•Technical impacts of PV integration into power systems are reviewed.•The PV characteristics causing the impacts, as well as the level and timeframe at which they occur are identified.•PV penetration ...limits reported in the literature are examined.•The tools and models to analyse the power system impacts are elaborated.
As the number of photovoltaic (PV) installations across the world keeps on increasing, their impacts on power systems are becoming more visible and more severe. In this two-part review, the implications of high PV penetration on the stability and reliability of power systems are comprehensively assessed. This paper, the first of the two, reviews the impacts of PV on the power systems’ voltage, frequency, protection, harmonics, rotor angle stability, and flexibility requirement in detail. Factors contributing to those impacts, as well as the level and timeframe at which they occur, are carefully analysed. Subsequently, the limits of PV penetration observed in the literature are reviewed. To allow the readers to verify these impacts and limits, the tools and models typically employed in power system analysis are also elaborated. The second part of the review then completes the investigation by assessing the existing solutions to the PV integration challenges and suggesting the way forward.
•LCOE estimation for Si-based monofacial and bifacial modules worldwide.•Monofacial PV systems are more cost-effective at latitudes below 40° for low albedo.•Bifacial PV systems are more ...cost-effective at latitudes beyond 40°.•Bifacial PV systems generate up to 12% more energy at latitudes below 65°, and up to 71% above 65°.
The present work studies the features of photovoltaic systems (PV) formed either by monofacial or bifacial crystalline p-type Si-based solar modules. To determine which module technology would be more favorable worldwide, a total of 55 locations around the globe are analyzed considering their weather profiles, market situation, and module electrical performance for 1 MWp systems. Levelized cost of electricity (LCOE) of the system has been used to decide which technology is more cost-effective. This is obtained for installations which allow any module orientation (AMO) or vertical module orientation (VMO). The results reveal that for latitudes above 40°, bifacial AMO designs are in general more cost-effective than monofacial AMO systems. This tendency is reversed, however, for latitudes below 40° with low albedo values. Nevertheless, if the albedo value is kept to a minimum between 0.12 and 0.30 (depending on the location), bifacial AMO designs can become more cost-effective. When comparing monofacial AMO against bifacial VMO, the latter is more cost-effective only for locations close to the poles, i.e., latitudes higher than 65°. Nonetheless, bifacial VMO designs could even reach lower LCOE values than the ones from monofacial AMO systems at latitudes below 65° if the albedo value is maintained to a minimum between 0.29 and 0.57 (depending on the location). This work will be useful not only to the scientific community, but also to PV installation companies to properly select the most adequate technology, and to optimize the installation design for particular projects.
•Hierarchical reconciliation techniques are demonstrated for temporal hierarchies.•Reconciliation revises the base forecasts and improves their accuracies significantly.•Reconciled forecasts are ...aggregate consistent across all hierarchies.•A day-ahead forecasting example is included for empirical evaluation.
Previously in “Reconciling solar forecasts: Geographical hierarchy” Solar Energy 146 (2017) 276–286, we have demonstrated that by reconciling the forecasts obtained from a geographical hierarchy (formed by levels such as transmission zones, distribution nodes, PV plants, subsystems and inverters), more accurate forecasts can be obtained as compared to forecasts produced using only the information from a single level. Furthermore, these reconciled forecasts are aggregate consistent, facilitating different power system operations and power plant management. In this paper, we continue our discussion on hierarchical reconciliation and consider another type of hierarchy, namely, temporal hierarchy.
A temporal hierarchy can be constructed by aggregating a high-frequency time series (e.g., hourly) into different low-frequency time series (e.g., 6-hourly and daily). While the measurements in a temporal hierarchy sum up consistently (e.g., the first two points in an hourly time series sum up to be the first point in the 2-hourly time series), the forecasts in general do not sum up, due to the different models used to generate forecasts. This inconsistency poses an apparent problem when selecting forecasts. Using reconciliation could mitigate the problem by reconciling different forecasts obtained at different timescales, and thus generating aggregate consistent forecasts. In addition, the reconciled forecasts reduce modeling uncertainties using combinations – similar to the ensemble forecasting used in numerical weather prediction (NWP) – and thus improve forecast accuracy.
The empirical part of the paper consists an NWP-based day-ahead forecast reconciliation example. Hourly data from 318 sites in California, over a period of 1year, is used. Over 50 million forecasts are produced in this paper, in an operational forecasting context. Temporal reconciliation is shown to significantly outperform NWP forecasts produced by 3TIER, with a forecast skill (computed based on 3TIER forecasts) up to 0.3. Since reconciliation does not require any additional information, such improvement is thus encouraging.
Issues and challenges of integrating intermittent renewable energy from large photovoltaic (PV) systems have been a significant area of study. Numerous research works have analyzed the impacts of ...solar PV on the grid and highlighted various aspects to be the limiting factors for PV penetration. This two-part review paper assesses the overall power system impacts of high PV penetration and the potential solutions for mitigating these impacts. This paper, the second of the two, focuses on the various solution measures that have been proposed in the literature such as accurate forecasting, voltage and frequency regulation techniques, harmonic compensation techniques, reactive power management, generator planning and dispatch strategies and adaptive protection schemes that are necessary to solve and mitigate the grid impacts caused by high PV penetration. The limiting factors in implementing these solution measures and their cost bearer have also been highlighted in this paper.
•Potential solutions for grid impacts caused by high PV penetration are reviewed.•Solution measures are broadly categorized based on their characteristics.•A combination of solution measures and the possible cost bearer are suggested.•Factors limiting the implementation of solution measures are elaborated.
