PSYCHIATRIC DISORDERS IN CHILDHOOD AND HYPERHOMOCYSTEINEMIA

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Wind-pv-thermal power aggregator in electricity market

This paper addresses the aggregation of wind, photovoltaic and thermal units with the aim to improve bidding in an electricity market. Market prices, wind and photovoltaic powers are assumed as data given by a set of scenarios. Thermal unit modeling includes start-up costs, variables costs and bounds due to constraints of technical operation, such as: ramp up/down limits and minimum up/down time limits. The modeling is carried out in order to develop a mathematical programming problem based in a stochastic programming approach formulated as a mixed integer linear programming problem. A case study comparison between disaggregated and aggregated bids for the electricity market of the Iberian Peninsula is presented to reveal the advantage of the aggregation

Influence of local wind speed and direction on wind power dynamics - Application to offshore very short-term forecasting

Wind power time series usually show complex dynamics mainly due to non-linearities related to the wind physics and the power transformation process in wind farms. This article provides an approach to the incorporation of observed local variables (wind speed and direction) to model some of these effects by means of statistical models. To this end, a benchmarking between two different families of varying-coefficient models (regime-switching and conditional parametric models) is carried out. The case of the offshore wind farm of Horns Rev in Denmark has been considered. The analysis is focused on one-step ahead forecasting and a time series resolution of 10 min. It has been found that the local wind direction contributes to model some features of the prevailing winds, such as the impact of the wind direction on the wind variability, whereas the non-linearities related to the power transformation process can be introduced by considering the local wind speed. In both cases, conditional parametric models showed a better performance than the one achieved by the regime-switching strategy. The results attained reinforce the idea that each explanatory variable allows the modelling of different underlying effects in the dynamics of wind power time series

Demand-Orientated Power Production from Biogas: Modeling and Simulations under Swedish Conditions

The total share of intermittent renewable electricity is increasing, intensifying the need for power balancing in future electricity systems. Demand-orientated combined heat and power (CHP) production from biogas has potential for this purpose. An agricultural biogas plant, using cattle manure and sugar beet for biogas and CHP production, was analyzed here. The model Dynamic Biogas plant Model (DyBiM) was developed and connected to the Anaerobic Digestion Model No. 1 (ADM1). Flexible scenarios were simulated and compared against a reference scenario with continuous production, to evaluate the technical requirements and economic implications of demand-orientated production. The study was set in Swedish conditions regarding electricity and heat price, and the flexibility approaches assessed were increased CHP and gas storage capacity and feeding management. The results showed that larger gas storage capacity was needed for demand-orientated CHP production but that feeding management reduced the storage requirement because of fast biogas production response to feeding. Income from electricity increased by 10%, applying simple electricity production strategies to a doubled CHP capacity. However, as a result of the currently low Swedish diurnal electricity price variation and lack of subsidies for demand-orientated electricity production, the increase in income was too low to cover the investment costs. Nevertheless, DyBiM proved to be a useful modeling tool for assessing the economic outcome of different flexibility scenarios for demand-orientated CHP production

Electric vehicle charging system model for accurate electricity system planning

This article presents a novel electric vehicle (EV) charging system model. The model introduces power constraints in the grid-to-battery converter to improve modelling accuracy. Simulation results of the presented model indicate EV charging impact on a low-voltage electricity grid. Even though most of the battery charging load is spread evenly during desired times (e.g. off-peak load during night), power constraints of the EV model result in narrow peak loads. Plug-in EVs bring additional load to the electricity grid. If not managed properly, high EV deployment may lead to unnecessary grid investments due to highpeak currents of EV charging. Rising numbers of grid connected EVs is a challenging task in the future electricity grid planning. Thus an accurate EV charging system model is essential for reliable analysis of EV deployment

Electricity independence of the Baltic States: Present and future perspectives

Due to historical and geographical reasons, the Baltic States are strongly interconnected to power transmission grids of Russia and Belarus. Current energy security policies and electricity interconnection targets in the EU trigger the need for studying and implementing alternative electricity supply options and power system configuration schemes for the Baltic countries. In order to provide a supporting analysis for the energy policy making, with a special focus on electricity, a framework with methodologies is proposed in this paper to assess the electricity independence of the Baltic States. To comprehensively assess the electricity independence, we provided three indices: “adequacy”, “security” and “economic factor”. The proposed framework and methodologies are applied for assessing the electricity independence of the Baltic States in the present (2014) and future scenarios: mid-term (2020), and long-term (2030) time frame. The analysis results show that the planned generation capacities are adequate to cover future electricity demand in the Baltic States in 2020 and 2030. Under the current electricity grid planning, power distribution in some local areas is limited in the future scenarios. Additional grid investments are necessary to keep high security level of power supply in 2020/30

The Impact of Large Renewable Deployment on Electricity High Voltage Systems

In the last decades an increasing integration of renewable energy sources (RES) in the extra high voltage (EHV) and high voltage (HV) networks, boosted by technical reasons and political decisions has been noticed. RES introduce significant environmental benefits, but also considerable difficulties to power system planning and operation. In fact, if RES are correctly allocated, they allow deferring network upgrade investments and decreasing Joule losses. On the other hand, the uncertainty of RES production may cause dispatching problems, malfunctioning of protection and voltage regulation systems, etc. Many European Union (EU) research projects concluded that RES might be useful to accomplish economic, environmental and reliability targets removing the existing barriers to innovation and liberalized market. The paper is part of a Research Project financed by the European Commission2 to study the influence of a large penetration of RES on the EHV and HV electrical grids. The case study proposed in the paper refers to a portion of the Italian grid, the Sardinian power system, interconnected to the Italian mainland by means of the existing 200 kV and 500 kV high voltage direct current (HVDC) submarine cables (SA.CO.I. and SA.PE.I). Sardinia is one of the most favorable Italian regions for the exploitation of wind and solar energy and it has been experiencing a great increment of wind power production, which will be doubled in the next ten years. In the paper, the models to predict at 2020 and 2030 the generation park, demand profiles, as well as the development of the electricity infrastructures in Sardinia are briefly described. The steady-state analysis of the Sardinian grid with AC Power Flow studies applied to the foreseen load and generation scenarios in 2020 and 2030 allowed identifying critical conditions of the grid caused by RES production, load profile, and the lack of homotheticity between generation and load

The role of facts and HVDC in the future pan-European transmission system development

The present paper focuses on FACTS (Flexible Alternating Current Transmission System) and HVDC (High Voltage Direct Current) transmission technologies. Particular attention is paid to different specific technical, economic and environmental features of these power electronics-based devices. Final aim of the paper is the investigation of the role that FACTS and HVDC may play towards the development of the future pan-European transmission system