Insolation Fluctuations Research Articles

Climate and Human Evolution: Insights from Marine Records.

The relationship between climate and human evolution is complex, and the causal mechanisms remain unknown. Here, we review and synthesize what is currently known about climate forcings on African landscapes, focusing mainly on the last 4 million years. We use information derived from marine sediment archives and data-numerical climate model comparisons and integration. There exists a heterogeneity in pan-African hydroclimate changes, forced by a combination of orbitally paced, low-latitude fluctuations in insolation; polar ice volume changes; tropical sea surface temperature gradients; the Walker circulation; and possibly greenhouse gases. Pan-African vegetation changes do not follow the same pattern, which is suggestive of additional influences, such as CO2 and temperature. We caution against reliance on temporal correlations between global or regional climate, environmental changes, and human evolution and briefly proffer some ideas on how pan-African climate trends could help create novel conceptual frameworks to determine the causal mechanisms of associations between climate/habitat change and hominin evolution.

A Particle Swarm Optimization–Adaptive Weighted Delay Velocity-Based Fast-Converging Maximum Power Point Tracking Algorithm for Solar PV Generation System

Photovoltaic (PV) arrays have a considerably lower output when exposed to partial shadowing (PS). Whilst adding bypass diodes to the output reduces PS’s impact, this adjustment causes many output power peaks. Because of their tendency to converge to local maxima, traditional algorithms like perturb and observe and hill-climbing should not be used to track the optimal peak. The tracking of the optimal peak is achieved by employing a range of artificial intelligence methodologies, such as utilizing an artificial neural network and implementing control based on fuzzy logic principles. These algorithms perform satisfactorily under PS conditions but their training method necessitates a sizable quantity of data which result in placing an unnecessary demand on CPU memory. In order to achieve maximum power point tracking (MPPT) with fast convergence, minimal power fluctuations, and excellent stability, this paper introduces a novel optimization algorithm named PSO-AWDV (particle swarm optimization–adaptive weighted delay velocity). This algorithm employs a stochastic search approach, which involves the random exploration of the search space, to accomplish these goals. The efficacy of the proposed algorithm is demonstrated by conducting experiments on a series-connected configuration of four modules, under different levels of solar radiation. The algorithm successfully gets rid of the problems brought on by current traditional and AI-based methods. The PSO-AWDV algorithm stands out for its simplicity and reduced computational complexity when compared to traditional PSO and its variant PSO-VC, while excelling in locating the maximum power point (MPP) even in intricate shading scenarios, encompassing partial shading conditions and notable insolation fluctuations. Furthermore, its tracking efficiency surpasses that of both conventional PSO and PSO-VC. To further validate our results, we conducted a real-time hardware-in-the-loop (HIL) emulation, which confirmed the superiority of the PSO-AWDV algorithm over traditional and AI-based methods. Overall, the proposed algorithm offers a practical solution to the challenges of MPPT under PS conditions, with promising outcomes for real-world PV applications.

Filtered X least mean fourth‐driven intelligent control for power quality augmentation and dynamic stability reinforcement of grid intertie wind–photovoltaic systems

SummaryAn advanced topology comprising a wind‐turbine driven synchronous generator (SG) and solar photovoltaic (PV) array to address the power quality (PQ) concerns and the uncertainty in renewable energy generation is proposed in this paper. The fluctuations in wind speed and insolation are soaked up by utilizing successively interfaced power electronic converters (PECs), namely, SG side converter (SGC) and utility grid side converter (UGC) integrated with a DC link capacitor and a PV array. SGC is controlled by estimating the rotor position from the stator voltage and current measurement data and maintains unity power factor (UPF) at stator terminals. UGC is controlled by employing filtered X least mean fourth (FXLMF) control, which ensures superior convergence performance and reduced computational complexity. Besides, it performs operations like reactive power compensation, enhancement of PQ, load and power balancing during steady‐state and dynamic conditions. The notion of optimal fuzzy reasoning is instilled which generates a fuzzy scheme with inherent optimal‐tuning characteristics to bring about considerable improvement in system performance. A water cycle algorithm (WCA) tuned fuzzy logic controller (FLC) is employed for dynamic stability enhancement leading to the generation of accurate loss component, , which bolsters the ability of VSC to accurately extricate weight signals and the fundamental load current component. This improves regulation of DC link voltage during dynamic load, insolation and wind conditions. The veracity of the proposed model is verified under wind gusts and the bell‐shaped irradiance curve. Extensive simulation results obtained in MATLAB corroborate the efficacy of the system.

