Grid integration of intermittent renewable energy sources using price-responsive plug-in electric vehicles

Plug-in electric vehicles (PEVs) are expected to balance the fluctuation of re-newable energy sources (RES). To investigate the contribution of PEVs, the availability of mobile battery storage and the control mechanism for load man-agement are crucial. This study therefore combined the following: a stochastic model to determine mobility behavior, an optimization model to minimize vehicle charging costs and an agent-based electricity market equilibrium model to esti-mate variable electricity prices. The variable electricity prices are calculated based on marginal generation costs. Hence, because of the merit order effect, the electricity prices provide incentives to consume electricity when the supply of renewable generation is high. Depending on the price signals and mobility behavior, PEVs calculate a cost minimizing charging schedule and therefore balance the fluctuation of RES. The analysis shows that it is possible to limit the peak load using the applied control mechanism. The contribution of PEVs to improving the integration of intermittent renewable power generation into the grid depends on the characteristic of the RES generation profile. For the Ger-man 2030 scenario used here, the negative residual load was reduced by 15 to 22 percent and the additional consumption of negative residual load was be-tween 34 and 52 percent. --Plug-in electric vehicles,demand-side management,variable prices,intermittent generation

Optimizing the charge profile: Considering users' driving profiles

PHEVs are discussed controversially. On the one hand, the evolutionary approach of a hybrid vehicle helps the consumer to adopt to electric driving, using the range extender when driving longer distances. On the other hand, PHEVs have a more complex propulsion system and a potentially low emission impact due to a low electric driving share. These factors, however, strongly depend on the consumers' driving and charging behavior. Therefore, this paper simulates realistic driving based on the national German travel survey. Firstly, battery profiles are modeled using further information about parking locations, charging scenarios, as well as different battery sizes. Secondly, total costs of different alternative vehicles are calculated and minimized varying the battery size. According to the simulation, PHEVs are less expensive and thus important for market adoption. High electric driving shares of more than 80% allow fair emission reductions. And for the few longer trips, PHEVs can use the fall-back option of the internal combustion engine. PHEVs thus do not require an oversized battery and are thus more economical. In the early market, PHEVs will be equipped with smaller batteries; and with higher market share, require customization of the battery size for different customer segments and vehicle types. --

Vehicle-to-grid regulation based on a dynamic simulation of mobility behavior

This study establishes a new approach to analyzing the economic impacts of vehicle-to-grid (V2G) regulation by simulating the restrictions arising from un-predictable mobility requests by vehicle users. A case study for Germany using average daily values (in the following also called the "static" approach) and a dynamic simulation including different mobility use patterns are presented. Comparing the dynamic approach with the static approach reveals a significant difference in the power a vehicle can offer for regulation and provides insights into the necessary size of vehicle pools and the possible adaptations required in the regulation market to render V2G feasible. In a first step, the regulation of primary, secondary and tertiary control is ana-lyzed based on previous static methods used to investigate V2G and data from the four German regulation areas. It is shown that negative secondary control is economically the most beneficial for electric vehicles because it offers the high-est potential for charging with 'low-priced' energy from negative regulation. In a second step, a new method based on a Monte Carlo simulation using stochastic mobility behavior is applied to look at the negative secondary control market in more detail. Our simulation indicates that taking dynamic driving behavior into account results in a 40% reduction of the power available for regulation. Be-cause of the high value of power in the regulation market this finding has a strong impact on the resulting revenues. Further, we demonstrate that, for the data used, a pool size of 10,000 vehicles seems reasonable to balance the var-iation in driving behavior of each individual. In the case of the German regula-tion market, which uses monthly bids, a daily or hourly bid period is recom-mended. This adaptation would be necessary to provide individual regulation assuming that the vehicles are primarily used for mobility reasons and cannot deliver the same amount of power every hour of the week. --

Optimizing plug-in electric vehicle charging in interaction with a small office building

