cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Aging-Effects of Polymeric Encapsulation on the Mechanical Characteristics of Solar Panels and Embedded Components
Creators: name: Fromm, A.
name: Trondl, A.
name: Strecker, H.
name: Krappitz, M.
name: Thissen, D.
name: Kübler, R.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
PV Modules

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3121-3125
description: Solar panels are exposed to varying external static and dynamic mechanical loads which determine the
lifetime of the whole multilayered structure. The induced mechanical stresses are originate with weather phenomena
such as wind, snow, and hail. Influences like these are strongly mechanically impacting on modules. Moreover,
environmental parameters such as humidity and UV-radiation influence mechanical properties of module components
in a yet not investigated way, thus influencing the modules’ response to aforementioned stresses.
The aging behavior – particularly the embrittlement – of the encapsulating polymer under UV-exposure was
investigated using ethylene vinyl acetate (EVA) as an example. A detailed numeric model of a PV-module and its
layer setup regarding front glass, encapsulation, silicon-cells and copper interconnectors was created. The
embrittlement of the polymer was implemented in the numeric model and mechanical
Universality of DC Electrical Conductivity from Holography
Creators: name: Ge, Xian-Hui
name: Sin, Sang-Jin
name: Wu, Shao-Feng
Publisher: name: arXiv
Year: 2015
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We propose a universal formula of dc electrical conductivity in rotational- and translational- symmetries breaking systems via the holographic duality. This formula states that the ratio of the determinant of the dc electrical conductivities along any spatial directions to the black hole area density in zero-charge limit has a universal value. As explicit illustrations, we give several examples elucidating the validation of this formula: We construct an anisotropic black brane solution, which yields linear in temperature for the in-plane resistivity and insulating behavior for the out-of-plane resistivity; We also construct a spatially isotropic black brane solution that both the linear-T and quadratic-T contributions to the resistivity can be realized.
description: 7 pages, references added, typos corrected
Power Electronics for Utility Scale PV Power Plants with Voltages Up to +/- 1500 VDC
Creators: name: Schönberger, S.
name: Görden, T.
name: Liese, S.
name: Rogalla, S.
name: Venkatapath, R.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3080-3083
description: Large grid-connected PV systems has shown a strong growth in their market share in the recent past.
To build and monitor these power plants, cost efficient new inverter stations with a higher power and voltage levels
are in demand. In this work four power plant models were compared. A state of the art model with 1000 VDC and a
near future model with 1500 VDC unipolar and floating PV generators were investigated. Furthermore a two stage
concept with a fixed voltage inverter and additional active string combiner is discussed. The string combiners have
two inputs with a maximum input voltage of 1500 VDC each. The outputs are connected to a fixed-voltage DC-bus.
The last model has a bipolar PV generator with a maximum voltage of +/- 1500 VDC. With the last two models an
output voltage of 1000 VAC can be realized. This leads to the maximum utilization of the voltage levels according to
the European Low Voltage Directive [1]. As the simulation shows that for all models, the power electronic concepts
with efficiencies of more than 98% are possible. An active string combiner required for the third concept has been
developed. The device shows very high power density and an efficiency of more than 99 %. Measurement results are
also analyzed in this paper.
An Egorov Theorem for avoided crossings of eigenvalue surfaces
Creators: name: Kammerer, Clotilde Fermanian
name: Lasser, Caroline
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mathematical Physics (math-ph)
subject: Analysis of PDEs (math.AP)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We study nuclear propagation through avoided crossings of electron energy levels. We construct a surface hopping semigroup, which gives an Egorov-type description of the dynamics. The underlying time-dependent Schroedinger equation has a two-by-two matrix-valued potential, whose eigenvalue surfaces have an avoided crossing. Using microlocal normal forms reminiscent of the Landau-Zener problem, we prove convergence to the true solution in the semi-classical limit.
description: 44 pages
PV Module Degradation in the Field and in the Lab - How Does It Fit Together?
Creators: name: Peike, C.
name: Hoffmann, S.
name: Dürr, I.
name: Weiß, K.-A.
name: Bogdanski, N.
name: Köhl, M.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
PV Modules

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3110-3114
description: To design realistic and quick accelerated aging tests, the comparison between the degradation mechanisms induced by outdoor exposure and by accelerated aging tests is indispensable. Various accelerated aging tests, i.e. heat aging, UV aging, damp-heat aging and combined UV / damp-heat aging, were performed on full-size PV modules from different PV module manufacturers. The climate-dependence of the degradation was investigated on identical PV modules which have been exposed in different extreme climates for up to six years. A comprehensive degradation analysis was performed, i.e. by means of power measurements, electroluminescence imaging and Raman spectroscopy. The electrical characterization showed a high stability of all investigated modules.
