ROLE OF PUMPED-STORAGE HYDROELECTRIC POWER PLANTS AND LARGE PENETRATION OF ELECTRIC VEHICLES IN INCREASING POWER SYSTEM FLEXIBILITY WITH LARGE SHARE OF RENEWABLE SOURCES

Sa？etak The European Union's (EU) goals of reducing energy dependence and reducing greenhouse gas emissions (GHG) are to be achieved primarily by increasing production from renewable energy sources (RES). However, due to the features of renewable sources such as unpredictability and lack of availability, it is necessary to increase the flexibility of the systems themselves. In other words, large penetration of RES into the power system requires a substantial increase in the capacity of various energy storage technologies. Pumped storage hydroelectric power plants (HPPs) represent 99% of global installed capacity of energy storage and are widely spread, providing energy storage capacity and transmission grid ancillary benefits in the US and Europe since 1920s, as well as in the rest of the world. Besides, new technologies are considered worldwide, and as one of the most prominent options considered today is the penetration of electric vehicles (EVs) into the power systems. The use of EVs reduces air pollution while connecting them to the smart grids creates the possibility of increasing the flexibility of the power system since vehicle batteries could be used as storage but also as sources of electricity. Using the PLEXOS energy market simulation software, the power system of the Republic of Croatia was modelled in this paper and based on the results of different scenarios, the role of pumped-storage power plants and large penetration of electric vehicles in increasing the power system flexibility with a large share of renewable sources was observed