Seasonal design and multi-objective optimization of a novel biogas-fueled cogeneration application

Switching from fossil fuels to biofuels is an effective option for small-scale power production and cogeneration systems. The target of the current study is to propose and investigate a novel seasonal combined cycle driven by a biogas-fueled gas turbine from thermodynamic and economic viewpoints. Regarding the high-temperature of the turbine's exhaust gases, an integration of Rankine and ejector refrigeration cycles is configured. The bottoming cycle is designated for winter and summer conditions, independently. Hence, a combined cycle capable of operating as a cogeneration system producing electricity/heating or electricity/cooling, individually, is designed. Moreover, a parametric study based on assessing the impact of key parameters on the essential variables and a multi-criteria optimization trough a genetic algorithm are performed to attain the facilities of the proposal. According to the results, the capability of the whole system in winter conditions is significantly higher than that for summer conditions due to the higher heating capacity. Also, the evaluated variables are more affected by change in the environment temperature in both seasons. Additionally, the optimal overall energy, exergy and levilized cost of products are calculated as 79.2%%, 45.6%, and 21.7 $/GJ for summer and 70.7%, 37.0%, and 17.6 $/GJ for winter, respectively.