• Energy Research

The objective of the presented paper is to verify economically justified levels of reactive energy compensation in the distribution network in the new market conditions, including the extensive use of smart metering systems, new types of load, or distributed generation. The proposed methodology is based on the minimization of annual costs of losses caused by the flow of reactive energy to the supplied loads through the equivalent resistance of the distribution system determined on the basis of statistical energy losses in this network. The costs of losses are compared to the costs of using compensating devices expressed by the levelized costs of reactive energy generation. The results are the relations describing the optimal annual average value of the tgφ factor to be maintained by customers to optimize the cost of loss of the distribution network caused by reactive energy flows. The dependence of the optimal tgφ value on the analyzed load and network parameters is also discussed. The resulting optimal tgφ levels should be considered in the tariffication process of services offered by distribution system operators to improve capacity and limit the costs of power network operation due to reactive energy transmission.

Розглянуто причини виникнення реактивної потужності в електромережі, її негативні наслідки, проаналізовано засобі для компенсації реактивної потужності та підвищення коефіцієнту потужності споживачів в електромережі. //// The causes of the occurrence of reactive power in the power grid, its negative consequences, means for compensation of reactive power and increasing the power factor of consumers in the power grid are analyzed.

The reactive power control mechanisms at the smart inverters will affect the voltage profile, active power losses and the cost of reactive power procurement in a different way. Therefore, this paper presents an assessment of the cost–benefit relationship obtained by enabling nine different reactive power control mechanisms at the smart inverters. The first eight reactive power control mechanisms are available in the literature and include the IEEE 1547−2018 standard requirements. The ninth control mechanism is an optimum reactive power control proposed in this paper. It is formulated to minimise the active power losses of the network and ensure the bus voltages and the reactive power of the smart inverter are within their allowable limits. The Vestfold and Telemark distribution network was implemented in DIgSILENT PowerFactory and used to evaluate the reactive power control mechanisms. The reactive power prices were taken from the default payment rate document of the National Grid. Simulation results demonstrate that the optimal reactive power control mechanism provides the best cost–benefit for the daily steady-state operation of the network.

В статье приведен сравнительный анализ различных редакций Методики расчета платы за перетекание реактивной энергии. Указаны концептуальные ошибки Методики в качестве экономического рычага для стимулирования потребителей к компенсации реактивной мощности в своих сетях. Намечены пути решения проблемы компенсации реактивной мощности в электрических сетях ; The paper presents a comparative analysis of different editions of the Methodology of calculation the payment for overflows of reactive energy. Сonceptual errors of the Methogology as economic lever for encourage consumers to compensate the reactive power in its networks were shown. The ways of solving the problem of reactive power compensation in electrical networks were scheduled

AbstractThe reactive dividing‐wall column (RDWC) is an example of extensive process integration. Recently, an energy saving potential of 23 % for the RDWC for an exemplary reaction system has been reported. However, little is known so far whether this magnitude represents a typical value and how the reaction system properties affect the energy saving of the RDWC. Clearly, a prerequisite for the industrial application of this apparatus is a profound understanding of the process and a quick assessment of the energy saving at an early stage of process synthesis. Therefore, the influence of separation properties of the reaction system on the energy saving potential is systematically investigated. Also, the saving mechanisms are analyzed and how they are affected. Heuristics are presented which can be applied easily during the industrial process synthesis.

Mit stetig steigender Verbreitung dezentraler Erzeugung in allen Spannungsebenen des Verteilnetzes steigt auch der Einsatz lokaler Q(U) Regler, um gegen Spannungslimit��berschreitungen vorzugehen, immer weiter an. Dies bewirkt einen unkontrollierten Blindleistungsfluss ��ber den Transformator. Diese Masterarbeit untersucht die Effekte der volatilen Einspeisung bei einem hohen Anteil an dezentraler Erzeugung und die daraus resultierenden Zusammenh��nge der Spannungen aus dem Hoch- und Mittelspannungsnetz. Zu beginn dieser Arbeit wird der Einfluss eines gro��en Anteils dezentraler Erzeugung auf das Hoch- und Mittelspannungsnetz des IEEE 30 Bus Test Netzwerks analysiert. Danach wird die Analyse auf ein reales europ��isches Verteilnetz ausgeweitet. Dieses hat bereits einen hohen Anteil an dezentraler Erzeugung in einem seiner Mittelspannungsnetze. Die Analyse erfolgt durch Variation der dezentralen Einspeisung. Dabei wird auch ein lokaler Q(U) Regler f��r die dezentrale Erzeugung eingesetzt und dessen Einfluss auf die Spannungen genau untersucht. F��r die Analyse des Mittel- und Hochspannungsnetzes werden Lastflusssimulationen in PSS Sincal durchgef��hrt. Ergebnisse dieser Arbeit haben gezeigt, dass mit der Erh��hung der dezentralen Einspeisung die Spannung und der Blindleistungsfluss der ��bergeordneten Spannungsebene beeinflusst werden. Bei einem kleinen Anteil an dezentraler Einspeisung der Gesamterzeugung konnte dieser Effekt nicht beobachtet werden. Der Blindleistungsfluss in der n��chsth��heren Spannungsebene ist nicht vorhersehbar, da er von einem lokalen Blindleistungsregler im Mittelspannungsnetz verursacht wird. Dieser Regler ist im Falle von dezentraler Erzeugung aus Wind und Sonne von der aktuellen Spannung im Netz und dem derzeitigen Wetter abh��ngig. The penetration of distributed generation is increasing continuously in all voltage levels of the distribution networks. The use of reactive power consumption and injection to suppress voltage violations in the medium voltage level has caused an uncontrolled reactive power flow over the HV/MV transformer. This Master Thesis investigates the volatile power effects and the resulting voltage interdependencies between the high voltage level and the medium voltage level in the presence of a high share of distributed generation. Firstly, the impact on the medium- and the high voltage grid of the IEEE 30 Bus Test Network, is analyzed. Secondly, the investigations are extended to a real European distribution grid, which already incorporates a high share of distributed generation in its medium voltage grid. The analyses are performed by varying the level of distributed generation in the medium voltage grid. The Q(U) local controllers are taken into account and their effect is analyzed in detail. The analyses of the medium- and high voltage grid are performed by load flow simulations in PSS Sincal. Results have shown that with an increasing share of distributed generation the voltage and reactive power flow on the superordinate grid are affected. This phenomenon is not visible for a small distributed generation share. The reactive power flow in the superordinate grid is unpredictable because the local reactive power controller in the medium voltage grid induces it. The reaction of the local controller in the case of wind and photovoltaic distributed generations is a function of the voltage level and the weather conditions.