Dark matter from gravitational particle production at reheating
Creators: name: Markkanen, Tommi
name: Nurmi, Sami
Publisher: name: arXiv
Year: 2015
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We show that curvature induced particle production at reheating generates adiabatic dark matter if there are non-minimally coupled spectator scalars weakly coupled to visible matter. The observed dark matter abundance implies an upper bound on spectator masses $m$ and non-minimal coupling values $ξ$. For example, assuming quadratic inflation, instant reheating and a single spectator scalar with only gravitational couplings, the observed dark matter abundance is obtained for $m\sim 0.1$ GeV and $ξ\sim 1$. Larger mass and coupling values of the spectator are excluded as they would lead to overproduction of dark matter.
description: 10 pages, 1 figure. v2: updated references. v3: substantial modifications, results and conclusions partially changed but bounds on spectator fields almost unaffected. New title. v4: expanded discussion, accepted for publication in JCAP
Counting Blanks in Polygonal Arrangements
Creators: name: Akopyan, Arseniy
name: Segal-Halevi, Erel
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computational Geometry (cs.CG)
subject: Metric Geometry (math.MG)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: Inside a two dimensional region ("cake"), there are $m$ non-overlapping tiles of a certain kind ("toppings"). We want to expand the toppings while keeping them non-overlapping, and possibly add some blank pieces of the same "certain kind", such that the entire cake is covered. How many blanks must we add? We study this question in several cases: (1) The cake and toppings are general polygons. (2) The cake and toppings are convex figures. (3) The cake and toppings are axes-parallel rectangles. (4) The cake is an axes-parallel rectilinear polygon and the toppings are axes-parallel rectangles. In all four cases, we provide tight bounds on the number of blanks.
description: A revised version of "Cutting a Cake without Harming the Toppings"
Requirements for Switches in Safety Devices of PV Systems
Creators: name: Müller, R.M.
name: Berghaus, A.
name: Bogdanski, N.
name: Häring, A.
name: Hopf, M.
name: Stanke, S.
name: Lang, V.
name: Meissner, J.
name: Meyer, D.
name: Schäffer, R.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3076-3079
description: With the increasing number of Photovoltaic (PV) installations the requirements regarding safety
aspects are increasing accordingly. As a result, the application of safety devices such as fuses, blocking diodes and
surge protection for PV systems for standard conditions are already comprehensively addressed by local and
international standards. To date the specifications in standards for switching devices for PV systems are not yet
clearly defined. Especially in cases of critical systems faults the switching devices may not be capable to safely shut
down the PV system. Nevertheless there are already several products available claiming to solve specific fault events
although the procedures how to handle these events and the requirements the corresponding switches have to fulfil
are not yet in place.
Within a joined research project supported by the German Ministry for Economic Affairs and Energy in which
several German companies and testing institutes are involved, procedures and designs are developed to provide PV
system installers measures to provide and install additional suitable switching devices, thereby increasing protection
against electrical shock in case of faults in PV systems which on the other hand may be associated with the risk of
decreasing operational reliability in PV Systems and thereby causing downtime.
Finite-size scaling in a 2D disordered electron gas with spectral nodes
Creators: name: Sinner, Andreas
name: Ziegler, Klaus
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study the DC conductivity of a weakly disordered 2D electron gas with two bands and spectral nodes, employing the field theoretical version of the Kubo--Greenwood conductivity formula. Disorder scattering is treated within the standard perturbation theory by summing up ladder and maximally crossed diagrams. The emergent gapless (diffusion) modes determine the behavior of the conductivity on large scales. We find a finite conductivity with an intermediate logarithmic finite-size scaling towards smaller conductivities but do not obtain the logarithmically divergence of the weak-localization approach. Our results agree with the experimentally observed logarithmic scaling of the conductivity in graphene with the formation of a plateau near $e^2/πh$.
description: 10 pages, 3 figures. Published without changes
Relative entropy for hyperbolic-parabolic systems and application to the constitutive theory of thermoviscoelasticity
Creators: name: Christoforou, Cleopatra
name: Tzavaras, Athanasios
Publisher: name: arXiv
Year: 2016
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics

description: We extend the relative entropy identity to the class of hyperbolic-parabolic systems whose hyperbolic part is symmetrizable. The resulting identity, in the general theory, is useful to provide stability of viscous solutions and yields a convergence result in the zero-viscosity limit to smooth solutions in an $L^p$ framework. Also it provides measure valued weak versus strong uniqueness theorems for the hyperbolic problem. The relative entropy identity is also developed for the system of gas dynamics for viscous and heat conducting gases, and for the system of thermoviscoelasticity with viscosity and heat-conduction. Existing differences in applying the relative entropy method between the general hyperbolic-parabolic theory and the examples are underlined.
