August Wierling

Høgskulen på Vestlandet | HVL · Department for Engineering and Natural Sciences

This paper examines the emergence of 1072 solar initiatives (268 associations and 804 cooperatives operating photovoltaic systems) from 2006 to 2018 in Germany. The study draws on organizational ecology theory to identify factors that influence the likelihood of establishing a solar initiative by investigating the impacts of two opposing effects: l...

Energy communities (ECs) are emerging as vital contributors to the United Nations' Sustainable Development Goals, despite being unnoticed. This article is the first to comprehensively discuss and quantify European citizen-led energy initiatives' contributions to SDGs 7 (ensure access to affordable and clean energy), 9 (fostering industry, innovatio...

Submitted to peer review. Abstract: We scrutinize widely-used, distinct methods to set city-level climate goals: Deadline 2020, One Planet City Challenge, and Tyndall Local Carbon Budget Tool. Through meticulous verification and validation of data input, calculation processes, and documentation, the exercise assesses whether the methods are fit-fo...

Climate change affects patterns and uncertainties associated with river water regimes, which significantly impact hydropower generation and reservoir storage operation. Hence, reliable and accurate short-term inflow forecasting is vital to face climate effects better and improve hydropower scheduling performance. This paper proposes a Causal Variat...

Statistical accounting of the impacts of citizen-led energy initiatives is absent, despite their impact on increased energy self-sufficiency and ramping up of renewable energies, local sustainable development, greater citizen engagement, diversification of activities, social innovation, and acceptance of transition measures. This paper quantifies t...

Numerous case studies show that citizens engage in various ways in renewable and low carbon energy projects, thereby contributing to the sustainable energy transition. To date, however, a systematic and cross-country database on citizen-led initiatives and projects is lacking. By performing a major compilation and reviewing copious data sources fro...

The digitalization of the energy sector is in progress, but Europe is about to fall behind. A human-centered design approach ensures that it takes place with, and for the benefit of, people, for which this letter puts forward policy recommendations. People need access to tailored and ready-for-use tools that help the realization of societal co-bene...

Energy markets have opened up to new actors and business models. We perform an empirical investigation of energy cooperatives (EC) investing in the photo-voltaic (PV) market. Deploying a unique database for Germany with 584 EC covering two decades of activities, we provide statistical evidence on their businesses, members and customer segments, pro...

It is essential to have accurate and reliable daily-inflow forecasting to improve short-term hydropower scheduling. This paper proposes a Causal multivariate Empirical mode Decomposition (CED) framework as a complementary pre-processing step for a day-ahead inflow forecasting problem. The idea behind CED is combining physics-based causal inference...

Statistical accounting of the impacts of citizen-led energy initiatives is absent. This paper quantifies the aggregate contributions of collective action in pursuit of the sustainable energy transition in Europe. We estimate the number of initiatives (10,540), projects (22,830), people involved (2,010,600), installed renewable capacities (7.2-9.9 G...

We confront empirical data on citizen-led renewable energy capacities in Poland with results obtained from a meta-theoretical, empirical analysis of the national energy system. We elicit and rank essential disabling and enabling factors that explain the current low level of citizen energy in Poland. Altogether, we estimate the contributions of indi...

With the continued digitization of the energy sector, the problem of sunken scholarly data investments and forgone opportunities of harvesting existing data is exacerbating. It compounds the problem that the reproduction of knowledge is incomplete, impeding the transparency of sciencebased targets for the choices made in the energy transition. The...

With the continued digitization of the energy sector, the problem of sunken scholarly data investments and forgone opportunities of harvesting existing data is exacerbating. It adds to the problem that the reproduction of knowledge is incomplete, impeding the transparency of science-based evidence for the choices made in the energy transition. We c...

The principles of Findability, Accessibility, Interoperability, and Reusability (FAIR) have been put forward to guide optimal sharing of data. The potential for industrial and social innovation is vast. Domain-specific metadata standards are crucial in this context, but are widely missing in the energy sector. This report provides a collaborative r...

