Circular carbon economy integration of smart grids and renewable hybrid systems for hydrogen ammonia and biogas production in wastewater treatment plants

In this thesis study, the technical, economic, and environmental feasibility of transforming a wastewater treatment plant located in Diyarbakır into an energy-positive structure through a hybrid energy system has been comprehensively evaluated. In line with the goals of sustainable development, a multi-component system model has been designed, not only to meet the energy needs of the plant but also to produce clean energy carriers such as green hydrogen and green ammonia. In this context, a biogas generator, electrolyzer, hydrogen tank, ammonia production unit, NH₃ cracker, and energy conversion systems were integrated, and modeling and optimization processes were carried out using the HOMER Pro software. Although photovoltaic modules were included in the initial system design, HOMER Pro simulations indicated that this component offered limited production contribution relative to the total system cost, and it was therefore excluded from the final economic-optimal configuration. The final system configuration relies on biogas and grid-supported electricity as energy sources, and on electrolysis and ammonia synthesis as the main conversion processes. The electrolyzer enables the storage of surplus energy in the form of hydrogen, while the ammonia production unit synthesizes this hydrogen with nitrogen into a chemical form that can be used as an energy carrier. The NH₃ cracker module, when needed, reconverts this ammonia into hydrogen to support electricity generation. The system's energy management performance has been modeled to fully align with the load profile, ensuring a continuous balance between production and consumption. The high efficiency of the energy conversion components has enhanced the system's stability and enabled uninterrupted electrical continuity. Especially with the inverter module, energy flow has been effectively converted from DC to AC; and with the grid connection, the system has been able to both receive support from external sources and export excess energy to the grid. According to the economic evaluation results, despite being based on high technology, the system offers a cost-effective structure in the long term. The initial investment costs have been brought to a sustainable level over time through balanced operating, fuel, and maintenance expenditures. Furthermore, the ability of the system to sell excess energy to the grid provides a favorable economic return. In terms of environmental impact, the most prominent feature of the system is its circular structure aimed at reducing the carbon footprint. The use of biogas derived from organic waste has lessened the environmental burden, while the utilization of hydrogen and ammonia as clean fuels has contributed to the control of greenhouse gas emissions. In this way, an environmentally friendly energy production process has been achieved, and the circular carbon economy has been supported by converting waste into energy.