Wind-solar power has an intrinsic huge volatility and the obvious question arises, is it possible to marginalize it to an extent that the power generation can sufficiently be synchronized with the electric power consumption being volatile as well. We present a novel function describing the volatile system as a whole. The new function, in turn, depends on three characteristic numbers, which means that the volatility of this system is characterized by those numbers. Using the data of the total electric power consumption and the total wind-solar power generation in Germany for the last seven years (2015–2021) taken every 15 minutes we determine the characteristic numbers from these data and get the result that marginalizing the volatility is possible with a minimum of required storage capacity, provided (i) a surplus of wind-solar power is supplied about doubling the number of devices, (ii) smart meters are installed, (iii) a different kind of wind turbines and solar panels is partially used. Our results suggest that all the present electric energy required in Germany can be obtained from wind-solar power if (i), (ii) and possibly (iii) are fulfilled. And our results indicate that, because of the minimal necessary storage capacity, controlled wind-solar power can in addition produce the energy for transportation, warm water, space heating and in part for process heating, requiring an increase of the electric energy production in total by a factor of 5. Then, however, a huge number of wind turbines and solar panels is required changing the appearance of German landscapes fundamentally. Our method can be applied to the wind-solar power problem of any country provided a reliable basis of power data exists over a sufficiently long period.

The main advantage of wind and solar power plants is the power production free of CO2. Their main disadvantage is the volatility of the generated power. According to the estimates of H.-W. Sinn[1], suppressing this volatility requires pumped-storage plants with a huge capacity, several orders of magnitude larger than the present available capacity in Germany[2]. Sinn concluded that wind-solar power can be used only together with conventional power plants as backups. However, based on German power data[3] of 2019 we show that the required storage capacity can significantly be reduced, provided i) a surplus of wind-solar power plants is supplied, ii) smart meters are installed, iii) partly a different kind of wind turbines and solar panels are used in Germany. Our calculations suggest that all the electric energy, presently produced in Germany, can be obtained from wind-solar power alone. And our results let us predict that wind-solar power can be used to produce in addition the energy for transportation, warm water, space heating and in part for process heating, meaning an increase of the present electric energy production by a factor of about 5[1]. Of course, to put such a prediction on firm ground the present calculations have to be confirmed for a period of many years. And it should be kept in mind, that in any case a huge number of wind turbines and solar panels is required.

Electrolytes with high ionic diffusivity at temperatures distinctively lower than the presently used ones are the prerequisite for the success of, e. g., solid oxide fuel cells. We have found a promising structure having an asymmetric but superior ionic mobility in the direction of the oxygen-ion current. Using a layering of zirconium and yttrium in the fluorite structure of zirconia, a high vacancy concentration and a low migration barrier in two dimensions are obtained, while the mobility in the third direction is basically sacrificed. According to our density functional theory calculations an electrolyte made of this structure could operate at a temperature reduced by approximate to 200 degrees C. Thus a window to a different class of electrolytes has been flung open. In our structure the price paid is a more complicated manufacturing method.

In this paper a setup for detecting malfunctioning areas of MEAs in fuel cell stacks is described. Malfunctioning areas generate electric cross currents inside bipolar plates. To exploit this we suggest bipolar plates consisting not of two but of three layers. The third one is a highly conducting layer and segmented such that the cross currents move along the segments to the surface of the stack where they can be measured by an inductive sensor. With this information a realistic model can be used to detect the malfunctioning area. Furthermore the third layer will prevent any current inhomogeneity of a malfunctioning cell to spread to neighbouring cells in the stack. In this work the results of measurements in a realistic cell setup will be compared with the results obtained in simulation studies with the same configuration. The basis for the comparison is the reliable characterisation of the electrical properties of the cell components and the implication of these results into the simulation model. The experimental studies will also show the limits in the maximum number of segments, which can be used for a reliable detection of cross currents.