This paper considers the integration of plug-in electric vehicles (PEVs) in micro-grids. Extending a theoretical framework for mobile storage connection, the economic analysis here turns to the interactions of commuters and their driving behavior with office buildings. An illustrative example for a real office building is reported. The chosen system includes solar thermal, photovoltaic, combined heat and power generation as well as an array of plug-in electric vehicles with a combined aggregated capaci-ty of 864 kWh. With the benefit-sharing mechanism proposed here and idea-lized circumstances, estimated cost savings of 5% are possible. Different pricing schemes were applied which include flat rates, demand charges, as well as hourly variable final customer tariffs and their effects on the operation of intermittent storage were revealed and examined in detail. Because the plug-in electric vehicle connection coincides with peak heat and electricity loads as well as solar radiation, it is possible to shift energy demand as desired in order to realize cost savings. --Battery storage,building management systems,dispersed storage and generation,electric vehicles,load management,microgrid,optimization methods,power system economics,road vehicle electric propulsion

Evaluation of European electric vehicle support schemes

Electric vehicles can reduce carbon dioxide emissions, increase energy efficiency, and help to reduce the dependency on oil imports. However, today's technical and economic challenges are preventing mass-market adoption. In order to create an early market and support economies of scale in production, some European countries have already established support schemes. This research study aims to provide an overview of the existing support schemes in Europe and to assess them using four criteria: effectiveness, efficiency, practicability, and political acceptance. The study concludes with an impact analysis of today's economic support schemes which considers the total costs of ownership. While one-time support schemes help to reduce the large initial investments for EVs, recurring instruments are often more effective and efficient but also smaller in volume. The comparison of the different regional incentive schemes reveals that EVs today are only economically attractive in Denmark and Norway, but at relatively high prices. Thus, regulators need to increase the volume and efficiency of the support schemes, establish high scoring instruments, and align these on a European scale. In addition, non-monetary support, e.g. free-parking, can help to overcome technical or smaller economic hurdles. --

Integration of intermittent renewable power supply using grid-connected vehicles: A 2030 case study for California and Germany

This paper describes a method to characterize the fluctuating electricity generation of renewable energy sources (RES) in a power system and compares the different parameters for California and Germany. Based on this method describing the fluctuation and residual load, the potential contribution of grid-connected vehicles to balancing generation from renewable energy sources is analyzed for a 2030 scenario using the agent-based simulation model PowerACE. The analysis reveals that integrating fluctuating RES is possible with less effort in California because of a higher correlation between RES generation and the load curve here. In addition, RES capacity factors are higher for California and therefore the ratio of installed capacity to peak load is lower. Germany, on the other hand, faces extreme residual load changes between periods with and without supply from RES. In both power system scenarios, grid-connected vehicles play an important role in reducing residual load fluctuation if smart charging is used. Uncontrolled charging or static time-of-use tariffs do not significantly improve the grid integration of RES

Vehicle-to-grid regulation based on a dynamic simulation of mobility behavior

This study establishes a new approach to analyzing the economic impacts of vehicle-to-grid (V2G) regulation by simulating the restrictions arising from un-predictable mobility requests by vehicle users. A case study for Germany using average daily values (in the following also called the "static" approach) and a dynamic simulation including different mobility use patterns are presented. Comparing the dynamic approach with the static approach reveals a significant difference in the power a vehicle can offer for regulation and provides insights into the necessary size of vehicle pools and the possible adaptations required in the regulation market to render V2G feasible. In a first step, the regulation of primary, secondary and tertiary control is ana-lyzed based on previous static methods used to investigate V2G and data from the four German regulation areas. It is shown that negative secondary control is economically the most beneficial for electric vehicles because it offers the high-est potential for charging with 'low-priced' energy from negative regulation. In a second step, a new method based on a Monte Carlo simulation using stochastic mobility behavior is applied to look at the negative secondary control market in more detail. Our simulation indicates that taking dynamic driving behavior into account results in a 40% reduction of the power available for regulation. Be-cause of the high value of power in the regulation market this finding has a strong impact on the resulting revenues. Further, we demonstrate that, for the data used, a pool size of 10,000 vehicles seems reasonable to balance the var-iation in driving behavior of each individual. In the case of the German regula-tion market, which uses monthly bids, a daily or hourly bid period is recom-mended. This adaptation would be necessary to provide individual regulation assuming that the vehicles are primarily used for mobility reasons and cannot deliver the same amount of power every hour of the week