Grid connected Photovoltaic (PV) systems are among the increasingly growing electric power generation units worldwide. The majority of new installations are expected to be residential PVs that are connected into distribution systems. However, the PV hosting capacity of low voltage (LV) grids is limited due to the voltage rise at the point of connection associated with the PV feed-in current. Reactive power management using PV inverters and using the electrical energystorage systems (EESS) are amongst the main solutions for increasing the PV hosting capacity in LV grids. In this paper, a method is developed in order to examine the effect of reactive power absorption by PV inverters on EESS capacity required for overvoltage prevention in LV grids. Simulations show thatreactive power absorption can effectively decrease the EESS capacity.

2011 Spring. ; Includes bibliographical references. ; Separations account for 60-80% of the processing costs of most mature chemical processes. Membrane based separations offer several advantages over conventional technology such as lower energy costs and easy scale up. Here we focus on membrane extraction for removal of acetic acid, sulfuric acid, furfural, HMF and other toxic compounds from biomass hydrolysates. As membrane extraction is non-dispersive it overcomes the disadvantages of conventional extraction. Experiments have been conducted using dilute sulfuric acid pretreated corn stover (hydrolysate). Acetic acid, in its protonated form, is extracted into an organic phase consisting of octanol/oleyl alcohol and Alamine 336, a tertiary amine, containing aliphatic chains of 8-10 carbon atoms. Co-extraction of sulfuric acid leads to an increase in hydrolyste pH. The effect of aqueous and organic phase flow rates and temperature, on the rate of extraction of acetic acid and sulfuric acid has been investigated. Changes in the rates of acetic and sulfuric acid extraction may be explained by considering the structure of the complexes formed in the organic phase. We conducted computational modeling to elucidate the extraction process of Alamine 336 in different solvents. Extraction of carboxylic acids, Furfural and HMF in water and octanol was simulated using the Gaussian 03 package. In the past the extraction process has been explained by the direct interaction of the carboxylic acid with the Alamine 336 to form an ion pair. More carboxylic acids could be extracted through hydrogen bonding forming a dimer or trimer complex form with the Alamine 336, stabilized by the organic solvent. Hydrolysates treated by membrane extraction and conventional conditioning technologies were fermented using a glucose-xylose fermenting bacteria to determine the viability of membrane technology to detoxify biomass hydrolysates. Membrane extraction could be a viable hydrolysate detoxification technology because the other conditioning ...

A methodology is proposed for explaining one of the central questions in the teaching of general chemistry courses to freshman students: why do chemical transformations occur? The answer to this question is based on thermodynamics but we propose arriving at an answer in a more intuitive way by using computational tools in a bid to increase the motivation of students for learning chemistry.

As power generation from variable distributed energy resources (DER) grows, energy flows in the network are changing, increasing the requirements for ancillary services, including voltage support. With the appropriate power converter, DER can provide ancillary services such as frequency control and voltage support. This paper outlines the economic potential of DERs coordinated in a microgrid to provide reactive power and voltage support at its point of common coupling. The DER Customer Adoption Model assesses the costs of providing reactive power, given local utility rules. Depending on the installed DER, the cost minimizing solution for supplying reactive power locally is chosen. Costs include the variable cost of the additional losses and the investment cost of appropriately over-sizing converters or purchasing capacitors. A case study of a large health care building in San Francisco is used to evaluate different revenue possibilities of creating an incentive for microgrids to provide reactive power.