Na3PO4 is a well-known ionic conductor [1,2] and serves in this work as a starting point to investigate the solid solution Na3-xKxPO4with 0 ≤ x ≤ 3. The aim is to elucidate the impact of potassium ions on the physical properties: crystalline phases, band gaps, activation energies and ionic conductivities. Various compositions in this solid solution are synthesised by annealing the starting materials at 1200°C according to the Na3PO4-K3PO4phase diagram [3]. Then the crystalline phases, band gaps, activation energies and ionic conductivities are determined experimentally and measured. Using density functional theory [4] the ground state energies and band gaps are calculated for the various phases. Energy barriers are calculated for various paths of the cations Na+ and K+by using the nudged elastic band (NEB) method [5]. The theoretical and experimental results, especially the simulated energy barriers and the equivalent activation energies, are compared and discussed. We think that our approach can be applied to more complex solid electrolytes with polyanionic structures like NASICON [6,7]. References: [1] A. Hooper, P. McGeehin, K. T. Harrison, B. C. Tofield, J. Solid State Chem. 24 (1978) 265-275 [2] J. T. S. Irvine, A. R. West, Solid State Ionics 28-30 (1988) 214-219 [3] I. B. Markina, N. K. Voskresenskaya, Russ. J. Inorg. Chem. 14 (1969) 1188-1192 [4] P. E. Blöchl, Phys. Rev. B 50 (1994) 17953-17979 [5] G. Henkelman, B. P. Uberuaga, H. Jónsson, J. Chem. Phys. 113 (2000) 9901-9904 [6] H.Y.P. Hong, Mat. Res. Bull. 11 (1976) 173-182 [7] H.Y.P. Hong, J.B. Goodenough, J.A. Kafalas, Mat. Res. Bull. 11 (1976) 203-220

Optimization is essential in many scientific and economical areas, but it is often too complex to be tackled by simple straightforward calculations or by trial and error. Two well-known methods to find low-lying minima in such complex systems are simulated annealing and the genetic algorithm. In these methods artificial fluctuations control the probability of the system to overcome a local minimum having a certain depth. Here we present a complementary scheme that is based on the nudged-elastic-band method ordinarily used to find saddle points and we apply the scheme to find the most stable isomers of the phosphorus ${P}_{4}$, ${P}_{8}$ molecules and the corresponding molecules of $A{s}_{n}$, $S{b}_{n}$, and $B{i}_{n}$ ($n=4,8$) in the framework of the density functional theory. In the case of $n=8$ we have found stable and metastable configurations, some of which are new and have similar energies. As a by-product we obtained an upper bound for the energy barriers between these configurations.

This chapter presents a collection of extended abstracts that summarizes the latest research as presented at "Frontiers in Electronic Materials", a Nature conference on correlation effects and memristive phenomena, which took place in 2012. The abstracts include: direct observation of transient negative capacitance in domain wall of ferroelectric thin films; strontium titanate ultra-thin film capacitors on silicon substrates for application in dynamic random access memory (DRAM); enhancement of ferroelectric polarization by interface engineering; synthesis and characterization of nanostructured materials for removal of exhaust gases; band alignment engineering with liquid dielectrics; and the behaviour of oxygen vacancies in the perovskite oxide strontium titanate and at its extended defects. Controlled Vocabulary Terms ferroelectric materials; nanostructured materials; silicon

The LaAlO3/SrTiO3 interface provides an intriguing 2-dimensional electron system in which the coexistence of superconductivity and magnetism has been observed. This chapter presents preliminary results of ongoing angular dependent torque magnetometry measurements on SrTiO3-LaAlO3 heterostructures at different magnetic fields and temperatures. The authors have calculated the lattice thermal conductivity in layered oxide thermoelectric (TE) materials using perturbed molecular dynamics methods and tried to reveal the mechanisms of thermal conduction, thereby building up a strategy to control it. In order to achieve the next generation of nanometer sized electronic devices a detailed understanding and control of electrical transport is essential. The chapter reports on electronic transport measurements of biphenylpropanethiol (BP3) capped gold nanoparticles (AuNPs) with a diameter of 4 nm used as functional units. Controlled Vocabulary Terms electronic structure; lattice dynamics; magnetic fields; superconductivity