Hydrodynamics, spin currents and torsion Gallegos, A. D.; Gürsoy, U.; Yarom, A.
The journal of high energy physics,
05/2023, Volume:
2023, Issue:
5
Journal Article
Peer reviewed
Open access
A
bstract
We construct the canonical constitutive relations for a fluid description of a system with a spin current, valid in an arbitrary number of dimensions in the absence of parity breaking or ...time reversal breaking terms. Our study encompasses the hydrostatic partition function, the entropy current, Kubo formula, conformal invariance, and the effect of charge. At some stages of the computation we turn on a background torsion tensor which naturally couples to the spin current.
•Reactive power costs for photovoltaic system and battery energy storage are proposed.•Providing reactive power locally is not always economically or technically beneficial.•Reactive power costs ...consideration is especially important in poorly distributed systems.•DERs are found to be competitive with switched capacitors for reactive power provision.•Inverter efficiency is the most crucial factor affecting DERs’ reactive power provision.
This work analyses the economic and technical impact of local reactive power provision in grid-connected microgrids with distributed energy resources. Costs of reactive power provision by photovoltaic systems and battery energy storage systems are explicitly formulated and an objective function incorporating the costs is proposed. The advantage of the proposed objective function is validated by comparing it with other objective functions frequently employed in the literature. From various case studies, the extent of economic and technical benefits of local reactive power provision for the microgrid is established. Subsequently, the technical and economic competitiveness of reactive power provision using inverter-based distributed energy resources are compared against those using switched capacitors. Extensive sensitivity analyses are performed to determine the scenarios in which one technology is more competitive than the other. Inverter efficiency has been identified as the most important parameter for reactive power provision from distributed energy resources while electricity price is the most crucial factor for switched capacitors’ competitiveness in producing reactive power.
This paper proposes an approach to optimize sizing and placement of photovoltaic solar panels (PV) and batteries in systems which employ diesel generators (DGs) as their only source of electrical ...energy, forming a PV hybrid system. Three objectives have been defined: reduction of the levelized cost of electricity (economic objective); levelized CO2 equivalent life cycle emissions (environmental objective); and accumulated grid voltage deviation (grid quality objective). As this is a multi-objective optimization problem, the current state-of-the-art meta-heuristic algorithm is applied, namely non-dominated sorting genetic algorithm III. Furthermore, a robust design has been developed by considering the worst case scenarios regarding weather conditions. Subsequently, its outcome is compared with non-robust designs. Optimal pareto fronts composed of many combinations are generated with a lot of freedom to choose for a desired design. The results show the advantages of PV hybrid system in remote locations ranging from being cost effective, reducing the accumulated emissions and even to improving the grid quality.
•A novel sizing and siting optimization method for PV + battery + diesel hybrid systems.•Employment of multiobjective and robust optimization approaches.•Lower life cycle cost, CO2e emissions and grid voltage deviations are achieved.•Generation of initial investments up to 16% of the life cycle cost.
A
bstract
Non-Riemannian gravitational theories suggest alternative avenues to understand properties of quantum gravity and provide a concrete setting to study condensed matter systems with ...non-relativistic symmetry. Derivation of an action principle for these theories generally proved challenging for various reasons. In this technical note, we employ the formulation of double field theory to construct actions for a variety of such theories. This formulation helps removing ambiguities in the corresponding equations of motion. In particular, we embed Torsional Newton-Cartan gravity, Carrollian gravity and String Newton-Cartan gravity in double field theory, derive their actions and compare with the previously obtained results in literature.
Summary
Cloud‐based services have proved useful in several research fields, such as engineering, health science, and astrophysics, to mention a few examples. The computational environmental science ...community developed a strong need for cloud facilities to store, process, and manage data from observations and numerical models for simulations and forecasts. Weather forecast models and global sensor networks deal with multidimensional geo‐referenced data∖sets. However, environmental data consumer applications usually require a relatively small amount of multidimensional input data slice to analyze a specific area or time interval. Hence, reducing data dimension for information retrieval is mandatory. This paper presents a twofold solution: a technique to load and retrieve the sliced multidimensional data set on different cloud services such as Amazon Web Service (AWS), Google Cloud Platform, and Microsoft Azure. The experimental results performed on these cloud services highlight that the proposed method can significantly speed up the process of loading and retrieving the data slices compared to working with the entire data set in bulk or OPeNDAP server.
Summary
The food industry is often described as having more power and influence in nutrition policymaking than nutrition professionals, scientists and other practitioners working for the public ...interest; yet authors often allude to this point as an assumed truth, rather than an evidence‐based fact. This paper applies social network analysis techniques to provide a concise evidence‐based demonstration of the food industry's capacity to influence nutrition policymaking networks in Australia. Network analysis using four rounds of data collection was undertaken, and the capacity of individual actors and occupational categories to influence policy decision makers were analysed. Network graphs were developed using cluster analysis to identify the structure of clusters and the path distance of actors from decision makers. The assumed advantage for the ‘food industry’ was present both strategically in overall network position and with respect to the number of direct access points to ‘decision makers’, whereas ‘nutrition professionals’ were densely clustered together with limited links to key ‘decision makers’. The results demonstrate that the food industry holds the strategic high ground in advocating their interests to policymakers in the contexts studied. Nutrition professionals may be hampered by their reliance on strong ties with other nutrition professionals as well as limited direct links to ‘decision makers’.
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