We present preliminary estimates for the contribution of collective prosumers to the energy transition across Europe. Drawing from the COMETS inventory, we report country-level and EU-level aggregates for current total numbers of initiatives and their historic evolution, the fields of engagement, the number of people involved, renewable capacities...

Energy communities (EC) are among the new actors in the energy market, playing an important role in the uptake of photovoltaics (PV) in European markets. This paper estimates their aggregate contribution to the low-carbon energy transition in terms of installed capacities for PV and evaluates their economic performance comparing with market prices....

The overall objective of this contribution is to investigate Collective Action Initiatives (CAIs) in the energy sector (e.g. energy communities, cooperatives and purchasing groups) as a trigger for the implementation of a strong sustainability paradigm. The assumption is that the active involvement of citizens in the energy chain is a crucial requi...

Broad acceptance by and support from the society for the sustainable energy transition is indispensable. Public participation and ownership-in particular through collective action initiatives-is seen as a means to foster this support. Starting with the origin of the cooperative model, we present how it has been evolving until today. We then discuss...

This conceptual paper applies a mobilization model to Collective Action Initiatives (CAIs) in the energy sector. The goal is to synthesize aspects of sustainable transition theories with social movement theory to gain insights into how CAIs mobilize to bring about niche-regime change in the context of the sustainable energy transition. First, we de...

The moral imperatives of sustainable development

The share of renewable energy is increasing throughout Europe. Yet, little is known about how much can be attributed to different actors, other than those commercially active. This paper provides empirical evidence of activities by energy cooperatives in the field of renewable energy in four different European countries. It draws from a database co...

The drive to expand renewable energies is often in direct conflict with sustainable development goals. Thus, it is important that energy policies account for potential trade-offs. We assess the interlinkages between energy, food, water and land, for two case studies, Okinawa and Sogn og Fjordane. We apply a range of assessment methods and study the...

The chapter is the introduction to our latest book: "The Imperatives of Sustainable Development: Needs, Justice, Limits" (Routledge, 2017). The book is available at https://www.routledge.com/sustainability

Thirty years ago, the UN report Our Common Future placed sustainable development firmly on the international agenda. The Imperatives of Sustainable Development takes the ethical foundations of Our Common Future and builds a model that emphasizes three equally important moral imperatives – satisfying human needs, ensuring social justice, and respect...

Abstract Data available from the recent boom in European offshore wind investments contradict widely held expectations about a decline in costs per kW. Our review shows that scenario projections for investment costs are systematically flawed by over-optimistic assumptions. Contrasting offshore wind technology with onshore wind and nuclear power, we...

We present results for the Lyman-α line of hydrogen in dense plasmas. Full line profiles are calculated within a quantum-statistical method, based on thermodynamic Green's functions. The contributions of plasma ions and electrons are considered separately. Linear and quadratic Stark effect as well as quadrupole effects are taken into account for io...

The recurrance relation method is employed to determine the dynamic structure factor for the single harmonic oscillator and a linear chain of harmonic oscillators. Approximative schemes based on this approach are proposed. Comparison is made with exactly known results (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An approximation for the dynamic structure factor S(q, ω) of the linear harmonic chain with periodic boundary conditions is obtained from a recurrence relation approach. It is compared with (numerically) exact results for S(q, ω). Explicit expressions for the moments of the structure factor are obtained from the short time expansion up to order n =...

Pressure broadening of Lyman-lines of hydrogen-like lithium (Li2+) has been studied using a quantum statistical approach to the line shape in dense plasmas, for details see [1]. In this communication, we concentrate on the electronic self-energy, which is a basic input to the theory of spectral line profiles. We discuss the effect of strong, i.e. c...

We re-examine several Balmer spectra obtained from high-pressure arc discharges (Radtke and Günther, Contrib. Plasma Phys. 26, 143 (1986); Radtke, Günther, and Spanke, ibid. 26, 151 (1986)). By matching synthetic spectra to the experimental line profiles, we infer plasma parameters such as density, temperature, and composition. Spectral line modeli...