Automatic adaptation of a Solar Plant Intelligent Control System

The article continues the authors’ scientific research in the field of solar plant intelligent control system. This paper presents a developed on-line and off-line automatic adaptation methods which allow solar plant intelligent control system to adapt to rapid dynamic of insolation in real time and to seasonal insolation fluctuations during night time. The experimental results show that the proposed solar plant intelligent self-adaptive control system produced robust and rapid maximum power point tracking, as compared to a classical solar plant MPPT system based on Perturb & Observe or particle swarm optimization under seasonal fluctuations or rapid dynamic of insolation.

Fluctuations in Insolation during 1962 - 2019 for Municipalities in Pernambuco, Brazil

This study evaluates the insolation calculations and their analysis soon after plotting their respective local historical average graph from 1962 to 2019 for some municipalities in Pernambucana. Monthly and annual insolation data for the study period was obtained from the National Institute of Meteorology.After homogenization, data consistency and failure filling of each series, the spatial and temporal insolation densities were performed for municipalities like Arcoverde, Cabrobó, Garanhuns, Ouricuri, Petrolina, Recife, Surubim and Triunfo. The average and its historical average were calculated and appropriate analysis was performed. The spatial distribution of the monthly insolation data showed great variability for the months studied, ranging from approximately 3 to 4 hours. The median values ​​ most likely occured during the months for the eight municipalities under study. The municipality of Garanhuns presented higher insolation values ​​than Petrolina. Comparing the values ​​obtained in this study with the values ​​of the Solarimetric Atlas of Brazil, indicated a good similarity of the recorded data.

Development of PSO for tracking Maximum Power Point of Photovoltaic Systems

For a photovoltaic system, the relationship of the output voltage and power is usually non-linear, so it is essential to equip a MPPT controller in PV systems. Furthermore, the hotspot problem is a common phenomenon, resulting from the PV system operating under PSC. Partial shading not only damages the PV cells, but also makes it difficult to find the global MPP in the characteristic curves of P-V. The paper proposes a novel version of PSO, namely PPSO in order to detect the global peak among the multiple peaks, known as the true maximum energy from PV panel. For this, the PPSO algorithm makes the velocity of each particle be perturbed once the particles are struck into a local minima state in order to find the best optimum solution in the MPPT problem. The perturbation in the velocity vector of each particle not only helps them tracking the MPP accurately under the changing environmental conditions, such as large fluctuations of insolation and temperature like PSC; but also removes the steady-state oscillation. The proposed approach has been tested on a MPPT system, which controls a dc-dc boost converter connected in series with a resistive load. Moreover, the obtained results are compared to those obtained without any MPPT controller to prove the efficiency of the suggested method. In addition, this novel version gives the highest accuracy of tracking the optimum power in the least iteration number as compared to the conventional PSO.

I.I. Smul’skii. New astronomical theory of the ice ages

Riga: Lap Lambert Academic Publishing, 2018. 132 Р.
 In this book, a new approach to the astronomical theory of climate change is considered, and problems of the orbital and rotational motion of the Earth are solved using the numerical method. The author of the monograph investigated the evolution of the earth’s axis and obtained the periods of its oscillations coinciding with observed oscillations. Calculations that covered 100,000 years showed a significant oscillation of the earth’s axis, which has led to fluctuations in insolation that can explain the changes in the paleoclimate.

Fluvio‐lacustrine sedimentation in the Agadir‐Tissint Feija (Anti‐Atlas, Morocco): A promising palaeoclimate archive for the last glacial cycle in northwest Africa

