Techno-economic analysis of cogeneration systems based on internal-combustion engines fueled with syngas from biomass gasification

This study presents an energy and techno-economic analysis of a biomass-fired cogeneration system consisting of a 38 kWe internal combustion engine and a biomass gasifier. A numerical model is developed to characterize the gasifier-engine system. Detailed thermodynamic sub-models for the biomass gasification reactor and for the internal combustion engine are implemented. After validation, a comprehensive analysis of the CHP (Combined Heat and Power) performance parameters is carried out under various operating conditions. The optimal configurations are identified in terms of gasifier equivalent ratio, optimal engine spark ignition advance, overall energy performance, and Primary Energy Saving index. The techno-economic analysis includes three scenarios: the baseline, in which the costs are actualized on 2019, and additional two cases with +25 % and + 50 % of energy cost increases to account for the current world geopolitical situation and analyze the sensitivity of the obtained results to cost variation. Furthermore, two functioning strategies are considered: the ON strategy, in which the system operates continuously at nominal conditions, and the ON-OFF one, in which the system is switched off during low-demand periods. The former is found to be less economically convenient, whereas the latter is proven to be economically viable. The selected optimal configuration achieved a 22.33 % Primary Energy Saving index. Furthermore, the electric and thermal efficiency are 23 % and 63 %, respectively, reaching 86 % total efficiency. Finally, the discounted payback period ranges from 4.7 to 5.9 years across the three scenarios, maintaining economic viability despite rising energy costs. Overall, our investigation provides an efficient and greener solution to exploit energy production systems based on internal combustion, contributing to a more sustainable energy transition to carbon-free technologies.