The role of electronic and ionic defects for the oxygen exchange reaction can nicely be studied on perovskite structured oxides ranging from semiconductors such as SrTiO3 to good electronic conductors such as (La,Sr)CoO3- δ. Strontium titanate (SrTiO3) is a perovskite-type transition metal oxide which exhibits insulating behavior, but can be reversibly switched into a conducting state by applying external voltage or current pulses. Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of solid oxide fuel cells (SOFC). Unlike traditional layered oxide based cathode materials for lithium-ion batteries, lithium and manganese rich oxide cathode materials form a structurally integrated nanocomposite of 2MnO3 and LiMO2 (where M=Co,Ni and Mn) by sharing a common oxide lattice. The chapter demonstrates that the lithium ion intercalation mechanism in these integrated cathodes is a complex process and the electrochemical performance of these cathode materials depends on various interrelated factors. Controlled Vocabulary Terms chemical exchanges; electrolytes; semiconductors; solid oxide fuel cells

It is well known that the already large dielectric constants of some electrolytes like BaTiO3 can be enhanced further by adding metallic (e.g. Ni, Cu or Ag) nanoparticles. The enhancement can be quite large, a factor of more than 1000 is possible. The consequences for the properties will be discussed in the present paper applying a brick-layer model (BLM) for calculating dc-resistivities of thin layers and a modified one (PBLM) that includes percolation for calculating dielectric properties of these materials. The PBLM results in an at least qualitative description and understanding of the physical phenomena: This model gives an explanation for the steep increase of the dielectric constant below the percolation threshold and why this increase is connected to a dramatic decrease of the breakdown voltage as well as the ability of storing electrical energy. We conclude that metallic electrolyte composites like BaTiO3 are not appropriate for energy storage.

Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of Solid Oxide Fuel Cells (SOFC). One promising candidate is doped zirconia. In the past its ionic conductivity has mainly been increased by decreasing its thickness. However, the influence of the thickness is only linear, whereas the impact of migration barriers is exponential. Therefore understanding the oxygen transport in doped zirconia is of fundamental importance. In this work we pursue the approach of the strain dependent ionic migration in zirconia. We investigate how the migration barriers for oxygen ions respond to a change of the atomic strain. We employ the method of Density Functional Theory (DFT) calculations to relax the atomic configurations to the ground state. In connection with the Nudged Elastic Band (NEB) method we obtain the migration barrier of the oxygen ion jumps in zirconia for a given lattice constant. Similar to other publications we observe a decrease in the migration barrier for expansive strain, but in addition we also find a migration barrier decrease for high compressive strains beyond a maximal height of the migration barrier at an intermediate compressive strain. We present a simple analytic model which, by using interactions of the Lennard-Jones type, gives an explanation for this behavior.

Accurate external measurements are required in tomographic problems to obtain a reasonable knowledge of the internal structures. Crucial is the distribution of the external measuring points. We suggest a procedure how to systematically optimize this distribution viz. to increase the precision (i.e. to shrink error bars) of the reconstruction by detecting the important and by eliminating the irrelevant measuring points. In a realistic numerical example we apply our scheme to magnetotomography of fuel cells. The result is striking: Starting from a smooth distribution of measuring points on a surface of a cuboid around the fuel cell, the number of measuring points can systematically be reduced by more than 90%. At the same time the precision increases by a factor of nearly 3.

A novel tomographic scheme for analysing the state of any single membrane electrode assembly (MEA) in a stack is suggested. Plates of very high conductivity placed between every fuel cell and slitted in an appropriate manner cause surface currents at well-defined locations of the stack. We show that knowing these surface currents, information about anomalies of the currents in a MEA can be obtained using the methods of tomography. The results are mathematically not unique. However, when assuming plausible defect structures, one can exclude improbable deficiencies by applying a special form of simulated annealing. We present numerical calculations of typical examples demonstrating that the essential defects of the MEA in any single cell of the stack can be detected and their extent can be determined. Copyright (C) 2009 John Wiley & Sons, Ltd.