and analyzing the spatial variability of solar radiation to determine the best sites for solar energy generation that are least affected by sandstorms in the country. It also explores the effects of sandstorms on solar panels, identifies preventive measures, analyzes their impact on productivity, and recommends best practices for future development. The study utilizes time series analysis to estimate the impact of dust on productivity and identify effective ways to mitigate it. The spatial suitability of solar cell placement in different regions of the country is also analyzed. The study reveals that the Al-Ahsa region is significantly affected by sandstorms, with an average of around 25 sandstorms annually, indicating the region's vulnerability to these environmental phenomena. The western region, specifically the Tabuk station, experiences a lower frequency of about 5.5 sandstorms per year. The Al-Ahsa region shows the highest daily average rate of sandstorms, ranging from 0.4 to 0.7 sandstorms per day, with the highest rates occurring from March to May. In terms of solar energy potential, the northwestern region in Tabuk exhibits the highest average potential of about 6 watts per square meter per day, followed by the southwestern region in Asir with approximately 5.5 watts per square meter per day. These findings provide valuable insights into understanding sandstorm patterns and identifying optimal locations for solar energy production, contributing to sustainable development efforts and climate change mitigation.

Control of three‐level bidirectional buck‐boost converter for battery energy storage system in bi‐polar DC microgrid

AbstractThis paper deals with the model predictive current control of a three‐level bidirectional buck‐boost converter for a battery energy storage system in a bi‐polar direct current (DC) microgrid. It comprises a solar photovoltaic system, a wind energy system, a battery and DC loads. The proposed control scheme provides voltage balance and voltage regulation at the bi‐polar DC link during dynamic operating conditions, such as variations in solar irradiance, wind velocity and load. Predictive current control utilises the converter's discrete behaviour to identify the suitable switching states that minimise the cost function. Furthermore, bidirectional power flow capabilities allow the connection of energy storage devices, such as batteries and ultra‐capacitors, to the bi‐polar DC microgrid. The proposed system is verified through simulations and validated on a lab‐scale prototype. The results have been found satisfactory with respect to steady‐state error, peak overshoot, and settling time.

A Discussion of Implausible Total Solar-Irradiance Variations Since 1700

The Sun plays a role in influencing Earth’s climate, making it important to have accurate information about variations in the Sun’s radiative output. Models are used to recover total solar-irradiance (TSI) variations in the past when direct space-based measurements are not available. One of the most cryptic such TSI reconstructions is the one by Hoyt and Schatten (J. Geophys. Res. 98, 18, 1993, HS93). The rather vague description of the model methodology, the arbitrary selection of solar indices it employs, and the short overlap between the HS93 series and directly measured TSI values has hindered any evaluation of the performance of this model to this day. Here, we aim at rectifying this by updating the HS93 model with new input data. In this way we are also contributing in the discussion on the possible long-term changes in solar irradiance.We find that the analysis by HS93 included a number of erroneous processing steps that led to an artificial increasing trend towards the end of the reconstructed TSI series as well as shifting the peak of the TSI in the mid-twentieth century back in time by about 11 years. Furthermore, by using direct measurements of the TSI we determined that the free parameter of the model, the magnitude of variations (here defined as percentage variations of the difference between the maximum to minimum values), is optimal when it is minimised (being ≤0.05%). This is in stark contrast to the high magnitude of variations, of 0.25%, that was imposed by HS93. However, our result is consistent with more recent estimates, such as those from the Spectral And Total Irradiance REconstruction (SATIRE) model and Naval Research Laboratory TSI (NRLTSI), which were used by the Intergovernmental Panel on Climate Change (IPCC). Overall, we find that the previously reported agreement of the HS93 TSI series to temperature on Earth was purely due to improper analysis and artefacts of the processing.