1,720,952 research outputs found
Erratum to: Energy management system with pv power forecast to optimally charge evs at the workplace (IEEE Transactions on Industrial Informatics (2018) 14:1 (311-320) DOI: 10.1109/TII.2016.2634624)
No full textIn [1], the name of one co-author, Germán Morales-Espana, was rendered incorrectly as Germán Morales-Espana Mouli. The correct byline is shown above. We sincerely regret the error.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & StorageAlgorithmic
Unit Commitment : Computational Performance, System Representation and Wind Uncertainty Management
No full textIn recent years, high penetration of variable generating sources, such as wind power, has challenged independent system operators (ISO) in keeping a cheap and reliable power system operation. Any deviation between expected and real wind production must be absorbed by the power system resources (reserves), which must be available and ready to be deployed in real time. To guarantee this resource availability, the system resources must be committed in advance, usually the day-ahead, by solving the so-called unit commitment (UC) problem. If the quantity of committed resources is extremely low, there will be devastating and costly consequences in the system, such as significant load shedding. On the other hand, if this quantity is extremely high, the system operation will be excessively expensive, mainly because facilities will not be fully exploited. This thesis proposes computationally efficient models for optimal day-ahead planning in (thermal) power systems to adequately face the stochastic nature of wind production in the real-time system operation. The models can support ISOs to face the new challenges in short-term planning as uncertainty increases dramatically due to the integration of variable generating resources. This thesis then tackles the UC problem in the following aspects: Power system representation: This thesis identifies drawbacks of the traditional energy-block scheduling approach, which make it unable to adequately prepare the power system to face deterministic and perfectly known events. To overcome those drawbacks, we propose the ramp-based scheduling approach that more accurately describes the system operation, thus better exploiting the system flexibility. UC computational performance: Developing more accurate models would be pointless if these models considerably increase the computational burden of the UC problem, which is already a complex integer and non-convex problem. We then devise simultaneously tight and compact formulations under the mixed-integer programming (MIP) approach. This simultaneous characteristic reinforces the convergence speed by reducing the search space (tightness) and simultaneously increasing the searching speed (compactness) with which solvers explore that reduced space. Uncertainty management in UC: By putting together the improvements in the previous two aspects, this thesis contributes to a better management of wind uncertainty in UC, even though these two aspects are in conflict and improving one often means harming the other. If compared with a traditional energy-block UC model under the stochastic (deterministic) paradigm, a stochastic (deterministic) ramp-based UC model: 1) leads to more economic operation, due to a better and more detailed system representation, while 2) being solved significantly faster, because the core of the model is built upon simultaneously tight and compact MIP formulations. To further improve the uncertainty management in the proposed ramp-based UC, we extend the formulation to a network-constrained UC with robust reserve modelling. Based on robust optimization insights, the UC solution guarantees feasibility for any realization of the uncertain wind production, within the considered uncertainty ranges. This final model remains as a pure linear MIP problem whose size does not depend on the uncertainty representation, thus avoiding the inherent computational complications of the stochastic and robust UCs commonly found in the literature.The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively. QC 20140923</p
An overview of research on gender in Spanish society
Full text linkThis article presents an overview of research on gender in Spanish society. Six areas of literature are examined including families, education, work, politics, sexuality, and men. The author argues that political factors have shaped the development of sociology of gender in Spain and that there are still important gaps in coverage in this area of sociological inquiry.Publicad
On the applicability of single-line equivalents on optimal operation of modern unbalanced distribution networks
No full textThe integration of Distributed Energy Resources (DERs) in distribution networks comes with challenges, like power quality concerns, but also opens up new opportunities, e.g., DERs can offer competitive energy prices for final users by leveraging time arbitrage. A suitable method to fully exploit such opportunities is to compute the optimal DER schedule, either with a full three-phase network model or a more computationally efficient single-line equivalent. This paper presents under which conditions a single-line equivalent can and cannot be used to properly represent a modern and unbalanced power distribution network able to dispatch high levels of DER integration optimally. Results show that single-line equivalents might be helpful when the problem objective function limits counterflows, for example, when minimizing active power losses. Moreover, single-line equivalents might be helpful for low levels of DER integration. However, enabling single-line equivalents results in a lower hosting capacity for high levels of DER integration.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Algorithmic
Are Optimal Day-Ahead Markets Able to Face RES Uncertainty?: Evaluating Perfect Stochastic Energy Planning Models
No full textApproximations made in day-ahead markets can result in suboptimal or even infeasible schedules for generating units and inaccurate predictions of actual costs and wind curtailment. Here we compare different optimal models of day-ahead markets based on unit commitment (UC) formulations, especially energy- vs. power-based UC; excluding or including startup and shutdown trajectories; and deterministic vs. “ideal” stochastic models to face wind uncertainty. The day-ahead hourly schedules are then evaluated against actual wind and load profiles using a (5-min) real-time dispatch model. We find that each simplification usually causes expected generation costs to increase by several percentage points, and results in significant understatement of expected wind curtailment and, in some cases, load interruptionsAlgorithmic
The chronicle of Alfonson lll and its significance for the historiography of the Asturian kingdom 718-910 AD
Full text linkThe Asturian kingdom provided the earliest organised
resistance in the Iberian peninsula to the Muslim invaders who overthrew the Visigothic state at the start of the 8th century. Information on the origins of the Asturian kingdom is regrettably sparse. Historians of the kingdom are totally reliant on a late 9th-century cycle of Asturian chronicles associated with the royal court, the most substantial of which is the Chronicle of Alfonso III. This work has survived in two fundamental recensions from the 10th century. Historians' gratitude for its existence is tinged with frustration at its readily apparent weaknesses, such as a chronological imprecision on events and an enigmatic brevity in the commentary.
