Speaker
Description
Grid stability and reliability problems related to renewable energy sources have hindered the transition to an eco-friendly future. Solar Power Tower (SPT) plants mitigate local, short-term energy supply fluctuations by achieving high thermodynamic cycle efficiency and employing thermal energy storage tanks to reuse excess heat later. Nevertheless, tackling long-term intermittency issues at regional and even global levels, coupled with the anticipated rise in energy demand, necessitates large-scale solutions. The integration of underground hydrogen storage (UHS) systems with SPT plants presents a promising strategy for significant energy storage, supporting various industries. High direct normal irradiation (DNI) values in California and Texas, combined with the abundance of suitable UHS sites, make this hybrid facility highly applicable. However, the potential financial returns of this hybrid approach, with federal tax incentives, have yet to be determined. Therefore, the research aims to conduct a techno-economic comparative analysis between salt caverns and depleted reservoirs to evaluate the viability of the novel SPT-UHS model within the USA.
The case study utilises the Aliso Canyon natural gas storage field in Southern California as a depleted reservoir for the UHS. After calculating its total working gas capacities, a system comprising multiple salt caverns is developed in the Permian Basin, West Texas, to achieve an equivalent capacity. Due to geological constraints and the limited availability of regions with high DNI, the SPT plant in each hybrid model is located inland at a moderate distance from the UHS site. The pure water required for a thermochemical Cu-Cl electrolysis process is obtained through the desalination of local aquifer water sources. To improve electrolyser efficiency, a photovoltaic (PV) station provides the necessary electricity for hydrogen (H₂) production and compression for subsurface injection at a specific SPT:PV ratio. Additionally, oxygen (O₂), a byproduct of electrolysis, is assumed to be sold to hospitals to increase profits.
The primary contribution of this research is a full techno-economic analysis of the SPT-UHS hybrid system, yielding extremely advantageous financial outcomes. The SPT configuration, with a gross capacity of 270 MW, supplies H₂ to 69 salt caverns, attaining the same working capacity in kg of the single depleted reservoir. The findings indicate that the highest net present value (NPV) and the shortest payback period (PBP) for the salt cavern system are approximately USD 7.4B and 6 years, respectively, while for the depleted reservoir, these values are around USD 8.8B and 4 years. The existing literature predominantly focuses on wind-UHS hybrid plants, which exhibit NPVs below USD 17MM. Compared to the system analysed in our study, their PBPs are extended by a factor of 2.1 for salt cavern storage and 1.6 for depleted reservoir storage. This highlights the benefits of the large-scale SPT-UHS facility with both O₂ sales and storage schemes. Although selling H₂ generates higher net cash flow, the sale of O₂ has a greater impact on NPV by enhancing the project's financial stability. Furthermore, applying tax incentives and O₂ sales boosts the SPT-UHS system’s economics, reducing PBPs by 6% and 49%, respectively, resulting in a combined 54% improvement.
| Country | Australia |
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