description: 54 pages, no figures
Quantitative convergence analysis of iterated expansive, set-valued mappings
Creators: name: Luke, D. Russell
name: Thao, Nguyen H.
name: Tam, Matthew K.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optimization and Control (math.OC)
subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 49J53, 65K10, 49K40, 49M05, 49M27, 65K05, 90C26

description: We develop a framework for quantitative convergence analysis of Picard iterations of expansive set-valued fixed point mappings. There are two key components of the analysis. The first is a natural generalization of single-valued averaged mappings to expansive, set-valued mappings that characterizes a type of strong calmness of the fixed point mapping. The second component to this analysis is an extension of the well-established notion of metric subregularity -- or inverse calmness -- of the mapping at fixed points. Convergence of expansive fixed point iterations is proved using these two properties, and quantitative estimates are a natural byproduct of the framework. To demonstrate the application of the theory, we prove for the first time a number of results showing local linear convergence of nonconvex cyclic projections for inconsistent (and consistent) feasibility problems, local linear convergence of the forward-backward algorithm for structured optimization without convexity, strong or otherwise, and local linear convergence of the Douglas--Rachford algorithm for structured nonconvex minimization. This theory includes earlier approaches for known results, convex and nonconvex, as special cases.
description: 41 pages 70 references. Detailed examples added and more historical commentary (with citations)
Scalable Quantum Simulation of Molecular Energies
Creators: name: O'Malley, P. J. J.
name: Babbush, R.
name: Kivlichan, I. D.
name: Romero, J.
name: McClean, J. R.
name: Barends, R.
name: Kelly, J.
name: Roushan, P.
name: Tranter, A.
name: Ding, N.
name: Campbell, B.
name: Chen, Y.
name: Chen, Z.
name: Chiaro, B.
name: Dunsworth, A.
name: Fowler, A. G.
name: Jeffrey, E.
name: Megrant, A.
name: Mutus, J. Y.
name: Neill, C.
name: Quintana, C.
name: Sank, D.
name: Vainsencher, A.
name: Wenner, J.
name: White, T. C.
name: Coveney, P. V.
name: Love, P. J.
name: Neven, H.
name: Aspuru-Guzik, A.
name: Martinis, J. M.
Publisher: name: arXiv
Year: 2015
Subjects: subject: Quantum Physics (quant-ph)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We report the first electronic structure calculation performed on a quantum computer without exponentially costly precompilation. We use a programmable array of superconducting qubits to compute the energy surface of molecular hydrogen using two distinct quantum algorithms. First, we experimentally execute the unitary coupled cluster method using the variational quantum eigensolver. Our efficient implementation predicts the correct dissociation energy to within chemical accuracy of the numerically exact result. Second, we experimentally demonstrate the canonical quantum algorithm for chemistry, which consists of Trotterization and quantum phase estimation. We compare the experimental performance of these approaches to show clear evidence that the variational quantum eigensolver is robust to certain errors. This error tolerance inspires hope that variational quantum simulations of classically intractable molecules may be viable in the near future.
description: 13 pages, 7 figures. This revision is to correct an error in the coefficients of identity in Table 1
Sensitivity of Different Bill of Materials to PID: Fast Test Method
Creators: name: Liciotti, C.
name: Cardinali, M.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
PV Modules

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3084-3092
description: Potential-induced degradation (PID) is a relevant problem in the PV industry. Working group IEC
TC82 WG2 is working on the standard IEC 62804 draft; the aim of this standard is the development of test methods
for evaluating the sensitivity of PV modules to PID effects. In this standard draft, 2 methods are introduced. Method
A requires a climatic chamber and around 96 h; Method B requires around 168 h. Both of them are developed to give
quantitative result. Many scientific studies have indicated the encapsulant and the cells as possible origin of PID.
The aim of this work is to define a faster test procedure that the industry could use internally to control the behavior
of different bill of materials and their sensitivity to PID in term of quality.
