Institutskolloquium des IPP 2016

Impact of renewable energy sources on electricity production

Europe is pursuing an aggressive programme to increase its share of renewable energy source (RES). However, the integration of intermittent RES (wind and photovoltaic) in the electrical system requires either maintaining in operation thermoelectric backup systems or providing a substantial amount of electricity storage. We analyze the Italian data for the year 2013 provided by the transmission system operator TERNA. Intermittent RES power is scaled-up to a level at which it generates an amount of electricity equal to the annual demand. While a substantial reduction of the energy annually produced by backup systems (and the associated CO2 emission) with respect to the no-RES case is possible in many scenarios considered here, the backup power is generally only marginally reduced below the value in the absence of RES. The strategy proposed is based on the combination of a modest amount of storage (0.5-5TWh) and base-load power (6-15GW, to be used during the seasons of low RES production). In this way the non-RES installed power can be reduced from ~50GW to less than 15GW and could be covered by a combination of biomasses and nuclear energy without any CO2 emission. [mehr]
The axisymmetric helical field of a tokamak leads to closed unperturbed particle orbits, thus arising as one of the most viable concepts for a fusion reactor. Orbit perturbations due to either Coulomb collisions or electromagnetic potential fluctuations ultimately determine the energy and particle confinement times. Macroscopic temperature and density profiles result from the balance of external sources and of the internally produced fusion power with the transport processes due to the aforementioned mechanisms. Thereby, the numerical design of a commercially viable tokamak fusion reactor requires integration of physics tools that describe both the fast/small scale processes and the slow/macroscopic evolution of the plasma profiles and the plasma shape. To this end, nowadays, progress in the theoretical description of the transport processes allows the application of increasingly realistic theory-based models. This also implies that any modeling activity should be performed keeping into account the assumptions and potential limitations of the models that are employed. In this talk, first a description of the logical coupling of the tools is given, clarifying the underlying physics of each piece of the system, from the small to the large spatial/temporal scales. Practical applications are then shown. These are based on the ASTRA-SPIDER transport/equilibrium package developed at IPP and in collaboration with TUAP (St. Petersburg), with inclusion of additional modules for turbulence-driven transport fluxes (e.g. TGLF, from General Atomics), and impurity particle transport (STRAHL, developed at IPP). Finally, an outlook is given on the open challenges in this research activity. [mehr]
"Planung, Aufbau und Betrieb der ersten ECRH - Anlage an ASDEX Upgrade " Fritz Leuterer "Electron heat transport studies with ECRH1: stiffness and critical gradient" Francois Ryter "Control of MHD instabilities by ECRH on ASDEX Upgrade" Hartmut Zohm "Co-existence of ECRH1 and ECRH2: W accumulation and high power experiments" Jörg Stober [mehr]
The steep gradients at the plasma edge in a tokamak result in Edge Localized Modes (ELMs), which when extrapolated to burning plasma conditions, will melt the first wall. In order to reduce the steep gradients to below the instability limit, resonant magnetic perturbation (RMPs), a 3D-field magnetic field perturbation are introduced. RMPs can succesfully suppress or mitigate ELMs through an increase in particle transport. In this presentation, I will first address how RMPs affect the magnetic topology at the plasma edge and whether this change in topology can explain the observed changes in particle transport and confinement. Next, I will discuss, how inadvertently RMPs also increase particle transport in the plasma core, which affect global confinement and the ultimate fusion gain factor. [mehr]

Global deposition of radioactive nuclides from the most recent near-Earth supernovae

A two million year old signal of 60Fe was detected in several terrestrial deep-sea archives and in lunar samples. This long-lived isotope is not produced on Earth, however, it is generated in massive stars and ejected during supernova explosions. The recent injection of 60Fe into the solar system coincides with the formation of the Local Bubble - a large cavity in the interstellar medium produced by multiple supernovae - into which our solar system is embedded. The most likely sources are stellar explosions within a moving group that passed the solar neighborhood, and whose surviving members are now in the Sco-Cen association. We have traced the trajectories of the member stars back in time and calculated the most probable explosion sites of the perished stars. By determining their masses and explosion times, we found a sequence of supernovae starting 13 Myr ago. With analytical and numerical methods we modeled the Local Bubble and, as a consequence of its formation, the terrestrial 60Fe signature. Similar calculations with another long-lived radionuclide, 26Al, show only a marginal supernova-signal. Accelerator mass spectrometry measurements of 26Al within samples of four deep-sea sediment cores from the Indian Ocean confirm this result. The data decreases exponentially towards larger depths as expected from 26Al produced in the Earth's atmosphere, which hides a contribution from nearby supernovae. [mehr]

