At present, new renewables like wind, solar and marine energy are having a strong development. The generation of energy by renewables has the disadvantage that it depends on atmospheric conditions. It means that they can generate energy at any moment independently if this energy is required or not by the consumers. For the stability of the electrical grid, supply and demand of energy has to be matched. The surplus of energy produced when consumption is low has to be stored and delivered again when consumption is high. Therefore, the future of renewables is tied directly to the future of energy storage. At present, the only system to store huge amounts of energy is pumped storage (Pump-turbine machines). In these plants the surplus of energy in the grid is used for pumping water to a higher reservoir (pump operation). At peak hours or in case of emergency this water goes down generating energy (turbine operation). To guarantee this operation these machines have to be available at any time.