Flexibility will play a crucial role for the integration of further intermittent Renewable Energy Sources (RES) into the European electricity system. The aggregation of RES producers and flexible demand can provide significant contributions to both, increasing system flexibility and market integration of renewables. In this context the BestRES project aims to develop innovative business models for RES Aggregators. This presentation gives an overview of current and improved business models for the aggregation of RES production, flexible demand and storage. Based on selected examples a methodology for designing and evaluating improved business models is presented.