1,720,995 research outputs found
Strategic decision-making on low-carbon technology and network capacity investments using game theory
Full text linkIn recent years, renewable energy technologies have been increasingly adopted and seen as
key to humanity’s efforts to reduce greenhouse gases emissions and combat climate change.
Yet, a side effect is that renewables have reached high penetration rates in many areas,
leading to undesired curtailment, especially if existing grid infrastructure is insufficient and
renewable energy generated cannot be exported at areas of high energy demand. The issue
of curtailment is compelling at remote areas, where renewable resources are abundant,
such as in windy islands. Not only renewable production is wasted, but often curtailment
comes with high costs for renewable energy developers and energy end-users. In fact,
procedures on how generators access the grid and how curtailment is applied, are key
factors that affect the decisions of investors about generation and grid capacity installed.
Part of this thesis studies the properties of widely used curtailment rules, applied in
several countries including the UK, and their effect on strategic interactions between self-interested and profit-maximising low-carbon technology investors. The work develops a
game-theoretic framework to study the effects of curtailment on the profitability of existing
renewable projects and future developments. More specifically, work presented in this
thesis determines the upper bounds of tolerable curtailment at a given location that allows
for profitable investments. Moreover, the work studies the effect of various curtailment
strategies on the capacity factor of renewable generators and the effects of renewable
resource spatial correlation on the resulting curtailment. In fact, power network operators
face a significant knowledge gap about how to implement curtailment rules that achieve
desired operational objectives, but at the same time minimise disruption and economic
losses for renewable generators. In this context, this thesis shows that fairness and equal
sharing of imposed curtailment among generators is important to achieve maximisation of
the renewable generation capacity installed at a certain area. A new rule is proposed that
minimises disruption and the number of curtailment events a generator needs to respond
to, while achieving fair allocation of curtailment between generators of unequal ratings.
While curtailment can be reduced by smart grid techniques, a long term solution is
increasing the network capacity. Grid reinforcements, however, are expensive and costs
weight to all energy consumers. For this reason, debate in the energy community has
focused on ways to attract private investment in grid reinforcement. A key knowledge
gap faced by regulators is how to incentivise such projects, that could prove beneficial,
especially in cases where several distributed generators can use the same power line to
access the main grid, against the payment of a transmission fee. This thesis develops
methods from empirical and algorithmic game theory to provide solutions to this problem. Specifically, a two-location model is considered, where excess renewable generation
and demand are not co-located, and where a private renewable investor constructs a power
line, providing also access to other generators, against a charge for transmission. In other
words, the privately developed line is shared among all generators, a principle known
as ‘common access’ line rules. This formulation may be studied as a Stackelberg game
between transmission and local generation capacity investors. Decisions on optimal (and
interdependent) renewable capacities built by investors, affect the resulting curtailment
and profitability of projects and can be determined in the equilibrium of the game.
A first approach to study the behaviour of investors at the game equilibrium, assumed a
simple model, based on average values of renewable production and demand over a larger
time horizon. This assumption allowed for an initial examination of the Stackelberg game
equilibrium, by achieving an analytical, closed-form solution of the equilibrium and the
investigation of its properties for a wide range of cost parameters.
Next, a refined model is developed, able to capture the stochastic nature of renewable
production and variability of energy demand. A theoretical analysis of the game is
presented along with an estimation of the equilibrium by utilisation of empirical game-theoretic techniques and production/demand data from a real network upgrade project in
the UK. The proposed method is general, and can be applied to similar case studies, where
there is excess of renewable generation capacity, and where sufficient data is available.
In practice, however, available data may be erroneous or experience significant gaps.
To deal with data issues, a method for generating time series data is developed, based on
Gibbs sampling. This attains an iterative simulation analysis with different time series data
as an input (Markov Chain Monte Carlo), thus achieving the exploration of the solution
space for multiple future scenarios and leading to a reduction of the uncertainty with
regards to the investment decisions taken.
Energy storage can reduce curtailment or defer network upgrades. Hence, the last part
of this thesis proposes a model consisted of a line investor, local generators and a third
independent storage player, who can absorb renewable production, that would otherwise
have been curtailed. The model estimates optimal transmission, generation and storage capacities for various financial parameters. The value of storage is determined by comparing
the energy system operation with and without energy storage. All models proposed in this
thesis, are validated and applied to a practical setting of a grid reinforcement project, in
the UK, and a large dataset of real wind speed measurements and demand.
In summary, the research work studies the interplay among self-interested and indepen dent low-carbon investors, at areas of excess renewable capacity with network constraints
and high curtailment. The work proposes a mechanism for setting transmission charges
that ensures that the transmission line gets built, but investors from the local community,
can also benefit from investing in renewable energy and energy storage. Overall, the
results of this work show how game-theoretic techniques can help energy system stakeholders to bridge the knowledge gap about setting optimal curtailment rules and determining
appropriate transmission charges for privately developed network infrastructure.Engineering and Physical Sciences Research Council (EPSRC
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Game-theoretic modeling of transmission line reinforcements with distributed generation
Full text link
Game-Theoretic Modeling of Transmission Line Reinforcements with Distributed Generation
No full textFavourable sites for renewable generation are often remote locations (such as islands) where installed capacity, e.g. from wind turbines, exceeds local aggregate demand. We study the effect that curtailment mechanisms - applied when there is excess generation - have on the incentives to build additional capacity and the profitability of the generators. Next, for a two-location setting, we study the combined effect that curtailment schemes and line access rules have on the decision to invest in transmission expansion. In particular, for "common access" rules, this leads to a Stackelberg game between transmission and local generation capacity investors, and we characterise the equilibrium of this game. Finally, we apply and exemplify our model to a concrete problem of a grid reinforcement project, between Hunterston and the Kintyre peninsula, in western Scotland, and we determine a mechanism for setting transmission charges that assures both the profitability of the line and local renewable investors
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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