Kai Vuorilehto

Statistical Charging Load Modeling of PHEVs in Electricity Distribution Networks Using National Travel Survey Data

In this paper, statistical charging load modeling of plug-in hybrid electric vehicles (PHEVs) in electricity distribution networks is studied. Usefulness of National Travel Survey data in the modeling is investigated, and a novel modeling methodology is proposed where detailed car use habits are taken into account and statistical distributions of charging energies can be produced. Using the modeling methodology some example calculation results of a Finnish case study are presented with further analysis and sensitivity studies. The example calculations are made mostly from viewpoint of the Finnish distribution networks and their modeling traditions but the method can be applied internationally when relevant travel survey data is available. Example calculations are analyzed in order to assess reasonability and practical usability of the models. The models produced by the methodology can easily be used in network calculation tools commonly used by distribution network operators.

Anodenmaterialien für Lithium-Ionen-Batterien

Die Anode einer Lithium Ionen Batterie besteht in der Regel aus einer dunnen Kupferfolie als Stromableiter, welche beschichtet ist. Die Beschichtung besteht zum Grosteil aus Aktivmaterial und wenigen Gewichtsprozenten an Binder und gegebenenfalls Leitfahigkeitsadditiven. Als Aktivmaterial wird in der Regel synthetischer Graphit oder Naturgraphit verwendet. Neben Graphit werden in sehr geringem Umfang amorphe Kohlenstoffe, Lithiumtitanat oder Silizium- bzw. Zinn-haltige Materialien eingesetzt.

Plug-in vehicle ancillary services for a distribution network

In this paper, we have investigated the possibilities of plug-in vehicles to produce ancillary services for distribution networks. First, special features of plug-in vehicles as controllable resources are discussed and then motivation and methods of four different types of ancillary services are discussed. These services are peak load management, network power flow management, customer back-up power and power quality improvement. Finally some conclusions are made and future work is proposed.

Anode materials for lithium-ion batteries

Secondary lithium cells initially had a metallic lithium foil as an anode (negative electrode) [1]. Pure lithium has a very high specific capacity (3,860 mAh/g) and a very negative potential, resulting in very high cell voltage. However, cycling efficiency decreases as lithium dissolves repeatedly while the cell is discharging and lithium is deposited as it is charging. This means that two or three times the normal amount of lithium must be used. In addition, lithium can be deposited as foam and as dendrites. The latter might grow through the separator [2, 3]. These dendrites can cause local short circuits, which might result in the cell completely self-discharging or, in the worst case, lead to an internal thermal chain reaction, fire, or explosion.

Materials and function

Lithium-ion batteries are hi-tech devices made of complex high-purity chemicals and other raw materials. The following chapters aim to give a comprehensive picture of these materials and their functions. One might think that the lithium-ion battery is lightweight due to the small mass of its main component, lithium. However, this is not quite true: only 2% of the battery mass is lithium, the rest being electrode materials, electrolyte, and inactive structural components.