AbstractMountainous depocentres are often the single available archives in intracontinental areas. As such, the investigation of their sedimentary dynamics is the only way to reconstruct palaeoenvironmental evolution in these peculiar regions. Here, the basin‐scale sedimentary dynamics of the Agadir‐Tissint Feija (i.e. feija is the local name for lowlands) are discussed together with new palaeoenvironmental information on the late Quaternary in the north‐western Sahara margin. The succession consists of up to ca 40 m thick fluvio‐lacustrine deposits subdivided into three depositional sequences (S1–S3) that were deposited between ca 75 ka and ca 10 ka. S1 and S2 reflect the evolution of a palaeolake intercalated by carbonate‐rich palustrine to alluvial plain environments, while S3 shows the transition to an entirely clastic alluvial plain environment. The three sequences are genetically associated with three pulses of tufa buildups at the outlet of the depocentre. Each pulse of tufa buildup is attributed to wet conditions, while each interruption is associated with drier conditions. The wet–dry alternation at the origin of S1 fits with summer insolation fluctuation suggesting that precession parameters may have paced long‐term climate variability in the area. Superimposed on wet–dry cycles, submillennial‐scale (750–900 year) shorter‐term lake fluctuations are identified in S1 and S2; their origins may be related to North Atlantic Oscillation mechanisms. Furthermore, the sudden increase in clastic sediment supply in S3 evidences a change in sediment production in the catchment area attributed to lower temperatures established during the last glacial period. Finally, this newly identified continental archive is unique at the northern Sahara margin; it enables reconstructions of the local and regional hydrological conditions during the last glacial cycle. Even if a more systematic investigation of palaeoclimate forcing is still necessary, the Agadir‐Tissint Feija will potentially bring important information to understand past and anticipate future regional climate change.

Overview of the existing heat storage technologies: sensible heat

Over the past several decades, much attention has been given to the development of technologies utilizing solar energy to generate inexpensive and clean heat for heating purposes of buildings and even for electricity generation in the concentrating solar thermal power (CSTP) plants. However, unlike conventional heatgenerating technologies consuming coal, natural gas, and oil, heat produced by solar energy is intermittent because it is significantly affected by daily (day-night) and seasonal fluctuations in solar insolation. This fact issues a considerable challenge to the adoption of solar energy as one of the main renewable heat sources in the future. Therefore, along with the development of the different solar technologies, the heat storage technologies have also been the focus of attention. Use of the storage devices, able to accumulate heat, enables not only enhance the performance of the heating systems based on solar energy but also make them more reliable. This paper gives an overview of the various sensible heat storage technologies used in tandem with the fluctuating solar heat sources.

Application and Comparison Between the Conventional Methods and PSO Method for Maximum Power Point Extraction in Photovoltaic Systems Under Partial Shading Conditions

Several algorithms have been offered to track the Maximum Power Point when we have one maximum power point. Moreover, fuzzy control and neural was utilized to track the Maximum Power Point when we have multi-peaks power points. In this paper, we will propose an improved Maximum Power Point tracking method for the photovoltaic system utilizing a modified PSO algorithm. The main advantage of the method is the decreasing of the steady state oscillation (to practically zero) once the Maximum Power Point is located. moreover, the proposed method has the ability to track the Maximum Power Point for the extreme environmental condition that cause the presence of maximum multi-power points, for example, partial shading condition and large fluctuations of insolation. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under very challenging circumstance, namely step changes in irradiance, step changes in load, and partial shading of the Photovoltaic array. Finally, its performance is compared with the perturbation and observation” and fuzzy logic results for the single peak, and the neural-fuzzy control results for the multi-peaks.

An 800‐year ultraviolet radiation record inferred from sedimentary pigments in the Ross Sea area, East Antarctica

High performance liquid chromatography (HPLC) combined with mass spectrometry (MS) was used to analyse deposited pigments (including chlorophyll a, phaeophytin a, canthaxanthin, echinenone, zeaxanthin, scytonemin and mycosporine‐like amino acids) from two sediment profiles of ponds in the Ross Sea area, East Antarctica. We explored the sources and characteristics of each pigment, reconstructed an 800‐year record of ultraviolet radiation (UVR) and total incoming light intensity, and identified the possible factors that may have influenced historical UVR changes in this region. The results indicated at least four UVR peaks during the past 800 years, corresponding to c. AD 1950–2000, 1720–1790, 1560–1630 and 1350–1480, with the intensity from the most recent sediments being the highest. A comparison between the changes in UVR and total incoming light intensity showed similar patterns between AD 1720 and 1830, suggesting that factors controlling the UVR intensity in the Ross Sea area may be related to insolation fluctuation at that time. The two proxies are, however, weakly correlated during other periods. Historically, there is a relationship between the reconstructed UVR and solar activity, but this natural process may be strongly affected by multiple factors, including climate parameter change and anthropogenic activities during the modern times.

