SMART HYDRO-ENERGY HYBRID SYSTEM POTENTIAL IN CROATIA—BEDNJA RIVER CASE STUDY

The smart hydro-energy hybrid system comprises a small hydroelectric power plant and a solar photovoltaic power plant as a part of energy input for the realization of smart cities. This paper introduces the critical period method (CPM), which can be used for system sizing. According to this method, if the total energy production is lower than the energy demand, a critical period should be defined based on the largest difference between demand and production. The period (day) in which that difference appears is called the critical period. If the energy demand during this period is satisfied, the demand on the remaining days of the year is also satisfied. Any possible breaks in energy production, caused by a reduction in the expected river-flow rates or insolation (in the case of cloudiness), will be reduced to a minimum. The use of such a hybrid system guarantees the production of electricity throughout the year. Such a hybrid system could facilitate the realization of a smart city and help achieve energy stability and security. Despite Croatia having great potential in terms of solar energy use and the large number of available watercourses, such a hybrid system has never been realized. In particular, CPM has not been applied previously anywhere in the world.