124 research outputs found
Economic and Non-Economic Barriers and Drivers for the Uptake of Renewables
This is the final versionLarge scale renewables raise new challenges and provide new opportunities across electricity systems. This paper considers the barriers faced by large scale renewables in electricity systems in Sub-Saharan Africa and South Asia. We review the current state of knowledge in relation to grid-connected renewables. This paper then explores key issues in electricity system structure, the main challenges to the uptake of renewables, and the various existing fiscal and policy approaches to encouraging renewables. The authors also highlight possible ways moving forward to ensure more widespread renewables deployment. This research was supported by the UK Department for International Development’s Energy and Economic Growth Applied Research Programme.The Applied Research Programme on Energy and Economic Growth (EEG) is led by Oxford Policy
Management in partnership with the Center for Effective Global Action and the Energy Institute @ Haas at the
University of California, Berkeley. The programme is funded by the UK Government, through UK Aid
Regeneration of Stochastic Processes: An Inverse Method
We propose a novel inverse method that utilizes a set of data to construct a
simple equation that governs the stochastic process for which the data have
been measured, hence enabling us to reconstruct the stochastic process. As an
example, we analyze the stochasticity in the beat-to-beat fluctuations in the
heart rates of healthy subjects as well as those with congestive heart failure.
The inverse method provides a novel technique for distinguishing the two
classes of subjects in terms of a drift and a diffusion coefficients which
behave completely differently for the two classes of subjects, hence
potentially providing a novel diagnostic tool for distinguishing healthy
subjects from those with congestive heart failure, even at the early stages of
the disease development.Comment: 5 pages, two columns, 7 figs. to appear, The European Physical
Journal B (2006
Stochastic analysis of different rough surfaces
This paper shows in detail the application of a new stochastic approach for
the characterization of surface height profiles, which is based on the theory
of Markov processes. With this analysis we achieve a characterization of the
scale dependent complexity of surface roughness by means of a Fokker-Planck or
Langevin equation, providing the complete stochastic information of multiscale
joint probabilities. The method is applied to several surfaces with different
properties, for the purpose of showing the utility of this method in more
details. In particular we show the evidence of Markov properties, and we
estimate the parameters of the Fokker-Planck equation by pure, parameter-free
data analysis. The resulting Fokker-Planck equations are verified by numerical
reconstruction of conditional probability density functions. The results are
compared with those from the analysis of multi-affine and extended multi-affine
scaling properties which is often used for surface topographies. The different
surface structures analysed here show in details advantages and disadvantages
of these methods.Comment: Minor text changes to be identical with the published versio
Statistical Derivation of the Evolution Equation of Liquid Water Path Fluctuations in Clouds
How to distinguish and quantify deterministic and random influences on the
statistics of turbulence data in meteorology cases is discussed from first
principles. Liquid water path (LWP) changes in clouds, as retrieved from radio
signals, upon different delay times, can be regarded as a stochastic Markov
process. A detrended fluctuation analysis method indicates the existence of
long range time correlations. The Fokker-Planck equation which models very
precisely the LWP empirical probability distributions, in
particular, their non-Gaussian heavy tails is explicitly derived and written in
terms of a drift and a diffusion coefficient. Furthermore, Kramers-Moyal
coefficients, as estimated from the empirical data, are found to be in good
agreement with their first principle derivation. Finally, the equivalent
Langevin equation is written for the LWP increments themselves. Thus rather
than the existence of hierarchical structures, like an energy cascade process,
{\it strong correlations} on different , from small to large
ones, are considered to be proven as intrinsic ingredients of such cloud
evolutions.Comment: 17 pages, 6 figures; to be published in Journal of Geophysical
Research - Atmosphere
Flow equations for Hamiltonians: Contrasting different approaches by using a numerically solvable model
To contrast different generators for flow equations for Hamiltonians and to
discuss the dependence of physical quantities on unitarily equivalent, but
effectively different initial Hamiltonians, a numerically solvable model is
considered which is structurally similar to impurity models. By this we discuss
the question of optimization for the first time. A general truncation scheme is
established that produces good results for the Hamiltonian flow as well as for
the operator flow. Nevertheless, it is also pointed out that a systematic and
feasible scheme for the operator flow on the operator level is missing. For
this, an explicit analysis of the operator flow is given for the first time. We
observe that truncation of the series of the observable flow after the linear
or bilinear terms does not yield satisfactory results for the entire parameter
regime as - especially close to resonances - even high orders of the exact
series expansion carry considerable weight.Comment: 25 pages, 10 figure
Functional renormalization group approach to zero-dimensional interacting systems
We apply the functional renormalization group method to the calculation of
dynamical properties of zero-dimensional interacting quantum systems. As case
studies we discuss the anharmonic oscillator and the single impurity Anderson
model. We truncate the hierarchy of flow equations such that the results are at
least correct up to second order perturbation theory in the coupling. For the
anharmonic oscillator energies and spectra obtained within two different
functional renormalization group schemes are compared to numerically exact
results, perturbation theory, and the mean field approximation. Even at large
coupling the results obtained using the functional renormalization group agree
quite well with the numerical exact solution. The better of the two schemes is
used to calculate spectra of the single impurity Anderson model, which then are
compared to the results of perturbation theory and the numerical
renormalization group. For small to intermediate couplings the functional
renormalization group gives results which are close to the ones obtained using
the very accurate numerical renormalization group method. In particulare the
low-energy scale (Kondo temperature) extracted from the functional
renormalization group results shows the expected behavior.Comment: 22 pages, 8 figures include
Solar Energy: Incentives to Promote PV in EU27
The growth in the use of renewable energies in the EU has been remarkable. Among these energies is PV. The average annual growth rate for the EU-27 countries in installed PV capacity in the period 2005-2012 was 41.2%. While the installed capacity of PV has reached almost 82 % of National Renewable Energy Action Plan (NREAP) targets for the EU-27 countries for 2020, it is still far from being used at its full potential. Over recent years, several measures have been adopted in the EU to enhance and promote PV. This paper undertakes a complete review of the state of PV power in Europe and the measures taken to date to promote it in EU-27. 25 countries have adopted measures to promote PV. The most widespread measure to promote PV use is Feed- in Tariffs. Tariffs are normally adjusted, in a decreasing manner, annually. Nevertheless, currently, seven countries have decided to accelerate this decrease rate in view of cost reduction of the installations and of higher efficiencies. The second instrument used to promote PV in the EU-27 countries is the concession of subsidies. Nevertheless, subsidies have the disadvantage of being closely linked to budgetary resources and therefore to budgetary constraints. In most EU countries, subsidies for renewable energy for PV are being lowered. Twelve EU-27 countries adopted tax measures. Low-interest loans and green certificate systems were only sparingly used
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