Modelling and experimentation on machines and integrated systems for energy conversion and storage based on waste heat valorization

The growing global energy demand and environmental concerns necessitate a transition from fossil fuels to sustainable solutions, increasing the use of renewable energy sources. Additionally, recovering low-grade waste heat from industrial processes, represents a major untapped opportunity for improving energy efficiency. However, the variability of waste heat sources necessitates customized solutions. This thesis explores advanced energy conversion technologies, focusing on Organic Rankine Cycles (ORCs), High-Temperature Heat Pumps (HTHPs), and Carnot Batteries (CBs) to optimize heat-to-power (H2P) and power-to-heat (P2H) processes. The first part investigates ORC and HTHP applications for electricity and thermal energy generation. Experimental studies on partial evaporation in ORCs highlight their potential for ultra-low-temperature heat recovery, demonstrating stable power production even under challenging off-design conditions. A validated off-design model assesses ORC integration in residential solar thermal systems and waste heat recovery from data centers, evaluating low-GWP working fluids. Results show that while R134a maximizes power output, alternative fluids improve environmental performance. For industrial applications, an innovative HTHP-based heat recovery system for ceramic manufacturing is proposed, achieving significant fuel savings and CO2 reductions while enhancing process efficiency. The second part examines CB integration for energy storage, improving renewable energy utilization. A novel CB prototype is developed and integrated with a district heating system, implementing an optimized rule-based control strategy to maximize economic benefits. Further analysis explores CB applications in data centers, demonstrating potential financial viability when coupled with photovoltaic power plants. Additionally, a thermodynamic assessment of a closed Brayton CB using supercritical CO2 is conducted for large-scale, high-temperature applications, identifying trade-offs between efficiency, cogeneration performance, and economic feasibility. By combining experimental data, modelling, and techno-economic assessments, this research advances H2P and P2H technologies, supporting their industrial and residential deployment. The findings contribute to improving energy efficiency, reducing emissions, and fostering a more sustainable and resilient energy future.