The wave-number k dependent current-correlation function is considered for a harmonic oscillator model. An explicit analytic expression for the Laplace transformed correlation function is derived. It is compared with numerical solutions and results obtained by the recurrence relation method. Several limiting cases such as the long-wavelength limit...

The electronic self-energy {Sigma}{sup e} is an important input in a quantum-statistical theory for spectral line profile calculations. It describes the influence of plasma electrons on bound state properties. In dense plasmas, the effect of strong, i.e. close, electron-emitter collisions can be considered by three-particle T-matrix diagrams. These...

The dynamic structure factor, which determines the Thomson scattering spectrum, is calculated via an extended Mermin approach. It incorporates the dynamical collision frequency as well as the local-field correction factor. This allows to study systematically the impact of electron-ion collisions as well as electron-electron correlations due to dege...

Plasma corrections to reaction rates for deuteriumburning in brown dwarfs and low-mass stars are revisited. A quantum-statistical approach is outlined. With the help of thermo-dynamic Green's functions, many-body and quantum effects are systematically taken into account. Specifically, the relevance of dynamical screening as well as degeneracy effec...

Based on a generalized linear response theory the dielectric function has been calculated via a generalized DRUDE formula with the dynamical collision frequency in different approximations. We apply these expressions for the dielectric function to latest experimental data on the reflectivity of a Xe-plasma under oblique incidence in extension to ea...

Two approaches to the dynamic local field correction for two-component plasmas are combined with each other. In the first one, we start from the Zubarev approach to linear response theory and use perturbative techniques such as thermodynamic Green's functions. Via this approach, we obtain an approximation for the dynamical collision frequency. In a...

Radiation hydrodynamics of laser-induced plasmas is usually treated by well-established hydrodynamic codes such as MEDUSA or MULTI, which require transport coefficients as inputs. Here, we present results for a hydrodynamical calculation taking advanced expressions for the collision frequency. In this way we generalize the Spitzer-Härm-like express...

In non-ideal plasmas, the dielectric function has to be treated beyond the random phase approximation. Correlations as well as collisions have to be included. These corrections are known as (dynamical) local field corrections. Based on the Zubarev approach to linear response theory, a relaxation time approximation is proposed leading to an interpol...

We present an approximation scheme for the dielectric response of thermal collisionless plasmas at arbitrary degeneracy. A T-fraction representation is obtained from the known expansions of the real part of the dielectric function for small and large arguments. The partial numerators and denominators of the continued fraction are generated by a mod...

In non-ideal plasmas, the dielectric function has to be treated beyond the random phase approximation. Correlations and well as collisions have to be included. These corrections are known as (dynamical) local field corrections. With the help of the Zubarev approach to linear response theory, a relaxation time approximation is proposed leading to an...

We report the creation of solid-density aluminum plasma using free-electron laser (FEL) radiation at 13.5nm wavelength. Ultrashort pulses were focused on a bulk Al target, yielding an intensity of 2x10;{14}Wcm;{2} . The radiation emitted from the plasma was measured using an xuv spectrometer. Bremsstrahlung and line intensity ratios yield consisten...

Pressure broadening of Lyman-lines of hydrogen-like lithium is studied using a quantum statistical approach to the line shape in dense plasmas. We report line widths (FWHM) and shifts for Lα, Lβ, and Lγ in a wide range of densities and temperatures relevant for laser-produced lithium plasmas. We estimate the influence of ion dynamics and strong col...

Collective Thomson scattering with extreme ultraviolet light or x rays is shown to allow for a robust measurement of the free electron density in dense plasmas. Collective excitations like plasmons appear as maxima in the scattering signal. Their frequency position can directly be related to the free electron density. The range of applicability of...

Bremsstrahlung is the predominant process of emission and absorption in a hot and dense plasma. The influence of correlations on the bremsstrahlung is of fundamental interest for plasma diagnostics. Dealing with dense and strongly correlated systems, classical formulae, such as Kramers’ expression for the emissivity are improved; the correcting Gau...

