The growing interest in the identification and adoption of clean generation technologies, at low environmental impact has led to the growing popularity of the so-called GFR (Generation from Renewable Source). Within this wide range of generation systems, it is possible to include different technologies such as photovoltaic, wind, hydroelectric, biomass, etc...

In particular, photovoltaic and wind power are the technologies that have become widespread over the past few years, at the point that, in Italy (2017), there are counted an installed power of photovoltaic systems equal to about 19 GW and wind power plants of about 9 GW , compared to an initial figure (2008) of approximately 500 MW and 3.5 GW for photovoltaic and wind energy respectively.

This trend is expected to grow over the next few years due to the policies adopted at Italian and European level. Consider, for example, with reference to the Italian context, at the SEN (National Energy Strategy) which provides, among others:

1. the objective of covering 55% of electricity consumption through renewable sources by 2030;
2. Phase-Out of coal for electricity production by 2025;

However, faced with these important benefits, there are a number of problems and inefficiencies in the use of electricity produced by these power plants, in particular by photovoltaic and wind energy, due to their uncertainty, that is the inability to plan their production, in the point that usually they are indicated with the term GFRNP (generation from non-programmable renewable source). More specifically , it is possible to list, among others, the following series of general problems:

1. Reduction of the reserve margin;
2. Reversal of energy flows in the electricity grid;
3. Loading ramps to satisfy.