This thesis considers the 9th-century Asturian chronicles in
the context of their own time. In particular, it examines the Chronicle of Alfonso III not as a disappointing source which fails to yield to modern scholars the information they crave on this obscure period of early Spanish history, but, rather, as an expression of the aims of a medieval author and his copyists. The Chronicle was the product of scarce and valuable resources. Its author, within the limits of his literary ability and source of information, transmitted a message which interacted with the individual understanding of its intended audience. This shift of
emphasis in analysing the Chronicle of Alfonso III rests on the assumption that its original text may be recognised in the later recensions which used it, by addition or omission, as a vehicle for their own interests
Energy Management System with PV Power Forecast to Optimally Charge EVs at the Workplace
No full textThis paper presents the design of an energy management system (EMS) capable of forecasting photovoltaic (PV) power production and optimizing power flows between PV system, grid, and battery electric vehicles (BEVs) at the workplace. The aim is to minimize charging cost while reducing energy demand from the grid by increasing PV self-consumption and consequently increasing sustainability of the BEV fleet. The developed EMS consists of two components: An autoregressive integrated moving average model to predict PV power production and a mixed-integer linear programming framework that optimally allocates power to minimize charging cost. The results show that the developed EMS is able to reduce charging cost significantly, while increasing PV self-consumption and reducing energy consumption from the grid. Furthermore, during a case study analogous to one repeatedly considered in the literature, i.e., dynamic purchase tariff and dynamic feed-in tariff, the EMS reduces charging cost by 118.44 % and 427.45% in case of one and two charging points, respectively, when compared to an uncontrolled charging policy.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & StorageAlgorithmic
Flexibility trading for aggregators of electrical vehicles within the Universal Smart Energy Framework: A research on trading flexibility in a USEF compliant market at distribution level for aggregators of electrical vehicles
No full textIncreased use of the distribution grid due to the uptake of distributed energy resources and the expected penetrations of Electrical Vehicles (EVs) could lead to congestion problems in the distribution grid. Congestion refers to issues related to the overheating of components or voltage issues in the distribution network. Avoiding these issues is crucial to maintain a stable, economical and reliable electricity grid. By using the flexibility of aggregated EVs large investments in grid reinforcement can be avoided. However, a holistic approach is necessary to manage the procurement of flexibility services for all stakeholders involved. One approach is the Universal Smart Energy Framework (USEF), a framework that integrates the existing electricity market with a market for flexibility services from the aggregator to the Distribution System Operator (DSO). This master thesis presents a study on the flexibility market as described by USEF from the perspective of a commercial aggregator of EVs. USEF presents a framework in which flexibility potentially provides financial opportunities for aggregators of EVs. However, it is not clear what the financial impact on the charging costs of an aggregator of EVs is and in what way an aggregator has to adapt its charging logic when trading with DSOs. Therefore, the aim of this thesis is to answer the following question: how can an aggregator of EVs offer flexibility services to a USEF compliant market at distribution level? This report presents an in-depth analysis on USEF, determines the impact of network constraints from USEF on the charging costs of an aggregator of EVs and improves the charging strategy under USEF constraints.Electrical Engineering | Sustainable Energy Technolog
When DICE meets the dice: Integrated Economic and Climate Assessment under Uncertainty
No full textWith the decision made to act upon climate change, the remaining question is: "How?". Economic theory suggests that the most efficient method is by means of market-based policies. These policies are often designed based on Integrated Assessment Models like DICE, which is the subject of this thesis. Integrating uncertainty into this model has been the aim of the thesis. The stochastic version of DICE, EICE, showed to be sensitive to the distribution of climate uncertainty, but results were less explicit then expected. Overall, the conclusion is that both modest and more strict mitigation policies can be justified based on EICE.Electrical Engineering | Sustainable Energy Technolog
A New Market Design For Day-ahead Markets with Power-Based Scheduling
No full textAlgorithmicsEnergie and Industri
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