Last glacial to post glacial climate changes in continental Asia inferred from multi-proxy records (geochemistry, clay mineralogy, and paleontology) from Lake Hovsgol, northwest Mongolia

Multi-proxy records (geochemistry, clay mineralogy and paleontology) from three sediment cores from Lake Hovsgol, northwest Mongolia, provide paleoenvironmental changes in continental Asia from the last glacial to the present (during the last 29calka BP). This paper presents the first continuous δ13C and δ18O dataset for ostracod shells (Cytherissa lacustris) from Lake Hovsgol sediments. A positive shift in ostracod δ13C values (from +0.5‰ to +3.2‰) began at ca. 21calka BP, and was associated with a decrease in δ13C values of total organic carbon (from −24.7‰ to −27.3‰) and an increase in the mass accumulation rate of total organic carbon (MAR-TOC). These results suggest that increased lake productivity led to the 13C-enrichment of dissolved inorganic carbon in Lake Hovsgol. In addition, decreases in clay content and the illite crystallinity index (full width at half maximum of the 10Å peak) began at ca. 21calka BP, indicating an increase in surface runoff and a change in sources of clastic materials in the watershed. The highest δ18Oostracod values (up to −4.8‰) at 16–15calka BP indicate the increases in precipitation from the East Asian monsoon. The total pollen amount increased, and Betula, Alnus, and Salix were dominant (up to 53%, 30%, and 6%, respectively) after 16–15calka BP. These findings indicate that broad-leaved trees expanded around Lake Hovsgol. In addition, fossil diatom valves appeared after 16–15calka BP, suggesting climate amelioration, and increased input of soil-derived nutrients and dissolved silica. Between 10 and 5calka BP (Holocene climate optimum), productivity was high in and around the lake (MAR-TOC, up to 47.3mg/cm2kyr; MAR-diatoms, up to 14.4×108 valves/cm2kyr; total pollen concentration, up to 9.0×105 grains/cm3). Environmental changes during the last 29kyr in and around Lake Hovsgol are clearly associated with fluctuations in summer insolation and East Asian monsoon intensity.

Eccentricity-paced late Paleozoic climate change

Cyclic sedimentary deposits characterize low-latitude late Paleozoic successions and preserve evidence of dynamic climate change on the Pangaean supercontinent. Although their orbitally paced glacioeustatic origins are widely accepted, their climatic signatures are open to interpretation. In this study, we utilize the GENESIS general circulation model (GCM) coupled to dynamic ice sheet and ecosystem components, to explore the response of low-latitude continental climate and high-latitude ice sheets to orbital and atmospheric pCO2 forcing. Our results suggest that atmospheric pCO2 concentration exerts the primary control over low-latitude continental climate and high-latitude glaciation. Our experiments constrain the atmospheric pCO2 window within which late Paleozoic climate was amenable to orbitally-driven glacial-interglacial fluctuations. The results suggest that both high-latitude ice-sheet accumulation and ablation and low-latitude climate change were paced by the eccentricity of Earth's orbit. Periods of high eccentricity amplified precession-driven changes in insolation and promoted high-latitude ice sheet volume fluctuations as well as increased low-latitude precipitation variability. When eccentricity was low, the amplification of precessionally-driven insolation fluctuations was reduced, which promoted high-latitude continental ice sheet stability and less variable low-latitude precipitation. Based on these modeling results we discuss the implications of eccentricity paced precessional-scale climatic changes on low-latitude Pangaean depositional environments.

An Improved Particle Swarm Optimization (PSO)–Based MPPT for PV With Reduced Steady-State Oscillation

This paper proposes an improved maximum power point tracking (MPPT) method for the photovoltaic (PV) system using a modified particle swarm optimization (PSO) algorithm. The main advantage of the method is the reduction of the steady- state oscillation (to practically zero) once the maximum power point (MPP) is located. Furthermore, the proposed method has the ability to track the MPP for the extreme environmental condition, e.g., large fluctuations of insolation and partial shading condition. The algorithm is simple and can be computed very rapidly; thus, its implementation using a low-cost microcontroller is possible. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under very challenging conditions, namely step changes in irradiance, step changes in load, and partial shading of the PV array. Its performance is compared with the conventional Hill Climbing (HC) method. Finally, an experimental rig that comprises of a buck-boost converter fed by a custom-designed solar array simulator is set up to emulate the simulation. The soft- ware development is carried out in the Dspace 1104 environment using a TMS320F240 digital signal processor. The superiority of the proposed method over the HC in terms of tracking speed and steady-state oscillations is highlighted by simulation and experimental results.