Summary form only given. Bremsstrahlung is the predominant process of emission and absorption in a hot and dense plasma. The knowledge of its spectral properties is of fundamental interest for plasma diagnostics. Dealing with dense and strongly correlated systems, classical formulas, such as Kramers' expression for the emissivity are improved: the...

A basic concept to calculate physical features of non-ideal plasmas, such as optical properties, is the spectral function which is linked to the self-energy. We calculate the spectral function for a non-relativistic hydrogen plasma in GW -approximation. In order to go beyond GW approximation, we include self-energy and vertex correction to the pola...

The interpretation of hydrogen Balmer spectra emitted from a high-pressure arc discharge (Radtke and Günther, Contrib. Plasma Phys. 26, 143 (1986)) is re-examined. Assuming local thermodynamic equilibrium, synthetic Balmer spectra are calculated for given temperature and density conditions. Radiation transport is accounted for using a one-dimension...

Shift and broadening of isolated neutral helium lines 7281 angstroms (2(1)P-3(1)S), 7065 angstroms (2(3)P-3(3)S), 6678 angstroms (2(1)P-3(1)D), 5048 angstroms (2(1)P-4(1)S), 4922 angstroms (2(1)P-4(1)D), and 4713 angstroms (2(3)P-4(3)S) in a dense plasma are investigated. Based on a quantum statistical theory, the electronic contributions to the sh...

New results for the reflection coefficient of shock-compressed dense xenon plasmas at pressures of 1.6–20 GPa and temperatures around 30 000 K are interpreted. Reflectivities typical of metallic systems are found at high densities. A consistent description of the measured reflectivities is achieved if a finite width of the shock wave front is consi...

Brilliance spectra of a carbon plasma generated by subpicosecond high intensity laser pulses are analysed (Wilhein et al 1998 J. Opt. Soc. Am. 15 1235). The plasma parameters such as electron density and temperature are determined using a plasma slab model. Synthetic carbon He-α and He-β line profiles are calculated for the inferred plasma paramete...

We determine the spectral photon yield from a hot dense plasma irradiated by VUV-FEL light in a Thomson scattering experiment. The Thomson signal is compared to the emission background mainly caused by bremsstrahlung photons. We determine experimental conditions that allow for a signal-to-background ratio larger than unity. By derivation of the Tho...

Experiences investigating the dynamic structure factor of dense plasmas are applied to complex plasmas, in particular to dusty plasmas and dimensionally reduced plasmas. Using generalized linear response theory, the dynamical structure factor is obtained from a density response function expressed in terms of equilibrium correlation function. Correc...

Shift and broadening of isolated neutral helium lines 7281Å (21P − 31S), 6678 Å (21P − 31D), and 4713 Å (23P − 43S) in a dense plasma are investigated. Based on a quantum statistical theory using thermodynamic Green's functions, where the electronic contributions to the shift and width are considered. Dynamical screening of the electron-atom intera...

The optical conductivity sigma (omega) for dense Coulomb systems is investigated using molecular dynamics simulations on the basis of pseudopotentials to mimic quantum effects. Starting from linear response theory, the response in the long-wavelength limit k=0 can be expressed by different types of autocorrelation functions (ACF's) such as the curr...

The suppression of the bremsstrahlung cross section due to multiple scattering of the emitting electrons is an important effect in dense media (Landau-Pomeranchuk-Migdal effect). Here, we study the emission from a dense, fully-ionized and non-relativistic hydrogen plasma. Using the dielectric approach, we relate optical properties such as emission...

The emission coefficient due to classical electron–ion bremsstrahlung is calculated for a non-ideal plasma with an effective interaction. An approach due to Gould is used to obtain the emission coefficient for bremsstrahlung. It is shown that this result can also be derived from an approximation to the force–force correlation function assuming no c...