Modified Single Variable Based Variable Step Size Maximum Power Point Tracker
Creators: name: Abdourraziq, M.A.
name: Maaroufi, M.
name: Ouassaid, M.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3046-3049
description: Maximum Power Point Tracking (MPPT) techniques are widely applied in photovoltaic system to produce the maximum power of the photovoltaic generator. In this paper, we present a modified single variable based variable step size MPPT algorithm for photovoltaic (PV) systems. The proposed method can greatly improve the response time MPPT. This method employs the relationship between the output current of photovoltaic array and duty cycle to adapt automatically the change of step in the duty cycle to reach the maximum power point of the PV array. The proposed method is compared with Perturb and observe (P&O). The proposed approach has been tested in MATLAB / Simulink environment, and the results show that the new algorithm is faster than the P&O method.
A Novel Test Bench for Central Inverters – R&D and Testing of Large-Scale Grid Connected PV Inverters
Creators: name: Lauss, G.
name: Bründlinger, R.
name: Mayr, C.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3062-3066
description: Based on the experience of PV inverter components, the lab infrastructure which is required to perform reproducible, valid tests is presented in this contribution. The need of the PV inverter industry to characterize of large-scale PV inverters (central inverters) on a suitable test bench exists, the concept of a large scale test bench in introduced and explained in detail. The fact that large-scale integration of MW solar plants leads to an increasing level of distributed power generation, pushing many distribution networks to their limits. One promising way to make the energy systems fit for the future is the use of smart grids, which enable intelligent energy management through bidirectional communication and coordination between generators, consumers and storage units. This laboratory infrastructure is developed to match the required testing facilities (accredited standardization testing [1][2][3][4][5], R&D works, prototype test bench, etc.) and the potential for supporting the PV inverter manufacturing industry is demonstrated with the help of some examples and experiments.
Testing Microinverters According to En 50530
Creators: name: Alonso-Abella, M.
name: Chenlo, F.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3104-3109
description: PV inverters have been tested according the procedure defined in the EN 50530 standard - overall
efficiency of grid connected photovoltaic inverters. Maximum power point tracking efficiency, static and dynamic,
power electrical conversion and overall efficiencies are measured. Results for two models of microinverters and for
one string inverter for comparison purposes are presented in this work.
Ultrafast Multi-MPPT PV Inverter Test Bench
Creators: name: Muntwyler, U.
name: Gfeller, D.
name: Borgna, L.
name: Schuepbach, E.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3041-3045
description: Many modern PV inverters up to 10kW have two or more MPP tracking inputs. These multi-MPPT inverters do not only affect the design of the PV plant, they are also new terrain for the institutes that are testing these devices. The PV lab of BFH-TI has carried out tests on grid connected PV inverters for the past 25 years. Ensuring to keep up with the market, it was decided to extend the PV lab's testing abilities by building up a new test bench for multi-MPPT PV inverters. A very important element of such a test stand is the PV array simulator, which has to be able to simulate the electrical characteristics of multiple independent PV sub arrays. Even though some devices for PV array simulation could be found on the market, none of them could completely satisfy the PV lab's requirements. Therefore it was decided to develop the simulator needed on our own, as it had been done before. This paper illustrates the reasons why most commercially available simulators are not completely adequate for inverter testing. It also gives some insight in the design of BFH-TI's own PV array simulators.
Observer-Based Feedback Stabilization of Linear Systems with Event-triggered Sampling and Dynamic Quantization
Creators: name: Tanwani, Aneel
name: Prieur, Christophe
name: Fiacchini, Mirko
Publisher: name: arXiv
Year: 2016
Subjects: subject: Dynamical Systems (math.DS)
subject: Systems and Control (eess.SY)
subject: FOS: Mathematics
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: We consider the problem of output feedback stabilization in linear systems when the measured outputs and control inputs are subject to event-triggered sampling and dynamic quantization. A new sampling algorithm is proposed for outputs which does not lead to accumulation of sampling times and results in asymptotic stabilization of the system. The approach for output sampling is based on defining an event function that compares the difference between the current output and the most recently transmitted output sample not only with the current value of the output, but also takes into account a certain number of previously transmitted output samples. This allows us to reconstruct the state using an observer with sample-and-hold measurements. The estimated states are used to generate a control input, which is subjected to a different event-triggered sampling routine; hence the sampling times of inputs and outputs are asynchronous. Using Lyapunov-based approach, we prove the asymptotic stabilization of the closed-loop system and show that there exists a minimum inter-sampling time for control inputs and for outputs. To show that these sampling routines are robust with respect to transmission errors, only the quantized (in space) values of outputs and inputs are transmitted to the controller and the plant, respectively. A dynamic quantizer is adopted for this purpose, and an algorithm is proposed to update the range and the centre of the quantizer that results in an asymptotically stable closed-loop system.
