Techno-economic analysis of integrated biomass gasification and alkaline electrolysis for 5th generation district energy networks in Quebec, Canada

This study presents a technical, thermo-economic, and environmental analysis of a biomass-based polygeneration system. This system is for fifth-generation district heating and cooling (5GDH) networks. The system integrates a biomass gasifier with an electrolyzer. The electrolyzer provides an on-site oxygen source for gasification, eliminating the need for energy-intensive Air Separation Units (ASUs). The generated syngas fuels a turbine to produce electricity. The waste heat from this process is then recovered for District Heating and Cooling networks. Additionally, the electrolyzer produces hydrogen (H2), which is injected into the syngas stream. This addition significantly boosts its heating value, resulting in an inert, nitrogen-free blend suitable for urban hydrogen, power, heating, and cooling applications. The produced electricity can also power commercial heat pumps, enabling efficient low-temperature DHC. The research examined three scenarios using an Engineering Equation Solver (EES) mathematical model. This model was validated, showing less than a 10 % deviation from experimental data. Scenarios one and two explored combined air and steam gasification for heat, power, and cooling production. The third scenario integrated the gasifier and electrolyzer, where an external power source operates the electrolyzer to generate oxygen (O2) for gasification and hydrogen (H2) for syngas enrichment. The system was analyzed at 2.2 MWe and 5.5 MWe capacities in a case study located in Quebec, Canada. Results highlight the strategic benefit of using electrolyzer-derived oxygen. The system was designed to meet peak demands (0.6 MW heating, 0.5 MW cooling, 1.1–4.9 MW electricity) and achieved high efficiency. Oxygen gasification, utilizing 16.14 MJ/kg LHV biomass, required 33–37 % less biomass than air gasification. It reached 78 % plant efficiency and 61 % exergy efficiency. The thermo-economic analysis confirmed its environmental and economic performance. It recorded a primary energy consumption of 4 GWh/year and direct CO2 emissions of 9 tCO2eq/year. This represents a 91 % Primary Energy Saving compared to reference systems. Operating costs dropped to 2511 k$/year (from 5603 k$/year for 5.5 MW reference). The 5.5 MWe system demonstrated a 12-year Simple Payback Period and a 40M Net Present Value. These findings strongly support this polygeneration system as a highly sustainable and economically advantageous model for energy-independent urban districts.