energy sources into the power network due to the two-way communication and regulation capability of smart grid. Studies in [@WuSun] give some inspiration for better utilization of distributed renewable energy generation. However, the uncertainty and intermittence of such renewable sources makes it difficult to use them stably and consecutively. A method to tackle this problem is to introduce storage devices, which can store renewable energy when it is abundant, and release the stored energy when renewable sources do not work. The objective of storage is similar with that in Rechargeable Sensor Networks [@HeChen]. Moreover, the storage device can be used to cut down the electricity cost by serving the load when electricity price is high. However, the time-diversity pattern of electricity price does not always match that of renewable energy generation, which depends on weather conditions mostly. Thus, how to minimize the non-renewable energy cost through optimal management of the storage device, renewable energy and on-grid energy comes to be a practical problem. As to PEV charging, there are already some real applications of renewable-powered charging stations, such as the wind powered stations in Barcelona, Spain [@ugei] and the charging stations with roof-top solar panels in Downtown Westport, Connecticut, USA 