A Study on Maximum Fluctuation Width within a few Hours regarding Ensemble Average Insolation Observed at Multi-points in Large Area

Based on the past studies regarding the insolation fluctuation, the smoothing effect of insolation among different locations would not be enough for the longer cycle than a few ten minutes. This study evaluated the maximum fluctuation width (MFW) within at most 120 min of ensemble average insolation of 40 points, its clearness index, and ensemble average insolation excluding sun-position dependent component. As the results, when the weather condition became worse after the noon in almost all area, the ensemble average insolation significantly reduced, resulting in MFW of 540W/m2 within 120 min. As other example, when the weather recovered during the morning in many areas, MFW was also large. By using the data observed for 6 months, this study calculated the cumulative frequency distribution of MFW of ensemble average insolation, its clearness index, and ensemble average insolation excluding sun-position dependent component. As the results, the absolute value of MFW of ensemble average insolation calculated with 120 min width window ranges mainly between 200-300W/m2. The absolute value of MWF of insolation excluding sun-position dependent component evaluated with 120 min width window is smaller than 200W/m2 in most days, and is not so different from MWF evaluated with 60 min width window. Finally, this study discussed the practical usability of insolation forecast.

Milankovitch and sub-Milankovitch cycles of the early Triassic Daye Formation, South China and their geochronological and paleoclimatic implications

The mass extinction at the end of Permian was followed by a prolonged recovery process with multiple phases of devastation–restoration of marine ecosystems in Early Triassic. The time framework for the Early Triassic geological, biological and geochemical events is traditionally established by conodont biostratigraphy, but the absolute duration of conodont biozones are not well constrained. In this study, a rock magnetic cyclostratigraphy, based on high-resolution analysis (2440 samples) of magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) intensity variations, was developed for the 55.1-m-thick, Early Triassic Lower Daye Formation at the Daxiakou section, Hubei province in South China. The Lower Daye Formation shows exceptionally well-preserved lithological cycles with alternating thinly-bedded mudstone, marls and limestone, which are closely tracked by the MS and ARM variations. Power spectral, wavelet and amplitude modulation (AM) analyses of the ARM and MS series reveal strong evidence for the presence of Milankovitch to sub-Milankovitch frequencies dominated by precession index signal and 4–5ka cycles. Cycles expressed by variations in MS and ARM were likely controlled by changes in the input of fine-grained detrital magnetite, which in turn may have been driven by astronomically induced changes in monsoon intensity in the equatorial eastern Paleotethys during the Early Triassic greenhouse period.On the basis of the 100-ka tuning results, the astronomically constrained duration of the Induan stage is 1.16Ma, with the Griesbachian and Dienerian substages of 490ka and 670ka, respectively. The new astronomical time scale also provides time constraints for the conodont and bivalve biozones and the carbonate carbon isotope (δ13C) records of the Lower Triassic Daye Formation. Time constraints for the conodont biozones include 34ka for Hindeodus parvus, 24ka for Isarcicella staschei–I. isarcica, 366ka for Neogondolella planata–Ng. carinata, 66ka for Neogondolella discreta, 255ka for Neospathodus kummeli and 415ka for Neospathodus dieneri. The duration for the negative δ13C shift from high δ13C values near the Indun/Olenekian boundary to the lowest value in the Early Smithian is estimated as 430ka. Global comparison indicates that Milankovitch and 4–5ka sub-Milankovitch forcing depositional rhythms may have been common in tropical and sub-tropical carbonate platforms during the Early and Middle Triassic time. The ultimate control on the 4–5ka cycles may have been millennial-scale fluctuations in solar insolation.

