Browsing by Author "Janse van Vuuren, Martin"

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    Techno-economic analysis of solid oxide electrolysis using concentrated solar energy for green hydrogen production in South Africa.
    (Stellenbosch : Stellenbosch University, 2024-02) Janse van Vuuren, Martin; McGregor, Craig; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: RRising global awareness about climate change, depletion of fossil reserves, and economic pressure are propelling many countries to decarbonise their energy sectors. Green hydrogen, which is produced by the electrolysis of water, may play a vital role in decarbonising the ‘hard to abate’ sectors. Solid oxide electrolysis cells (SOECs), currently the most electrically efficient electrolysis technology, operate with high-temperature steam between 700-1000°C, which leads to a reduction in the electrical requirement for electrolysis but introduces a thermal energy demand. Concentrated solar thermal (CST) energy with thermal energy storage (TES) is a potential candidate for providing dispatchable renewable high-temperature heat for an SOEC system. This thesis presents a techno-economic analysis and optimisation of a 100 MW hypothetical SOEC plant with heat integration from CST+TES in the Northern Cape of South Africa for green hydrogen export. The primary objective was to perform a direct economic comparison between a hybrid system that sources thermal energy integration from CST+TES, and a reference system that uses thermal energy from electric heating. Both the hybrid and reference systems rely on electricity generated by dedicated photovoltaic (PV) and wind turbine plants. The capacities of the CST, TES, PV and wind turbine plant models for both systems were optimised to achieve the minimum levelised cost of hydrogen (LCOH) produced by the SOEC. Results from the SOEC plant model showed that up to 16.6 % of the electricity demand of the SOEC plant can be replaced by integrating CST+TES to augment the thermal demand of the electric boiler for steam production. For the hybrid system, a parabolic trough CST plant with a twotank direct oil storage was modelled which delivered 92 % of the annual thermal demands of the hybrid system. The hybrid system with CST exhibited an LCOH of 5.88 $/kg compared to the reference system’s 6.13 $/kg. A sensitivity analysis showed that the hybrid system maintains its economic competitiveness over the reference system over a wide range of CST, TES, PV and wind turbine capacities. In conclusion, this thesis demonstrated the economic advantages of integrating CST+TES into a SOEC plant which is powered by PV and wind turbines, leading to a 4.1 % reduction in LCOH. However, this integration introduces complexity and associated operational and financial risks, which will influence investment decisions.