| Author: | Luo, Haojie |
| Title: | The in-depth investigation and optimisation of hybrid ocean energy and storage systems for supporting zero-energy buildings with novel operations of onshore and offshore energy storages |
| Advisors: | Cao, Sunliang (BEEE) |
| Degree: | Ph.D. |
| Year: | 2026 |
| Department: | Department of Building Environment and Energy Engineering |
| Pages: | 128 pages : color illustrations |
| Language: | English |
| Abstract: | Rapid urbanisation drives economic growth and escalates energy demand and greenhouse gas emissions, underscoring the urgency of transitioning to renewable energy systems. This study investigates the feasibility of integrating wave energy converters and offshore wind turbines to support coastal zero-energy buildings, emphasising energy flexibility, resilience, and cost-effectiveness. A simulation framework in the TRNSYS 18 modelled building services, storage systems, and renewable energy units, evaluating performance through energy matching criteria, techno-economic analyses, and dynamic control strategies. This study first evaluated ocean thermal energy integration in heating and cooling systems, revealing that seawater-source heat exchangers with higher effectiveness over 0.85 improve chiller performance, though increased pump energy can offset gains. The immersed heat exchanger achieved superior system efficiency and reduced total energy use intensity by 10.9% compared to air-cooled systems. Replacing electric heaters with seawater-source heat pumps reduced heating electricity demand by 26%, demonstrating significant energy-saving potential. Hybrid wave-wind scenarios demonstrated enhanced energy matching, with a 62% wave and 38% wind ratio, achieving on-site electrical energy matching of 0.69. Integrating batteries further improved efficiencies by mitigating demand-generation mismatches. The hybrid wave-wind systems mitigated power shortages, achieving a 90% reduction in annual CO₂ emissions. Techno-economic evaluations confirmed project feasibility within a 20-year period, with a relative net present value highlighting cost-effectiveness. Battery and wave energy storage controls were implemented to enhance energy flexibility. Battery systems demonstrated 100% peak-shaving capability, reducing operational costs by 1%, while novel wave energy converter reservoir controls improved energy matching by 10% and lowered costs to 83.99%, boosting net present value by 40%. Dynamic storage strategies, including real-time adjustments based on electricity tariffs and demand patterns, further optimise performance. For instance, varying reservoir discharge limits reduced operational costs by 4.5%, and integrating additional batteries enhanced peak shaving, cutting costs by 6.4–10.8%. Further, the system introduced the floating photovoltaic and electric vehicles system. The system's flexibility and resilience were tested under a demand response programme and power outages. Coordinating flexibility sources, wave energy storage, building batteries, and electric vehicles increased the flexibility index to 199.89% and reduced operational costs to 79.52%. During outages, resilience improved from 83% to over 99%, minimising reliance on diesel generators and CO₂ emissions. This study further investigates the impact of relative time series of outages and demand response events on resilience. Results indicate that a 100% outage response index significantly enhances resilience, with renewable energy and storage effectively meeting demand during outages, reducing reliance on diesel, and achieving cost savings. Integrating ocean renewable energy and adaptive storage controls offers a robust solution for coastal zero-energy buildings, harmonising energy flexibility, resilience, and cost savings. Significant fuel cost reductions and emissions savings justify the approach. This research advances dynamic control strategies for ocean energy systems, providing actionable insights for optimising grid interactions, mitigating outages, and accelerating the transition to sustainable urban energy infrastructures. This study demonstrates novelty across multiple dimensions. It proposes a coastal zero-energy building supported by a hybrid ocean-renewable energy system, confirming the techno-economic feasibility of this ocean-resourced integrated thermal and electrical design. Innovatively, this system incorporates control strategies with both the generation and storage sides' flexibility. Specifically, the wave energy converter's characteristic reservoir is utilised as a mechanical energy storage unit, thereby enhancing energy matching and reducing costs. The research highlights dynamic control based on a time-of-use electricity tariff to minimise operational costs. Its originality also lies in introducing hybrid storage coordination to achieve two goals: flexibility and resilience, along with efficient control strategies that address incentive maximisation and grid outage survivability. This research offers practical solutions for reducing reliance on fossil fuels and maintaining stable operations during grid disruptions. It is especially relevant for coastal urban regions with ocean energy potential and high electric vehicle adoption. Additionally, it offers a replicable framework for facilitating the transition to net-zero emissions. |
| Rights: | All rights reserved |
| Access: | open access |
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