Evaluation of European electric vehicle support schemes

Electric vehicles can reduce carbon dioxide emissions, increase energy efficiency, and help to reduce the dependency on oil imports. However, today's technical and economic challenges are preventing mass-market adoption. In order to create an early market and support economies of scale in production, some European countries have already established support schemes. This research study aims to provide an overview of the existing support schemes in Europe and to assess them using four criteria: effectiveness, efficiency, practicability, and political acceptance. The study concludes with an impact analysis of today's economic support schemes which considers the total costs of ownership. While one-time support schemes help to reduce the large initial investments for EVs, recurring instruments are often more effective and efficient but also smaller in volume. The comparison of the different regional incentive schemes reveals that EVs today are only economically attractive in Denmark and Norway, but at relatively high prices. Thus, regulators need to increase the volume and efficiency of the support schemes, establish high scoring instruments, and align these on a European scale. In addition, non-monetary support, e.g. free-parking, can help to overcome technical or smaller economic hurdles

Bewertung des Aufbaus einer Ladeinfrastruktur für eine Redox-Flow-Batteriebasierte Elektromobilität

Eine Erreichung ambitionierter internationaler Klimaziele ist bei wachsendem Mobiliätsbedarf ohne Elektromobilität nicht möglich. Elektromobilität in Verbindung mit regenerativen Energien wird als wichtiger Baustein zur Reduktion der Treibhausgasemissionen angesehen. Gleichzeitig ist die Verbreitung von Elektrofahrzeugen gering, da diese gegenüber Verbrennungsfahrzeugen mit Einschränkungen verbunden sind. Neben den Anschaffungsausgaben stehen lange Ladezeiten und eine beschränkte Reichweite dem heutigen Einsatz von Elektrofahrzeugen oft entgegen. Eine mögliche Abhilfe könnten betankbare Batterien leisten. In der vorliegenden Arbeit soll erstmalig ein möglicher Infrastrukturaufbau für Elektrofahrzeuge mit sogenannten Redox-Flow-Batterien untersucht werden. Redox-Flow-Batterien besitzen die Eigenschaft, dass aktive Materialien gelöst in Flüssigelektrolyten außerhalb der Zelle gespeichert werden. Dieser Aufbau ermöglicht das Aufladen der Batterie, indem der entladene Elektrolyt durch geladenen ausgetauscht wird. Dieser Tausch kann an einer Tankstelle durchgeführt werden. Ein wesentlicher Nachteil von Redox-Flow-Batterien ist ihre geringe Energie- und Leistungsdichte, weshalb Redox-Flow-Batterien für den mobilen Einsatz bislang kaum erforscht wurden. Ausgehend von einer technischen Betrachtung der RFB-Technologie wurde die Vanadium-Sauerstoff-Redox-Flow-Brennstoffzelle (VOFC) als aussichtsreiche Alternative dieser Technologie identifiziert. Sie bietet herkömmlichen Redox-Flow-Batterien gegenüber den Vorteil einer deutlich höheren Energiedichte, befindet sich aber noch im frühen Entwicklungsstadium. Unter der Annahme einer best-case-Betrachtung wurde eine mögliche Tankstelleninfrastruktur für das Betanken von Fahrzeugen mit einer VOFC untersucht und mit den Konzepten von reinen Batteriefahrzeugen (BEV) und Brennstoffzellenfahrzeugen (FVEV) verglichen. Es ergab sich, dass Elektromobilität basierend auf einer VOFC unter den Annahmen eine konkurrenzfähige Alternative zu heute bekannten Elektromobilitätskonzepten sein kann. Jedoch sind hierzu, ähnlich wie im Bereich der Brennstoffzellenfahrzeuge in der Vergangenheit, weitere Fortschritte bei den technischen und wirtschaftlichen Herausforderungen notwendig