Modelling and Techno-economic Analysis of a Hybrid CSP/PV System using Solid Oxide Electrolyser for Hydrogen Production

Abstract: This project proposes a solar-driven hybrid system for electricity generation and hydrogen production, which includes concentrated solar power (CSP), photovoltaic (PV), solid oxide electrolyser (SOEC). Electricity from the CSP and PV provides a continuous 24/7 supply to meet demand-side power consumption. When demand-side power consumption is low, the excess power is used to electrolyse water in the SOEC system. In this study, an SOEC is modelled, operation strategy for the solar-driven hybrid system is developed, the techno-economic performance of the overall system is evaluated, and sensitivity analysis is performed. For the modelling part, first develop an SOEC component in Matlab and Trnsys by considering the electrochemical model, thermal model and electric model. Second, design the hybrid system layout and simulate the system under 8760 hours in Matlab and Trnsys. The hybrid system is divided into five blocks: Heat Energy Source Block, Thermal Energy Storage Block, Rankine Cycle Block, Photovoltaic Block, Power to Hydrogen (PtH) Block. The operation strategy is: the heat is collected using a tower solar receiver and stored in tanks by heat transfer fluid molten salt. These thermal energy heats the water in heat exchangers and the resulting high temperature water vapour is used in steam turbine to generate electricity; at the same time part of the heat transfer fluid heats the feedwater in the PtH block and the resulting high temperature water vapour is used in SOEC for hydrogen production, if the operation temperature of steam in SOEC is not reached after heat exchange, the electric heater will heat the steam to raise the temperature. The CSP and PV provide electricity to demand side and SOEC. The produced hydrogen will be transported by truck or ship after compressed. For results part, the minimum CSP configurations to provide a 24/7 demand-side electricity consumption is a solar multiple (SM) with 2 and thermal storage (TES) size of 14 hours. SOEC stack has the best techno-economic performance at a nominal power of 275 Watt. The hybrid system has a levelised cost of electricity (LCOE) at 0.219 USD/kWh and a levelised cost of hydrogen (LCOH) at 7.5 USD/Kg. There are several sensitivity parameters for increase the energy productivity and decrease levelised cost. The larger the SM, the better the ability to generate power. The larger the TES size, the more the hourly generation is similar, otherwise it will fluctuate more. Increasing the SM results in a higher LCOE and a significantly lower LCOH. Increasing TES size also increases the LCOE, whereas the TES size has a marginal impact on the decrease of LCOH. Increased installed capacity inevitably leads to increased power generation. The increasing total power capacity makes the surplus power at the same demand side increase, so the SOEC runs at higher input power and the total hydrogen production increases, resulting in a lower LCOH. The effect of SOEC capacity on LCOH depends on the relationship between input power and SOEC nominal power. Higher operation temperature of SOEC leads to the lower the reversible voltage and an increasing consumption for water vapour. However, when the water vapour concentration is too high, the electrolysis current will instead drop, meaning that the rate of hydrogen production will drop.