Tracker System Based on Silicon Photovoltaic Sensor
Creators: name: Okhorzina, A.
name: Yurchenko, A.
name: Kitaeva, M.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3067-3069
description: In paper, active type of solar tracking has been presented. Active tracking system has been created. Estimation of efficiency of single-axis and dual–axis tracking has been presented. A directivity chart of each sensor element has been determined per day. Required accuracy of orientation has been determined experimentally and has been composed 5˚. This tracker is powered by PV module, which is oriented.
The power gains by using tracking systems during few years have been analyzed. The results of the system for Tomsk (Western Siberia) have been offended.
Grid Influences from Reactive Power Flow of Photovoltaic Inverters with a Power Factor Specification of One
Creators: name: Spring, A.
name: Becker, G.
name: Witzmann, R.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3000-3005
description: The quantity of installed photovoltaic (PV) systems in the German distribution grid is still increasing. In some areas the installed PV capacity exceeds 5.0 kWp [SPR-13a] per house connection (HC). Therefore the load flow changes its characteristics and leads to new requirements for grid dimensioning. In some areas the power feedback is higher than the delivery and the installed PV capacity becomes the decisive factor for grid planning. This article discusses unintended reactive power flows of PV inverter systems. The focus hereby is on the power factor (PF) specification of one. Hence these PV inverters should feed-in only active and no reactive power into the grid. Various observations in low voltage grids show a dispersion of the active and apparent power feed-in and thus a reactive power flow. To investigate these unintended reactive power flows, numerous commercially available inverters in the single and double digit kilowatt range are analyzed. Every single inverter with a power factor specification of one shows a reactive power flow. Finally it is proved, that there is an influence of the unintended reactive power flow on the grid voltage and grid losses. This influence has to be considered in grid planning and power system management.
Conservative classical and quantum resolution limits for incoherent imaging
Creators: name: Tsang, Mankei
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: I propose classical and quantum limits to the statistical resolution of two incoherent optical point sources from the perspective of minimax parameter estimation. Unlike earlier results based on the Cramér-Rao bound, the limits proposed here, based on the worst-case error criterion and a Bayesian version of the Cramér-Rao bound, are valid for any biased or unbiased estimator and obey photon-number scalings that are consistent with the behaviors of actual estimators. These results prove that, from the minimax perspective, the spatial-mode demultiplexing (SPADE) measurement scheme recently proposed by Tsang, Nair, and Lu [Phys. Rev. X 6, 031033 (2016)] remains superior to direct imaging for sufficiently high photon numbers.
description: 12 pages, 2 figures. v2: focused on imaging, cleaned up the math, added new analytic and numerical results. v3: restructured and submitted
Hybrid Simulation of Maximum Power Point Tracking Methods (the P&O and Counter Reaction of Voltage Method Using Pilot Cell) for a Stand Alone Photovoltaic System
Creators: name: Aouchiche, N.
name: Ait Cheikh, M.S.
name: Malek, A.
name: Badia, A.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Balance of System Components

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 3024-3028
description: The power generated by solar photovoltaic (PV) module depends on surrounding irradiance and temperature. This paper presents a hybrid simulation model of PV module and system using Matlab®/Simulink® and Pspice®, combined together using Cadence® software SLPS®. The hybrid simulation model includes the solar PV panel and the boost converter with MPPT controller. The target of this work is to find the possibilities of Pmax control using the maximum power point methods (MPPT). Many algorithms for searching MPP are proposed. In this study, the methods simulated are perturbation and observation (P&O) and voltage feedback using pilot cell. This simulation is done under different atmospheric conditions. This last permit to study behaviour of photovoltaic chain components.
Decongestion of urban areas with hotspot-pricing
Creators: name: Solé-Ribalta, Albert
name: Gómez, Sergio
name: Arenas, Alex
Publisher: name: arXiv
Year: 2016
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Computers and Society (cs.CY)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: The rapid growth of population in urban areas is jeopardizing the mobility and air quality worldwide. One of the most notable problems arising is that of traffic congestion which in turn affects air pollution. With the advent of technologies able to sense real-time data about cities, and its public distribution for analysis, we are in place to forecast scenarios valuable to ameliorate and control congestion. Here, we analyze a local congestion pricing scheme, hotspot pricing, that surcharges vehicles traversing congested junctions. The proposed tax is computed from the estimation of the evolution of congestion at local level, and the expected response of users to the tax (elasticity). Results on cities' road networks, considering real-traffic data, show that the proposed hotspot pricing scheme would be more effective than current mechanisms to decongest urban areas, and paves the way towards sustainable congestion in urban areas.
