Date of Award

7-7-2026

Thesis Type

PhD

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Divisions

Institute for Advanced Studies

Institution

Universiti Malaya

Abstract

Solar thermal technology has advanced significantly in recent years. It enables new renewable pathways for clean hydrogen fuel production, with considerable environmental and economic benefits. The proposed system integrates a heliostat field with high-temperature thermal energy storage (tes), a supercritical carbon dioxide (s-co2) brayton power cycle, photovoltaic-thermal (pv/t) modules coupled to reverse osmosis desalination (for water supply), a solid oxide electrolysis cell (soec) for hydrogen generation, and a claude cycle for hydrogen liquefaction. The plant is designed to operate in three modes (low, high, and zero solar radiation) to utilize solar energy during the day and stored heat at night. A rigorous performance evaluation is conducted from thermodynamic, environmental (sustainability/exergoenvironmental), and economic perspectives. The methodology includes an initial sensitivity analysis to identify key design parameters, followed by multi-objective optimization under three distinct scenarios (maximizing exergy efficiency vs. Sustainability vs. Environmental performance, each balanced with cost). Surrogate models of the objective functions are trained using an artificial neural network (ann) and a multi-objective grey wolf optimizer (mogwo) algorithm is employed to find pareto-optimal solutions. The topsis decision-making method is then applied to select the final optimal design from the pareto set. Key results from the analysis underscore the influence of design parameters and the system’s viability. The molten-salt mass flow split ratio in the thermal storage loop emerged as the most influential parameter, with a mean sensitivity index of 0.27 – the highest among variables studied. The sensitivity of other factors (turbine inlet Temperature, compressor pressure ratio, electrolyzer current density, and heat-exchanger temperature approach) was comparatively lower, highlighting the critical role of efficient thermal management. Among the optimization scenarios, the exergy–economic scenario (maximizing exergetic efficiency and minimizing hydrogen cost) yielded the best performance. In this scenario, the optimal design achieved an exergetic round-trip efficiency of approximately 19.3% and a daily liquefied hydrogen output yielding several hundred kilograms under representative global solar conditions. Economic analysis of the optimized system indicates that its feasibility is strongly dependent on hydrogen pricing. For instance, increasing the hydrogen selling price from $9 to $15 per kg boosts the net present value (npv) from about $10.5 million to $150.2 million and shortens the payback period from approximately 18.7 to 8.5 years, highlighting the critical role of market conditions in determining project viability. A comparative case study using real solar data from three malaysian coastal regions (alor setar, kelantan, and kuantan) was performed to evaluate location-specific performance. Alor setar was identified as the most favorable site, enabling an average production of about 1494 kg of liquefied h2 per day at an estimated hydrogen cost of $7.77/kg, given its superior solar irradiance. This finding demonstrates the system’s practical viability in high-insolation areas. Overall, the integrated solar-driven hydrogen production and liquefaction process — optimized via advanced ann-based multi-objective techniques — demonstrates significant potential as a clean energy solution. While the system can technically achieve round-the-clock hydrogen production using renewable resources, its economic feasibility hinges on favorable hydrogen market prices, optimal operational strategies, and consistent solar availability.

Initial

khm

Additional Information

Thesis (PhD) – Institute for Advanced Studies, Universiti Malaya, 2026.

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