Techno-economic Feasibility of Hybrid PV/wind/battery/thermal Storage Trigeneration System: Toward 100% Energy Independency and Green Hydrogen Production

With the clear adverse impacts of fossil fuel-based energy systems on the climate and environment, ever-growing interest and rapid developments are taking place toward full or nearly full dependence on renewable energies in the next few decades. Estonia is a European country with large demands for electricity and thermal energy for district heating. Considering it as the case study, this work explores the feasibility and full potential of optimally sized photovoltaic (PV), wind, and PV/wind systems, equipped with electric and thermal storage, to fulfill those demands. Given the large excess energy from 100% renewable energy systems for an entire country, this excess is utilized to first meet the district heating demand, and then to produce hydrogen fuel. Using simplified models for PV and wind systems and considering polymer electrolyte membrane (PEM) electrolysis, a genetic optimizer is employed for scanning Estonia for optimal installation sites of the three systems that maximize the fulfillment of the demand and the supply–demand matching while minimizing the cost of energy. The results demonstrate the feasibility of all systems, fully covering the two demands while making a profit, compared to selling the excess produced electricity directly. However, the PV-driven system showed enormous required system capacity and amounts of excess energy with the limited solar resources in Estonia. The wind system showed relatively closer characteristics to the hybrid system but required a higher storage capacity by 75.77%. The hybrid PV/wind-driven system required a total capacity of 194 GW, most of which belong to the wind system. It was also superior concerning the amount (15.05 × 109 tons) and cost (1.42 USD/kg) of the produced green hydrogen. With such full mapping of the installation capacities and techno-economic parameters of the three systems across the country, this study can assist policymakers when planning different country-scale cogeneration systems.