description: 12 pages, 10 figures
Solar Potential in Castilla y León, Spain
Creators: name: Díez-Mediavilla, M.
name: Rodríguez-Amigo, M.C.
name: Mediavilla-Trabada, A.
name: Pérez-Burgos, A.
name: Alonso-Tristán, C.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2971-2974
description: The feasibility of exploiting solar energy in Castilla y León, Spain, is investigated in this study. The temporal and the geographical solar resources in the region and their trends were studied over a seven year period. Maximum, minimum, and average values of monthly and annual global horizontal radiation and the clearness index were calculated from the data recorded at forty-six weather stations. The experimental data sets were then filtered and validated using the procedures indicated by WMO. The region is considered to have a high solar potential, with high values of global irradiation and a low percentage of cloudy days.
Differential operators on the superline, Berezinians, and Darboux transformations
Creators: name: Li, Simon
name: Shemyakova, Ekaterina
name: Voronov, Theodore
Publisher: name: arXiv
Year: 2016
Subjects: subject: Differential Geometry (math.DG)
subject: Mathematical Physics (math-ph)
subject: Quantum Algebra (math.QA)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We consider differential operators on a supermanifold of dimension $1|1$. We define non-degenerate operators as those with an invertible top coefficient in the expansion in the "superderivative" $D$ (which is the square root of the shift generator, the partial derivative in an even variable, with the help of an odd indeterminate). They are remarkably similar to ordinary differential operators. We show that every non-degenerate operator can be written in terms of `super Wronskians' (which are certain Berezinians). We apply this to Darboux transformations (DTs), proving that every DT of an arbitrary non-degenerate operator is the composition of elementary first order transformations. Hence every DT corresponds to an invariant subspace of the source operator and, upon a choice of basis in this subspace, is expressed by a super-Wronskian formula. We consider also dressing transformations, i.e., the effect of a DT on the coefficients of the non-degenerate operator. We calculate these transformations in examples and make some general statements.
description: 24 pages, LaTeX, some editorial changes (as compared with the earlier version)
How can medical school support students with mental health and wellbeing issues: the students’ view
Creators: name: Cooke, Siobhan
name: Griffin, Ann
name: O'Keeffe, Catherine
Publisher: name: F1000 Research Limited
Year: 2023

description: Background High levels of stress and burnout among medical students globally is likened to a “public health crisis”. Yet medical students are reluctant to seek help from medical school to manage their stresses and particularly for mental health issues. Previous research has identified barriers; mental health issues viewed as weakness with future career implications, lack of confidentiality, stigma, fear of regulatory fitness to practice proceedings with possible expulsion, reputational damage and failure to meet parents’ expectations. Despite extensive literature over 20 years, evidence-based strategies to optimize the mental health and wellbeing in medical students are lacking.

 Summary of Work This institutional case study aimed to develop an understanding of the current barriers for medical students in seeking support from medical school from students’ perspectives. Medical students’ understanding of wellbeing, their major stressors, their sources of support and barriers to seeking support were the research questions explored. I used qualitative case study methodology and purposive sampling to select participants. Data was collected using individual semi-structured online interviews and analysed using interpretative phenomenological analysis.

 Summary of Results 21 medical students from Years 1 – 5, from diverse backgrounds were interviewed and included students with mental health and learning disabilities. Key findings included that students define wellbeing according to physiological needs and having safe accommodation. Their wellbeing was closely linked to academic studies. Isolation was a major stressor and negative factors on wellbeing included examination stress, lack of motivation, both exacerbated by remote learning, and comparing themselves to other students. Positive influences on wellbeing included supportive close relationships, "checking in" with family and good experience on clinical placements. Support from peers and tutors was protective. Lack of a clear personal tutor system was identified as detrimental to accessing student support services in medical school.

 Discussion and Conclusion Students viewed learning to seek support as a developmental process. My findings suggest that personal and professional identity formation are central to student wellbeing in medical school. Points of transition; on entry to medical school, learning in the clinical environment and becoming a Foundation Programme doctor are critical learning points for identity development.

 Take-home Message Personal and professional identity formation are central to student wellbeing in the medical school. Understanding how medical students develop personal and professional identity through social interaction in different years has future implications for developing effective medical school student support policies.