Sensitivity of Red Sea circulation to sea level and insolation forcing during the last interglacial

Abstract. This study investigates the response of Red Sea circulation to sea level and insolation changes during termination II and across the last interglacial, in comparison with termination I and the Holocene. Sediment cores from the central and northern part of the Red Sea were investigated by micropaleontological and geochemical proxies. The recovery of the planktic foraminiferal fauna following high salinities during marine isotopic stage (MIS) 6 took place at similar sea-level stand (~50 m below present day), and with a similar species succession, as during termination I. This indicates a consistent sensitivity of the basin oceanography and the plankton ecology to sea-level forcing. Based on planktic foraminifera, we find that increased water exchange with the Gulf of Aden especially occurred during the sea-level highstand of interglacial MIS 5e. From MIS 6 to the peak of MIS 5e, northern Red Sea sea surface temperature (SST) increased from 21 °C to 25 °C, with about 3 °C of this increase taking place during termination II. Changes in planktic foraminiferal assemblages indicate that the development of the Red Sea oceanography during MIS 5 was strongly determined by insolation and monsoon strength. The SW Monsoon summer circulation mode was enhanced during the termination, causing low productivity in northern central Red Sea core KL9, marked by high abundance of G. sacculifer, which – as in the Holocene – followed summer insolation. Core KL11 records the northern tip of the intruding intermediate water layer from the Gulf of Aden and its planktic foraminifera fauna shows evidence for elevated productivity during the sea-level highstand in the southern central Red Sea. By the time of MIS 5 sea-level regression, elevated organic biomarker BIT values suggest denudation of soil organic matter into the Red Sea and high abundances of G. glutinata, and high reconstructed chlorophyll-a values, indicate an intensified NE Monsoon winter circulation mode. Our results imply that the amplitude of insolation fluctuations, and the resulting monsoon strength, strongly influence the Red Sea oceanography during sea-level highstands by regulating the intensity of water exchange with the Gulf of Aden. These processes are responsible for the observation that MIS 5e/d is characterized by higher primary productivity than the Holocene.

2地点における日射変動のコヒーレンスとアンサンブル平均値に基づく地点間距離と日射変動独立性との関係評価

Power output fluctuation of high penetration photovoltaic power generation systems (PVSs) may cause negative impacts on the load frequency control (LFC) of an electric power utility. For the cost-effective mitigation, the proper evaluation of apparent electricity demand fluctuation is important, taking the power output of PVSs into account as a negative demand. If the actual power output patterns are independent among several points, the standard deviation (STD) of total power output fluctuation of PVSs located in several points can be estimated based on the addition theorem of variance. Moreover, the central limit theorem may be applied if the probability distribution of insolation fluctuation is the same among several points. As a fundamental study to apply the stochastic methods, this study evaluates the following two factors to determine the distance between two points with which the insolation patterns of two points can be considered as independent: 1) the coherence of insolation fluctuation for various combinations of two points with different distances, 2) the correlation diagram of two different STDs, i.e. the STD of ensemble average insolation fluctuation observed at two points and the averaged STD of each STD of insolation fluctuation at two points. The results suggest that the insolation fluctuation consisting of the cycles shorter than 30min can be considered as independent if the distance between two points is longer than 5km-10km.

広域多地点における日射変動の独立性を考慮した平均日射変動特性の評価

Power output fluctuation of photovoltaic power generation systems (PVSs) of high penetration may cause negative impact on the load frequency control (LFC) of existing electric power utility. For the cost-effective mitigation, the proper evaluation of power output fluctuation of PVSs dispersed in large-area is very important. Based on the independence in insolation fluctuation among various points, this paper discusses the practical usability of the standard deviation (STD) of total power output fluctuation of PVSs simply calculated as 1/√N value of STD at the representative point. The statistical evaluation using the insolation observed at 5 points within 25km × 25km reveals that STD with simplified calculation would be useful to evaluate STD of ensemble average of insolation on average for a certain period. Besides, the probability density of STD with simplified calculation is almost the same with that of STD of ensemble average for the period with large STD. As a result, the simplified calculation of STD would be useful for the stochastic evaluation of STD of ensemble average insolation among area at least 25km × 25km.

日射変動の独立性を考慮した太陽光発電システム群の合計出力変動特性に関する一検討

日射変動の独立性を考慮した太陽光発電システム群の合計出力変動特性に関する一検討