As the energy transition accelerates, there is growing interest in exploring different renewable energy sources to help reduce emissions from heating and electricity. One of the more promising options, under the right conditions, is geothermal energy, which can provide a stable and relatively low-carbon supply of heat and/or power. In the Netherlands, medium-depth (>500 m) geothermal heat has mostly been used for heating greenhouses, with electricity production from geothermal sources not yet explored.

This thesis provides a techno-economic assessment of medium-depth geothermal energy systems in South Holland, the Netherlands, evaluating their potential to meet local heat and electricity demands sustainably and with a profit. Two case studies were analyzed in this thesis. The first investigated a geothermal district heating system for the TU Delft campus, incorporating a large-scale heat pump to increase heat extraction from the reservoir. The second examined a combined heat and power (CHP) system for the Royal IHC facilities in Kinderdijk, based on an Organic Rankine Cycle (ORC). The work relied on thermodynamic modeling together with subsurface and economic simulations to select working fluids, size the main components, and assess economic indicators such as Levelized Costs of Heat/Electricity (LCOH/LCOE), Net Present Value (NPV), payback times, and internal rate of return (IRR).

The findings reveal a sharp difference in feasibility between the two cases. The geothermal heat pump project in Delft proved to be promising for district heating applications, whereas the ORC-based power generation system proved to be both technically and economically unviable under the assessed conditions, mainly due to the low temperature of the geothermal brine and the small scale of the project. A subsequent evaluation of a heat pump alternative for the Kinderdijk site indicated limited economic competitiveness under the current market price assumptions for heating.

Overall, the work suggests that the viability of geothermal projects is highly dependent on the quality of the geothermal resource, the scale of implementation, and the end-use requirements. Integrating heat pumps with medium-depth hydrothermal resources appears as a technically promising and financially attractive strategy for decarbonizing district heating networks, whereas low-temperature ORC systems for power generation remain unsuitable in regions with insufficient subsurface temperatures. The study shows the importance of site-specific assessments in ensuring the successful deployment of geothermal energy systems.

The constant pressure on the maritime sector to reduce Greenhouse Gas (GHG) emissions has led the shipping industry to search for alternatives, such as zero-emissions propulsion systems, which would allow meeting the 2050 target imposed by International Maritime Organization (IMO) regulation. Fuel cells have demonstrated to substantially contribute to the greening of energy conversion technologies. Specifically, Solid Oxide Fuel Cells have proven to be a reliable technology to produce energy from Liquid Natural Gas (LNG). However, the limited understanding of the effect of the components around the stack (also known as Balance of Plant, BoP) in SOFC power generation system represents one of the reasons of the slow development of this technology. The main objective of this research is to gain insight in the performance of the BoP components and their influence on the SOFC power generation system for maritime applications. A dynamic model describing a complete SOFC power generation system is developed in this work. The chosen system configuration consists of three blowers, two heat exchangers, a mixer, an external pre-reformer, an SOFC stack and an afterburner. Specifically, each BoP component is modelled dynamically using a 0-D approach and verified individually by using the software Cycle-Tempo. Then, the BoP models are integrated with an existing 1-D SOFC stack model. A dedicated control system is implemented and the load following capabilities of the complete system are studied. The model developed is able to simulate the time variation of all the BoP component characteristics and provides insights in the system efficiency when varying operating parameters such as stack current, anode recirculating ratio and fuel utilization. In particular, it is proven that working at low current enables higher cell voltage and, thus, higher system and stack efficiency. System fuel utilization significantly contributes to the system efficiency, which reaches the highest value for the highest fuel utilization. Additionally, the effect of the fuel utilization rate on the stack and system is the highest at lower currents. System and stack efficiency of respectively 58 % and 66 % are possible with the chosen system configuration. Anode recirculating contributes more to the system efficiency than the stack efficiency. The highest system efficiency is obtained for low current values and high recirculating ratio. Moreover, significant CO2 emission reduction is obtained for high recirculating ratio. The chosen control strategy succeeds on ensuring thermal safe operation, but does not guarantee fast response to load changes. In particular, a system response within 2 hours is achieved with the controller developed when the stack current is changed from 27 A to 23 A . Moreover, a load ramp of the stack current is a better choice in terms of thermal safe operation than a stepped change. The developed model represents a solid base for future development and research in the modelling of SOFC power generation systems for maritime applications. Nevertheless, future investigations on model validation, control system, start-up operations and system optimization are recommended.