Die Macht der Sprache

Mit unserer Sprache beschreiben wir unsere Wirklichkeit. Was wir benennen ist auch vorhanden. Für was wir kein Wort haben, kann sich auch unser Hirn schlecht vorstellen. Unser Sprachgebrauch ist Teil unserer Wirklichkeit und sie beeinflusst unsere Wahrnehmung. Soweit die Sprachphilosophie. [mehr]

Connectomics: The dense reconstruction of neuronal networks

Brains are highly interconnected networks of millions to billions of neurons. For a century, we have not been able to map these connectivity networks. Only recently, using novel electron microscopy techniques and machine-learning based data analysis, the mapping of neuronal networks has become possible at a larger scale. This new field of connectomics is still limited by technology and requires next-generation human-machine interaction for data analysis, but it is already starting to provide exciting insights into how neuronal circuits operate in the brain. Our goal is to make connectomics a high-throughput screening technique for neuroscience, to use connectomes for discovering brain-implemented algorithms, which may inspire novel machine learning, to map the imprints of sensory experience onto neuronal networks in the brain, and to investigate connectome alterations in models of psychiatric disease. [mehr]

Direct observation of gravitational waves from the merger and inspiral of two black holes

This talk follows the annoucement made on February 11th by the LIGO Scientific Collaboration. On September 14, 2015, we detected the gravitational waves emitted by the final few orbits and merger of two black holes. In this talk, I present the main results, as well as some of the "behind the scenes" details of the discovery and subsequent analysis. Reference: P. Abbott et al., Phys. Rev. Lett. 116, 061102, 2016. [mehr]

Wird die deutsche „Energiewende“ scheitern?

Die Bundesregierung versucht, mit Hilfe von Solar-und Windenergie eine alternative Stromversorgung zu Kernenergie und Kohleverstromung zu schaffen. Dazu dient das „Erneuerbare-Energien-Gesetz EEG“ aus dem Jahre 2000. Hinzu kam der 2011 im Eiltempo beschlossene Ausstieg aus der Nutzung der Kernenergie. Jetzt zeigt sich, dass die „Wende“ große Risiken bei der Versorgungssicherheit, der Finanzierbarkeit, den Auswirkungen auf die wirtschaftliche Entwicklung und die soziale Gerechtigkeit birgt. Diese Wende droht an ihren Widersprüchen zu scheitern. Selbst der zuständige Bundesminister für Wirtschaft und Energie, Sigmar Gabriel, äußerte im April 2014: “Die Wahrheit ist, dass die Energiewende kurz vor dem Scheitern steht.” Im Vortrag wird versucht, die Probleme zu benennen und Lösungen zu finden. Die Energieversorgung muss dem Wohl des Ganzen dienen und dem Industriestandort Deutschland nutzen. Ein Blackout wäre eine Katastrophe für das ganze Land, er muss unter allen Umständen vermieden werden. Der Vortragende ist Autor des Buches „Risiko Energiewende - Wege aus der Sackgasse“, Springer Verlag 2015. [mehr]