Sun at School - Monitoring Several 100 PV Systems for Nearly 20 Years
Creators: name: Becker, G.
name: Flade, F.
name: Schiebelsberger, B.
name: Weber, W.
name: Wotruba, G.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2990-2993
description: About 20 years ago, more than 900 schools spread all over Germany have received various grid connected PV systems of about 1 kW. Some years after the start of the promotion program, it has become clear, that for a successful operation some monitoring and supervision and appropriate reports would be necessary. Thus, a central coordinator has been installed. The task of the coordinator was as well to collect operation data, i.e. monthly yields and information about malfunction and generate out of these data a report to send to the schools. This monitoring started in the year 1998. As the first PV systems have been installed in 1994, now operation results are available in a time span of max. 20 years for several hundred grid-connected PV systems in schools. Additionally investigations about the technical state of the components for randomly selected PV systems have been organized.
Pseudo-Data Reflecting Statistical Characteristics of Residential Load for Large-Scale Electrical Grid Analysis with Large Amount of PV
Creators: name: Inouchi, S.
name: Aoshima, Y.
name: Wakao, S.
name: Fujimoto, Y.
name: Hyashi, Y.
name: Osaka, T.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2927-2931
description: When PV systems are introduced widely, it is indispensable to carry out the computational simulation taking account of the fluctuations of PV output and residential load. However, a large-scale simulation requires accurate load data of a large number of houses. Therefore, the techniques of creating pseudo-data, which reflect the statistical characteristics of practical residential load, from limited amount of measured data are important. In this paper, we propose the method of generating a pseudo-residential load reflecting an7 characteristics of residential load. And we demonstrate the validity of using pseudo load data for the large-scale electrical grid simulations with PV.
Innovative Integration of Storage and Forecast Techniques Enabling Large-Scale PV Power Plants Active Integration in the Grid
Creators: name: Lanuzza, L.
name: Papa, C.
name: Bizzarri, F.
name: Lanzetta, C.
name: Ruffini, F.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2965-2967
description: In this paper a project is presented which has the aim to propose and test solutions for limiting the intermittency of energy generation from unpredictable Renewable Energy Sources (RES), meantime reducing the need for curtailment of RES and even potentially increasing the amount of renewable generation capacity that can be connected to existing network, thus making such RES generators as much as possible similar to conventional generators, and the RES becoming an active resource for the grid. In order to achieve such results, a combination of advanced power plant management solutions integrated with electrochemical storage and advanced forecast techniques will be applied to an existing large-scale PV power plant. The project is currently under executive engineering definition, with start of operation foreseen during Q4 2014.
Oscillatory rheotaxis of active droplets in microchannels
Creators: name: Dey, Ranabir
name: Buness, Carola M.
name: Hokmabad, Babak Vajdi
name: Jin, Chenyu
name: Maass, Corinna C.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: Biological microswimmers are known to navigate upstream of an external flow (positive rheotaxis) in trajectories ranging from linear, spiral to oscillatory. Such rheotaxis stems from the interplay between the motion and complex shapes of the microswimmers, e.g. the chirality of the rotating flagella, the shear flow characteristics, and the hydrodynamic interaction with a confining surface. Here, we show that an isotropic, active droplet microswimmer exhibits a unique oscillatory rheotaxis in a microchannel despite its simple spherical geometry. The swimming velocity, orientation, and the chemical wake of the active droplet undergo periodic variations between the confining walls during the oscillatory navigation. Using a hydrodynamic model and concepts of dynamical systems, we demonstrate that the oscillatory rheotaxis of the active droplet emerges primarily from the interplay between the hydrodynamic interaction of the finite-sized microswimmer with all the microchannel walls, and the shear flow characteristics. Such oscillatory rheotactic behavior is different from the directed motion near a planar wall observed previously for artificial microswimmers in shear flows. Our results provide a realistic understanding of the behaviour of active particles in confined microflows, as will be encountered in majority of the applications like targeted drug delivery.
Martinique Island: First Full Application of the MotherPV Method
Creators: name: Guérin De Montgareuil, A.
name: Rosamont, P.
name: Darivon, S.
name: Bellemare, L.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2843-2847
description: The Martinique energy agency (AME) and CEA lead a common research program on the performance of PV under the specific (tropical) climate of Martinique Island. AME has set up more than 25 roof integrated PV systems in the different climatic regions of the Island, from 7.5 kWp to 229 kWp. This 229 kWp system has been carefully monitored in order to apply the CEA’s MotherPV method which allows 1- an estimation of the installed PV peak power and 2- a very accurate modelling of the behaviour of the system, which is able to detect even very slight problems in the energy production. This article describes the specific monitoring of the system and the result of the first full application of the MotherPV with its 2 approaches: previous indoor/outdoor measurements versus in situ measurements (new method). The two approaches give very similar results (difference of 0.4 %) and can be used for the assessment of the power of photovoltaic systems and for the monitoring of the production.
