The strive for sustainable energy systems will most likely lead to an increased use of renewable energy sources which to a large extent are fluctuating. Therefore, a larger demand for balancing capacity will be required to maintain system security. Plug-in Hybrid Electric Vehicles (PHEV) represent a potential storage which could offer additional balancing power. Here, the applicability of PHEVs for this purpose is investigated. The study is performed in a system including a wind farm. The PHEV storage management approaches are based on a heuristic-and on a model predictive control scheme. They are compared in case studies. It is shown that the heuristic scheme is scalable while both schemes are able to balance the forecast error of renewable sources to an acceptable level.Index Terms-PHEV, V2G, balancing energy, MPC, wind power forecast, energy hub, heuristic

The electric utility of the city of Zurich, ewz, expects the grid load to receive additional intermittent components due to distributed generation and electric vehicles. Although the distribution grid generally has reserve capacity to cope with altered and additional loading, local temporary congestions are probable-especially during peak production and peak demand. Instead of the conventional method, grid reinforcements, battery energy storage systems (BESS) have the potential to mitigate the congestion by shifting the peak loads. Therefore, the investigations in this paper comprise the utilization of BESS as grid components. Three applications of BESS in the distribution grid and their economic aspects are presented in this paper. A pilot project is planned to demonstrate the feasibility of the applications and to gain experience with BESS.

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Long-term distribution grid planning for a sustainable, active and flexible energy system is challenged with many new uncertainties. In a referendum held in 2008, the population of Zurich voted in favour of achieving the 2000-Watt Society by 2050. In order to reach this goal energy efficiency, renewable energies and mobility have been identified as important fields of action. In addition to the unknown penetration of the renewable production in the future, uncertainties for the distribution system operators (DSOs) include the impact of storages, regulatory framework, technological innovations and the Internet of Things. ewz, the DSO of the city of Zurich is currently investigating the impact of these drivers on the future distribution grid.