In a world characterized by a continuous growth of the population, the energy sources management becomes the most important challenge. In order to guarantee the sustainable development using the different sources in a smart way first of all it is necessary to have a large variety in the energy mix. Renewable energy sources play a fundamental role in this challenge and they find the optimal exploitation in the distributed power generation organized through smart grids. One of the bigger problems of the renewables it is the non-concurrence in time between energy production and energy loads. The solution of this problem is another great challenge: the development and the design of efficient energy storage. Depending on the area of interest and on the particular power plant it will be critical to make a convenient and suitable choice of the storage type: thermal, electrical, chemical, mechanical. The technology that I am developing with my research group is a Wave Energy Converter (WEC) which exploits the gyroscopic effects of a flywheel in order to convert the mechanical energy of the sea waves into electrical energy. This device already presents a mechanical storage consisting in the flywheel but the real challenge to deal with is on the electrical part of the energy conversion. Being the energy source (sea waves) strongly irregular and characterized by high power peaks, in order to have a feasible grid connection it is necessary to have a smoother electrical power profile. A storage capacity can absolutely help in this problem. For this purpose the most suitable technology has not been already identified. To study the different opportunities and to gain a whole comprehension of the advantages and of the disadvantages for each one is essential in order to make the right choice for the technology that I’m dealing with. On the other hand it will be very useful to understand which kind of storage is the most suitable for each kind of renewable energy system. Furthermore to have the chance to apply the storage concept to a real innovative application it would be very interesting to highlight all the properties required by a good energy storage for smart grids development.