Textbook in PDF format Process systems engineering (PSE) is a discipline that delivers tools for guided decision-making in the development of new processes and products. Proven successful in the pharmaceutical-, food- and water sectors, it has also breached the field of energy systems. The future energy systems aim to be more efficient, cost-effective, environmentally benign, and interconnected. Preface 1 Hydrogen production via water splitting over graphitic carbon nitride (g-C3N4)-based photocatalysis 2 Optimization of electrolysis and carbon capture processes for sustainable production of chemicals through Power-to-X 3 Optimization of hydrogen supply from renewable electricity including cavern storage 4 Integrating multi-objective superstructure optimization and multi-criteria assessment: a novel methodology for sustainable process design 5 Process intensification and digital twin–the potential for the energy transition in process industries 6 The role of bioprocess systems engineering in extracting chemicals and energy from microalgae 7 Exergy analysis of an atmospheric residue desulphurization hydrotreating process for a crude oil refinery 8 Supply chain optimization framework for CO2 capture, utilization, and storage in Germany 9 Design of hydrogen supply chains under demand uncertainty–a case study of passenger transport in Germany 10 Multi-objective optimization of CCUS supply chains for European countries with higher carbon dioxide emissions 11 Certainty through uncertainty: stochastic optimization of grid-integrated large-scale energy storage in Germany 12 Shaping the future energy markets with hybrid multimicrogrids by sequential least squares programming 13 Development of future-proof supply concepts for sector-coupled district heating systems based on scenario-analysis 14 Power to the city: Assessing the rooftop solar photovoltaic potential in multiple cities of Ecuado