Efficient CO2 reduction in microwave plasma via vibrational excitation

IPP Kolloquium: Institutskolloquium
Sustainable energy generation by means of wind or from solar radiation through photovoltaics or concentrated solar power will be a significant part of the energy mix in 2025. Intermittency (due to e.g. day/night cycle) as well as regional variation of these energy sources requires means to store and transport energy on a large scale. A promising option is creating artificial solar fuels (or CO2 neutral fuels) with sustainable energy, which can easily be deployed within the present infrastructure for conventional fossil fuels. A candidate raw material would be CO2 itself (fitting in carbon capture and utilization, CCU, strategies). Presently, no efficient schemes are yet available for the conversion of CO2 into fuels. A plasma chemical approach potentially offers high energy efficiency (up to 90%) due to selectivity in the reaction processes that can be tailored via its inherently strong out-of-equilibrium processing conditions. At the same time, it is characterized by efficient and fast power switching, low investment costs, no scarce materials required, and high power density, which are all advantageous for addressing intermittency. In this presentation, the plasma chemical approach will be introduced and examples will be discussed of research carried out at the DIFFER to ultimately enable a scale up to industrial applications. In particular, a common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures (up to ~3000 K) and conversion degrees (up to 30%), respectively. The results are interpreted on basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favorable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry still to dominate the initial experiments. Pulsing the power is shown to decrease gas temperatures and improve efficiency. Novel reactor approaches are proposed to tailor the plasma dynamics to achieve the non-equilibrium in which vibrational excitation is dominant. [mehr]
Eine der Kernfragen der Sozialwissenschaften besteht in der Erklärung der ungeheuren wirtschaftlichen Dynamik, die sich seit dem Beginn der Industrialisierung im späten 18. Jahrhundert entfaltet. In meinem Vortrag zeige ich, dass die Orientierung an einer als offen aber auch mit Risiken behafteten Zukunft ein wichtiger Aspekt der Dynamik des Kapitalismus ist. Anhand von Innovationsprojekten und Beispielen aus anderen Bereichen wirtschaftlichen Handelns verdeutlicht der Vortrag, welche Rolle imaginierte Zukünfte für wirtschaftliches Wachstum aber auch für wirtschaftliche Krisen spielen. [mehr]

En route to electron/positron pair plasmas

The large mass imbalance between ions andelectrons — and the resulting separation of the two species’ length and timescales — is a cornerstone of traditional plasma physics.  Therefore, to consider the novel behavior ofa “pair plasma”, comprising particles with opposite charge but equal mass, isto revisit much of plasma physics from the ground up.  To date, over a thousand journal articleshave been devoted to this topic, describing a variety of analytical andcomputational treatments, but the experimental side of the investigation isstill in its nascence.  Laboratorycreation and confinement of electron/positron plasmas would enable the firsttests of many theory and simulation predictions (e.g., the stabilization ofanomalous transport mechanisms), with implications for our understanding notonly of pair plasmas (and astrophysical phenomena in which they play a role)but also of traditional electron/ion plasmas. This is the goal of the APEX/PAX (APositron-Electron eXperiment/PositronAccumulation eXperiment) project, in which a world-class positron beam(NEPOMUC, at FRM-II) is being combined with state-of-the-art techniques fromnon-neutral plasma physics.  This talkwill give an overview of milestones achieved in the past several years,including the demonstration of efficient ExB injection and subsequentconfinement (τ = 3-5 ms) of cold positrons in a dipole magnetic field, as wellas the upcoming upgrade from a supported permanent magnet to a supported HTSC(high-temperature superconductor) coil, then to a levitated HTSC coil suitablefor the simultaneous confinement of electrons and positrons. [mehr]

Transition to Darwinian evolution - towards the origin of the very first species

The concept of Darwinian evolution relies on vertical gene transfer from one generation to the next. Such evolution brings about ever more species that originated from a universal common ancestor, the very first species. In contrast, it is hypothesized that in the era just before that species existed, life was fundamentally collective with genetic material freely shared through massive horizontal gene transfer (HGT). How did the era of collective evolution come to an end and start the Darwinian era we live in today? Here we propose a stochastic model dynamics that offers a fundamental mechanism for such a way out of collective evolution. The model suggests that HGT-dominated dynamics may have been intermittently interrupted by selection-driven processes during which genotypes became fitter and decreased their inclination towards HGT. Stochastic switching in the population dynamics with three-point (hypernetwork) interactions may have destabilized the HGT-dominated collective state and essentially contributed to the emergence of vertical descent and the first well-defined species in early evolution. A systematic nonlinear analysis of the stochastic model dynamics supports this view. Our findings thus suggest a viable direction out of early collective evolution, potentially enabling the start of individuality and vertical Darwinian evolution. [mehr]
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