Hybrid [formula omitted]-fuelled MGT and solar-wind powered SOEC for micro-CHP system: Toward a sustainable utility system

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Green H2 production and utilisation in MGT-CHP (micro gas turbine - combined heat and power) systems can decarbonise small-scale applications like residential and commercial buildings. Although, H2 combustion with air presents some challenges such as reduced thermal efficiency, high NOx formation at higher operating temperatures, increased thermal stress on the combustor walls and flashback because of elevated burner temperatures. For these reasons, a H2-based MGT-CHP with a fitted H2O heat exchanger was developed. The main motivation behind this project is to explore the feasibility of producing H2O electrolysis feed (steam) that can feed H2 to the MGT combustor, along with reducing NOx formation and cooling the combustor and fuel injector walls with steam addition. This approach addresses the challenges of H2 delivery, thermal stress on the combustor wall and higher electricity input to the electrolyser stack. In this hybrid CHP system for small-scale applications, solar and wind powered SOEC (solid oxide electrolysis cell) was incorporated to utilise the generated steam from the micro-combustor wall to produce H2 fuel for the combustor. The results of the H2-fuelled micro-combustor with a diluent showed better flame stability, temperature distribution, reduced wall thermal stress and NOx formation. The presence of a coolant increased the reactant residence time and reduced the high thermal stress of the fuel injector walls. The use of ceria electrolyte SOEC demonstrated excellent fuel conversion efficiency of ≥ 91%. The addition of a coolant (steam) in the micro-combustor also increased the density of the exhaust gas which resulted in higher turbine power output. This study recorded < 6 ppm NOx emissions and maximum power output at an irradiance of 1200 W/m2 in mesophilic conditions and a wind speed of 17m/s. The proposed integrated system achieved a combined efficiency of ≥ 90% and recommends the use of renewable energy sources available in an area of operation.