Parallel Operation of Photovoltaic Inverters with Autonomous Voltage Control Strategies - Comparison of Q(V)/P(V) and Automatic Voltage Limitation
Creators: name: Wang, H.
name: Stetz, T.
name: Kraiczy, M.
name: Birk, A.
name: Töbermann, C.
name: Braun, M.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2921-2926
description: A major issue for distribution system operators is to maintain voltage quality in their networks. This holds especially for networks with high local PV penetration. In times of high solar irradiation, reverse power flows can lead to voltage rises and violations of voltage limits at critical nodes. Inverter-based autonomous voltage control strategies can be applied to mitigate voltage violations in distribution systems. In this study, two autonomous voltage control strategies for PV-inverters, Q(V)/P(V) and automatic voltage limitation, are investigated. The investigated control approaches are implemented in the control loop of real PV inverters from “Triphase”. The stability, voltage support - and load-sharing capability of two parallel operated inverters with proposed local control strategies have been investigated in laboratory environment. As results, both control strategies could successfully mitigate voltage rises under parallel operation. The load-sharing capability of two inverters, however, can be significantly influenced by the grid impedance and voltage filter time constant of the inverter.
Using the Loss Factors Model to Improve PV Performance Modelling for Industrial Needs
Creators: name: Ransome, S.
name: Sutterlueti, J.
Publisher: name: WIP
Year: 2014
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (from Cells to Systems)
Operation of PV Systems and Plants

description: 29th European Photovoltaic Solar Energy Conference and Exhibition; 2870-2875
description: The Loss Factors Model (LFM) developed by TEL Solar and SRCL is very useful in analysing indoor and outdoor instantaneous PV performance based on IV scans as well as summed energy yields. Its normalised orthogonal coefficients allow a sanity check of data to determine bad measurements, also any underperformance due to faults or degradation can be identified and responsible causes found. It corrects discrepancies and limitations in models such as the 1-diode by having correct low light, temperature and RSHUNT coefficients by being based on real world IV curves, not just one data sheet value. Residuals between measured and predicted are found in the range of +/- 1% allowing earlier identification of the root cause. This combination of improved understanding and faster detection is leading to more accurate and the higher quality modelling required for future industry needs to reduce risks and uncertainties.
Normality of algebras over commutative rings, crossed pairs, and the Teichmueller class
Creators: name: Huebschmann, Johannes
Publisher: name: arXiv
Year: 2015
Subjects: subject: Rings and Algebras (math.RA)
subject: FOS: Mathematics
subject: 11R33, 12G05, 13B05, 16H05, 16K50, 16S35, 20J06, 46L10, 46M20, 55R99

description: Let S be a commutative ring, Q a group that acts on S, and let R be the subring of S fixed under Q. A Q-normal S-algebra consists of a central S-algebra A and a homomorphism s from Q to the group Out(A) of outer automorphisms of A that lifts the Q-action on S. We associate to a Q-normal S-algebra (A,s) a crossed 2-fold extension which, in turn, represents a class, the Teichmueller class of (A,s), in the third cohomology group of Q with coefficients in the group U(S) of units of S, endowed with the obvious Q-module structure. Suitable equivalence classes of Q-normal Azumaya S-algebras constitute an abelian group XB(S,Q), the crossed Brauer group of S relative to the Q-action on S, and the classical results, suitably rephrased in terms of a generalized Teichmueller cocycle map defined on the abelian group XB(S,Q) and crucially involving crossed 2-fold extensions, extend to the more general situation. The Teichmueller cocycle map is even defined on the abelian group kRep(Q,B((S,Q))) of classes of representations of Q in the Q-graded Brauer category B((S,Q)) of S relative to the Q-action on S, and the obvious homomorphism from XB(S,Q) to kRep(Q,B((S))) is injective, an isomorphism when the image of Q in the group of automorphisms of S is a finite group. Furthermore, in that case, the equivariant and crossed Brauer groups fit into various exact sequences generalizing among others the corresponding low degree group cohomology five term exact sequence in the classical case over a field. Crossed pair algebras defined relative to a suitable notion of Q-equivariant Galois extension of commutative rings lead to a comparison of the theory with the appropriate group cohomology groups and with the corresponding abelian group of classes of crossed pairs defined relative to the data. A number of examples illustrating the theory are included.
description: 116 pages; relative theory refined; material split into two chapters; a third chapter containing a number of examples added