Results for the reflection coefficient of shock-compressed dense xenon plasmas at pressures of 1.6–20 GPa and temperatures around 30 000 K are interpreted. In addition to former experiments using laser beams with λ = 1.06 µm, measurements at λ = 0.694 µm have been performed recently. Reflectivities typical for metallic systems are found at high den...

Starting from a generalized response theory, the inverse response function can be expressed in terms of equilibrium correlation functions for which a perturbation expansion is carried out. In the long-wavelength limit, this can be exploited to obtain an approximation for the dynamic collision frequency. Utilizing the Mermin ansatz, the dynamical st...

Experimental results for the reflection coefficient of shock-compressed dense Xenon plasmas at pressures of 1.6 - 17 GPa and temperatures around 30 000 K using a laser beam with \lambda = 1.06 10^-6 m are compared with calculations based on different theoretical approaches to the dynamical collision frequency. It is found that a reasonable descript...

The dynamic structure factor of one-component plasmas at moderate coupling (Gamma=0.5-8) is studied analytically and by molecular dynamics simulations. The recurrence relation technique is used to derive a parameterization of the dynamic structure factor taking into account analytically accessible moments. These moments are calculated from the pair...

The Mermin dielectric function is extended by including energy conservation. Within the framework of the relaxation time ansatz, the Zubarev approach to linear response theory is used which allows to incorporate the exact Hamiltonian dynamics of the relevant degrees of freedom. Analytical expressions for the dielectric function in the entire (k, w)...

Analytical results for the structure factor of a two-component model plasma that describe an electron-ion plasma with modified interaction are derived from a Green function approach in different approximations. The random-phase approximation is improved by including the dynamic collision frequency, and results for the long-wavelength limit are exte...

The free–free absorption coefficient for radiation in hot, weakly coupled plasmas is determined from a systematic approach to the dynamical conductivity. Based on a generalized linear-response theory, it is expressed in terms of determinants of equilibrium correlation functions permitting a perturbative treatment. Within a Gould–DeWitt-type approac...

The electron capture rate by 7Be is reexamined. Starting from a quantum statistical expression for the capture rate, dynamical screening effects are taken into account. Corrections on the single-particle level are determined by a self-consistent calculation of the electron spectral function. Two-particle corrections are treated by a dynamical T-mat...

The interpretation of a measured x-ray spectrum from a carbon plasma induced by subpicosecond laser pulses [Wilhein, T., et al., J. Opt. Soc. Am. B 15, 1235 (1998)] is reexamined. We calculate a synthetic Lyman spectrum emitted from a plasma layer at a given temperature and density, using a microscopic approach to the line shape in dense, non-ideal...

The absorption coeffient for radiation in hot and dense plasmas is determined from a systematix approach to the dynamical conductivity. Based on a generalized linear-response theory it is expressed in terms of determinants of equilibrium correlation functions. Within a generalized Gould-DeWitt approach dynamical screening is a counted for by a part...

Starting from a quantum statistical approach, general expressions are given for the shape of spectral lines in dense plasmas. Special attention is paid to the dynamical treatment of the ionic microfield. As an example for the application of the theory of line profiles, the diagnostics of short-pulse laser induced plasmas is considered.

Recently, the study of low frequency modes in dusty plasmas has attracted much attention. Because of the high charge of the macro-particles, interaction effects play a dominant role, leading to a solid-like state with long range order. Under these conditions, dust lattice waves (DLW) are expected to occur as excitations of the ordered crystal-like...

This chapter proposes an expression for the dynamical structure factor, which accounts for collisions and is based on generalized linear response theory. For high values of the coupling parameter, dust grains in a dusty plasma exhibit a solid-state like structure with long range order. Whereas for small values of coupling parameter, a perturbative...

A systematic approach to the optical conductivity is given within a dielectric function formalism. The response function as well as the dynamical local-field factor G(k-->,omega) of an electron-ion plasma can be expressed in terms of determinants of equilibrium correlation functions which allow for a perturbative treatment. The dynamical collision...